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Mariner 2

Mariner 2 (Mariner-Venus 1962), an American space probe to Venus, was the first robotic space probe to report successfully from a planetary encounter. The first successful spacecraft in the NASA Mariner program, it was a simplified version of the Block I spacecraft of the Ranger program and an exact copy of Mariner 1. The missions of the Mariner 1 and 2 spacecraft are sometimes known as the Mariner R missions. Original plans called for the probes to be launched on the Atlas-Centaur, but serious developmental problems with that vehicle forced a switch to the much smaller Agena B second stage. As such, the design of the Mariner R vehicles was greatly simplified. Far less instrumentation was carried than on the Soviet Venera probes of this period—for example, forgoing a TV camera—as the Atlas-Agena B had only half as much lift capacity as the Soviet 8K78 booster. The Mariner 2 spacecraft was launched from Cape Canaveral on August 27, 1962, and passed as close as 34773 km to Venus on December 14, 1962.

The Mariner probe consisted of a 100 cm (39.4 in) diameter hexagonal bus, to which solar panels, instrument booms, and antennas were attached. The scientific instruments on board the Mariner spacecraft were: two radiometers (one each for the microwave and infrared portions of the spectrum), a micrometeorite sensor, a solar plasma sensor, a charged particle sensor, and a magnetometer. These instruments were designed to measure the temperature distribution on the surface of Venus and to make basic measurements of Venus' atmosphere.

The primary mission was to receive communications from the spacecraft in the vicinity of Venus and to perform radiometric temperature measurements of the planet. A second objective was to measure the interplanetary magnetic field and charged particle environment.

En route to Venus, Mariner 2 measured the solar wind, a constant stream of charged particles flowing outwards from the Sun, confirming the measurements by Luna 1 in 1959. It also measured interplanetary dust, which turned out to be scarcer than predicted. In addition, Mariner 2 detected high-energy charged particles coming from the Sun, including several brief solar flares, as well as cosmic rays from outside the Solar System. As it flew by Venus on December 14, 1962, Mariner 2 scanned the planet with its pair of radiometers, revealing that Venus has cool clouds and an extremely hot surface.

Background

With the advent of the Cold War, the two then-superpowers, the United States and the Soviet Union, both initiated ambitious space programs with the intent of demonstrating military, technological, and political dominance. The Soviets launched the Sputnik 1, the first Earth orbiting satellite, on October 4, 1957. The Americans followed suit with Explorer 1 on February 1, 1958, by which point the Soviets had already launched the first orbiting animal, Laika in Sputnik 2. Earth's orbit having been reached, focus turned to being the first to the Moon. The Pioneer program of satellites consisted of three unsuccessful lunar attempts in 1958. In early 1959, the Soviet Luna 1 was the first probe to fly by the Moon, followed by Luna 2, the first artificial object to impact the Moon.

With the Moon achieved, the superpowers turned their eyes to the planets. As the closest planet to Earth, Venus presented an appealing interplanetary spaceflight target. Every 19 months, Venus and the Earth reach relative positions in their orbits around the Sun such that a minimum of fuel is required to travel from one planet to the other via a Hohmann Transfer Orbit. These opportunities mark the best time to launch exploratory spacecraft, requiring the least fuel to make the trip.

The first such opportunity of the Space Race occurred in late 1957, before either superpower had the technology to take advantage of it. The second opportunity, around June 1959, lay just within the edge of technological feasibility, and U.S. Air Force contractor Space Technology Laboratory (STL) intended to take advantage of it. A plan drafted January 1959 involved two spacecraft evolved from the first Pioneer probes, one to be launched via Thor-Able rocket, the other via the yet-untested Atlas-Able. STL was unable to complete the probes before June, and the launch window was missed. The Thor-Able probe was repurposed as the deep space explorer Pioneer 5, which was launched March 11, 1960, and designed to maintain communications with Earth up to a distance of 20000000 mi as it traveled toward the orbit of Venus. (The Atlas Able probe concept was repurposed as the unsuccessful Pioneer Atlas Moon probes.) No American missions were sent during the early 1961 opportunity. The Soviet Union launched Venera 1 on February 12, 1961, and on May 19–20 became the first probe to fly by Venus; however, it had stopped transmitting on February 26.

For the summer 1962 launch opportunity, NASA contracted Jet Propulsion Laboratory (JPL) in July 1960 to develop "Mariner A", a 1250 lb spacecraft to be launched using the yet undeveloped Atlas-Centaur. By August 1961, it had become clear that the Centaur would not be ready in time. JPL proposed to NASA that the mission might be accomplished with a lighter spacecraft using the less powerful but operational Atlas-Agena. A hybrid of Mariner A and JPL's Block 1 Ranger lunar explorer, already under development, was suggested. NASA accepted the proposal, and JPL began an 11-month crash program to develop "Mariner R" (so named because it was a Ranger derivative). Mariner 1 would be the first Mariner R to be launched followed by Mariner 2.

Spacecraft
Three Mariner R spacecraft were built: two for launching and one to run tests, which was also to be used as a spare. Aside from its scientific capabilities, Mariner also had to transmit data back to Earth from a distance of more than 26000000 mi, and to survive solar radiation twice as intense as that encountered in Earth orbit.

Structure
All three of the Mariner R spacecraft, including Mariner 2, weighed within 3 lb of the design weight of 447 lb, 406 lb of which was devoted to non-experimental systems: maneuvering systems, fuel, and communications equipment for receiving commands and transmitting data. Once fully deployed in space, with its two solar panel "wings" extended, Mariner R was 12 ft in height and 16.5 ft across. The main body of the craft was hexagonal with six separate cases of electronic and electromechanical equipment:

 * Two of the cases comprised the power system: switchgear that regulated and transmitted power from the 9800 solar cells to the 33.3 lb rechargeable 1000 watt silver-zinc storage battery.
 * Two more included the radio receiver, the three-watt transmitter, and control systems for Mariner's experiments.
 * The fifth case held electronics for digitizing the analog data received by the experiments for transmission.
 * The sixth case carried the three gyroscopes that determined Mariner's orientation in space. It also held the central computer and sequencer, the "brain" of the spacecraft that coordinated all of its activities pursuant to code in its memory banks and on a schedule maintained by an electronic clock tuned into equipment on Earth.

At the rear of the spacecraft, a monopropellant (anhydrous hydrazine) 225 N rocket motor was mounted for course corrections. A nitrogen gas fueled stabilizing system of ten jet nozzles controlled by the onboard gyroscopes, Sun sensors, and Earth sensors, kept Mariner properly oriented to receive and transmit data to Earth.

The primary high-gain parabolic antenna was also mounted on the underside of Mariner and kept pointed toward the Earth. An omnidirectional antenna atop the spacecraft would broadcast at times that the spacecraft was rolling or tumbling out of its proper orientation, to maintain contact with Earth; as an unfocused antenna, its signal would be much weaker than the primary. Mariner also mounted small antennas on each of the wings to receive commands from ground stations.

Temperature control was both passive, involving insulated, and highly reflective components; and active, incorporating louvers to protect the case carrying the onboard computer. At the time the first Mariners were built, no test chamber existed to simulate the near-Venus solar environment, so the efficacy of these cooling techniques could not be tested until the live mission.

Background
At the time of the Mariner project's inception, few of Venus' characteristics were definitely known. Its opaque atmosphere precluded telescopic study of the ground. It was unknown whether there was water beneath the clouds, though a small amount of water vapor above them had been detected. The planet's rotation rate was uncertain, though JPL scientists had concluded through radar observation that Venus rotated very slowly compared to the Earth, advancing the long-standing (but later disproven ) hypothesis that the planet was tidally locked with respect to the Sun (as the Moon is with respect to the Earth). No oxygen had been detected in Venus' atmosphere, suggesting that life as existed on Earth was not present. It had been determined that Venus' atmosphere contained at least 500 times as much carbon dioxide as the Earth's. These comparatively high levels suggested that the planet might be subject to a runaway greenhouse effect with surface temperatures as high as 600 K, but this had not yet been conclusively determined.

The Mariner spacecraft would be able to verify this hypothesis by measuring the temperature of Venus close-up; at the same time, the spacecraft could determine if there was a significant disparity between night and daytime temperatures. An on-board magnetometer and suite of charged particle detectors could determine if Venus possessed an appreciable magnetic field and an analog to Earth's Van Allen Belts.

As the Mariner spacecraft would spend most of its journey to Venus in interplanetary space, the mission also offered an opportunity for long-term measurement of the solar wind of charged particles and to map the variations in the Sun's magnetosphere. The concentration of cosmic dust beyond the vicinity of Earth could be explored as well.

Due to the limited capacity of the Atlas Agena, only 40 lb of the spacecraft could be allocated to scientific experiments.

Instruments

 * A two-channel microwave radiometer of the crystal video type operating in the standard Dicke mode of chopping between the main antenna, pointed at the target, and a reference horn pointed at cold space. It was used to determine the absolute temperature of Venus' surface and details concerning its atmosphere through its microwave-radiation characteristics, including the daylight and dark hemispheres, and in the region of the terminator. Measurements were performed simultaneously in two frequency bands of 13.5 mm and 19 mm. The total weight of the radiometer was 22 lb. Its average power consumption was 4 watts and its peak power consumption 9 watts.
 * A two-channel infrared radiometer to measure the effective temperatures of small areas of Venus. The radiation that was received could originate from the planetary surface, clouds in the atmosphere, the atmosphere itself or a combination of these. The radiation was received in two spectral ranges: 8 to 9 μm (focused on 8.4 μm) and 10 to 10.8 μm (focused on 10.4 μm). The latter corresponding to the carbon dioxide band. The total weight of the infrared radiometer, which was housed in a magnesium casting, was 1.3 kg, and it required 2.4 watts of power. It was designed to measure radiation temperatures between approximately 200 and 500 K.

 * A three-axis fluxgate magnetometer to measure planetary and interplanetary magnetic fields. Three probes were incorporated in its sensors, so it could obtain three mutually orthogonal components of the field vector. Readings of these components were separated by 1.9 seconds. It had three analog outputs that had each two sensitivity scales: ± 64 γ and ± 320 γ (1 γ = 1 nanotesla). These scales were automatically switched by the instrument. The field that the magnetometer observed was the super-position of a nearly constant spacecraft field and the interplanetary field. Thus, it effectively measured only the changes in the interplanetary field.

 * An ionization chamber with matched Geiger-Müller tubes (also known as a cosmic ray detector) to measure high-energy cosmic radiation.

 * A particle detector (implemented through use of an Anton type 213 Geiger-Müller tube) to measure lower radiation (especially near Venus), also known as the Iowa detector, as it was provided by the University of Iowa. It was a miniature tube having a 1.2 mg/cm2 mica window about 0.3 cm in diameter and weighing about 60 g. It detected soft x-rays efficiently and ultraviolet inefficiently, and was previously used in Injun 1, Explorer 12 and Explorer 14. It was able to detect protons above 500 keV in energy and electrons above 35 keV. The length of the basic telemetry frame was 887.04 seconds. During each frame, the counting rate of the detector was sampled twice at intervals separated by 37 seconds. The first sampling was the number of counts during an interval of 9.60 seconds (known as the 'long gate'); the second was the number of counts during an interval of 0.827 seconds (known as the 'short gate'). The long gate accumulator overflowed on the 256th count and the short gate accumulator overflowed on the 65,536th count. The maximum counting rate of the tube was 50,000 per second.

 * A cosmic dust detector to measure the flux of cosmic dust particles in space.
 * A solar plasma spectrometer to measure the spectrum of low-energy positively charged particles from the Sun, i.e. the solar wind.

The magnetometer was attached to the top of the mast below the omnidirectional antenna. Particle detectors were mounted halfway up the mast, along with the cosmic ray detector. The cosmic dust detector and solar plasma spectrometer were attached to the top edges of the spacecraft base. The microwave radiometer, the infrared radiometer and the radiometer reference horns were rigidly mounted to a 48 cm diameter parabolic radiometer antenna mounted near the bottom of the mast. All instruments were operated throughout the cruise and encounter modes except the radiometers, which were only used in the immediate vicinity of Venus.

In addition to these scientific instruments, Mariner 2 had a data conditioning system (DCS) and a scientific power switching (SPS) unit. The DCS was a solid-state electronic system designed to gather information from the scientific instruments on board the spacecraft. It had four basic functions: analog-to-digital conversion, digital-to-digital conversion, sampling and instrument-calibration timing, and planetary acquisition. The SPS unit was designed to perform the following three functions: control of the application of AC power to appropriate portions of the science subsystem, application of power to the radiometers and removal of power from the cruise experiments during radiometer calibration periods, and control of the speed and direction of the radiometer scans. The DCS sent signals to the SPS unit to perform the latter two functions.

Not included on any of the Mariner R spacecraft was a camera for visual photos. With payload space at a premium, project scientists considered a camera an unneeded luxury, unable to return useful scientific results. Carl Sagan, one of the Mariner R scientists, unsuccessfully fought for their inclusion, noting that not only might there be breaks in Venus' cloud layer, but "that cameras could also answer questions that we were way too dumb to even pose".

Prelude to Mariner 2

The launch window for Mariner, constrained both by the orbital relationship of Earth and Venus and the limitations of the Atlas Agena, was determined to fall in the 51-day period from July 22 through September 10. The Mariner flight plan was such that the two operational spacecraft would be launched toward Venus in a 30-day period within this window, taking slightly differing paths such that they both arrived at the target planet within nine days of each other, between the December 8 and 16. Only Cape Canaveral Launch Complex 12 was available for the launching of Atlas-Agena rockets, and it took 24 days to ready an Atlas-Agena for launch. This meant that there was only a 27-day margin for error for a two-launch schedule.

Each Mariner would be launched into a parking orbit, whereupon the restartable Agena would fire a second time, sending Mariner on its way to Venus (errors in trajectory would be corrected by a mid-course burn of Mariner's onboard engines). Real-time radar tracking of the Mariner spacecraft while it was in parking orbit and upon its departure the Atlantic Missile Range would provide real-time radar tracking with stations at Ascension and Pretoria, while Palomar Observatory provided optical tracking. Deep space support was provided by three tracking and communications stations at Goldstone, California, Woomera, Australia, and Johannesburg, South Africa, each separated on the globe by around 120° for continuous coverage.

On July 22, 1962, the two-stage Atlas-Agena rocket carrying Mariner 1 veered off-course during its launch due to a defective signal from the Atlas and a bug in the program equations of the ground-based guidance computer; the spacecraft was destroyed by the Range Safety Officer.

Two days after that launch, Mariner 2 and its booster (Atlas vehicle 179D) were rolled out to LC-12. The Atlas proved troublesome to prepare for launch, and multiple serious problems with the autopilot occurred, including a complete replacement of the servoamplifier after it had suffered component damage due to shorted transistors.

Launch

At 1:53 AM EST on August 27, Mariner 2 was launched from Cape Canaveral Air Force Station Launch Complex 12 at 06:53:14 UTC. The bug in the rocket’s software that resulted in the loss of Mariner 1 had not been identified at the time of the launch. In the event the bug caused no issues with the launch since it was in a section of code that was only used when the data-feed from the ground was interrupted and there were no such interruptions during the launch of Mariner 2.

The flight proceeded normally up to the point of the Agena booster engine cutoff, at which point the V-2 vernier engine lost pitch and yaw control. The vernier started oscillating and banging against its stops, resulting in a rapid roll of the launch vehicle that came close to threatening the integrity of the stack. At T+189 seconds, the rolling stopped and the launch continued without incident. The rolling motion of the Atlas resulted in ground guidance losing its lock on the booster and preventing any backup commands from being sent to counteract the roll. The incident was traced to a loose electrical connection in the vernier feedback transducer, which was pushed back into place by the centrifugal force of the roll, which also by fortunate coincidence left the Atlas only a few degrees off from where it started and within the range of the Agena's horizontal sensor. As a consequence of this episode, GD/A implemented improved fabrication of wiring harnesses and checkout procedures.

Five minutes after liftoff, the Atlas and Agena-Mariner separated, followed by the first Agena burn and second Agena burn. The Agena-Mariner separation injected the Mariner 2 spacecraft into a geocentric escape hyperbola at 26 minutes 3 seconds after liftoff. The NASA NDIF tracking station at Johannesburg, South Africa, acquired the spacecraft about 31 minutes after launch. Solar panel extension was completed approximately 44 minutes after launch. The Sun lock acquired the Sun about 18 minutes later. The high-gain antenna was extended to its acquisition angle of 72°. The output of the solar panels was slightly above the predicted value.

As all subsystems were performing normally, with the battery fully charged and the solar panels providing adequate power, the decision was made on August 29 to turn on cruise science experiments. On September 3, the Earth acquisition sequence was initiated, and Earth lock was established 29 minutes later.

Mid-course maneuver
Due to the Atlas-Agena putting Mariner slightly off course, the spacecraft required a mid-course correction, consisting of a roll-turn sequence, followed by a pitch-turn sequence and finally a motor-burn sequence. Preparation commands were sent to the spacecraft at 21:30 UTC on September 4. Initiation of the mid-course maneuver sequence was sent at 22:49:42 UTC and the roll-turn sequence started one hour later. The entire maneuver took approximately 34 minutes. As a result of the mid-course maneuver, the sensors lost their lock with the Sun and Earth. At 00:27:00 UTC the Sun re-acquisition began and at 00:34 UTC the Sun was reacquired. Earth re-acquisition started at 02:07:29 UTC and Earth was reacquired at 02:34 UTC.

Loss of attitude control
On September 8 at 12:50 UTC, the spacecraft experienced a problem with attitude control. It automatically turned on the gyros, and the cruise science experiments were automatically turned off. The exact cause is unknown as attitude sensors went back to normal before telemetry measurements could be sampled, but it may have been an Earth-sensor malfunction or a collision with a small unidentified object which temporarily caused the spacecraft to lose Sun lock. A similar experience happened on September 29 at 14:34 UTC. Again, all sensors went back to normal before it could be determined which axis had lost lock. By this date, the Earth sensor brightness indication had essentially gone to zero. This time, however, telemetry data indicated that the Earth-brightness measurement had increased to the nominal value for that point in the trajectory.

Solar panel output
On October 31, the output from one solar panel (with solar sail attached) deteriorated abruptly. It was diagnosed as a partial short circuit in the panel. As a precaution, the cruise science instruments were turned off. A week later, the panel resumed normal function, and cruise science instruments were turned back on. The panel permanently failed on November 15, but Mariner 2 was close enough to the Sun that one panel could supply adequate power; thus, the cruise science experiments were left active.

Encounter with Venus
Mariner 2 was the first spacecraft to successfully encounter another planet, passing as close as 34773 km to Venus after 110 days of flight on December 14, 1962.

Post encounter
After encounter, cruise mode resumed. Spacecraft perihelion occurred on December 27 at a distance of 105,464,560 km. The last transmission from Mariner 2 was received on January 3, 1963, at 07:00 UTC, making the total time from launch to termination of the Mariner 2 mission 129 days. After passing Venus, Mariner 2 entered heliocentric orbit.

Results
The data produced during the flight consisted of two categories—viz., tracking data and telemetry data. One particularly noteworthy piece of data gathered during the pioneering fly-by was the high temperature of the atmosphere, measured to be 500 C. Various properties of the solar wind were also measured for the first time.

Scientific observations
The microwave radiometer made three scans of Venus in 35 minutes on December 14, 1962, starting at 18:59 UTC. The first scan was made on the dark side, the second was near the terminator, and the third was located on the light side. The scans with the 19 mm band revealed peak temperatures of 490 ± 11 K on the dark side, 595 ± 12 K near the terminator, and 511 ± 14 K on the light side. It was concluded that there is no significant difference in temperature across Venus. However, the results suggest a limb darkening, an effect which presents cooler temperatures near the edge of the planetary disk and higher temperatures near the center. This was evidence for the theory that the Venusian surface was extremely hot and the atmosphere optically thick.

The infrared radiometer showed that the 8.4 μm and 10.4 μm radiation temperatures were in agreement with radiation temperatures obtained from Earth-based measurements. There was no systematic difference between the temperatures measured on the light side and dark side of the planet, which was also in agreement with Earth-based measurements. The limb darkening effect that the microwave radiometer detected was also present in the measurements by both channels of the infrared radiometer. The effect was only slightly present in the 10.4 μm channel but was more pronounced in the 8.4 μm channel. The 8.4 μm channel also showed a slight phase effect. The phase effect indicated that if a greenhouse effect existed, heat was transported in an efficient manner from the light side to the dark side of the planet. The 8.4 μm and 10.4 μm showed equal radiation temperatures, indicating that the limb darkening effect would appear to come from a cloud structure rather than the atmosphere. Thus, if the measured temperatures were actually cloud temperatures instead of surface temperatures, then these clouds would have to be quite thick.

The magnetometer detected a persistent interplanetary magnetic field varying between 2 γ and 10 γ (nanotesla), which agrees with prior Pioneer 5 observations from 1960. This also means that interplanetary space is rarely empty or field-free. The magnetometer could detect changes of about 4 γ on any of the axes, but no trends above 10 γ were detected near Venus, nor were fluctuations seen like those that appear at Earth's magnetospheric termination. This means that Mariner 2 found no detectable magnetic field near Venus, although that did not necessarily mean that Venus had none. However, if Venus had a magnetic field, then it would have to be at least smaller than 1/10 the magnetic field of the Earth. In 1980, Pioneer 12 indeed showed that Venus has a small weak magnetic field.

The Anton type 213 Geiger-Müller tube performed as expected. The average rate was 0.6 counts per second. Increases in its counting rate were larger and more frequent than for the two larger tubes, since it was more sensitive to particles of lower energy. It detected seven small solar bursts of radiation during September and October and 2 during November and December. The absence of a detectable magnetosphere was also confirmed by the tube; it detected no radiation belt at Venus similar to that of Earth. The count rate would have increased by 104, but no change was measured.

It was also shown that in interplanetary space, the solar wind streams continuously, confirming a prediction by Eugene Parker, and the cosmic dust density is much lower than the near-Earth region. Improved estimates of Venus' mass and the value of the Astronomical Unit were made. Also, research, which was later confirmed by Earth-based radar and other explorations, suggested that Venus rotates very slowly and in a direction opposite that of the Earth.

title: Mariner 2


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Particle (disambiguation)

A particle in the physical sciences is a small localized object to which can be ascribed physical properties.

Particle may also refer to:

Science

 * Particle (ecology), in marine and freshwater ecology, a small object
 * Colloidal particle, part of a one-phase system of two or more components where the particles aren't individually visible
 * Particle, the solid or liquid particles in an aerosol
 * Granular material
 * Particulates, in the areas of atmospheric physics and air pollution
 * Nanoparticle, an object between 1 and 100 nanometers that behaves as a whole unit
 * Point particle, or point mass, an idealization of an object with finite mass but of zero size
 * A particle of a medium in continuum mechanics, meaning an infinitesimal portion of it.
 * Self-propelled particles, a concept used in statistical physics to model swarms
 * Subatomic particle:
 * Elementary particle, or fundamental particle, a particle of which other particles are composed
 * Particle physics, the study of subatomic particles
 * See list of particles for more uses
 * Suspended solids, in a liquid

Arts, entertainment, and media

 * Particle (band), a 2000 jam band from Los Angeles, California
 * Particle (film), a 2012 Turkish film
 * Particles (film), a 2019 French film
 * "Particles" (song), a 2021 single by Jessica Simpson

Computing

 * Particle, a US HTML5 web app company acquired by Apple in 2012
 * Particle system, in computer graphics, a technique to simulate certain fuzzy phenomena

Other uses

 * Grammatical particle, a function word

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Particle (disambiguation)


text:
Mariner 6 and 7

Mariner 6 and Mariner 7 (Mariner Mars 69A and Mariner Mars 69B) were two uncrewed NASA robotic spacecraft that completed the first dual mission to Mars in 1969 as part of NASA's wider Mariner program. Mariner 6 was launched from Launch Complex 36B at Cape Canaveral Air Force Station and Mariner 7 from Launch Complex 36A. The two craft flew over the equator and south polar regions, analyzing the atmosphere and the surface with remote sensors, and recording and relaying hundreds of pictures. The mission's goals were to study the surface and atmosphere of Mars during close flybys, in order to establish the basis for future investigations, particularly those relevant to the search for extraterrestrial life, and to demonstrate and develop technologies required for future Mars missions. Mariner 6 also had the objective of providing experience and data which would be useful in programming the Mariner 7 encounter five days later.

Launch
Three Mariner probes were constructed for the mission, with two intended to fly and one as a spare in the event of a mission failure. The spacecraft were shipped to Cape Canaveral with their Atlas-Centaur boosters in December 1968 – January 1969 to begin pre-launch checkouts and testing. On February 14, Mariner 6 was undergoing a simulated countdown on LC-36A, electrical power running, but no propellant loaded in the booster. During the test run, an electrical relay in the Atlas malfunctioned and opened two valves in the pneumatic system which allowed helium pressure gas to escape from the booster's balloon skin. The Atlas began to crumple over, however two pad technicians quickly activated a manual override switch to close the valves and pump helium back in. Although Mariner 6 and its Centaur stage had been saved, the Atlas had sustained structural damage and could not be reused, so they were removed from the booster and placed atop Mariner 7's launch vehicle on the adjacent LC-36B, while a different Atlas was used for Mariner 7.

NASA awarded the quick-thinking technicians, Bill McClure and Charles (Jack) Beverlin, an Exceptional Medal of Bravery for their courage in risking being crushed underneath the 124 ft rocket. In 2014, an escarpment on Mars which NASA'S Opportunity rover had recently visited was named the McClure-Beverlin Ridge in honor of the pair, who had since died.

Mariner 6 lifted off from LC-36B at Cape Canaveral on February 25, 1969, using the Atlas-Centaur AC-20 rocket, while Mariner 7 lifted off from LC-36A on March 27, using the Atlas-Centaur AC-19 rocket. The boost phase for both spacecraft went according to plan and no serious anomalies occurred with either launch vehicle. A minor LOX leak froze some telemetry probes in AC-20 which registered as a drop in sustainer engine fuel pressure; however, the engine performed normally through powered flight. In addition, BECO occurred a few seconds early due to a faulty cutoff switch, resulting in longer than intended burn time of the sustainer engine, but this had no serious effect on vehicle performance or the flight path. AC-20 was launched at a 108-degree azimuth.

The Centaur stage on both flights was set up to perform a retrorocket maneuver after capsule separation. This served two purposes, firstly to prevent venting propellant from the spent Centaur from contacting the probe, secondly to put the vehicle on a trajectory that would send it into solar orbit and not impact the Martian surface, potentially contaminating the planet with Earth microbes.

Spaceflight
On July 29, 1969, less than a week before closest approach, Jet Propulsion Laboratory (JPL) lost contact with Mariner 7. The center regained the signal via the backup low-gain antenna and regained use of the high gain antenna again shortly after Mariner 6's close encounter. Leaking gases from a battery (which later failed) were thought to have caused the anomaly. Based on the observations that Mariner 6 made, Mariner 7 was reprogrammed in flight to take further observations of areas of interest and actually returned more pictures than Mariner 6, despite the battery's failure.

Closest approach for Mariner 6 occurred July 31, 1969, at 05:19:07 UT at a distance of 3431 km above the martian surface. Closest approach for Mariner 7 occurred August 5, 1969 at 05:00:49 UT at a distance of 3430 km above the Martian surface. This was less than half of the distance used by Mariner 4 on the previous US Mars flyby mission.

Both spacecraft are now defunct and in heliocentric orbits.

Science data and findings
By chance, both spacecraft flew over cratered regions and missed both the giant northern volcanoes and the equatorial grand canyon discovered later. Their approach pictures did, however, photograph about 20 percent of the planet's surface, showing the dark features long seen from Earth – in the past, these features had been mistaken for canals by some ground-based astronomers. When Mariner 7 flew over the Martian south pole on August 4, 1969, it sent back pictures of ice-filled craters and outlines of the south polar cap. Despite the communication defect suffered by Mariner 7 earlier, these pictures were of better quality than what had been sent by its twin, Mariner 6, a few days earlier when it flew past the Martian equator. In total, 201 photos were taken and transmitted back to Earth, adding more detail than the earlier mission, Mariner 4. Both crafts also studied the atmosphere of Mars.

Coming a week after Apollo 11, Mariner 6 and 7's flyby of Mars received less than the normal amount of media coverage for a mission of this significance.

The ultraviolet spectrometer onboard Mariners 6 and 7 was constructed by the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP).

The engineering model of Mariners 6 and 7 still exists, and is owned by the Jet Propulsion Laboratory (JPL). It is on loan to LASP, and is on display in the lab's lobby.

Mariner 6 and 7 infrared radiometer observations helped to trigger a scientific revolution in Mars knowledge. The Mariner 6 and 7 infrared radiometer results showed that the atmosphere of Mars is composed mostly of carbon dioxide (CO2), and they were also able to detect trace amounts of water on the surface of Mars.

Spacecraft and subsystems
The Mariner 6 and 7 spacecraft were identical, consisting of an octagonal magnesium frame base, 138.4 cm diagonally and 45.7 cm deep. A conical superstructure mounted on top of the frame held the high-gain 1 m diameter parabolic antenna and four solar panels, each measuring 215 cm x 90 cm, were affixed to the top corners of the frame. The tip-to-tip span of the deployed solar panels was 5.79 m. A low-gain omnidirectional antenna was mounted on a 2.23 m high mast next to the high-gain antenna. Underneath the octagonal frame was a two-axis scan platform which held scientific instruments. Overall science instrument mass was 57.6 kg. The total height of the spacecraft was 3.35 m.

The spacecraft was attitude stabilized in three axes, referenced to the Sun and the star Canopus. It utilized 3 gyros, 2 sets of 6 nitrogen jets, which were mounted on the ends of the solar panels, a Canopus tracker, and two primary and four secondary Sun sensors. Propulsion was provided by a 223-newton rocket motor, mounted within the frame, which used the mono-propellant hydrazine. The nozzle, with 4-jet vane vector control, protruded from one wall of the octagonal structure. Power was supplied by 17,472 photovoltaic cells, covering an area of 7.7 m2 on the four solar panels. These could provide 800 watts of power near Earth, and 449 watts while on Mars. The maximum power requirement was 380 watts, once Mars was reached. A 1200 watt-hour, rechargeable, silver-zinc battery was used to provide backup power. Thermal control was achieved through the use of adjustable louvers on the sides of the main compartment.

Three telemetry channels were available for telecommunications. Channel A carried engineering data at 8⅓ or 33⅓ bit/s, channel B carried scientific data at 66⅔ or 270 bit/s and channel C carried science data at 16,200 bit/s. Communications were accomplished through the high- and low-gain antennas, via dual S-band traveling wave tube amplifiers, operating at 10 or 20 watts, for transmission. The design also included a single receiver. An analog tape recorder, with a capacity of 195 million bits, could store television images for subsequent transmission. Other science data was stored on a digital recorder. The command system, consisting of a central computer and sequencer (CC&S), was designed to actuate specific events at precise times. The CC&S was programmed with both a standard mission and a conservative backup mission before launch, but could be commanded and reprogrammed in flight. It could perform 53 direct commands, 5 control commands, and 4 quantitative commands.

Instrumentation

 * 1) IR Spectrometer
 * 2) Two-Channel IR Radiometer Mars Surface Temperature
 * 3) UV Spectrometer
 * 4) S-Band Occultation
 * 5) Thermal Control Flux Monitor (Conical Radiometer)
 * 6) Mars TV Camera
 * 7) Celestial Mechanics
 * 8) General Relativity

title: Mariner 6 and 7


text:
David Boies

David Boies (born March 11, 1941) is an American lawyer and chairman of the law firm Boies Schiller Flexner LLP. Boies rose to national prominence for three major cases: leading the U.S. federal government's successful prosecution of Microsoft in United States v. Microsoft Corp., his unsuccessful representation of Democratic presidential candidate Al Gore in Bush v. Gore, and for successful representation of the plaintiff in Hollingsworth v. Perry, which invalidated California Proposition 8 banning same-sex marriage. Boies has also represented various clients in US lawsuits, including Theranos, tobacco companies, Harvey Weinstein, and Jeffrey Epstein's victims including Virginia Roberts Giuffre.

Early life
Boies was born in Sycamore, Illinois, to two teachers, and raised in a farming community. He has four siblings. His first job was when he was 10 years old—a paper route with 120 customers. Boies has dyslexia and he did not learn to read until the third grade.

Journalist Malcolm Gladwell has described the unique processes of reading and learning Boies experienced due to his dyslexia. Boies' mother, for instance, would read stories to him when he was a child and Boies would memorize them because he could not follow the words on the page.

In 1954, the family moved to California. Boies graduated from Fullerton Union High School in Fullerton, California. Boies attended the University of Redlands from 1960 to 1962, received a B.S. degree from Northwestern University in 1964, a J.D. degree magna cum laude from Yale Law School in 1966 and an LL.M. degree from New York University School of Law 1967; he was awarded an honorary LL.D. from the University of Redlands in 2000.

He currently serves on the board of trustees of the National Constitution Center in Philadelphia, which is a museum dedicated to the U.S. Constitution.

Law firm
Boies was an attorney at Cravath, Swaine & Moore, where he started upon law school graduation in 1966 and became a partner in 1973. He left Cravath in 1997 when a major client objected to his representation of the New York Yankees even though the firm itself had found no conflict. He left the firm within 48 hours of being informed of the client's objection and created his own firm with his friend Jonathan Schiller, now known as Boies, Schiller & Flexner LLP. It is currently rated 23rd in "overall prestige" and 15th among New York law firms by Vault.com, a website on legal career information.

Notable cases
From 1984 to 1985, Boies defended CBS in the libel suit Westmoreland v. CBS, but after dragging on for two years, the case was dropped. Following the 2000 U.S. presidential election, he represented Vice President Al Gore in Bush v. Gore. In Jay Roach's Recount, which focuses on the case, Boies is played by Ed Begley Jr. In his 2001 book, prosecutor and author Vincent Bugliosi criticized Boies' abilities as a trial lawyer, arguing that Boies "wasn't forceful or eloquent at all in making his points" in Bush v. Gore. "[A]lthough he seemed to have a very good grasp of the facts, he seemed completely incapable of drawing powerful, irresistible inferences from those facts that painted his opposition into a corner".

In 2000 Boies lost the first important file-sharing case which ultimately put Napster into bankruptcy. In 2001 Boies represented the Justice Department in the United States v. Microsoft Corp. case. Boies won a victory at trial, and the verdict was upheld on appeal. The appellate court overturned the relief ordered (breakup of the company) back to the trial court for further proceedings. Thereafter, the George W. Bush administration settled the case. Bill Gates said Boies was "out to destroy Microsoft". In 2001, the Washington Monthly called Boies "a brilliant trial lawyer", "a latter-day Clarence Darrow", and "a mad genius" for his work on the Microsoft case. In 2006, Boies, Schiller & Flexner LLP negotiated a major settlement with The American International Group on behalf of its client, C. V. Starr, a firm controlled by Maurice R. Greenberg, the former chairman and chief executive of A.I.G. In 2015 Boies won at trial a claim that the government's $85 billion bailout of AIG had been unfair to the company's owners. Boies has appealed, asking for greater money damages. In 2008 Boies negotiated on behalf of American Express two of the highest civil antitrust settlements ever for an individual company: $2.25 billion from Visa, and $1.8 billion from MasterCard.

In 2009, following the California Supreme Court ruling on Strauss v. Horton, Boies joined former Solicitor General Theodore Olson, the opposing attorney in Bush v. Gore, in the lawsuit Perry v. Brown seeking to overturn the state of California's Proposition 8 ban on same-sex marriage. In August 2010, the District Court judge ruled in their clients' favor, finding Proposition 8 to be unconstitutional. On June 26, 2013, the Supreme Court of the United States ruled that the proponents of Proposition 8 did not have standing to challenge the ruling, allowing the District Court judgment to stand. Same-sex marriages resumed in California on June 28, 2013. Also in 2009, the Golden Gate Yacht Club retained Boies for their ongoing dispute with Société Nautique de Genève regarding the 33rd America's Cup.

In March 2010, Boies joined the team of attorneys representing Jamie McCourt in her divorce from Los Angeles Dodgers owner Frank McCourt. In 2011 Boies represented filmmaker Michael Moore regarding a Treasury Department investigation into Moore's trip to Cuba while filming for Sicko. Boies, Schiller & Flexner LLP assisted the government in obtaining a $155 million settlement from Medco Health Solutions related to a qui tam complaint which alleged that Medco helped some pharmaceutical companies make more money by driving prescriptions to them; along with making the payment Medco also signed a corporate integrity agreement. Boies was part of the legal team representing the National Football League in their antitrust litigation, Brady v. NFL. Boies represented the National Basketball Players Association during the 2011 NBA lockout. He joined sides with Jeffrey Kessler, who opposed Boies as a representative for the players in the 2011 NFL lockout. Boies was the lead counsel for Oracle Corporation in its lawsuit against Google on the use of Java programming language technology in the Android operating system. The case decided that Google did not infringe on Oracle's patents.

In 2011, Boies began working as legal representation for the now defunct blood testing company, Theranos. Prior to joining their board, he served founder Elizabeth Holmes and her company as special adviser and attended all of the company's board meetings in this role. In February 2016, Boies agreed to both sit on the board of directors and act as the attorney for troubled Silicon Valley startup. The controversial dual role was deemed difficult as he would have to represent both the company (as lawyer) and investors (as a director). In the 2022 Hulu miniseries The Dropout, Boies was portrayed by Kurtwood Smith.

In 2012, Boies represented three tobacco companies, Philip Morris USA Inc., R.J. Reynolds Tobacco Co. and Liggett Group LLC, in their appeal of a $2.5 million Tampa jury verdict in the death of smoker Charlotte Douglas. Later in 2012 Boies defended Gary Jackson, former president of Academi (previously known as BlackWater), in a federal prosecution which alleged he and his co-defendants illegally hid firearm purchases from the Bureau of Alcohol, Tobacco, Firearms and Explosives.

In 2015, Boies represented Bob Weinstein and Harvey Weinstein in renegotiating the Weinsteins' employment contract. According to The Wall Street Journal, Boies negotiated Harvey Weinstein's contract without informing Weinstein Co. directors that he had investment in the company's movies. In 2017, Boies agreed to join the legal team for Lawrence Lessig's legal fight against winner-take-all Electoral College vote allocations in the states. Dallas Cowboys owner Jerry Jones hired Boies in 2017 to advise on Jones's legal strategy against NFL commissioner Roger Goodell and the NFL compensation committee in the wake of the suspension of running back Ezekiel Elliott.

Presently, Boies represents several of Jeffrey Epstein's victims including Virginia Roberts Giuffre.

Involvement in defence of Harvey Weinstein
Boies helped Weinstein fend off journalist Ken Auletta's inquiry into Weinstein's alleged rape of Rowena Chiu at the Venice Film Festival in 1998. Rose McGowan claimed that Jennifer Siebel Newsom attempted to arrange a deal between her and Boies in an attempt to make her stay quiet about her allegations against Harvey Weinstein whom Boies was representing at the time.

In 2017, Boies' firm reportedly directed the Israeli private intelligence company Black Cube to spy on alleged victims of Harvey Weinstein's sexual abuse and on reporters who were investigating Weinstein's actions. Over the course of a year, Weinstein had Black Cube and other agencies "target", or collect information on, dozens of individuals, and compile psychological profiles that sometimes focused on their personal or sexual histories. "Boies personally signed the contract directing Black Cube to attempt to uncover information that would stop the publication of a Times story about Weinstein's abuses, while his firm was also representing the Times, including in a libel case."

Months after Cyrus Vance Jr. dropped an investigation into a sexual assault allegation against Weinstein, he received a $10,000 donation from Boies who was representing Weinstein at the time. Andrew Cuomo opened an investigation into Vance's handling of the Weinstein probe. However, after receiving a $25,000 campaign donation from Boies' firm, Cuomo ended the investigation.

Boies' firm was representing The New York Times at the same time. A few days after The New Yorker broke the story "Harvey Weinstein's Army of Spies", The New York Times announced it had "terminated its relationship" with Boies' firm. According to its contract with Weinstein, Black Cube's assignment had been to kill the paper's negative reporting on Weinstein.

Boies' involvement in defending Weinstein received criticism from New York, and Bloomberg Businessweek. In 2021, several attorneys resigned from Boies Schiller Flexner, citing Boies' defence of Weinstein as one of the reasons.

Involvement with Theranos
Boies served as a lawyer for Blood testing company Theranos. His dual roles as attorney and board member of the defunct company is recounted in the book, Bad Blood: Secrets and Lies in a Silicon Valley Startup by then The Wall Street Journal investigative reporter John Carreyrou. Boies, along with lawyers Heather King and Michael Brille, and his firm are described as protecting the startup using surveillance of witnesses and journalists, weaponized use of non-disclosure agreements and affidavits, intimidation tactics, and other heavy-handed practices. Boies Schiller Flexner LLP is portrayed by Carreyrou as acting as an extension of Theranos, including the use of the law firm's New York offices for hosting promotional meetings such as a faked blood test administered to Fortune writer Roger Parloff.

Boies also served on the Theranos board of directors, raising questions about conflicts of interest. Boies agreed to be paid for his firm's work in Theranos stock, which he expected to grow dramatically in value. Boies' participation in and support for Theranos directly contributed to the misleading treatment of Walgreen patients, potentially resulting, cited within the report on Theranos by the federal agency CMS (Centers for Medicare & Medicaid Services), in "serious injury or harm, or death". Boies eventually left the Theranos board of directors, after the U.S. federal government had initiated multiple investigations into the firm.

Personal life
Boies owns a home in Westchester County, New York, Hawk and Horse Vineyards in Northern California, an oceangoing yacht, and a large wine collection.

Boies is dyslexic. He is frequently described as having a photographic memory that enables him to recite exact text, page numbers, and legal exhibits. Colleagues attribute his courtroom success in part to this ability.

Philanthropy
David and Mary Boies also fund the "Mary and David Boies Fellowships" for foreign students at the Harvard Kennedy School. The Boieses give an annual picnic at their home for the incoming Teach for America corps for New York City (300–500 people). They support the Central European and Eurasian Law Institute (CEELI), a Prague-based institute that trains judges from newly democratized countries in Eastern Europe and the Middle East. There is a "Mary and David Boies Reading Room" at the CEELI Institute in Prague.
 * Professorial chairs:
 * Daryl Levinson is the "David Boies Professor of Law" at New York University School of Law.
 * $1.5 million to the Tulane University Law School to establish the "David Boies Distinguished Chair in Law". Two of Boies' children earned their law degrees at Tulane.
 * A "David Boies Professor" was established at the University of Pennsylvania and is currently held by professor of history Kathleen M. Brown. The professorship is named after Boies' father, a high school teacher of government and economics.
 * A "David Boies Chair" at the Yale Law School was formerly held by Professor Robert Post before he became dean of the law school.
 * David and Mary Boies endowed a chair in government at the University of Redlands, the college that David Boies attended. Arthur Svenson currently holds this chair.
 * Mary and David Boies also endowed a "Maurice Greenberg Chair" at the Yale Law School.
 * David Boies and his wife, Mary, donated $5 million to Northern Westchester Hospital, in Mount Kisco, New York. Part of an ongoing capital campaign, the Boieses' money was used to build the hospital's new emergency room.

Awards and honors

 * Time magazine named Boies "Lawyer of the Year" in 2000.
 * Boies received the Golden Plate Award of the American Academy of Achievement in 2014.

title: David Boies


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Mariner 10

Mariner 10 was an American robotic space probe launched by NASA on 3 November 1973, to fly by the planets Mercury and Venus. It was the first spacecraft to perform flybys of multiple planets.

Mariner 10 was launched approximately two years after Mariner 9 and was the last spacecraft in the Mariner program. (Mariner 11 and Mariner 12 were allocated to the Voyager program and redesignated Voyager 1 and Voyager 2.)

The mission objectives were to measure Mercury's environment, atmosphere, surface, and body characteristics and to make similar investigations of Venus. Secondary objectives were to perform experiments in the interplanetary medium and to obtain experience with a dual-planet gravity assist mission. Mariner 10's science team was led by Bruce C. Murray at the Jet Propulsion Laboratory.

Design and trajectory

Mariner 10 was the first mission to use a gravity assist from one planet (in this case, Venus) to reach another planet. It used Venus to bend its flight path and bring its perihelion down to the level of Mercury's orbit. This maneuver, inspired by the orbital mechanics calculations of the Italian scientist Giuseppe Colombo, put the spacecraft into an orbit that repeatedly brought it back to Mercury. Mariner 10 ê the solar radiation pressure on its solar panels and its high-gain antenna as a means of attitude control during flight, the first spacecraft to use active solar pressure control.

The components on Mariner 10 can be categorized into four groups based on their common function. The solar panels, power subsystem, attitude control subsystem, and the computer kept the spacecraft operating properly during the flight. The navigational system, including the hydrazine rocket, would keep Mariner 10 on track to Venus and Mercury. Several scientific instruments would collect data at the two planets. Finally, the antennas would transmit this data to the Deep Space Network back on Earth, as well as receive commands from Mission Control. Mariner 10's various components and scientific instruments were attached to a central hub, which was roughly the shape of an octagonal prism. The hub stored the spacecraft's internal electronics. The Mariner 10 spacecraft was manufactured by Boeing. NASA set a strict limit of US$98 million for Mariner 10's total cost, which marked the first time the agency subjected a mission to an inflexible budget constraint. No overruns would be tolerated, so mission planners carefully considered cost efficiency when designing the spacecraft's instruments. Cost control was primarily accomplished by executing contract work closer to the launch date than was recommended by normal mission schedules, as reducing the length of available work time increased cost efficiency. Despite the rushed schedule, very few deadlines were missed. The mission ended up about US$1 million under budget.

Attitude control is needed to keep a spacecraft's instruments and antennas aimed in the correct direction. During course correction maneuvers, the spacecraft may need to rotate so that its rocket engine faces the proper direction before being fired. Mariner 10 determined its attitude using two optical sensors, one pointed at the Sun, and the other at a bright star, usually Canopus; additionally, the probe's three gyroscopes provided a second option for calculating the attitude. Nitrogen gas thrusters were used to adjust Mariner 10's orientation along three axes. The spacecraft's electronics were intricate and complex: it contained over 32,000 pieces of circuitry, of which resistors, capacitors, diodes, microcircuits, and transistors were the most common devices. Commands for the instruments could be stored on Mariner 10's computer, but were limited to 512 words. The rest had to be broadcast by the Mission Sequence Working Group from Earth. Supplying the spacecraft components with power required modifying the electrical output of the solar panels. The power subsystem used two redundant sets of circuitry, each containing a booster regulator and an inverter, to convert the panels' DC output to AC and alter the voltage to the necessary level. The subsystem could store up to 20 ampere hours of electricity on a 39-volt nickel–cadmium battery.

The flyby past Mercury posed major technical challenges for scientists to overcome. Due to Mercury's proximity to the Sun, Mariner 10 would have to endure 4.5 times more solar radiation than when it departed Earth; compared to previous Mariner missions, spacecraft parts needed extra shielding against the heat. Thermal blankets and a sunshade were installed on the main body. After evaluating different choices for the sunshade cloth material, mission planners chose beta cloth, a combination of aluminized Kapton and glass-fiber sheets treated with Teflon. However, solar shielding was unfeasible for some of Mariner 10's other components. Mariner 10's two solar panels needed to be kept under 115 °C. Covering the panels would defeat their purpose of producing electricity. The solution was to add an adjustable tilt to the panels, so the angle at which they faced the sun could be changed. Engineers considered folding the panels toward each other, making a V-shape with the main body, but tests found this approach had the potential to overheat the rest of the spacecraft. The alternative chosen was to mount the solar panels in a line and tilt them along that axis, which had the added benefit of increasing the efficiency of the spacecraft's nitrogen jet thrusters, which could now be placed on the panel tips. The panels could be rotated a maximum of 76°. Additionally, Mariner 10's hydrazine rocket nozzle had to face the Sun to function properly, but scientists rejected covering the nozzle with a thermal door as an undependable solution. Instead, a special paint was applied to exposed parts on the rocket so as to reduce heat flow from the nozzle to the delicate instruments on the spacecraft.

Accurately performing the gravity assist at Venus posed another hurdle. If Mariner 10 was to maintain a course to Mercury, its trajectory could deviate no more than 200 km from a critical point in the vicinity of Venus. To ensure that the necessary course corrections could be made, mission planners tripled the amount of hydrazine fuel Mariner 10 would carry, and also equipped the spacecraft with more nitrogen gas for the thrusters than the previous Mariner mission had held. These upgrades proved crucial in enabling the second and third Mercury flybys.

The mission still lacked the ultimate safeguard: a sister spacecraft. It was common for probes to be launched in pairs, with complete redundancy to guard against the failure of one or the other. The budget constraint ruled this option out. Even though mission planners stayed sufficiently under budget to divert some funding for constructing a backup spacecraft, the budget did not permit both to be launched at the same time. In the event that Mariner 10 failed, NASA would only allow the backup to be launched if the fatal error was diagnosed and fixed; this would have to be completed in the two and a half weeks between the scheduled launch on 3 November 1973 and the last possible launch date of 21 November 1973. The unused backup was sent to the Smithsonian museum for display.

Instruments

Mariner 10 conducted seven experiments at Venus and Mercury. Six of these experiments had a dedicated scientific instrument to collect data. The experiments and instruments were designed by research laboratories and educational institutions from across the United States. Out of forty-six submissions, JPL selected seven experiments on the basis of maximizing science return without exceeding cost guidelines: together, the seven scientific experiments cost US12.6 million dollars, about one-eighth of the total mission budget.

Television photography
The imaging system, the Television Photography Experiment, consisted of two 15 cm Cassegrain telescopes feeding vidicon tubes. The main telescope could be bypassed to a smaller wide angle optic, but using the same tube. It had an 8-position filter wheel, with one position occupied by a mirror for the wide-angle bypass.

TV camera exposures ranged from 3 ms to 12 s with each camera being able to take a picture every 42 s. The picture resolution was 832 x 700 pixels, 8-bit coded. The entire imaging system was imperiled when electric heaters attached to the cameras failed to turn on immediately after launch. To avoid the Sun's damaging heat, the cameras were deliberately placed on the spacecraft side facing away from the Sun. Consequently, the heaters were needed to prevent the cameras from losing heat and become so cold that they would become damaged. JPL engineers found that the vidicons could generate enough heat through normal operation to stay just above the critical temperature of -40 °C; therefore they advised against turning off the cameras during the flight. Test photos of the Earth and Moon showed that image quality had not been significantly affected. The mission team was pleasantly surprised when the camera heaters started working on 17 January 1974, two months after launch. Later investigation concluded that a short circuit in a different location on the probe had prevented the heater from turning on. This allowed the vidicons to be turned off as needed.

Of the six main scientific instruments, the 43.6 kg cameras were by far the most massive device. Requiring 67 watts of electricity, the cameras consumed more power than the other five instruments combined. The system returned about 7,000 photographs of Mercury and Venus during Mariner 10's flybys.

Infrared radiometer
The infrared radiometer detected infrared radiation given off by the surface of Mercury and the atmosphere of Venus, from which the temperature could be calculated. How quickly the surface lost heat as it rotated into the planet's dark side revealed aspects about the composition of the surface, such as whether it was made out of rocks, or out of finer particles. The infrared radiometer contained a pair of Cassegrain telescopes fixed at an angle of 120° to each other and a pair of detectors made from antimony-bismuth thermopiles. The instrument was designed to measure temperatures as cold as -193 °C and as hot as 427 °C. Stillman C. Chase, Jr. of the Santa Barbara Research Center headed the infrared radiometer experiment.

Ultraviolet spectrometers
Two ultraviolet spectrometers were involved in this experiment, one to measure UV absorption, the other to sense UV emissions. The occultation spectrometer scanned Mercury's edge as it passed in front of the Sun, and detected whether solar ultraviolet radiation was absorbed in certain wavelengths, which would indicate the presence of gas particles, and therefore an atmosphere. The airglow spectrometer detected extreme ultraviolet radiation emanating from atoms of gaseous hydrogen, helium, carbon, oxygen, neon, and argon. Unlike the occultation spectrometer, it did not require backlighting from the Sun and could move along with the rotatable scan platform on the spacecraft. The experiment's most important goal was to ascertain whether Mercury had an atmosphere, but would also gather data at Earth and Venus and study the interstellar background radiation.

Plasma detectors
The plasma experiment's goal was to study the ionized gases (plasma) of the solar wind, the temperature and density of its electrons, and how the planets affected the velocity of the plasma stream. The experiment contained two components, facing in opposite directions. The Scanning Electrostatic Analyzer was aimed toward the Sun and could detect positive ions and electrons, which were separated by a set of three concentric hemispherical plates. The Scanning Electron Spectrometer has aimed away from the Sun, and detected only electrons, using just one hemispherical plate. The instruments could be rotated about 60° to either side. By gathering data on the solar wind's movement around Mercury, the plasma experiment could be used to verify the magnetometer's observations of Mercury's magnetic field. Using the plasma detectors, Mariner 10 gathered the first in situ solar wind data from inside Venus' orbit.

Shortly after launch, scientists found that the Scanning Electrostatic Analyzer had failed because a door shielding the analyzer did not open. An unsuccessful attempt was made to forcibly unfasten the door with the first course correction maneuver. The experiment operators had planned to observe the directions taken by positive ions prior to the ions' collision with the Analyzer, but this data was lost. The experiment was still able to collect some data using the properly functioning Scanning Electron Spectrometer.

Charged particle telescopes
The goal of the charged particles experiment was to observe how the heliosphere interacted with cosmic radiation. In connection with the plasma detectors and magnetometers, this experiment had the potential to provide additional evidence of a magnetic field around Mercury, by showing whether such a field had captured charged particles. Two telescopes were used to collect highly energetic electrons and atomic nuclei, specifically oxygen nuclei or less massive. These particles then passed through a set of detectors and were counted.

Magnetometers
Two fluxgate magnetometers were entrusted with discerning whether Mercury produced a magnetic field, and studying the interplanetary magnetic field between flybys. In designing this experiment, scientists had to account for interference from the magnetic field generated by Mariner 10's many electronic parts. For this reason, the magnetometers had to be situated on a long boom, one closer to the octagonal hub, the other one further away. Data from the two magnetometers would be cross-referenced to filter out the spacecraft's own magnetic field. Drastically weakening the probe's magnetic field would have increased costs.

Celestial Mechanics and Radio Science experiment
This experiment investigated the mass and gravitational characteristics of Mercury. It was of particular interest because of the planet's closeness to the Sun, large orbital eccentricity, and unusual spin-orbit resonance.

As the spacecraft passed behind Mercury on the first encounter there was an opportunity to probe the atmosphere and to measure the radius of the planet. By observing phase changes in the S-band radio signal, measurements of the atmosphere could be made. The atmosphere was assessed as having a density of about $molecules per cm^{3}$.

Departing Earth

Boeing finished building the spacecraft at the end of June 1973, and Mariner 10 was delivered from Seattle to JPL's headquarters in California, where JPL comprehensively tested the integrity of the spacecraft and its instruments. After the tests were finished, the probe was transported to the Eastern Test Range in Florida, the launch site. Technicians filled a tank on the spacecraft with 29 kg of hydrazine fuel so that the probe could make course corrections, and attached squibs, whose detonation would signal Mariner 10 to exit the launch rocket and deploy its instruments. The planned gravity assist at Venus made it feasible to use an Atlas-Centaur rocket instead of a more powerful but more expensive Titan IIIC. The probe and the Atlas-Centaur were attached together ten days prior to liftoff. Launch posed one of the largest risks of failure for the Mariner 10 mission; Mariner 1, Mariner 3, and Mariner 8 all failed minutes after lift-off due to either engineering failures or Atlas rocket malfunctions. The mission had a launch period of about a month in length, from 16 October 1973, to 21 November 1973. NASA chose 3 November as the launch date because it would optimize imaging conditions when the spacecraft arrived at Mercury.

On 3 November at 17:45 UTC, the Atlas-Centaur carrying Mariner 10 lifted off from pad SLC-36B. The Atlas stage burned for around four minutes, after which it was jettisoned, and the Centaur stage took over for an additional five minutes, propelling Mariner 10 to a parking orbit. The temporary orbit took the spacecraft one-third of the distance around Earth: this maneuver was needed to reach the correct spot for a second burn by the Centaur engines, which set Mariner 10 on a path towards Venus. The probe then separated from the rocket; subsequently, the Centaur stage diverted away to avoid the possibility of a future collision. Never before had a planetary mission depended upon two separate rocket burns during the launch, and even with Mariner 10, scientists initially viewed the maneuver as too risky.

During its first week of flight, the Mariner 10 camera system was tested by taking five photographic mosaics of the Earth and six of the Moon. It also obtained photographs of the north polar region of the Moon where prior coverage was poor. These photographs provided a basis for cartographers to update lunar maps and improve the lunar control net.

Cruise to Venus

Far from being an uneventful cruise, Mariner 10s three-month journey to Venus was fraught with technical malfunctions, which kept mission control on edge. Donna Shirley recounted her team's frustration: "It seemed as if we were always just patching Mariner 10 together long enough to get it on to the next phase and next crisis". A trajectory correction maneuver was made on 13 November 1973. Immediately afterward, the star-tracker locked onto a bright flake of paint which had come off the spacecraft and lost tracking on the guide star Canopus. An automated safety protocol recovered Canopus, but the problem of flaking paint recurred throughout the mission. The on-board computer also experienced unscheduled resets occasionally, which necessitated reconfiguring the clock sequence and subsystems. Periodic problems with the high-gain antenna also occurred during the cruise. On 8 January 1974, a malfunction thought to be caused by a short-circuited diode occurred in the power subsystem. As a result, the main booster regulator and inverter failed, leaving the spacecraft dependent on the redundant regulator. Mission planners feared that the same problem could recur in the redundant system and cripple the spacecraft.

In January 1974, Mariner 10 made ultraviolet observations of Comet Kohoutek. Another mid-course correction was made on 21 January 1974.

Venus flyby
The spacecraft passed Venus on 5 February 1974, the closest approach being 5768 km at 17:01 UTC. It was the twelfth spacecraft to reach Venus and the eighth to return data from the planet, as well as the first mission to succeed in broadcasting images of Venus back to Earth. Mariner 10 built upon observations made by Mariner 5 six years earlier; importantly, Mariner 10 had a camera whereas the prior mission lacked one. As Mariner 10 veered around Venus, from the planet's night side to daylight, the cameras snapped the probe's first image of Venus, showing an illuminated arc of clouds over the north pole emerging from darkness. Engineers initially feared that the star-tracker could mistake the much brighter Venus for Canopus, repeating the mishaps with flaking paint. However, the star-tracker did not malfunction. Earth occultation occurred between 17:07 and 17:11 UTC, during which the spacecraft transmitted X-band radio waves through Venus' atmosphere, gathering data on cloud structure and temperature. Although Venus's cloud cover is nearly featureless in visible light, it was discovered that extensive cloud detail could be seen through Mariner's ultraviolet camera filters. Earth-based ultra-violet observation had shown some indistinct blotching even before Mariner 10, but the detail seen by Mariner was a surprise to most researchers. The probe continued photographing Venus until 13 February 1974 Among the encounter's 4165 acquired photographs, one resulting series of images captured a thick and distinctly patterned atmosphere making a full revolution every four days  just as terrestrial observations had suggested.

The mission revealed the composition and meteorological nature of the atmosphere of Venus. Data from the radio science experiment measured the extent to which radio waves passing through the atmosphere were refracted, which was used to calculate the density, pressure, and temperature of the atmosphere at any given altitude. Overall, atmospheric temperature is higher closer to the planet's surface, but Mariner 10 found four altitudes where the pattern was reversed, which could signify the presence of a layer of clouds. The inversions occurred at the 56, levels, confirming previous observations made by the Mariner 5 encounter. The ultraviolet spectrometers identified the chemical substances that comprise Venus' atmosphere. The elevated concentration of atomic oxygen in the upper atmosphere showed that the atmosphere is stratified into upper and lower layers that do not mix with each other; photographs of the upper and lower cloud layers corroborated this hypothesis. Mariner 10s ultraviolet photographs were an invaluable information source for studying the churning clouds of Venus' atmosphere. The mission researchers believed the cloud features they photographed were located in the stratosphere and upper troposphere, created by condensation; they also concluded that the contrast between darker and lighter features was due to differences in the cloud's absorptivity of UV light. The subsolar region was of particular interest: as the sun is straight overhead, it imparts more solar energy to this area than other part of the planet. Compared to the rest of the planet's atmosphere, the subsolar region was highly active and irregular. "Cells" of air lifted by convection, each up to 500 km wide, were observed forming and dissipating within the span of a few hours; some had polygonal outlines.

The gravity assist was also a success, coming well within the acceptable margin for error. In the four hours between 16:00 and 20:00 UTC on 5 February 1974, Mariner 10's heliocentric velocity dropped from 82,785 mph to 72,215 mph. This changed the shape of the spacecraft's elliptical orbit around the Sun, so that the perihelion now coincided with the orbit of Mercury.

First Mercury flyby
The spacecraft flew past Mercury three times. The first Mercury encounter took place at 20:47 UTC on 29 March 1974, at a range of 703 km, passing on the shadow side.

Second Mercury flyby
After looping once around the Sun while Mercury completed two orbits, Mariner 10 flew by Mercury again on 21 September 1974, at a more distant range of 48069 km below the southern hemisphere.

Third Mercury flyby
After losing roll control in October 1974, a third and final encounter, the closest to Mercury, took place on 16 March 1975, at a range of 327 km, passing almost over the north pole.

End of mission
With its maneuvering gas just about exhausted, Mariner 10 started another orbit of the Sun. Engineering tests were continued until 24 March 1975, when final depletion of the nitrogen supply was signaled by the onset of an un-programmed pitch turn. Commands were sent immediately to the spacecraft to turn off its transmitter, and radio signals to Earth ceased.

Mariner 10 is presumably still orbiting the Sun, although its electronics have probably been damaged by the Sun's radiation. Mariner 10 has not been spotted or tracked from Earth since it stopped transmitting. The only ways it would not be orbiting would be if it had been hit by an asteroid or gravitationally perturbed by a close encounter with a large body.

Discoveries
During its flyby of Venus, Mariner 10 discovered evidence of rotating clouds and a very weak magnetic field. Using a near-ultraviolet filter, it photographed Venus's chevron clouds and performed other atmospheric studies.

The spacecraft flew past Mercury three times. Owing to the geometry of its orbit – its orbital period was almost exactly twice that of Mercury's – the same side of Mercury was sunlit each time, so it was only able to map 40–45% of Mercury's surface, taking over 2,800 photos. It revealed a more or less Moon-like surface. It contributed enormously to the understanding of Mercury, whose surface had not been successfully resolved through telescopic observation. The regions mapped included most or all of the Shakespeare, Beethoven, Kuiper, Michelangelo, Tolstoj, and Discovery quadrangles, half of Bach and Victoria quadrangles, and small portions of Solitudo Persephones (later Neruda), Liguria (later Raditladi), and Borealis quadrangles.

Mariner 10 also discovered that Mercury has a tenuous atmosphere consisting primarily of helium, as well as a magnetic field and a large iron-rich core. Its radiometer readings suggested that Mercury has a nighttime temperature of -183 °C and maximum daytime temperatures of 187 °C.

Planning for MESSENGER, a spacecraft that surveyed Mercury until 2015, relied extensively on data and information collected by Mariner 10.

Mariner 10 Commemoration

In 1975, the US Post Office issued a commemorative stamp featuring the Mariner 10 space probe. The 10-cent Mariner 10 commemorative stamp was issued on 4 April 1975, at Pasadena, California.

title: Mariner 10


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Mariner 1

Mariner 1, built to conduct the first American planetary flyby of Venus, was the first spacecraft of NASA's interplanetary Mariner program. Developed by Jet Propulsion Laboratory, and originally planned to be a purpose-built probe launched summer 1962, Mariner 1's design was changed when the Centaur proved unavailable at that early date. Mariner 1 (and its sibling spacecraft, Mariner 2), were then adapted from the lighter Ranger lunar spacecraft. Mariner 1 carried a suite of experiments to determine the temperature of Venus as well to measure magnetic fields and charged particles near the planet and in interplanetary space.

Mariner 1 was launched by an Atlas-Agena rocket from Cape Canaveral's Pad 12 on July 22, 1962. Shortly after liftoff, errors in communication between the rocket and its ground-based guidance systems caused the rocket to veer off course, and it had to be destroyed by range safety. The errors were traced to a mistake in a specification of the hand-written guidance equations which were then subsequently codified in the computer program.

Background

With the advent of the Cold War, the two then-superpowers, the United States and the Soviet Union, both initiated ambitious space programs with the intent of demonstrating military, technological, and political dominance. The Soviets launched the Sputnik 1, the first Earth orbiting satellite, on October 4, 1957. The Americans followed suit with Explorer 1 on February 1, 1958, by which point the Soviets had already launched the first orbiting animal, Laika in Sputnik 2. Earth's orbit having been reached, focus turned to being the first to the Moon. The Pioneer program of satellites consisted of three unsuccessful lunar attempts in 1958. In early 1959, the Soviet Luna 1 was the first probe to fly by the Moon, followed by Luna 2, the first artificial object to impact the Moon.

With the Moon achieved, the superpowers turned their eyes to the planets. As the closest planet to Earth, Venus presented an appealing interplanetary spaceflight target. Every 19 months, Venus and the Earth reach relative positions in their orbits around the Sun such that a minimum of fuel is required to travel from one planet to the other via a Hohmann Transfer Orbit. These opportunities mark the best time to launch exploratory spacecraft, requiring the least fuel to make the trip.

The first such opportunity of the Space Race occurred in late 1957, before either superpower had the technology to take advantage of it. The second opportunity, around June 1959, lay just within the edge of technological feasibility, and U.S. Air Force contractor Space Technology Laboratory (STL) intended to take advantage of it. A plan drafted January 1959 involved two spacecraft evolved from the first Pioneer probes, one to be launched via Thor-Able rocket, the other via the yet-untested Atlas-Able. STL was unable to complete the probes before June, and the launch window was missed. The Thor-Able probe was repurposed as the deep space explorer Pioneer 5, which was launched March 11, 1960, and designed to maintain communications with Earth up to a distance of 20000000 mi as it traveled toward the orbit of Venus. (The Atlas Able probe concept was repurposed as the unsuccessful Pioneer Atlas Moon probes.) No American missions were sent during the early 1961 opportunity. The Soviet Union launched Venera 1 on February 12, 1961, and on May 19–20 became the first probe to fly by Venus; however, it had stopped transmitting on February 26.

For the summer 1962 launch opportunity, NASA contracted Jet Propulsion Laboratory (JPL) in July 1960 to develop "Mariner A", a 1250 lb spacecraft to be launched using the yet undeveloped Atlas-Centaur. By August 1961, it had become clear that the Centaur would not be ready in time. JPL proposed to NASA that the mission might be accomplished with a lighter spacecraft using the less powerful but operational Atlas-Agena. A hybrid of Mariner A and JPL's Block 1 Ranger lunar explorer, already under development, was suggested. NASA accepted the proposal, and JPL began an 11-month crash program to develop "Mariner R" (so named because it was a Ranger derivative). Mariner 1 was the first Mariner R to be launched.

Spacecraft
Three Mariner R spacecraft were built: two for launching and one to run tests, which was also to be used as a spare. Aside from its scientific capabilities, Mariner also had to transmit data back to Earth from a distance of more than 26000000 mi, and to survive solar radiation twice as intense as that encountered in Earth orbit.

Structure
All three of the Mariner R spacecraft, including Mariner 1, weighed within 3 lb of the design weight of 447 lb, 406 lb of which was devoted to non-experimental systems: maneuvering systems, fuel, and communications equipment for receiving commands and transmitting data. Once fully deployed in space, with its two solar panel "wings" extended, Mariner R was 12 ft in height and 16.5 ft across. The main body of the craft was hexagonal with six separate cases of electronic and electromechanical equipment:

 * Two of the cases comprised the power system: switchgear that regulated and transmitted power from the 9800 solar cells to the 33.3 lb rechargeable 1000 watt silver-zinc storage battery.
 * Two more included the radio receiver, the three-watt transmitter, and control systems for Mariner's experiments.
 * The fifth case held electronics for digitizing the analog data received by the experiments for transmission.
 * The sixth case carried the three gyroscopes that determined Mariner's orientation in space. It also held the central computer and sequencer, the "brain" of the spacecraft that coordinated all of its activities pursuant to code in its memory banks and on a schedule maintained by an electronic clock tuned into equipment on Earth.

At the rear of the spacecraft, a monopropellant (anhydrous hydrazine) 225 N rocket motor was mounted for course corrections. A nitrogen gas fueled stabilizing system of ten jet nozzles controlled by the onboard gyroscopes, Sun sensors, and Earth sensors, kept Mariner properly oriented to receive and transmit data to Earth.

The primary high gain parabolic antenna was also mounted on the underside of Mariner and kept pointed toward the Earth. An omnidirectional antenna atop the spacecraft would broadcast at times that the spacecraft was rolling or tumbling out of its proper orientation, to maintain contact with Earth; as an unfocused antenna, its signal would be much weaker than the primary. Mariner also mounted small antennas on each of the wings to receive commands from ground stations.

Temperature control was both passive, involving insulated, and highly reflective components; and active, incorporating louvers to protect the case carrying the onboard computer. At the time the first Mariners were built, no test chamber existed to simulate the near-Venus solar environment, so the efficacy of these cooling techniques could not be tested until the live mission.

Background
At the time of the Mariner project's inception, few of Venus' characteristics were definitely known. Its opaque atmosphere precluded telescopic study of the ground. It was unknown whether there was water beneath the clouds, though a small amount of water vapor above them had been detected. The planet's rotation rate was uncertain, though JPL scientists had concluded through radar observation that Venus rotated very slowly compared to the Earth, advancing the long-standing (but eventually disproven) hypothesis that the planet was tidally locked with respect to the Sun (as the Moon is with respect to the Earth). No oxygen had been detected in Venus' atmosphere, suggesting that life as existed on Earth was not present. It had been determined that Venus' atmosphere contained at least 500 times as much carbon dioxide as the Earth's. These comparatively high levels suggested that the planet might be subject to a runaway greenhouse effect with surface temperatures as high as 600 K, but this had not yet been conclusively determined.

The Mariner spacecraft would be able to verify this hypothesis by measuring the temperature of Venus close-up; at the same time, the spacecraft could determine if there was a significant disparity between night and daytime temperatures. An on-board magnetometer and suite of charged particle detectors could determine if Venus possessed an appreciable magnetic field and an analog to Earth's Van Allen Belts.

As the Mariner spacecraft would spend most of its journey to Venus in interplanetary space, the mission also offered an opportunity for long-term measurement of the solar wind of charged particles and to map the variations in the Sun's magnetosphere. The concentration of cosmic dust beyond the vicinity of Earth could be explored as well.

Experiments
Experiments for the measurement of Venus and interplanetary space included:

 * A crystal microphone for measurement of the density of cosmic dust, mounted on the central frame.
 * A proton detector for counting low-energy protons in the solar wind, also mounted on the central frame.
 * Two Geiger-Müller (GM) tubes and an ion chamber, for measuring high-energy charged particles in interplanetary space and in the Venusian equivalent of Earth's Van Allen Belts (which were later shown not to exist). These were mounted on Mariner's long axis to avoid the magnetic fields of the control equipment as well as secondary radiation caused by cosmic rays hitting the metal structure of the spacecraft.
 * An Anton special-purpose GM tube, for measuring lower energy radiation, particularly near Venus, also mounted away from the central frame.
 * A three-axis fluxgate magnetometer for measuring the Sun's and Venus' magnetic fields, also mounted away from the central frame.
 * A microwave radiometer, a 20 in diameter, 3 in deep, parabolic antenna designed to scan Venus up and down at two microwave wavelengths (19 mm and 13.5mm), slowing down and reversing when it found a hot spot. The 19 mm wavelength was for measuring the temperature of the planet's surface while the 13.5mm wavelength measured the temperature of Venus' cloudtops. The instrument was mounted just above the central frame.
 * Two infrared optical sensors for parallel measurement of the temperature of Venus, one at 8 to 9 microns, the other at 10-10.8 microns, also mounted above the central frame.

Not included on any of the Mariner R spacecraft was a camera for visual photos. With payload space at a premium, project scientists considered a camera an unneeded luxury, unable to return useful scientific results. Carl Sagan, one of the Mariner R scientists, unsuccessfully fought for their inclusion, noting that not only might there be breaks in Venus' cloud layer, but "that cameras could also answer questions that we were way too dumb to even pose".

Flight plan and ground operations

The launch window for Mariner, constrained both by the orbital relationship of Earth and Venus and the limitations of the Atlas Agena, was determined to fall in the 51 day period between from July 22 through September 10. The Mariner flight plan was such that the two operational spacecraft would be launched toward Venus in a 30-day period within this window, taking slightly differing paths such that they both arrived at the target planet within nine days of each other, between the December 8 and 16. Only Cape Canaveral Launch Complex 12 was available for the launching of Atlas-Agena rockets, and it took 24 days to ready an Atlas-Agena for launch. This meant that there was only a 27-day margin for error for a two-launch schedule.

Each Mariner would be launched into a parking orbit, whereupon the restartable Agena would fire a second time, sending Mariner on its way to Venus (errors in trajectory would be corrected by a mid-course burn of Mariner's onboard engines). Real-time radar tracking of the Mariner spacecraft while it was in parking orbit and upon its departure the Atlantic Missile Range would provide real-time radar tracking with stations at Ascension and Pretoria, while Palomar Observatory provided optical tracking. Deep space support was provided by three tracking and communications stations at Goldstone, California, Woomera, Australia, and Johannesburg, South Africa, each separated on the globe by around 120° for continuous coverage.

Launch failure

The launch of Mariner 1 was scheduled for the early morning of July 21, 1962. Several delays caused by trouble in the range safety command system delayed the beginning of the countdown until 11:33 p.m. EST the night before. At 2:20 a.m., just 79 minutes before launch, a blown fuse in the range safety circuits caused the launch to be canceled. Countdown was reset that night and proceeded, with several holds, planned and unplanned, from 11:08 p.m., through the early morning of the next day.

At 9:21:23 a.m. on July 22, 1962, Mariner 1's Atlas-Agena lifted off from Pad 12. Soon after launch, the booster began drifting northeast of its planned trajectory. Corrective steering commands were sent to the rocket, but the Atlas-Agena instead proceeded further off course, imperiling North Atlantic Ocean shipping and/or inhabited areas in the event of a rocket crash. At 9:26:16 a.m., just six seconds before the Agena second stage was scheduled to separate from the Atlas, at which point destruction of the rocket would be impossible, a range safety officer ordered the rocket to self-destruct, which it did.

Cause of the malfunction
Because of the gradual rather than sharp deviation from its course, JPL engineers suspected the fault lay in the flight equations loaded into the computer that guided Atlas-Agena from the ground during its ascent. After five days of post-flight analysis, JPL engineers determined what had caused the malfunction on Mariner 1: an error in the guidance computer logic combined with a hardware failure.

The hand-written guidance equations contained the symbol "R" (for "radius"). This "R" should have had a line over it ("R-bar" or R̄), denoting smoothing or averaging of the track data coming from an earlier calculation. But the bar was missing, and so the computer program based on those equations was incorrect. The error was in the original specification, and not in the process of writing the program.

During its ascent, Mariner 1's booster briefly lost guidance-lock with the ground. Because this was a fairly common occurrence, the Atlas-Agena was designed to continue on a preprogrammed course until guidance-lock with the ground resumed. When lock was reestablished, however, the faulty guidance logic caused the program to erroneously report that the "velocity was fluctuating in an erratic and unpredictable manner", which the program tried to correct for, causing actual erratic behavior, which prompted the range safety officer to destroy the rocket.

The incorrect logic had previously been used successfully for Ranger launches; it was the combination of the erroneous formula and a hardware fault which led to Mariner's destruction.

The catastrophic effects of a small error "summed up the whole problem of software reliability" and contributed to the development of the discipline of software engineering.

Subsequent popular accounts of the accident often referred to the erroneous character as a "hyphen" (describing the missing component of the symbol) rather than an "R-bar"; this incorrect mischaracterization was fueled by Arthur C. Clarke's description of the malfunction as "the most expensive hyphen in history".

Legacy
The loss of America's first interplanetary spacecraft constituted an $18.5 million ($ in today's dollars) setback for NASA. The incident underscored the importance of a thorough pre-launch debugging of software as well as a need to engineer programs such that minor errors could not cause catastrophic failures. The procedures implemented as a result served NASA well, ultimately salvaging the Project Apollo Moon landings; though there were program errors in the Lunar Excursion Module software during descent, they did not cause mission failure.

With the logic error quickly discovered, no undue delay was necessary. The identical Mariner 2 was already on hand, and a second launch from the same pad was manageable before the end of August. On August 27, 1962, Mariner 1's sister spacecraft was successfully launched, becoming on December 14, 1962, the first spacecraft to return data from the vicinity of Venus.

title: Mariner 1


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Mariner 3

Mariner 3 (together with Mariner 4 known as Mariner-Mars 1964) was one of two identical deep-space probes designed and built by the Jet Propulsion Laboratory (JPL) for NASA's Mariner-Mars 1964 project that were intended to conduct close-up (flyby) scientific observations of the planet Mars and transmit information on interplanetary space and the space surrounding Mars, televised images of the Martian surface and radio occultation data of spacecraft signals as affected by the Martian atmosphere back to Earth.

Although the launch was initially successful, there was a separation issue and Mariner 3 stopped responding when its batteries ran out of power. It was the third of ten spacecraft within the Mariner program.

Background

Mariner 2 had been a modified Ranger lunar probe, however Mariner 3 used a new, larger bus with four solar panels, a TV camera, and additional instrumentation. Because of the greater mass, the new Agena D stage would be used instead of the Agena B. Mariner 3 also utilized a new, larger fiberglass payload fairing. Of the two Atlas-Agena pads at Cape Canaveral, LC-13 became available first following the launch of an Air Force Vela satellite in July 1964. Atlas vehicle 289D was erected on the pad on August 17, with the backup Mariner probe and booster (Atlas 288D) erected on LC-12 on September 28.

Launch failure
Mariner 3 was launched at 2:22 PM EST on November 5, 1964, from Cape Kennedy Air Force Station Launch Complex 13. After an uneventful boost phase, the Agena completed its burn to place the probe on a trajectory towards Mars. One hour after launch, the first telemetry transmissions from Mariner 3 were received, indicating that the scientific instruments were functioning correctly but there was no indication of any solar panel operation. Unsure of the exact problem, ground controllers issued a command to turn off the rate gyros to conserve power while they worked to figure out what had happened. Telemetry data suggested a separation failure of either the Agena or the payload fairing, but a below-normal velocity appeared to indicate that the fairing had not separated properly. A command was sent to manually jettison the payload shroud, but nothing happened. The ground controllers next considered firing Mariner 3's midcourse correction engine to blow off the shroud, but they ran out of time. Eight hours after launch, the batteries in the probe died and the mission was officially terminated. Even if the shroud could be removed, the mission would have failed, since the low velocity meant that Mariner 3 would miss Mars by several million miles.

Three weeks later, on November 28, 1964, Mariner 4 was launched successfully on a 7½-month voyage to Mars.

Instruments
The instruments on Mariner 3 included:
 * 1) Television camera
 * 2) Magnetometer
 * 3) Plasma probe
 * 4) Cosmic ray telescope
 * 5) Trapped radiation detector
 * 6) Cosmic ray ionization chamber
 * 7) Cosmic dust detector

title: Mariner 3