PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM RELEASE_ID = 0001 REVISION_ID = 0000 OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2014-07-16 NOTE = "Overview of the OMEGA archive volume" END_OBJECT = TEXT END Data Archive Mission Mars Express Experiment OMEGA (Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite) Archive manager Yves Langevin Institut d'Astrophysique Spatiale Batiment 121, 91405 Orsay Campus, France ========================================================================= INTRODUCTION ========================================================================= This archive contains the decommuted science data acquired by the OMEGA experiment since the launch of the Mars Express mission in June 2003. Data were first obtained during the Cruise phase (from the launch to Mars Orbit Insertion on the 23rd of December, 2003), then during the orbital phase. After insertion, the data are classified according to the orbit number around Mars. The archive is operated using the "release" concept, with a new release being generated every 100 orbits. This means that the OMEGA data archive consists in a single volume, regularly updated. ========================================================================= DATA SET INFORMATION ========================================================================= The primary data set is constituted by level 1B data files in the "cube" PDS format (.QUB), which have been generated by decommutation of the relevant OMEGA science packets, then decompression. All observations between a given switch-on, then switch-off of OMEGA constitute a group. Each observation with the same set of operational parameters constitutes an independent pds cube. During the cruise file, each data cube is named from its date: CRUISEYYYYMMDD_R.QUB where YYYY is the year, MM is the month and DD is the day R is the rank of the cube after switch-on, starting from 0, in hexadecimal format (0 to 9, then A to F) During the orbital file, each data cube is named from its orbit number: ORBNNNN_R.QUB where NNNN is the orbit number and R is the rank of the cube since switch-on. As there are up to 3.7 orbits per day, this scheme is valid until orbit 9999, more than 2800 days, nearly 8 years, which far exceeds the expected lifetime of the OMEGA coolers. The data files are classified into subdirectories of the /DATA directory: /DATA/CRUISE for the cruise data /DATA/ORBNN for the orbital phase data, where NN consists of the first two digits of the corresponding orbit numbers (orbit 1370 goes into /DATA/ORB13) A geometry cube is associated to each data file in the orbital phase. It contains information on the regions which have been imaged by each pixel for each of the three channels of OMEGA (VIS, IR-C, IR-L). The geometry cubes corresponding to the data files of the directory /DATA/ORBNN can be found in the directory /DATA/GEMNN The detailed description of the content of the data cubes and the geometry cubes can be found in the EAICD in the /DOCUMENT directory of the data set. The diagram below shows the organization of the volume, starting from the root of the compact disc. root | |- AAREADME.TXT |- VOLDESC.CAT | |- CATALOG | | | |- CATINFO.TXT PDS catalog files for | |- MISSION.CAT mission, host, instrument, | |- INSTHOST.CAT references | |- INSTRUMENT.CAT | |- REF.CAT | ... | |- DOCUMENT | | | |- DOCINFO.TXT Overview of directory | |- OMEGA_EAICD.HTM | |- OMEGA_EAICD_FIG1.PNG | |- OMEGA_EAICD_FIG2.PNG | |- OMEGA_EAICD_FIG3.PNG | |- OMEGA_EAICD.PDF | |- OMEGA_DESC.TXT | |- OMEGA_HK.TXT | |- OMEGA_CALIBRATION.TXT | ... | |- INDEX | | | |- INDXINFO.TXT Overview of directory | |- INDEX.LBL Label to INDEX.TAB | |- INDEX.TAB List of data file contents, this volume | ... | | SOFTWARE | | SOFT01.LBL | | SOFT01.ZIP | `- DATA | |- CRUISE |- ORB00 |- ORB01 | ... |- ORBNN |- GEM00 |- GEM01 | ... `- GEMNN ============================================================================== SOFTWARE ============================================================================== The data reduction process is extremely complex for imaging spectrometers, and variations with time of the instrument behavior have been observed (in particular, but not only, for the long wavelength IR channel). Therefore the approach selected by the OMEGA team is to provide level 1B data and releases of data reduction software which reflect the up to date knowledge of the instrument behavior. Given the very high signal to noise of OMEGA (up to 1000 and more), the understanding of instrumental effects such as registration, linearity, cross-talk or hysteresis is constantly being revised. Each new software release is constituted by a ZIP file and its label, which contains the list of zipped files. In each new software release, a new software_readme.txt file gives information on the new features and modified data reduction parameters an indication is also given on the level of confidence of the data reduction both in absolute and relative terms. THE USER IS EXPLICITELY WARNED TO TAKE HEED OF THESE INDICATIONS, AS THERE IS OTHERWISE A HIGH RISK OF JUMPING TO WRONG CONCLUSIONS On no account should the user consider that a final truth has been achieved when very small variations are under consideration. ============================================================================== COGNIZANT PERSONNEL ============================================================================== The persons most directly responsible for the support of this data set are Gilles Poulleau and Yves Langevin: Institut d'Astrophysique Spatiale Batiment 121 91405 Orsay Campus France Gilles Poulleau, telephone: 33-169858608 e-mail: gilles.poulleau@ias.u-psud.fr Yves Langevin, telephone: 33-169858681 e-mail: yves.langevin@ias.u-psud.fr