A dataset provided by the European Space Agency

Name VEX-V-VRA-1-2-3-NMP-0088
URL ftp://npsa01.esac.esa.int/pub/mirror/VENUS-EXPRESS/VRA/VEX-V-VRA-1-2-3-NMP-0088-V1.0
DOI https://doi.org/10.5270/esa-u8ynm4k
Abstract This is a Occultation measurement covering the time 2007-01-20T07:18:19.050 to 2007-01-20T08:32:01.950. This data set contains archival raw, processed, and supporting radio science Doppler data acquired from the Venus Express Radio Science Experiment (VeRa). The data were recorded using the closed loop receiver facilities at the European Space Agency (ESA) groundstations or at the NASA Deep Space Network (DSN) groundstations. The data set contains one Venus measurement recorded in earth occultation geometry starting before the ingress (ingoing) phase and ending after the egress (outgoing) phase of the occultation pass. The data can be used to derive electron density profiles in the ionosphere and profiles of neutral number density, pressure and temperature in the neutral atmosphere of Venus. The neutral atmosphere profiles deduced from these occultation measurements usually cover the altitude range between about 45 - 90 km.
Description Data Set Overview The Venus Express (VEX) Radio Science (VeRa) Data Archive is a time-ordered collection of raw and partially processed data collected during the Venus Express Mission. This is a Occultation measurement covering the time 2007-01-20T07:18:19.050 to 2007-01-20T08:32:01.950. VeRa radio occultation observations start shortly before the occultation ingress, when the VEX spacecraft moves behind the planetary disk as seen from the Earth and stop shortly after the occultation egress, when the probe emerges from behind the planet. VeRa occultation data usually cover three recording phases: the occultation ingress (1), the time when the spacecraft is occulted by the planet (2) and the occultation egress (3). The different observation phases can be distinguished by regarding the AGC data, which records the strength of the received signal. In phase (1) and (3) the AGC level is high compared to phase (2). In Phase (2) still a signal may be received at the groundstation due to the strong bending of the radio waves in the dense atmosphere. The strength of the signal is significantly reduced and weakens further the deeper the radio waves penetrate the atmosphere until the groundstation may be unable to lock. Therefore, the beginning of phase (2) is recognized at first order by a sharp drop of the AGC down to -95 dB and lower and ends with a sharp rise in the AGC data back to the former AGC level. For the derivation of higher science products it is recommended to divide the level 2 data into an ingress and an egress part and to process these data seperatetly. This is a radio occultation measurement of the Venusian atmosphere. It was done during occultation by the planet during the second occultation season from 2006-12-07 to 2007-01-31. The number of occultation measurements during the second occultation season can be found in DOCUMENT/VRA_DOC/VERA_OPS_LOGBOOK_06.PDF and DOCUMENT/VRA_DOC/VERA_OPS_LOGB...
Instrument VRA
Temporal Coverage 2007-01-20T07:18:19Z/2007-01-20T08:32:01Z
Version V1.0
Mission Description Mission Overview Venus Express is ESA's first mission to Venus. It reuses the design of the Mars Express spacecraft. Many of the instruments are simply upgraded versions of those developed for ESA's Mars Express and Rosetta missions. The scientific objectives of the mission is to study the atmosphere, the plasma environment, and the surface of Venus in great detail. Venus Express was launched by a Soyuz-Fregat launcher from the Baikonour Cosmodrome on 9 November 2005. After separation, Venus Express, of mass 1244 kg, was placed into an interplanetary transfer orbit during approximately 150 days. After a 153 day cruise to Venus the spacecraft entered Venusian orbit on 11 april 2006. The first capture orbit was an eccentric polar and lasted 9 days. Several manoeuvres over the period 15 April-6 May 2006 lowered the spacecraft into its operational orbit: a 24-hour elliptical, quasi-polar orbit. The pericentre altitude is 250 kms and the apocentre altitude is 66000 kms. Pericentre altitude 250 km Apocentre altitude 66000 km Period 24 h Inclination ~90 deg Pericentre latitude 80 deg The mission has been described in many papers [ESABUL2005; HUNTER2004]. Details about the mission launch sequence and timeline can be obtained from the Mission Calendar [VEX-ESC-TN-5002] and from the Consolidated Report on Mission Analysis (CREMA)[VEX-ESC-RP-5500]. Mission Phases The mission timeline defines the different spacecraft and payload operations required per phase to prepare the spacecraft for Venus operational orbit acquisition, science data acquisition and transmission. Six nominal mission phases plus the pre-launch phase are defined for achieving the scientific mission objectives. They are detailed below. PRELAUNCH --------- Pre-launch operations started approximately 6 months before the launch and covered the period from delivery of the spacecraft to the launch site until L-8 hrs in the launch count...
Date Published 2010-10-15
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, 2010-10-15, VEX-V-VRA-1-2-3-NMP-0088, V1.0. https://doi.org/10.5270/esa-u8ynm4k