Laurent Lamy

Baptiste Cecconi

Laura Debiscchop

Agnès Fave

Marie-Agnès Dubos

Aleth Tisseau

Escotais

Véronique Stoll

Pierre Le Sidaner

Florence Henry

Typeset using L A T E X default style in AASTeX631

Keywords:

Since 1970, decametric observations of the Sun and Jupiter have been acquired on a daily basis from the radio observatory of Nançay, France. The resulting database now forms the worldwide largest set of low frequency observations of the Solar Corona between 10 and 100 MHz and of the Jovian magnetosphere between 10 and 40 MHz. The Nançay Decameter Interferometer (NDI), a two-antenna interferometer, acquired pioneer observations from 1970 to 1978, using analog radio receivers tested on the Arecibo giant radiotelescope. The large Nançay Decameter array (NDA), a phased array of 144 helical antennas, was then constructed in the late 1970s as a ground-based support to the Voyager mission and started routine observations in January 1978 in replacement of the NDI, using similar spectrometers. The NDA is still in operation today and its observations, recorded in a digital format since 1990, are public and daily made accessible to the heliospheric and magnetospheric communities at https://www.obs-nancay.fr/reseau-decametrique/. Before 1990, though, the Nançay decametric observations were recorded on analog devices, such as 35-mm films, magnetic tapes and other paper supports, physically archived at the Observatory of Paris, on its site of the Observatory of Meudon, where they could only be accessed on demand. The NDA team recently undertook a multi-year effort to inventory all the Nançay decametric archives, to refurbish and digitize them in order to preserve and promote this historical data collection, most notably by extending the current public database over the 1970-1990 time interval. We digitized the full collection of 35-mm films, corresponding to a total film length of ∼ 45.5 km, with a specific high resolution scanner. Each roll was scanned by a series of pixel-to-pixel contiguous images recorded in TIF format with adequate metadata and naming convention. The final ∼ 40 Tb data volume was archived at Paris Astronomical Data Centre and the physical films were refurbished to be archived in a perennial way. We also digitized the associated observations sheets. Finally, we took advantage of this project to also digitize a sample of 35-mm films extracted from four other historical solar data collections hosted at the Observatory of Paris and dealing with two distinct Nançay radiotelescopes and two Lyot heliographs located at the Observatories of Meudon and Haute-Provence. The digitized, documented, Nançay decametric archives have been publicly released to the community in 2020 at http://archives-decametriques.obspm.fr. After having described the instruments, the data collections and the digitization pipeline, this articles ends with a few scientific case studies, focussing on the search for Jupiter-satellite decametric emissions. This work is a concrete example of how historical astronomical measurements can be preserved and archived along the IAU recommandation, to the benefit of the astronomical community.

Created in 1956 in the Sologne forest (France) under the responsibility of the Observatory of Paris, the radio observatory of Nançay hast hosted since then a variety of radiotelescopes covering a wide spectral range from a few MHz to several GHz. The exploration of the low frequency sky, ranging from the terrestrial ionospheric cutoff of ∼ 10 MHz to 120 MHz (decameter wavelengths) rose in the early 1960s under the impulsion of the Meudon research group of decametric radioastronomy of André Boischot.

While developing low frequency radio receivers, which were tested at the giant parabola of Arecibo in 1970 Boischot et al. (1971), the group led the the construction and operation of two successive decameter radiotelescopes in Nançay, devoted to the quasi-daily monitoring Sun andJupiter. Between 1970 and[START_REF] Aubier | ATP Plan tologie Aubier[END_REF], a 2-antenna interferometer, hereafter referred to as the Nançay Decameter Interferometer (NDI), acquired pioneer observations Boischot (1974). After Jan. 1978, solar system observations were acquired by the Nançay Decameter Array, a phased-array with a larger effective area, designed as a sensitive ground-based support to the Voyager mission Boischot et al. (1980) and still in operation today. Pictures of these instruments are displayed in Figure 1.

Altogether, this 52 years-long Nançay decametric database now forms what appears to be the worldwide largest set of low frequency observations of the Solar Corona between 10 and 100 MHz, and of the Jovian magnetosphere between 10 and 40 MHz, sampling ∼ 4.7 solar cycles and ∼ 4.2 jovian revolutions, with high resolution observations acquired with a series of receivers of increasing performances. The NDA data are acquired in digital format since 1990, and the observations obtained with its Routine (survey) receiver are daily publicly released to to the heliospheric and magnetospheric communities at https://www.obs-nancay.fr/reseau-decametrique. This digital 32 years-long database has continuously fed in research efforts on heliospheric radio emissions and the unique length of the database yielded pioneer statistical analyses of Jovian and Solar radio bursts. Recent examples include the detection of new decametric emissions induced by Ganymede, Europa or unrelated to satellites from a 26-30 years-long catalog of NDA observations of Jupiter Marques et al. (2017); Zarka et al. (2018); [START_REF] Jácome | [END_REF] or the characterization of solar type III bursts automatically tracked over half a solar cycle Zhang et al. (2018).

However, the NDA/NDI measurements collected between 1970 and 1990 were recorded analog devices, such as 35mm films, magnetic tapes and other paper supports. These archives were conserved at the Observatory of Paris on its site of the Observatory of Meudon, where they could only be accessed on demand [START_REF] Lamy | [END_REF]. This situation prevented from a wide scientific use of pioneer measurements. The conservation state and duration of analog archives was also unknown with a significant risk of loss of historical measurements. In this article, we present a multi-year effort recently undertook by the NDA team to inventory all the Nançay decametric archives, to refurbish and digitize them in order to preserve and promote this historical data collection, most notably by extending the current public database over the 1970-1990 time interval.

The importance and urgency of the preservation and digitization of historical observations has been acknowledged recently by the XXXth General Assembly of the International Astronomical Union (IAU) in its Resolution B3: "on preservation, digitization and scientific exploration of historical astronomical data" International Astronomical Union (2018), which starts by stating that historical observations provide irreplaceable information regarding changes in the Sun, stars, and other objects of astronomical interest and thereby allow researchers to investigate the time domain and the nature of those transient, evolutionary or recurring changes across a far greater interval than is possible from the relatively short time-span of modern-age (born digital) observations alone.

Hereafter, section 2 describes the concerned radiotelescopes and section 3 the associated inventoried collections of analog decametric archives. We present in section 4 how we digitized the full collection of 1492× 35-mm films at high spatial resolution and intensity dynamics together with the associated observation sheets. Section 5 indicates how the data can be accessed and used scientifically, while section 6 presents a few scientific case studies, focussing on the search for Jupiter-satellite decametric emissions. Finally, section 7 presents 10 digitized films extracted from four other 35-mm data collections of radio and visible solar observations also conserved at the Observatory of Paris, corresponding to decades of measurements acquired by two other Nançay radiotelescopes and two solar heliographs respectively located at the Observatories of Meudon and Haute-Provence (France).

THE RADIOTELESCOPES

The Nançay Decameter Interferometer (NDI)

The NDI was a two-antenna decameter interferometer (Fig. 1, left), originally designed for solar observations (and therefore also sometimes called solar interferometer) but which rapidly also targeted Jupiter. It operated between 1970[START_REF] Aubier | ATP Plan tologie Aubier[END_REF]Boischot (1974) with daily observations before to be supplied by the NDA. Its two antennas were mounted on top of 10-m high mobile towers able to track moving targets. Each antenna was made of 4 log-periodic dipoles, sensitive to the 20 -80 MHz range with a 10 dB gain. One antenna was settled at a fixed position and the other one along a 1500-m long East-West tail track, yielding variable baselines for interferometric purposes, although the interferometric mode was rarely used.

The sensed signal was recorded by various radio receivers specifically developed for the radio observatory of Nançay. Two swept-frequency spectrographs measured the signal over the 20-40 and 40-80 MHz ranges, with spectral bandwidth of 20 kHz and 100 kHz, respectively, at a variable sweeping rate within 1-500 Hz. Alternately, two swept-frequency receivers using the same sweep-generators and recording devices could be used in interferometric mode. One multichannel receiver sampled a 1 MHz band (within the 10-110 MHz range), with 50 × 20 kHz-wide adjacent channels. Four fixed-frequency spectrographs measured the signal at 30, 36, 60 and 72 MHz over a 250 kHz bandwidth.

The devices used to collect the data included magnetic tapes, 35-mm films, fac-similés and foldable paper, as illustrated in Figure 2, reproduced from Leblanc & Groupe de Radioastronomie Décamétrique (1975).

The scientific research conducted with NDI observations has been early reviewed by Boischot (1974).

Decametric observations of the Sun at Arecibo

Between 15th July and 25th August 1970, the decametric research team of Meudon conducted solar observations with the giant parabola of Arecibo (Puerto Rico). This observing program, requested to the director of the Arecibo observatory, aimed at detecting the quiet solar corona at decameter wavelengths Boischot et al. (1971).

The observations were carried out with the swept-and fixed-frequency receivers described above, namely two sweptfrequency receivers covering the 20-40 and 40-80 MHz ranges and sensitive to two polarizations, and fixed-frequency spectrographs at 29, 36 and 60 MHz sensitive to one polarization. The signal was collected with a specifically-conceived feed antenna placed at the focal point of the 300-m large dish and made of two perpendicular log-periodic antennas sensing either both right-and left-handed circularly polarized emissions or two perpendicular linearly polarized ones.

The observations were executed from 16th July to 16th August, with 50 h of solar observing time spread over 18 days, complemented by 12 h for calibration sources (pulsars) and 5 h to observe the moon. The data were recorded on magnetic tapes (which benefit the best, 40 dB, dynamics) and on 35-mm films.

The fixed-frequency measurements of the Sun were for instance analyzed by Aubier et al. (1971) who proposed that wave scattering by the inhomogeneous corona affects the solar decametric brightness, or by Aubier & Boischot (1971) to measure the temporal profile of type-III bursts and infer coronal temperatures.

The scientific research conducted with NDI observations has been early reviewed by [START_REF] Aubier | [END_REF]; Boischot (1974).

The Nançay Decameter Array (NDA)

The NDA, also known as the large decameter array, is a steerable phased-array with an effective area of ∼7000 m 2 at 25 MHz, a maximal gain of 25 dB and a wide main lobe (∼ 6 × 10 • ). It is made of 144 Tee-Pee log-periodic broadband fixed antennas sensitive to the 10-120 MHz range, inspired by those of the Clark Lake Observatory Erickson & Fisher (1974) except that they have been inclined by 20 • southward to facilitate the tracking of solar systems targets. These conical antennas form 2 sub-arrays respectively sensitive to right-handed and left-handed circularly polarized emissions Boischot et al. (1980); [START_REF] Lecacheux | [END_REF].

The NDA has been originally conceived as a ground-based stereoscopic support to the exploration probes which based the expriment known as STEREO-MJS 77 (for Mariner-Jupiter-Saturn 1977) which ultimately became the Voyager mission Leblanc & Groupe de Radioastronomie Décamétrique (1975). The latter observed heliospheric radio emissions with the Planetary Radio Astronomy (PRA) experiment, the spare model of which has been lent to the radio Observatory of Nançay for stereoscopic observations with the same receiver Aubier et al. (1978a); Boischot et al. (1981). The NDA was therefore built between 1975 (the primary set of 32 antennas array is displayed in Figure 2) and late 1977. It has been observing since then the Sun and Jupiter on a daily basis, together with other intense radiosources, with a series of successive radio receivers which were analog before 1990 and digital beyond [START_REF] Lamy | [END_REF]. A tentative summary of the spectrometers employed by the NDI and the NDA is provided in table 1.

The NDA analog data were recorded on the same devices as those employed for the NDI, as illustrated in Figure 2.

Overall, the results obtained from the analysis of NDA measurements, published in ∼ 200 articles, have been successively reviewed in [START_REF] Lecacheux | [END_REF]; Zarka (2011); [START_REF] Lamy | [END_REF].

THE DECAMETRIC ARCHIVES

From 2016 to 2018, the NDA team conducted an exhaustive inventory of the decametric archives conserved at the Observatory of Paris on the site of the Observatory of de Meudon (which was merged with the Observatory of Paris in 1926). The archives, stored in different buildings, overall consisted of collections of 35-mm films, of fac-similés, of foldable papers, of observation sheets together with some handwritten catalogs. This inventory unfortunately revealed that the magnetic tapes mentioned above had all been lost.

Films

We retrieved a total of 1492 × 35-mm rolls, each long of ∼ 30.5 m in average, yielding a total film length of ∼ 45.5 km. These rolls sub-divide in three different sets : 601 rolls correspond to NDI observations, 13 to the Arecibo campaign and 878 to NDA measurements. The rolls were generally in good conservation state. They were stored in metallic boxes showing frequent traces of rust, themselves conserved in metallic cabinets. Each box was labelled with a sticker indicating the number of the roll in a given data collection (a data collection consisting of a combination of an instrument with a receiver, see below), the observing date, the target and the acronym of the receiver, as illustrated in Figure 3. This basic information enabled us to classify the films precisely.

The NDI archives can be separated into 3 data collections : 436 rolls obtained with the 'S' (Spectograph) receiver, 149 rolls with the 'MCX' (Multi-Channel) one and 16 rolls corresponding to tests (unused rolls, duplicated ones, tests of instrumental modes etc.).

The Arecibo campaign was treated as a single data collection made of 13 rolls, obtained with different receivers.

The NDA, largest, set of films consists of 4 data collections : 682 rolls acquired with the 'S' receiver between 1978 and 1980 (most likely the same receiver as that used with the NDI), 154 rolls obtained with the 'R' (Routine) receiver between 1979 and 1989, 40 rolls obtained with the 'RN' (Routine-New) from 1990 to 1991 and 2 rolls obtained with the 'SAO' (Spectrographe Acousto-Optique or Acousto-Optical Spectrograph) in 1983.

The structure of a given film generally consists of several separated observations each made of 1 or 2 dynamic spectra with the frequency (y) axis perpendicular to the roll direction and the time (x) axis along it. Handwritten notes were sometimes found directly on the film (to mark events of interest, the start of an observation, a change in instrumental mode). The NDI/NDA observations exclusively deal with quasi-daily observations of Jupiter and the Sun, most of the time recorded in alternance with long (up to 8 h) observations. Different time and frequency markers, depending on the inspected data collection, were visible on the films, providing references for both axes. The Arecibo observations contained dynamic spectra together with time series of the recorded signal at fixed frequencies. They targeted the Sun, the moon and historical pulsars such as CP-1919, the first pulsar discovered only 3 years earlier before the observing campaign.

The overall structure of 35-mm films, the nature of the recorded signals and the coding of the time/frequency markers were understood by comparing the films (either by eye or with historical visualization devices) with the 35-mm data published in the literature, such as in Boischot et al. (1971); Aubier et al. (1978b); Boischot et al. (1980), as illustrated in Figure 4. Interestingly, we noticed at several occasions some perforations marked with colored sewing threads corresponding to published observations.

Observation sheets

We also retrieved and inventoried a total of 10219 individual paper sheets, displayed in Figure 5, stored in pasteboard boxes. Each sheet describes an individual observation executed with both the NDI and the NDA over the time interval ranging from 1st Sept. 1977to 14th Nov. 1997. This time interval does not coincide with the NDI lifetime, either because such observations sheets were not in use or have been lost before 1977. Interestingly, they have been produced on a daily basis up to 1997, covering 7 years of NDA observations also acquired in digital format, which will be helpful for the scientific validation of NDA analog data.

Such observations sheets contain handwritten essential information for the understanding of the recorded decametric observations such as the name of the observer, the date and duration of the observation, the target, the pointing parameters (manual or automatic, tracking, scan or transit mode), the used receiver and the employed instrumental mode together with the data outputs (number of channels, analog device on which the data were recorded).

Four different models of observation sheets have been identified, all being displayed in Figure 5 (right).

Paper-based data records

In addition to the observation sheets, we also retrieved two types of paper-based data records.

Fac-similés

The first type consists of so-called Fac-similés, which are 30 cm large paper print-out rolls long of a few meters (up to 12 m) aimed at plotting specific data intervals at high resolution.

We inventoried 812 individual rolls from Dec. 1975 until June 1987, stored in pasteboard boxes. Each roll was labelled with a sticker describing the content of the roll (source, observation interval, and handwritten comments on the nature of observed emissions). Most of the rolls where in good state. Figure 6 shows pictures of this collection. All these archives deal with Jupiter and the Sun, except one which corresponds to one observation of Cassiopea A.

Figure 6. Fac-similés rolls on which were drawn high resolution decametric observations.

Foldable papers

The second type of paper-based archived measurements consists of foldable sheets of paper, sometimes referred to as Sefram (as the name of the company producing those). The signal recorded on this medium corresponded to fixedfrequency measurements of transiting radiosources at high cadence. We inventoried 17/8 individual foldable sheets for the NDA RH/LH polarized observations obtained from 4th Nov. 1977to 14th March 1979and from 22th Feb. 1977to 25th Feb. 1979, respectively. The targeted sources were Cygnus A, Cassiopea A, Taurus A and Virgo A. These observations, matching the construction timeline of the NDA, were devoted to calibration purposes as indicated by handwritten notes. An exemple of foldable paper record is displayed in Figure 7. The digitization of the large collection of 35-mm rolls, corresponding to a total film length of 45.5 km, required a substantial work. This work was achieved in several steps between 2018 and 2020 including most notably : drafting a digitization project, applying to funding calls to assemble the required budget (∼ 100 ke, including the cost of the digitization process, of the required digital storage volume and the full time of an archivist for a period of 9 months), the publication of an open call with the digitization requirements, the selection of a digitization company equipped with an adequate, high performance, scan, the testing and validation of scanning parameters on a subset of rolls, the digitization of the full dataset itself, the storage of the digitzed observations together with the cleaning, refurbishment and final archiving of the physical 35-mm rolls.

Digitization parameters

The employed scanner was a CS 8850 WW model of the Wicks & Wilson 8800 series. It enabled to digitize the 35-mm rolls with the following characteristics. Each roll was first cleaned and uncharged from static electricity by a broom preceding the scan. The flatness of the film was ensured by a mechanical tension imposed by two 10 cm-distant supports. The roll was continuously read and scanned with a theoretical 8-bits dynamics in intensity. In practice, the final dynamics was slightly adjusted to sample both the background and most intense pixels without saturation, resulting in a loss of ∼ 0.5 dB. The obtained scans were recorded in the TIF format as 15744 × 5408 pixels images. They covered the full extent of the film across the rolling direction (y-axis or spectral direction), therefore including the perforations. They were also strictly adjacent in the rolling direction (x-axis or temporal direction) with a 1 pixel precision. Overall, a ∼ 30.5 m-long film in average was entirely scanned through a total of ∼ 320 TIF images. Examples of the quality of the digitization process are displayed in Figure 8. The x and y axes were not necessarily constant along a full film, because of some intrinsic variability linked to the camera used to plot the data onto the film. This variability was generally related to a change of instrumental mode (it was for instance possible to adapt the speed at which the film was printed) or a change of observation. The x and y axes could nonetheless be fairly precisely located within a given sequence of observation.

Digital conservation

The final set of TIF images represents a ∼ 40 Tb total volume. These images were stored by data collection onto a server of the Observatory of Paris maintained by the Paris Astronomical Data Centre (PADC) and accompanied by a Data Management Plan. We kept the definition of a data collection as the observations obtained with one instrument (e.g. the NDA) and one receiver (e.g. the S receiver).

The individual TIF images were accompanied by standard metadata and labelled with a specific nomenclature, which we describe below on the basis of the following example : FR751142302 RDN S 0416 1982 0243.tif. The FR751142302 NDA/RN : Sun, 5 Jan. 1991 near 13:00 UT NDA/RN : Jupiter, 5 Jan. 1991 near 21:00 UT code identifies the library of the Observatory of Paris, where the data collection is hosted. The RDN code refers to the french acronym (Réseau Décamétrique de Nançay) for the NDA, and could be alternately IDN (for NDI) or Arecibo. The 'S' letter refers to the used receiver and could be alternately R, RN, M, SAO or TEST (for test observations).

0416 identifies the roll number within a data collection (here RDN S). 1982 corresponds to the starting year for the scanned roll. Finally, 0243 indicates the number of the scan for a given roll.

Preservation of physical archives

The original storage of 35-mm films used metallic devices (rolling core and storage box) not adapted to long-term conservation. Once digitized, each scanned film was re-rolled around a plastic core and stored in an individual acid-free paper box compliant with the current policy of archive conservation. Both the the roll and its associated box were labelled with the unique identifier of the film within a data collection. The refurbished films were ultimately packed by groups and definitely inventoried for long-term archiving at the Observatory of Paris and stored in a dedicated archiving room on the site of the Observatory of Meudon. Figure 9 displays examples of refurbished rolls after digitization.

Observation sheets

The observation sheets have been straightforwardly digitized individually with a standard digital photocopier. All the information that they contain have additionally been manually extracted and used to construct a digital base of metadata.

Other paper records

Although we tested the digitization of at least one Fac-similé roll, we chose not to digitize the collections of paper records. As these were precisely inventoried, a list of those is nevertheless available and, as for the other decametric physical archives, can be accessed on demand to the NDA team.

DATA AVAILABILITY

In order to release the digitized Nançay decametric archives to the scientific community, we created the online portal http://archives-decametriques.obspm.fr, which both describes the digitization project and provides access to the digitized data with an associated documentation.

The 35-mm digitized dataset, which decomposes into 8 separated data collections, is distributed under the Creative Commons-BY-4.0 licence format and is referenced as [START_REF] Lamy | Nançay Decametric 35mm Film Observations Digitized Collection[END_REF]. The digitized observation sheets are accessible together with the 35-mm data and referenced as [START_REF] Debisschop | Nançay Decametric 35mm Film Observations Logs Collection[END_REF], with an online documentation describing how to read them with usecases. Intensity calibration of the NDA data can be performed by using the hourly calibration sequences with noise diodes of known flux (one example of which is seen on Figure 2, top), exactly as for digital data.

Interestingly, the NDA decametric archives of Jupiter obtained between 1978 and 1990 were specifically cataloged in the literature throughout a series of articles successively published by [START_REF] Leblanc | [END_REF]Leblanc et al. ( , 1983Leblanc et al. ( , 1989Leblanc et al. ( , 1990Leblanc et al. ( , 1993)), likely because the NDA team realized that analog records of the observations could not be easily re-used. These catalogs consist of time-frequency boxes in which Jovian decametric bursts were detected. However, the published versions were only available as raster scans which prevented the community from easily utilizing easily them. This issue motivated a recent, parallel, digitization effort of (Cecconi et al., to be submitted to the Planetary and Heliospheric Radio Emissions IX proceedings). The digitized catalogs in their orginal formatting are now also accessible online together with the Jovian digitized data they refer to and referenced as Leblanc & et al. (2020a,b,c,d,e). A final catalogue, referenced as [START_REF] Cecconi | A catalogue of Jovian decametric radio observations from January 1978 to[END_REF], compiles all of them, while fixing a few events and adding more contextual metadata (such as the phase of non-Io moons).

SCIENTIFIC USE CASES

We used the digitized set of NDA archives to perform the preliminary comparisons and data analyses presented below.

Comparison with published observations

No observations sheets were retrieved for the Arecibo campaign, for which only the handwritten notes found on top of the films helped us to figure out the content of the records. Nonetheless, we retrieved the solar observation published by Boischot et al. (1971) in their Figure 2, replicated on top of Figure 9. The original caption mentions two types of solar radio bursts, together with a vertical lightning flash but the original display of the Figure has a poor dynamics which prevents from tracking finely the behaviour of the bursts, despite the huge sensitiivity of the Arecibo dish.

Figure 9, bottom shows the portion of the digitized film corresponding to this observation. We can immediately notice the gain in dynamics and identify fainter radio bursts near 46 MHz before the vertical lightning flash which could not be tracked from the original Figure . The bottom portion of the film additionally shows a dynamic spectrum at higher frequencies which reveal continuous solar emission during the observed interval. The observed intervals were chosen specifically as they correspond to the first two records of Jupiter emissions cataloged by [START_REF] Leblanc | [END_REF]. The corresponding time-frequency boxes are superimposed on the data by dashed white boxes. While fairly matching the bursts, some weak emission can also be identified outside the boxes.

Jupiter-satellite decametric emissions

The emission visible in Figure 12, vertex-late and RH-polarized, reaching frequencies as high as 28 MHz, is characteristic of the Io-A component. We checked with the online Jupiter probability tool recently developed by the NDA team (Cecconi et al., in prep.) at https://jupiter-probability-tool.obspm.fr that this actually corresponds to the Io-A' type of emission statistically identified by Marques et al. (2017) from a catalog of 26 years of digital NDA/Routine observations.

The weaker bursts visible in Figure 11, vertex-late and RH-polarized and barely reaching 20 MHz are a non-Io emission. Surprizingly, the Jupiter probability tool shows that it is consistent with a Ganymede-A emission, which was only very recently statistically detected by Zarka et al. (2018) [START_REF] Leblanc | [END_REF]. The vertex-late, RH polarized emission is consistent with a Ganymede-A decametric emission.

The full 12 years-long digitized catalog of NDA archived observations of Jupiter provides an occasion to check the persistence of planet-satellite decametric emissions from 1978 to 1990 and to extend the results of Marques et al. (2017); Zarka et al. (2018) obtained over the 1990-2016 interval. Figure 13a plots the Jupiter cataloged emissions as a function of the Io phase and the longitude of the observer. As expected, the distribution reproduces that already published by Leblanc et al. (1993) (with the same dataset but over the 1978-1988 interval only). The emissions clustered within the colored regions defined by Marques et al. (2017) are attributed to Io with some differences, though. For instance, the [START_REF] Leblanc | [END_REF]. The vertex-late, RH polarized emission is consistent with a Io-A decametric emission.

Io-B (Io-D, resp.) component near the bottom left blue (red, resp.) box was more (less, resp.) visible than in Marques et al. (2017). The comparative occurrence of the various Io components within the 1978-1990 and 1990-2022 intervals is left for future analysis. Once the Io components were removed, we plotted the rest of the emissions as a function of the phase of the satellites Europa, Ganymede and Callisto as an attempt to track decametric emissions induced by those moons Zarka et al. (2017). A modest cluster consistent with the Gan-A and B emissions identified by Zarka et al. (2018) 13c, though. These results are likely affected by the poorer resolution of the boxes defined in the 1978-1990 catalog when compared to the polygons employed in the 1990-2020 but might also reveal an additional long-term trend. A more detailed analysis of the long-term occurrence of Jupiter-satellite emissions is beyond the scope of this paper.

OTHER 35-MM DATASETS ARCHIVED AT THE OBSERVATORY OF PARIS

In parallel to the above-described work of the NDA team on decametric archives, the 'archive and legacy' commission from the scientific council of the LESIA laboratory has identified four other collections of 35-mm archives conserved at the Observatoire de Paris on its site of Meudon. These consist of two sets of radio observations of the Sun acquired in Nançay (i) with the Radio Spectrographe Multicanal de Nançay (RSMN) over 110-470 MHz, consisting of 758× 35mm films recorded between 1978et 1991[START_REF] Dumas | [END_REF] and (ii) with the Nançay Radio Heliograph (NRH), in operation since 1956, and providing routine images between 150 and 450 MHz [START_REF] Kerdraon | Coronal Physics from Radio and Space Observations[END_REF] We took advantage of this project to digitize a sample of each of these four collections, yielding a total of 10 digitized films targeting periods of active solar activity. The radio observations were scanned as the decametric ones. Examples Lamy et al.

of digitized images are provided at https://archives-decametriques.obspm.fr/. The solar images were scanned with a different scanner, whose frequency of acquisition was adjusted on the frequency of images acquired along the film. Figure 14 shows Hα images of the Sun acquired at the Observatory of Meudon in 1957 (left) and at the Observatoire de Haute Provence in 1958 (right). Despite a background noise on the film, the quality of the images is excellent and enables one to easily track active regions on the solar surface.

The further analysis of these images and the possible future digitization of the associated 35-mm collections is left to interested colleagues of the solar community.

SUMMARY AND PERSPECTIVES

In this article, we have presented a multi-year effort of the NDA team to fully refurbish the Nançay decametric archives conserved at the Observatory of Paris. These consist of quasi-daily observations of Jupiter and the Sun successively acquired between 1970 and 1990 with three radiotelescopes : the NDI, the Arecibo parabola and the NDA, which is still in operation today.

The observations were recorded on analog devices such as 35-mm films and other paper based supports that we have fully inventoried. We have then digitized and documented the entire 35-mm data collection and the associated daily observation sheets. We have ensured in parallel a long-term preservation of the refurbished physical archives. We have shown how the digitized data can be used for scientific purposes with use cases. A preliminary analysis of the Jovian decametric emissions for instance suggests that the first ever NDA record of Jupiter displays an arc consistent with a Gan-A emission. Interestingly, the statistical occurrence of Jupiter emissions cataloged by the NDA team throughout 1978-1990 supports the presence of Gan-A and B emissions, but no obvious evidence of radio emissions induced by Ganymede or Europa, which needs further investigation.

The digitized, documented, data have been publicly released in 2020 through the online portal http:// archives-decametriques.obspm.fr. This extends the current 32 years-long NDA digital database with 20 years of novel observations and offers new perspectives to the community for unprecedented long-term analyses of the Solar Corona and the Jovian magnetosphere over half a century.

We have finally presented digitized samples of four other 35-mm solar data collections also conserved at the Observatory of Paris, acquired by two other radiotelescopes of the radio Observatory of Nançay (RSMN and NRH) and two Lyot heliographs which acquired Hα images of the Sun at both the Observatories of Meudon and Haute Provence.

This project is a concrete example of how historical astronomical measurements can be preserved and digitized to facilitate their scientific exploration along the IAU recommandation. Its success is thanks to synergistic efforts between researchers, archivists, data engineers and web designers involving the LESIA laboratory, the library of the Observatory of Paris and the Paris Astronomical Data Centre.

Figure 1 .

 1 Figure 1. Pictures of (left) the Nançay Decameter Interferometer (NDI), (middle) the Nançay Decameter Array in 1980 and in 2017 and (right) of the Arecibo parabolic dish.

Figure 2 .

 2 Figure 2. Data acquisition pipeline for the NDI and NDA (in its early 32-antennas configuration) instruments. Data were recorded on 35-mm films, magnetic tapes, fac-similés and paper sheets. Reproduced from Fig. 23 of Leblanc & Groupe de Radioastronomie Décamétrique (1975).

Figure 3 .

 3 Figure 3. Collection of Nançay decametric archives stored on 35-mm rolls in their original metallic boxes. (a-c) Pictures of the NDI, Arecibo and NDA sub-collections. The different acronyms refer to the receivers used for the observations. (e-d) Original metallic storage cabinets and inventoried films before digitization.

Figure 4 .

 4 Figure 4. Visual inspection of 35-mm films. (Top) Data recorded through two channels with time markers, vertical radio frequency interferences and a calibration sequence. (Bottom) Comparison with a published dynamic spectrum Boischot et al. (1981).

Figure 5 .

 5 Figure 5. (Left) Decametric observation sheets stored in boxes, ranging from 1st Sept. 1977 to 14th Nov. 1997. (Right) Four models of observation sheets have been successively employed to described the NDI/NDA daily measurements.

Figure 7 .

 7 Figure 7. Picture of data recorded on a Sefram foldable paper sheet showing transit observations of Cas A.

Figure 8 .

 8 Figure 8. (Left) Test images of digitized observations of Jupiter and the Sun together with (right) full resolution extracts.

Figure 9 .

 9 Figure 9. Refurbished 35-mm rolls after digitization.

Figure 10 .

 10 Figure 10. (Top) Dynamic spectrum of Boischot et al. (1981).

Figures

  Figures 11 and 12 display full resolution dynamic spectra reconstructed from the NDA Jupiter observations of 3rd and 5th Feb. 1978 respectively, as the very first observations of the completed array. The two observations were indeed recorded on the first and second roll of the NDA/S data collection. The observation sheets confirmed the use of the S receiver with the RH sub-array and provided the observed spectral range for both channels. The data are of excellent quality and displayed decametric emission with high dynamics and high temporal and spectral resolution.The observed intervals were chosen specifically as they correspond to the first two records of Jupiter emissions cataloged by[START_REF] Leblanc | [END_REF]. The corresponding time-frequency boxes are superimposed on the data by dashed white boxes. While fairly matching the bursts, some weak emission can also be identified outside the boxes.

Figure 11 .

 11 Figure 11. NDA/S dynamic spectra of Jupiter acquired with the RH sub-array on 3rd Feb. 1978 from 10 to 50 MHz. The white dashed box corresponds to the first reported detection of Jupiter in the NDA catalog of[START_REF] Leblanc | [END_REF]. The vertex-late, RH polarized emission is consistent with a Ganymede-A decametric emission.

Figure 12 .

 12 Figure 12. NDA/S dynamic spectra of Jupiter acquired with the RH sub-array on 5th Feb. 1978 over two spectral ranges covering 10-100 MHz. The white dashed box corresponds to the second reported detection of Jupiter in the NDA catalog of[START_REF] Leblanc | [END_REF]. The vertex-late, RH polarized emission is consistent with a Io-A decametric emission.

Figure 13 .

 13 Figure 13. Jupiter emissions recorded with the NDA from 1978 to 1990 plotted as function of the phase of (a) Io, (b) Ganymede, (c) Europa and (d) Callisto and of the central meridian longitude (CML) of the observer. The colored regions in panels (a) and b) mark the most probable regions for Io-and Ganymede-Jupiter decametric emissions, according to Zarka et al. (2018). Panel (a) displays all NDA/Jupiter records, while panels (b-d) display only those without the Io-Jupiter emissions.

  Figure 14. Individual Hα images of the Sun acquired with the Lyot Heliographs at the Observatory of Meudon on 19 Dec. at 14:27 UT 1957 (left) and at the Observatory of Haute-Provence on 30 Apr. 1958 at 17:35 UT (right).

  is visible on Figure 13b. No obvious cluster consistent with the Europa emissions recently identified by Jácome et al. (2022) appears on Figure

DIGITIZATIONOnce inventoried, the digitization of the above-described archives became an obvious priority of the NDA team[START_REF] Lamy | [END_REF];[START_REF] Cecconi | Digitizing analogic spectrograms recorded by the Nançay Decameter Array on 35mm film rolls from 1970 to[END_REF].

https://observations-solaires.obspm.fr/Les-heliographes

We thank the NDA team and especially P. Zarka and L. Denis for their precious memories. We also thank M.-P. Issartel for her long-lasting inventory work, S. Cnudde for his pictures of the archives and design work of the webpage, C. Colon for her unvaluable work on budgetary aspects, I. Bualé for managing the solar archives in Meudon, C. Briand and S. Corbel for their support and L. Klein and J.-M. Malherbe for useful advice. We also acknowledge the work of the 'archive and legacy' commission at LESIA and PADC. We warmly thank C. Higgins, W. S. Kurth, E. Echer, A. Konovalenko and H. Rucker for their official support to this digitization project.

This work was funded by the GIS CollEx-Persée from the French Ministry of Higher Education and Research, the CNES (Centre National d'Etudes Spatiales) french spatial agency, the scientific council of the Observatory of Paris and its ESTERS (Environnement Spatial de la Terre : Recherche, Surveillance & Société) axis, the radio Observatory of Nançay and the LESIA laboratory.


Chukri Soueidi
email: chukri.a.soueidi@inria.fr

Yliès Falcone
email: ylies.falcone@inria.fr

Capturing Program Models with BISM

Keywords: Theory of computation → Regular languages, • Software and its engineering → Software verification, Dynamic analysis, Runtime Verification, Typestate Analysis, Parametric Monitoring, Instrumentation, Java Bytecode, Control Flow

Capturing program models with BISM

Chukri Soueidi, Yliès Falcone

INTRODUCTION

Runtime verification (RV) [START_REF] Bartocci | Introduction to Runtime Verification[END_REF][START_REF] Falcone | A Tutorial on Runtime Verification[END_REF][START_REF] Falcone | A taxonomy for classifying runtime verification tools[END_REF][START_REF] Havelund | Verify Your Runs[END_REF][START_REF] Leucker | A brief account of runtime verification[END_REF]] is a formal method that allows verifying a run of a system with respect to a specification. The specification usually formalizes a correctness property and is written in a suitable formalism based for instance on temporal logic or finitestate machines. Runtime verification can complement and has been used in combination with other formal static verification methods such as model checking [START_REF] Leucker | Sliding between Model Checking and Runtime Verification[END_REF], deductive verification [START_REF] Jesús | Starvoors: A tool for combined static and runtime verification of java[END_REF] and static analysis [START_REF] Bodden | Partially Evaluating Finite-State Runtime Monitors Ahead of Time[END_REF], as well as informal dynamic methods such as testing [START_REF] Jesús | Testing Meets Static and Runtime Verification[END_REF] and debugging [START_REF] Jakse | Interactive Runtime Verification -When Interactive Debugging Meets Runtime Verification[END_REF]. While a complete a priori verification is ideally desirable for verifying program correctness, proving the correctness of many properties is fundamentally undecidable statically. However, static verification often relies on conservative approximations that produce sound results (i.e. should not give incorrect results) sacrificing completeness. Combining static and runtime verification for a more complete verification scheme seems natural. For static verification, it improves completeness by deferring verification of undecidable fragments until runtime. For runtime verification, it reduces the overhead of monitoring by pruning pieces of the program that can be statically analyzed.

Several approaches and tools have been presented that combine static and runtime verification [START_REF] Azzopardi | CLARVA: Modelbased Residual Verification of Java Programs[END_REF][START_REF] Bodden | Clara: a Framework for Statically Evaluating Finite-state Runtime Monitors[END_REF][START_REF] Bodden | Partially Evaluating Finite-State Runtime Monitors Ahead of Time[END_REF][START_REF] Jesús | Starvoors: A tool for combined static and runtime verification of java[END_REF]. Many of these approaches fall under residual analysis where a residual part that cannot be proven statically is left for monitoring at runtime. However, these tools are provided as specialized frameworks that specifically apply their own techniques. In this paper, we provide a basic block of such analyses that can be used freely within the aspect-oriented instrumentation tool BISM [START_REF] Soueidi | BISM: Bytecode-Level Instrumentation for Software Monitoring[END_REF]. Given that our chosen instrumentation tool BISM [START_REF] Soueidi | BISM: Bytecode-Level Instrumentation for Software Monitoring[END_REF] facilitates combining static and dynamic analysis, our work can be used in the context of different combination approaches.

We see our contributions as follows. We present an extension of the Java bytecode instrumentation tool BISM [START_REF] Soueidi | BISM: Bytecode-Level Instrumentation for Software Monitoring[END_REF] that captures and prepares a program model that abstracts the program behavior at the intra-procedural level. We analyze a program method and construct a control-flow graph automaton where the states represent actions of the program that produce events we are interested in. Directed towards monitoring general behavioral properties at runtime, the resulting model is presented for the users to write static analyzers and combine both static and runtime verification. For instance, this model that represents the control-flow graph can help in finding code paths that can never influence the monitors.

The rest of this paper is structured as follows. Section 2 motivates our approach with a running example. Section 3 reviews the background. Section 4 describes how we capture program models. Section 5 gives a brief summary about our tool implementation. Section 6 discusses the related work. Section 7 concludes and presents some perspectives.

MOTIVATING EXAMPLE

We start by introducing our running example of a Java program. We are interested in monitoring the SafeIterator property which specifies that "A collection should not be updated when an iterator associated with it is being used". A violation of the property can be expressed by 𝑐.𝑛 * .𝑢 + .𝑛, where the 𝑐 event captures a creation of a Iterator, the 𝑢 captures any modification on the list, and 𝑛 captures a call to next() on the iterator.

Figure 1, shows a contrived Java method that creates a list (line 3), updates it (lines 4, 10, 11), creates an iterator (lines 5, 16), and calls "next" operation on the iterator (lines [START_REF] Hopcroft | Introduction to Automata Theory, Languages, and Computation[END_REF][START_REF] Leucker | Sliding between model checking and runtime verification[END_REF]. The figure also shows the control-flow graph (CFG) for method m, where basic blocks are labeled with the line numbers of the instructions they contain.

By observing the program we can see that, at runtime, it may violate the property in one execution path where the program enters the if block, labeled [START_REF] Falcone | A Tutorial on Runtime Verification[END_REF][START_REF] Falcone | A Taxonomy for Classifying Runtime Verification Tools[END_REF] in the graph. More precisely, a violation can occur if someflag evaluates to true. Moreover, from the control-flow graph one can see that there are some relevant instructions that are insignificant in deciding the violation of a property such as lines 16 and 17, as well as line 4. Hence any analysis aiming to statically verify the SafeIterator property needs to obtain a model from the control flow graph and consider the different possible execution paths.

BACKGROUND

We assume basic familiarity with automata theory in particular the definition of a finite-state machine and refer to [START_REF] Hopcroft | Introduction to Automata Theory, Languages, and Computation[END_REF] for more details.

BISM. BISM (Bytecode-Level Instrumentation for Software Monitoring) [START_REF] Soueidi | BISM: Bytecode-Level Instrumentation for Software Monitoring[END_REF] is a lightweight bytecode instrumentation tool for Java programs that features an expressive high-level instrumentation language. It is inspired by AOP and adopts an instrumentation model that is more directed towards runtime verification. BISM is controlflow aware. That is, it generates CFGs for all methods and provides access to them in its language. Moreover, BISM provides several control-flow properties, such as capturing conditional jump branches and retrieving successor and predecessor basic blocks. Such features can provide support to tools relying on a control-flow analysis.

Control-flow Graphs. Given a program, we denote by Methods the set of all methods in the program, and by Instructions the set of all byte-code instructions. Moreover, let Instructions m represent all instructions of a method 𝑚 in Methods. The CFG of a method is a directed graph where nodes are basic blocks of instructions and edges represent jumps in the control flow. Given a CFG m = ⟨Blocks m , Edges m ⟩ for a method 𝑚 in Methods, where Blocks m is the set of basic blocks, and Edges m ⊆ Blocks m × Blocks m . For a basic block 𝑏 in Blocks m , the sequence of instructions in the block is denoted by 𝑏.𝑖𝑛𝑠𝑡𝑟 , and 𝑏.𝑒𝑛𝑡𝑟𝑦 (resp. 𝑏.𝑒𝑥𝑖𝑡) is a Boolean which holds true if 𝑏 is the entry block (resp. is an exit block).

Instrumentation. In runtime verification, the program is instrumented to generate traces of events. Given a property defined over alphabet Σ, the instrumentation of an instruction to generate an event is given by function instrument : Instructions → Σ. The function instrument is usually specified in the language of the instrumentation tool where the user specifies which joinpoints in the program execution produce the events.

CAPTURING PROGRAM MODELS

In this section, we demonstrate how we capture the behavior of methods using their control-flow graphs provided to us by BISM. This section describes how we first map instructions in the CFG to events, then how we split the CFG nodes such that each node represents an event, finally how we construct a CFG Automaton that represents the behavior of the method.

Preparing the CFG

For each method 𝑚 in Methods, we map two types of instructions to events and discard all other instructions as they are irrelevant to our analysis.

We keep instructions that produce events in Σ, given by the function instrument specified by the user. We also keep instructions that may allow any variable to escape from 𝑚 and introduce the new escape event (#) for such instructions. More precisely, these are invocations to sub-methods that pass on objects as arguments. However, our analysis allows the user to specify a safe list of instructions, denoted by the set SafeList, defined over the compile type information of methods and instructions. Such information includes method names, package and type names, and opcodes. All instructions that are escape events and are not in SafeList are added to the set Esc m .

Given the alphabet of a property Σ and the control-flow graph CFG m = ⟨Blocks m , Edges m ⟩, then for all 𝑏 in Blocks m , we replace it with 𝑏 ′ and map the instructions to events as follows.

𝑏 ′ .𝑖𝑛𝑠𝑡𝑟 = 𝑏.𝑖𝑛𝑠𝑡𝑟 .map 𝑖 ↦ →        𝑖 if instrument (𝑖) ∈ Σ, # else if 𝑖 ∈ Esc m 𝜖 otherwise
That is, we erase all instructions we are not interested in and replace them with 𝜖, and keep the others intact. Method calls that are not in SafeList are replaced by escape events #.

We now proceed in splitting the nodes of CFG m such that each remaining instruction is represented in a unique node containing its mapped event. We modify the control-flow graph, by constructing a new graph as follows.

Definition 4.1 (Split CFG). Given the CFG m = ⟨Blocks m , Edges m ⟩ with instructions mapped to events, we construct a new modified graph SG 𝑚 = ⟨𝐵 𝑚 , 𝐸 𝑚 ⟩ as follows:

𝐵 𝑚 = 𝑏 ∈ Blocks m split(𝑏) , (1)
𝐸 𝑚 = { ⟨𝑏 ′ , 𝑏 𝑖 ⟩ | ⟨𝑏 ′ , 𝑏⟩ ∈ Edges m , 𝑏 𝑖 ∈ split(𝑏) : idx 𝑏 (𝑖) = 0 } (2) ∪ { ⟨𝑏 𝑖 , 𝑏 𝑗 ⟩ | 𝑏 𝑖 , 𝑏 𝑗 ∈ split(𝑏) : 0 ≤ idx 𝑏 (𝑖) < |𝑏.𝑖𝑛𝑠𝑡𝑟 | -1 ∧ idx 𝑏 ( 𝑗) = idx 𝑏 (𝑖) + 1 } (3) ∪ { ⟨𝑏 𝑖 , 𝑏 ′ ⟩ | ⟨𝑏, 𝑏 ′ ⟩ ∈ Edges m , 𝑏 𝑖 ∈ split(𝑏) : idx 𝑏 (𝑖) = |𝑏.𝑖𝑛𝑠𝑡𝑟 | -1 } (4)
where:

• idx 𝑏 : 𝑏.𝑖𝑛𝑠𝑡𝑟 → N returns the index of an instruction in a block 𝑏. • split : Blocks m → 2 Blocks m defined as split(𝑏) = {𝑏 𝑖 | 𝑖 ∈ 𝑏.𝑖𝑛𝑠𝑡𝑟 } is a function that splits a basic block into multiple nodes, such each one contains an instruction, 𝜖 or the escape event #. The first node of an entry block is set as the entry node and the last node of an exit block is set as the the exit node.

The newly created graph, SG 𝑚 , is constructed as follows. All basic blocks in CFG m are split into multiple nodes, one node per instruction [START_REF] Azzopardi | CLARVA: Modelbased Residual Verification of Java Programs[END_REF]. All incoming edges to an original block, are connected to the node representing the first instruction of the original block [START_REF] Bartocci | First international Competition on Runtime Verification: rules, benchmarks, tools, and final results of CRV 2014[END_REF]. All nodes that are created from a single original block are connected sequentially [START_REF] Bartocci | Introduction to Runtime Verification[END_REF]. All outgoing edges from the original block are now outgoing from the last split node [START_REF] Bodden | Clara: a Framework for Statically Evaluating Finite-state Runtime Monitors[END_REF].

A node in the new graph SG 𝑚 contains one letter which represents: either an instruction that generates events in Σ, or an escape event #, or an 𝜖. The entry block in the new graph contains the first event of interest having 𝑏.entry equals true. We merge two consecutive nodes containing 𝜖, and move their edges accordingly.

Constructing the CFG Automaton

We now show how the CFG Automaton is constructed from the Split CFG SG 𝑚 . Definition 4.2 (CFG Automaton). Given the newly constructed graph SG 𝑚 = ⟨𝐵 𝑚 , 𝐸 𝑚 ⟩, the CFG Automaton is an NFA A 𝑐 𝑚 = (Σ ∪ {#}, 𝑄, 𝛿, 𝑞 0 , 𝐹 ) constructed as follows:

• 𝑄 = {𝑞 𝑏 | 𝑏 ∈ 𝐵 𝑚 } • 𝑞 0 = {𝑞 𝑏 | 𝑏 ∈ 𝐵 𝑚 ∧ 𝑏.entry = true } • 𝛿 = {⟨𝑞 𝑏 , 𝑠, 𝑞 𝑏 ′ ⟩ | ⟨𝑏, 𝑏 ′ ⟩ ∈ 𝐸 𝑚 ∧ 𝑏.instr = 𝑠} • 𝐹 = {𝑞 𝑏 | 𝑏 ∈ 𝐵 𝑚 ∧ 𝑏.exit = true }
Each node in the new control-flow graph is now represented as a state in the CFG Automaton. All nodes set as exit nodes are final states in the automaton. Correctness of Model Capture. The transitions in the automaton represent the execution of actions in the program. Any execution of the target program filtered out on the alphabet Σ is a sequence of the CFG Automaton. However, if there exist escape events #, each event must be replaced by Σ * . That is since we handle methods separately, any variable escaping the method might be producing events elsewhere in the execution. In other words, the set of executions in the CFG Automaton is a superset of the executions of the initial program filtered. And, the CFG Automaton over-approximates the behavior of the method it has been constructed from.

IMPLEMENTATION

We implement our work as a plugin (1 KLOC) to the BISM [START_REF] Soueidi | BISM: Bytecode-Level Instrumentation for Software Monitoring[END_REF] Java byte-code instrumentation tool. To implement our work, we extend BISM with a module that generates the CFG Automata as described in the previous sections.

Using the BISM language, the user selects the joinpoints that produce events in a BISM transformer. For each method in the base program with selected joinpoints, the module queries BISM to retrieve its control-flow graph. BISM provides the CFG with an API to traverse it and visit each basic block and instruction. Our module handles the creation of the CFG Automaton of the method, by first erasing all irrelevant instructions from the blocks and then mapping the relevant ones to events in the alphabet of the property. The blocks are then split such that each state in the automaton represents the generation of one event at runtime. The module also includes methods to run the automaton as well as basic automata operations that allow performing language intersection, complement, and union.

RELATED WORK

We position our work in the direction of combining static and runtime verification. Any tool to merge both verifications would benefit from the ability to perform static analysis while also having an abstract and aspect-oriented instrumentation language. Writing static analysis can be done with bytecode manipulation libraries such as ASM [START_REF] Bruneton | ASM: A code manipulation tool to implement adaptable systems[END_REF], BCEL [START_REF]Apache Commons[END_REF], Javassist [START_REF] Chiba | Load-Time Structural Reflection in Java[END_REF] and Soot [START_REF] Vallée-Rai | Soot: A Java Bytecode Optimization Framework[END_REF]. However, these tools are often too low-level, making the instrumentation too verbose and error-prone. For Java programs, runtime verification tools [START_REF] Bartocci | First international Competition on Runtime Verification: rules, benchmarks, tools, and final results of CRV 2014[END_REF][START_REF] Falcone | A Taxonomy for Classifying Runtime Verification Tools[END_REF] have long relied on AspectJ [START_REF] Kiczales | Getting started with AspectJ[END_REF], which is one of the most adopted AOP implementations for Java. AspectJ cannot capture bytecode instructions and basic blocks joinpoints, and implementing a static analyzer often requires extending its underlying compiler. DiSL [START_REF] Marek | DiSL: a domain-specific language for bytecode instrumentation[END_REF] is a bytecode instrumentation framework that enables flexible low-level instrumentation and, at the same time, provides a high-level language. However, static analyzers in DiSL can be run only before the main DiSL instrumentation process, and the developer still needs to revert to low-level bytecode manipulation frameworks to implement them. We choose to extend BISM because it offers both capabilities, of writing static analyzers as well as aspectoriented instrumentation for runtime verification, as part of its main workflow. Several approaches and tools have been presented that combine static and runtime verification and rely on the control flow to perform the analysis. We mention CLARA [START_REF] Bodden | Clara: a Framework for Statically Evaluating Finite-state Runtime Monitors[END_REF][START_REF] Bodden | Partially Evaluating Finite-State Runtime Monitors Ahead of Time[END_REF], CLARVA [START_REF] Azzopardi | CLARVA: Modelbased Residual Verification of Java Programs[END_REF], STARVOORS [START_REF] Jesús | Starvoors: A tool for combined static and runtime verification of java[END_REF] and the approaches [START_REF] Leucker | Sliding between model checking and runtime verification[END_REF][START_REF] Zhang | Runtime verification with predictive semantics[END_REF]. However, these tools are provided as specialized frameworks that specifically apply their own techniques. Our approach is generic and purposed to serve as a basis to implement static analysis on program behavior.

CONCLUSION AND PERSPECTIVES

This paper introduces a fully implemented extension of BISM which allows capturing the CFG Automaton of methods. Directed towards monitoring general behavioral properties at runtime, the resulting model is presented for the users to write static analyzers and combine both static and runtime verification.

We aim to incorporate more static analysis techniques, such as static call graph construction, data-flow, pointer, and escape analysis, to reduce the over-approximation of the constructed model and increase precision. We see our presented work as an essential building block of a framework that we plan to develop to democratize merging static and runtime verification. We will start by incorporating residual runtime verification targeting parametric monitoring. The work will be extended to identify safe regions in methods with respect to bad prefixes of the monitored properties. Identifying safe regions allows not instrumenting the associated code regions. A second perspective is to leverage the over-approximation of the program behavior to implement effective predictive runtime verification [START_REF] Pinisetty | Predictive runtime verification of timed properties[END_REF][START_REF] Zhang | Runtime verification with predictive semantics[END_REF] and enforcement [START_REF] Pinisetty | Predictive runtime enforcement[END_REF] approaches for Java programs.

Figure 1 :

 1 Figure1: A method using an Iterator in Java, and its CFG.

Example 4 . 3 (

 43 CFG Automaton).

Figure 2 ,

 2 shows the CFG Automaton constructed from the Java program from Section 2. Each state corresponds to an instruction that we are interested in the program. State 0 to line 4, state 1 to line 5, state 2 and 3 to lines 10 and 11, state 4 to line 14, state 5 to line 16, state 6 to line 17.

Figure 2 :

 2 Figure 2: The constructed CFG Automaton A 𝑐 𝑚


Mathias Bruyand

Rodolphe Thiébaut

Sylvie Lawson-Ayayi

Pierre Joly

Annie-Jeanne Sasco

Patrick Mercié

Jean Luc Pellegrin

Didier Neau

François Dabis

Philippe Morlat

Rodolphe Thi

Patrick Merci

Jean Luc Pellegrin

Fran Ois Dabis

Genevi Ve Ch

Fabrice Bonnet

S Geffard

G Palmer

D Touchard

M Dupon

M Longy-Boursier

J M Ragnaud

Role of uncontrolled HIV RNA level and immunodeficiency in the occurrence of malignancy in HIV-infected patients during the combination antiretroviral therapy era: Agence Nationale de Recherche sur le Sida (ANRS) CO3 Aquitaine Cohort

Keywords: Adult, CD4 Lymphocyte Count, Cohort Studies, Female, Follow-Up Studies, HIV Infections, complications, immunology, Humans, Incidence, Male, Middle Aged, Models, Statistical, Multivariate Analysis, Neoplasms, epidemiology, RNA, Viral, blood, Viral Load HIV, malignancy, risk, immunodeficiency, CD4+ count ' Data management

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Conclusions

Uncontrolled plasma HIV RNA was independently associated with a higher likelihood of developing AIDS-defining malignancies, while immunosuppression was associated with a higher risk of developing any types of malignancies. Antiretroviral treatment should aim at reaching and maintaining a CD4 count >500/mm to prevent the occurrence of malignancy, this should be integrated to

Introduction

The association between HIV infection and the occurrence of certain types of malignancies has been established for a long time .

[1 ]

Due to their high incidence rates among HIV-infected patients, Kaposi s sarcoma (KS), non-Hodgkin s lymphoma (NHL) and invasive ' ' cervical cancer are considered as AIDS-defining malignancies . Their high incidence may be explained by cellular immunosuppression

[2 ]
and chronic infection with oncogenic viruses , . Since 1996, the substantial improvement in survival after HIV infection related to the [1 3 ] increasing use of combination antiretroviral therapy (cART) has been associated with changes in the spectrum of HIV morbidity and mortality . Indeed, the incidence of non-AIDS-defining malignancies among people living with HIV is two to three times higher than [4 -6 ] within the general population and malignancies, whether AIDS-defining or not, have become the most frequent cause of death in HIV-infected patients . Such an increase in the proportion of deaths due to malignancies may be explained by prolonged survival, [6 -8 ] overall ageing of the HIV-infected population and a decreasing mortality related to opportunistic infections . The high prevalence [9 -13 ] of traditional risk factors for malignancies, such as tobacco or alcohol consumption, infection with hepatitis B virus (HBV) or hepatitis C virus (HCV) will act as contributing factors . In addition, the role of HIV related immunosuppression as a specific risk factor for [14 -16 ] non-AIDS-defining malignancies is strongly suspected, and a relationship between the risk of hepatocarcinoma and HIV related immunosuppression was recently shown . Furthermore, a direct role of HIV in the occurrence of malignancies is suggested .

[17 ] [18 -22 ] Finally, as exposure to immunodeficiency or uncontrolled plasma HIV RNA viral load can be considered as cumulative over the time or current, it remains unclear which type of exposure should be considered in assessing the risk of malignancy. Our objective was to investigate the association between the occurrence of a first malignancy in HIV-infected patients and the immuno-virological characteristics observed over time in a large cohort of HIV-infected patients in care, in which malignancies are prospectively recorded.

Methods

Study population

Data collected between January were not included in this study.

Risk factors and outcomes

The primary outcome was a confirmed diagnosis of a first malignancy during the follow-up period. All cases were validated through histological reports or source medical files documenting the diagnosis. The following time-updated variables were considered: time spent with a CD4 cell count less than two pre-defined thresholds; latest available CD4 cell count; time spent with plasma HIV RNA above

+ +
two pre-defined thresholds; latest available plasma HIV RNA measurement; duration of cART exposure and latest cART prescription. We considered 200 CD4 /mm as a marker of severe immunosuppression and 500 CD4 /mm as a marker of immune restoration . We

+ 3 + 3 [24 ]
used 500 copies/mL as the lowest threshold of plasma HIV RNA that could be detected throughout the 10-year study period. We also considered the threshold of 10,000 copies/mL as a high level of HIV replication. To estimate the time spent with plasma HIV RNA above the defined thresholds, we assumed that the value of the measurement reported at a given follow-up visit remained stable until the next follow-up visit. We made the same assumptions to estimate the time spent in each CD4 cell count category and the duration of cART + exposure. When plasma HIV RNA or CD4 cell count value was missing at a recorded follow-up clinic visit, it was estimated using the + last observation carried forward method. Missing values were counted as such when the delay between the last available value and the missing one was >6 months. cART was defined as a regimen including at least three antiretroviral drugs.

Statistical analysis

Proportional hazards regression models with delayed entry were used to estimate the association between time-updated variables, gender, and the risk of occurrence of a first new diagnosis of malignancy for a given patient during the study period. Age was the baseline time as, in such a Cox model, we assume that the risk of malignancy is strongly age dependent. However, this introduces a left truncation problem and we considered a delayed entry at the date of the follow-up visit reporting the first plasma HIV RNA after January 1 , 1998. The main analyses considered separately AIDS-defining malignancies and non-AIDS-defining malignancies, while robustness analyses considered KS and NHL.

In the models taking into account the latest measurement, plasma HIV RNA and CD4 cell count were considered as binary variables + (higher or lower than the threshold considered), and cART was considered as prescribed or not. All adjusted models considered the following variables: CD4 cell count lower than the threshold pre-specified in the model (duration of exposure or latest measurement), + plasma HIV RNA higher than the threshold considered in the model (duration of exposure or latest measurement), cART exposure (duration of exposure or last prescription) and gender. In addition to the latest values of plasma HIV RNA and CD4 cell count, + representing the current exposure, we calculated a cumulative exposure to clinically relevant cut-offs of these markers as malignancy usually occurs after a long exposure to potential determinants and current values might be a consequence rather than a cause of malignancy. Both types of summary statistics are studied in separate models since they are highly correlated. The models were compared with the Akaike criterion (AIC), the lower the better fit. In all analyses, patients affected by a malignancy that was not included in the outcome definition were right-censored at the time of the diagnosis. This means that the follow-up of patients affected by an AIDS-defining malignancy was right-censored while the hazard of non-AIDS-defining malignancies was estimated. As a history of malignancy was an exclusion criterion, no prevalent cases were included.

Due to incomplete data regarding traditional risk factors for non-AIDS malignancies (tobacco consumption, HBV and HCV infections), they were not considered in the analyses performed on the entire dataset. Hence, a robustness analysis adjusted for these risk factors, considering them as fixed-effect variables, was conducted on patients with available data concerning tobacco consumption, HBV and HCV infections. SAS software (version 9.1, SAS Institute, Cary, NC) was used to perform the analyses.

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Results

During the study period 4,828 patients were followed-up in the ANRS CO3 Aquitaine Cohort, 324 of them had a diagnosis of malignancy at study entry and were excluded from the analyses. In addition, 310 patients did not meet the study inclusion criteria. Thus, among 4,194 eligible patients, accounting for 22,389 person-years (py), 251 first new diagnosis of malignancy were validated through histological (111 cases) or medical reports (140 cases). The cohort was predominantly male (72 ), the 144 non-AIDS-defining % malignancies and the 107 AIDS-defining malignancies were experienced by 83 and 78 men. The incidence rates of AIDS-defining shows the distribution of malignancies and the characteristics of these patients.

% -

Table 1 Among the 97,893 follow-up visits recorded during the study period, 5,033 concerned patients affected by a malignancy. At least two plasma HIV RNA and CD4 measuremens were reported among 4,145 patients (240 malignancies) and 4,155 patients (241 malignancies), respectively.

AIDS-defining malignancies

Both CD4 <200 cells/mm and plasma HIV RNA viral load >500 copies/mL were strongly and independently associated with a + 3 higher risk of AIDS-defining malignancy, whatever the type of exposure considered (cumulative or current:

). Each additional year table 2 of exposure to cART was associated with a lower risk of AIDS-defining malignancy, while current exposure to cART and gender were not related to the hazard of AIDS-defining malignancy (

). table 2 Sixty-one cases of NHL were diagnosed over the study period among the 4,194 patients included, accounting for 57 of all diagnoses % of AIDS-defining malignancies. Current exposure to both plasma HIV RNA viral load >500 copies/mL and CD4 <200 cells/mm was -Considering the cumulative exposure, each year spent with plasma HIV RNA viral load >500 copies/mL and CD4 <200 cells/mm + 3 was independently associated with a higher risk of NHL: HR 1.34 (95 CI: 1.19 1.51; p <0.001) and HR 1.31 (95 CI: 1.12 1.53; p = % -= % -<0.001), respectively; whereas each year of cART exposure was associated with a lower risk of NHL: HR 0.86 (95 CI: 0.75 0.98).

= % -

In another adjusted model, each year spent with a plasma HIV RNA viral load >10,000 copies/mL was associated with a higher hazard of NHL (HR 1.59; 95 CI: 1.38 1.83; p <0.001), while each year spent with a CD4 <200 cells/mm and each year of cART exposure = % -+ 3 tended to be associated with a higher risk (HR 1.18; p 0.057) and a lower risk of NHL (HR 0.88; p 0.052), respectively. Thirty-nine

= = = =
cases of KS were reported among the 4,194 patients, accounting for 36 of the AIDS-defining malignancies diagnosed. Multivariable % analyses considering cumulative exposure showed that each year spent with CD4 <200 cells/mm was associated with a higher hazard of

Non-AIDS-defining malignancies

A CD4 cell count <500 cells/mm was independently associated with a higher hazard of non-AIDS-defining malignancy, whatever

+ 3
the exposure considered ( ). Plasma HIV RNA and cART were not associated with the risk of non-AIDS-defining malignancy, table 3 whatever the model considered, while female gender was related to a lower hazard ( ). Analyses using higher thresholds for plasma table 3 HIV RNA and considering the cumulative exposure led to similar results (data not shown). In analyses considering lower thresholds for CD4 cell count, each year spent with CD4 <200 cells/mm was independently associated with a higher risk of non-AIDS-defining Adjustment for other risk factors of malignancy Among 3,210 patients with available data regarding tobacco consumption and HBV or HCV co-infection status, 113 non-AIDS-defining malignancies occurred.

The thresholds considered were 500 copies/mL for plasma HIV RNA and 500 cells/mm for CD4 . The results of these analyses 3 + adjusted for gender, CD4 cell count, HIV RNA, cART, tobacco consumption, HBV and HCV co-infections are presented considering two + durations of cART exposure because of an interaction between the durations with CD4 <500 cells/mm and cART exposure (p 0.02). A + 3 = longer exposure to CD4 cell count <500 cells/mm remained associated with a higher risk of non-AIDS-defining malignancy (HR 1.26

+ 3 =
per each additional year, 95 CI: 1.07 1.50; p 0.007) in patients who remained free of cART. This association no longer existed among

% - =
cART treated patients (p 0.12 after 4 years of cART exposure).

= Moreover, our results were not affected by robustness analysis considering the transmission group, whatever the type of malignancy considered.

Comparison between cumulative and current exposure

The difference in AIC between the model taking into account the current exposure to latest measurement compared to the model considering the cumulative exposure ( and ) could be considered as negligible in each instance . tables 2 3

[27 ]

Discussion

Immunodeficiency is known to be associated with a higher hazard of AIDS-defining malignancy and our results are in accordance with this body of knowledge. Moreover, our study shows that HIV replication, as both current and cumulative exposure to uncontrolled plasma HIV RNA viral load were associated with a higher hazard AIDS-defining malignancy, has a major impact on the risk of occurrence of AIDS-defining malignancies, particularly NHL. This suggests that the control of plasma HIV RNA is a key factor to prevent NHL occurrence, at all stages of immune deficiency. HIV replication, through activation of the immune system, could be independently involved in the occurrence of NHL in patients with high CD4 cell counts . The fact that exposure to cART was only associated with a + [START_REF] Deeks | Immune activation set point during early HIV infection predicts subsequent CD4 T-cell changes independent of viral load +[END_REF] lower risk of AIDS-defining malignancy needs to be further explored. However, it is difficult to disentangle the proper effect of cART, immune deficiency and viral replication and one may speculate that the absence of significant association between cART exposure and non-AIDS-defining malignancy is linked to the absence of association with HIV replication. Thus, the potential benefit of cART for controlling non-AIDS-defining malignancy might be due to immune reconstitution rather than control of viral replication per se. In other hand, both longer and current exposure to uncontrolled plasma HIV RNA and immunosuppression were associated with a higher risk of AIDS-defining malignancy, underlining that the best possible control of HIV infection is warranted to prevent AIDS-defining malignancies and especially NHL occurrence.

Several cohort studies have shown a higher risk of non-AIDS-defining malignancy in HIV-infected patients when compared with the general population but none of them considered the duration of exposure to immunodeficiency , , , . Another large study failed [9 11 12 29 ] to show any relationship between immunodeficiency at AIDS diagnosis and the risk of malignancy . Our results are consistent with a [START_REF] Frisch | Association of cancer with AIDS-related immunosuppression in adults[END_REF] higher incidence of non-AIDS-defining malignancies observed in solid organ transplant recipients, chronically exposed to immunosuppressive therapy, indirectly suggesting that immunodeficiency is independently associated with a higher risk of non-AIDS-defining malignancies in HIV-infected patients , . Furthermore, our results regarding the latest CD4 cell count showed [31 32 ] + that current immunodeficiency may be involved in the risk of malignancy. This suggests that, following a prescription of cART, the risk of malignancy may decrease when the CD4 cell count rises above 500 cells/mm . Our results regarding cumulative exposure to CD4 <500 + 3 + cells/mm conveys important additional results, since they suggest that patients with longstanding immunodeficiency experience a higher 3 rate of malignancy compared to patients without immunodeficiency. This could help to target a high risk population to implement prevention and screening policies.

Based on Akaike criterion, our analysis does not indicate a particular advantage of cumulative exposure to low CD4 cells in + comparison to the latest CD4 cell count for both AIDS-defining and non-AIDS-defining malignancies. However, the consistent finding of + a raised risk of AIDS and non-AIDS-defining malignancies associated with cumulative time spent below CD4 < 200/mm or 500/mm

+ 3 3
provides a stronger argument that HIV infected patients may benefit from early initiation of antiretroviral treatment to decrease the risk of AIDS and non-AIDS-defining malignancies.

Burgi et al found that the use of cART was protective for malignancies, and the D:A:D cohort collaboration found that the [START_REF] Burgi | Incidence and risk factors for the occurrence of non-AIDS-defining cancers among human immunodeficiency virus-infected individuals[END_REF] incidence of fatal non-AIDS malignancies was related to exposure to cART . Our main objective was not to estimate the independent [START_REF] Arminio Monforte | Malignancy-related deaths among HIV-infected patients[END_REF] effect of cART exposure on the risk of malignancy, and further studies including more patients should specifically address this issue.

However, our results show that early control of HIV replication and maintenance of high levels of CD4 cell count are associated with + lower risk of malignancies.

The incidence rate of non-AIDS-defining malignancies was higher in men than in women, as it is commonly observed in the general population in France . [START_REF] Remontet | Cancer incidence and mortality in France over the period 1978 2000[END_REF] Due to incomplete data regarding the risk factors for non-AIDS-defining malignancies (tobacco consumption, HBV or HCV infections), we could not take these risk factors into account in the analyses of the entire cohort. However, these confounding factors were controlled for in analyses estimating the risk of non-AIDS-defining malignancy in a large subgroup of patients free of missing values concerning these data. The association between immunosuppression and the occurrence of specific non-AIDS-defining malignancies could not be explored in this study. We acknowledge that larger number of cases is needed to reach larger statistical power to adequately address this issue for each type of non-AIDS-defining malignancy.

Finally, our study showed that exposure to uncontrolled plasma HIV-RNA was associated with a higher risk of AIDS-defining malignancy, regardless of CD4 cell count and the use of cART. Furthermore, immunodeficiency was associated with a higher risk of + malignancy, whether AIDS-defining or not. Considering the global ageing of the HIV-infected population in developed countries, malignancy, which is already one of the main causes of mortality, is likely to become the first clinical and public health challenge in the long-term management of HIV-infected patients.

According to our observations, the objective of cART should aim at reaching and maintaining not only an undetectable plasma HIV RNA, but also a CD4 cell count higher than 500 cells/mm to prevent the occurrence of malignancy, AIDS-defining or not. In HIV + Footnotes:

These results were presented in part at the [START_REF] Friis-Moller | Cardiovascular disease risk factors in HIV patients--association with antiretroviral therapy. Results from the DAD study[END_REF]

3 =

 3 Patients consecutively enrolled in the hospital based ANRS CO3 Aquitaine Cohort were included if their follow-up was >3 months between 1998 and 2006. Multivariate modelling used an extended Cox proportional hazards models for time-dependent covariates and delayed entry. Results The 4,194 patients included developed 251 first malignancies during 22,389 person-years. A higher incidence of AIDS-defining malignancies (107 cases) was independently associated with: (i) both longer and current exposures to plasma HIV RNA >500 copies/ml: Hazard ratio HR 1.27 per year; p<0.001 and HR 3.30; p<0.001, respectively, and (ii) both longer and current exposure to cases) was independently associated with longer and current exposure to CD4 count<500/mm (HR 1.13 per year; + p 0.01 and HR 2.07; p<0.001, respectively), and male gender (HR 1.69; p 0.02) but not plasma HIV RNA (p 0.49 and p 0.10 for

st

  In these survival analyses, the risk of malignancy is estimated as a function of ageing and age is not included as a variable in the models [ , . Patients without a diagnosis of malignancy and still alive on December 31 , 2006 were right-censored at the date of their last 25 26 ] st follow-up visit. The proportional hazards assumption was checked graphically and by testing interactions between covariates and time for time-updated variables.

+ 3 independentlyCI: 3 .

 33 associated with a higher hazard of NHL: Hazard Ratio (HR) 3.02 (95 CI: 1.65 5.52; p <0.001) and HR 5.12 (95 01 8.70; p <0.001), respectively.

+ 3 KS (HR 1 .

 31 55, 95 CI: 1.24 1.93; p <0.001), whereas remaining with a plasma HIV RNA viral load >500 copies/mL did not affect the KS = % hazard (p 0.22). Female gender was associated with a lower incidence of KS (HR 0.13; 95 CI: 0.03 0.53; p 0.005).

  The incidence rates of non-AIDS-defining malignancies were 7.5 cases per 1,000 py (95 CI: 6.1 8.8) in men and 3.8 cases

	%	%
	malignancies were 5.2 cases per 1,000 py (95 Confidence Interval CI : 4.1 6.4) in men and 3.6 cases per 1,000 py (95 CI: 2.1 5.1) % [ ] -% -
	in women. %	-
	per 1,000 py (95 CI: 2.3 5.3) in women.

Table 1

 1 Conference on retroviruses and opportunistic infections (Hynes Convention center, Boston, th MA, US, February 3-6, 2008), abstract 15. Conflict of interest: M Bruyand: no conflict R Thi baut: no conflict é S Lawson-Ayayi: no conflict P Joly: no conflict A.J Sasco: no conflict P Merci : no conflict é JL Pellegrin: no conflict D Neau: no conflict F Dabis: no conflict P Morlat: no conflict G Ch ne: no conflict Characteristics of the 251 new cases of malignancy (ANRS CO3 Aquitaine Cohort, 1998 2006)

ê F Bonnet: no conflict -Type of malignancy All (n 251)

infected population, this should be integrated to malignancy prevention policies.

Ackowledgements:

Sponsorship:

The ANRS CO3 Aquitaine Cohort is supported by a grant from the Agence Nationale de Recherches sur le SIDA et les H patites Virales é (ANRS, France) within the Coordinated Action no. 7 (AC7).

Appendix Composition of the GECSA

The Groupe d Epidemiologie Clinique du Sida en Aquitaine (GECSA) steering the ANRS CO3 ' Aquitaine Cohort is organized as follows:

Epidemiology, Methodology M. Bruyand, G. Ch ne, F. Dabis (Principal Investigator), S. Lawson-Ayayi, R. Thi baut.