Data Set Overview:This data set contains neutral atmosphere temperature-pressureprofiles and ionospheric electron density profiles derived from 12Mars Express radio occultations spread over the first three years oforbital operations (2004-2007).The data set was created as a prototype for future data setscontaining a larger number of profiles.PARAMETERS:The neutral atmosphere profiles are ASCII tables containing values ofpressure, temperature, and number density (with uncertainties) as afunction of radius from the Mars center of mass, geopotential heightrelative to a reference model, latitude, longitude, and time. Pressure and temperature are derived using an inversion procedure; the resultsfor three starting conditions are included.The ionospheric profiles are ASCII tables giving electron numberdensity (and uncertainty), refractivity, and signal level as afunction of radius, latitude, longitude, and time.PROCESSING:Measurements of radio signal frequency/phase collected during anoccultation were corrected for known Doppler effects such as motion ofthe spacecraft and ground receiving station, for drift of thefrequency reference, and for effects of the intervening medium (suchas Earth?s atmosphere and ionosphere). The residual frequency shiftsare presumed to result from refractive bending by the atmosphere ofMars. Variation of the bending angle, ray asymptote, and refractivityof the neutral atmosphere are related by an Abel transform, which canbe inverted [FJELDBOETAL1971] using knowledge of the spacecrafttrajectory. If hydrostatic equilibrium and a mean molecular weightfor the atmosphere (primarily CO2) are assumed, number density,pressure, and temperature can be derived from the refractivity profileof the neutral atmosphere. For the ionosphere, the procedures aresimilar but assumptions such as hydrostatic equilibrium do not apply,so the details are more complicated. See also ESA publicationESA-SP-1291 for details.DATA:The data set comprises 12 neutral atmosphere temperature-pressureprofiles and 12 ionospheric electron density profiles derived fromMars Express radio occultation measurements collected in 2004-2007.These are example profiles created to test analysis and archivingprocedures, anticipating more profiles in future data sets.Profiles are stored in the DATA directory. Under the DATA heading are subdirectories OCC_ATMO and OCC_IONO, into which the neutralatmosphere and ionospheric profiles are divided. Under these twoheadings are directories which organize the data by year (2004, 2005,2006, and 2007). Under the yearly headings are directories with names DOY_ddd_ooo_yyyy, where ddd is the day of year, ooo is the orbitnumber for the measurements, and yyyy is the year.Each directory DOY_ddd_ooo_yyyy contains an ASCII table(extension *.TAB) which contains the temperature-pressure or electrondensity file. A companion PDS label (same file name, but *.LBLextension) describes the format and content of the table. A thirdfile with extension *.TXT gives supplementary information about theoccultation itself and some of the initial parameters used in theinversion process. A fourth file is the label for the file with thesupplementary information.The dataset, volume, directory, and file naming conventions aredescribed in MEX_MRS_RIU_IS_3050.PDF in the DOCUMENT directory of thisarchive.Coordinate Systems:Latitudes and longitudes are given in areo centric (east) longitudeand areo centric (north) latitude. As rotation rate for Mars thefollowing value was used: Omega : 7.088218081*10**-5 s**-1.Software:Since these are ASCII files containing high level science results,no software is needed to display or process these data, and none isincluded in the archive.Documents: The DOCUMENT directory contains files that provide documentation and supplementary information to assist in understanding and using the data products in the volume. MEX-MRS-RIU-IS-3050.PDF/ASC File naming convention for higher Science Products MEX-MRS-RIU-IS-3050 _APP.ASC File naming convention for higher Science Products Appendix, PDS Example labels M00SUMML03_OC1_040930000_05.TAB/LBL Additional information about first occultation season M00SUMML03_OC2_043430000_05.TAB/LBL Additional information about second occultation season M00SUMML03_OC3_052000000_05.TAB/LBL Additional information about third occultation season M00SUMML03_OC7_071150000_05.TAB/LBL Additional information about seventh occultation season MARS_OPS_LOGBOOK_04.PDF Operations logbook 2004 MARS_OPS_LOGBOOK_05.PDF Operations logbook 2005 MARS_OPS_LOGBOOK_06.PDF Operations logbook 2006 MARS_OPS_LOGBOOK_07.PDF Operations logbook 2007 MEX-MRS-IGM-MA-3008.PDF MaRS Users Manual.Media/Format: The archival data are written to hard discs for distribution.

Overview: Data in this archival data set have been processed as part of prototyping effort to test analysis and archiving procedures for reduced data from Mars Express radio occultation experiments. In general, this is a good data set.Review: This archival data set was reviewed by the MEX Radio Science Team prior to submission to the Planetary Science Archive (PSA).Data Coverage and Quality:The products in this data set were derived from the following MarsExpress ingress radio occultations with the spacecraft in 'two-way'mode: Year Day of Year Orbit ---- ----------- ----- 2004 139 414 2004 180 559 2004 181 564 2004 183 570 2004 355 1184 2004 362 1212 2005 234 2061 2005 268 2182 2006 025 2619 2006 084 2829 2007 118 4253 2007 134 4312In 'two-way' mode, the spacecraft radio system uses a signaltransmitted from the ground as its frequency reference when radiatingits own signal. The frequencies of the 'uplink' and 'downlink' differby about 10 percent so there is no interference. The two-way modeprovides better frequency stability on the downlink than can beachieved using the spacecraft's on-board oscillator, yielding moreaccurate atmospheric profiles. However, the fact that both the uplink and downlink pass through the atmosphere of Mars complicates theanalysis since refractive bending occurs during each passage and theraypaths are at slightly different altitudes.During an egress occultation, the spacecraft's radio system must findand lock onto the uplink signal before transmitting 'coherently' backto Earth. The 'lock-up' time can be several seconds, during which the raypath is traversing a significant fraction of the atmosphere. Theuplink signal reaching the spacecraft is also somewhat unstablebecause of perturbations introduced by the atmosphere of Mars. Forthese reasons, only ingress occultations were collected by the MarsExpress Radio Science Team.Limitations: The limitations in this data set follow from the quality of the execution, which is described above under Data Coverage and Quality.ACRONYMS:DSN Deep Space NetworkESA European Space AgencyIFMS Intermediate Frequency Modulation SystemJPL Jet Propulsion LaboratoryMEX Mars ExpressNNO New Norcia Station (Perth)PDS Planetary Data SystemPSA Planetary Science ArchiveRSR Radio Science ReceiverS/C Spacecraft