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<\/p>\nThe VVEx data service provides access to the VIRTIS \/ Venus-Express dataset with detailed description of each observation. Calibrated files are described by a variety of parameters retrieved from the PI team database, and are linked to ESA’s Planetary Science Archive (PSA). The detailed description allows for accurate searches in the dataset.<\/p>\n
The optical and infrared spectrometer VIRTIS was originally developed for the Rosetta mission. When the Venus-Express mission was designed, the spare model of VIRTIS was proposed and selected for the scientific payload. The instrument results from a collaboration between Italy (IAPS\/INAF providing the mapping channel VIRTIS-M), France (LESIA providing the high-resolution channel VIRTIS-H) and Germany (DLR providing the electronics and on-board sotfware).<\/p>\n
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The instrument was composed of two imaging spectrometers (M-vis and M-IR, 0.4-5 \u00b5m) and an echelle spectrometer providing 10x higher resolution in a single pixel (VIRTIS-H, 2-5 \u00b5m). VIRTIS operated in Venus orbit from June 2006 to October 2014, until the end of mission; the two IR channels stopped operations in 2011 at the end of cryocoolers lifetime. The dataset is distributed on ESA’s Planetary Science Archive (PSA) in PDS3 format.<\/p>\n
A Virtual Observatory (VO) data service has been setup to provide easier access to the dataset.<\/p>\n
Calibrated and geometry files (not raw data) are included for the whole mission except the cruise phase. Files are described with the most relevant parameters from the PI team database, including observing modes, location on planet, and illumination conditions. Files can be searched and selected based on these parameters. Selected thumbnails are provided for the two M channels.<\/p>\n
This data service is responsive to the EPN-TAP data access protocol, and can be queried from the VESPA portal of Solar System data: https:\/\/vespa.obspm.fr\/ Future prospects include the addition of derived products (maps, profiles, etc) from publications. Direct access to individual spectra with description is being evaluated. The use of a more handy data format (fits with embedded geometry) is also under study.<\/p>\n Important search parameters include: The result of a selection in the VESPA portal can be sent to various VO tools for analysis. However, PDS3 spectral cubes<\/strong> are notoriously difficult to read. Metadata<\/strong> are more easily handled, and can be sent to VO tools from the portal: Cube footprints<\/strong> are provided in MOC format in the “coverage” parameter. Footprints include only spectra intercepting the cloud layer (at 60 km) and are provided on top of this layer (i.e., pixels pointing above the clouds are not included in the footprints); beware that these MOC are limited in resolution and may look discontinued in some cases, in particular for H sessions. MOC can be used for 2D searches in tools such as Aladin or the VESPA geoportal.<\/p>\n A tutorial<\/a> is available to illustrate data handling of VVEx cubes in VO tools.<\/p>\n \u2022 The VIRTIS Venus-Express data are distributed on ESA’s Planetary Science Archive<\/a> (PSA) which has both a search interface and direct access through https <\/a>(called ftp access for historical reasons). It provides full access to the dataset, including raw data files, ancillary files (complete set of browse images, calibration files, instrument Spice kernels, etc) and documentation (catalogues, etc). Mission Spice kernels are available on another ftp server<\/a> as described here<\/a>. \u2022 A hands-on manual<\/a> to manipulate VIRTIS data has been produced for an ESA workshop in 2014. This goes with a tutorial<\/a> and solutions<\/a>.<\/p>\n Contact the helpdesk for comments: support.vespa@obspm.fr<\/a><\/p>\n _____________________<\/p>\n This data service is provided in the framework of the VESPA activity in Europlanet-2020 and\u00a0Europlanet-2024 by Paris Astronomical Data Centre (PADC).<\/p>\n The Europlanet 2020 and Europlanet 2024 Research Infrastructure projects have received funding from the European Union\u2019s Horizon 2020 research and innovation programme under grant agreements No 654208 & No 871149. Additional support was provided in France by the Action Sp\u00e9cifique Observatoire Virtuel and Programme National de Plan\u00e9tologie \/ INSU.<\/p>\n The VVEx data service provides access to the VIRTIS \/ Venus-Express dataset with detailed description of each observation. Calibrated files are described by a variety of parameters retrieved from the PI team database, and are linked to ESA’s Planetary Science … Continue reading
\n<\/a>See the complete data service<\/a> in VESPA (the schema name is vvex).<\/p>\nSearching for data files<\/h2>\n
\nc1 \/ c2<\/strong> \u2013 longitude and latitude of the FOV projected at the surface, with min and max values (bounding box for cubes) – the detailed footprint is also provided in MOC format under coverage<\/strong>, see below
\nincidence, emergence, phase<\/strong> \u2013 illumination angles on the surface
\ntarget_distance_min \/ max<\/strong> \u2013 measured along the line of sight (= PDS’ slant distance), <\/strong>related to spatial resolution
\nsolar_longitude_min \/ max<\/strong> \u2013 provides the season (= Ls)
\nlocal_time_min \/ max<\/strong> \u2013 provides local time at surface
\n<\/strong>time_min \/ max<\/strong> \u2013 time of acquisition (UTC, provided in Julian Days)
\nRA, Dec<\/strong> \u2013 sky coordinates, provided for inertial pointing mode
\ntarget_name<\/strong> \u2013 standard name of the objet, IAU spelling (a few observations are not related to Venus)
\nspectral_range_min \/ spectral_range_max<\/strong> \u2013 limits of the spectral range (given in Hz in the table)
\nspectral_sampling_step_min \/ spectral_sampling_step_max<\/strong> \u2013 accounts for binning mode
\ntime_exp_min \/ time_exp_max<\/strong> \u2013 global integration time , including on-board summing
\nmeasurement_type<\/strong> \u2013 measured quantity provided as a UCD (all data are calibrated in radiance)
\nsun_distance <\/strong>\u2013 controls the heating of atmosphere; required to calibrate in reflectance
\nscience_case_id<\/strong> \u2013\u00a0 relates to spacecraft operations
\nsc_pointing_mode<\/strong> \u2013\u00a0 provides pointing mode, related to science cases
\nchannel_id<\/strong> \u2013 identifies the 3 VIRTIS channels
\ngranule_gid<\/strong> \u2013 a tag to distinguish calibrated data from geometry files<\/p>\nDisplaying spectral cubes<\/h2>\n
\n\u2022 For on-line quicklook, APERICubes will receive data sent as “VIRTIS PDS cubes” from the portal. It will extract images and spectra, and can send the results in fits format to specialized tools (CASSIS or SPLAT-VO for spectra, Aladin or ds9 for images).
\n\u2022 For detailed analysis, the team software<\/a> accesses the data under IDL and its open source clone GDL – this is a versatile PDS3 library with special support for VIRTIS files.<\/p>\n
\n\u2022 TOPCAT will receive metadata sent as table, to display all sort of parameters, including footprints.
\n\u2022 Mizar can display bounding boxes (C1\/C2 parameters) in real time.
\n\u2022 Aladin can display footprints (“coverage” parameter) on Venus maps.<\/p>\nAccess to VIRTIS VEx data and documentation<\/h2>\n
\n\u2022 The PSA as a whole also has an EPN-TAP interface which allows for cross-searches between datasets. Data description and search parameters are common to all files in the PSA, and are less detailed than on the VVEx service.
\n\u2022 The VEx mission catalog<\/a> describes operations, events, and science goals during the course of the mission (this is the latest version, dated May 2015).
\n\u2022 The VIRTIS archive document (EAICD)<\/a> provides essential information about the instrument and dataset (other docs are included in the PSA archive).<\/p>\n![\"\"](\"https:\/\/sites.lesia.obspm.fr\/data-services\/files\/2017\/08\/logo_europlanet_0-300x136.jpg\"){kind=logo}
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