| Description |
SPICAV CRUISE/VENUS IR EDR-RAW Data Set Overview ================================================ The SPICAV CRUISE/VENUS IR EDR-RAW (level 0B) dataset contains raw measurements from the infra red SPICAV spectrometer collected during the cruise and VENUS phases of Venus Express. Data are stored in the VEXSPI_0BIR/DATA directory, divided into mission phases subdirectories (CRUISE, VENUS, ...). An easily viewed version of each record of the SPICAV CRUISE/VENUS IR EDR-RAW data set is shown in VEXSPI_0BIR/BROWSE. Essential Readings ================== Some of the documents, located in the DOCUMENT/ and CALALOG/ directories in the IR dataset, are essential for the understanding of the instrument and the analysis of the data. Here we list some of those readings: ESA Science Plan :SPICAV, Spectroscopy for the Investigation of the Characteristics of The Atmosphere of Venus ESA_SP_P1 Flight User Manual :Venus Express SPICAV Flight User Operations Manual SPVFUM25 EAICD :Description of the Instrument Design, data process, scientific objectives , archive format and content, convention and other essentiel information SA_VEX_ARCH_xxx_vv.PDF SPICAV Technical Note TN :The Calibration factors of the SPICAV IR spectrometer channel SPICAV_NT_IRCALIB_V1.PDF Processing =========== The SPICAV data collected between each switch ON and switch OFF of SPICAV are transferred to ESOC and stored at ESOC on the Data Disposition System (DDS) in Darmstadt (Germany). They are then transferred via ftp from the DDS to the Laboratoire Atmospheres, Milieux, Observations Spatiales (LATMOS). All new data files concerning UV and IR channels are processed at LATMOS. Retrieval algorithms and softwares which are used throughout the processing steps from level to level are developed within the Spicav Team. They are writen in IDL. The processing from level 0 ( ESOC DDS data) to level 0AUV includes the following features: - data are not modified: starting from level 0 data, ESA packets are disassembled and reformatted to build level 0A data files. - a header is added to each record to comply to our requirement. - a UTC time is added to in the header The processing of IR from level 0 to level 0A is similar to the processing of UV data. However we use level 0B for IR data. The 0B IR data files contain all reconstructed spectra of an IR SPICAV observations collected by the two detectors of the infrared channel. Many r^ant informations are also included in those files (i.e: parameters of command, frequency array, system monitors values....) File Naming Convention ======================= Data products provided by the SPICAV team have the following name: SPIV_YYT_nnnnApp_M_vv.DAT Where: YY 2 letters describing the SPICAV data level (eg. 0A, 1A, 1B, ...) T 1 letter describing the type of data collected (U for UV and R for IR) nnnn 4 digits for the orbit number App sequence number indicating the order that data were collected for the nnnn orbit (A01, A02,...). M 1 letter describing the type of observation vv version number of the file NOTE: For the CRUISE and VOCP phases: - The orbit number is not applicable. The 4 digits will contain the day of the year (doy of 2005/2006) of the observation, preceeded by the letter C (for the IC phase) or by the letter P (for the VOCP phase). - M is the: Type of Observation . It may represent: E: Star ( occultation ) S: Sun ( occultation ) L: Limb N: Nadir A: Alignment ( in Nadir direction ) W: Mercury observation M: Mars observation H: Earth observation Y: Sky ( Sky observation or observation with spicav no master) T: Techno ( calibration ) C: Comet observation During the Cruise, Star and Sun observations are technological (T) observations with no occultation. However, during the CRUISE , E and S (observations types) are used in the data file name. But to immediately know which target is observed during the cruise, E and S are used in the name of the data file. Examples : SPIV_0AU_C016A02_E_04.DAT Star UV observation during the CRUISE phase. SPIV_0AU_P104A01_Y_04.DAT Sky UV observation during the VOCP phase. SPIV_0AU_nnnnA01_E_04.DAT Stellar UV occultation on orbit nnnn Associated detached label files and browse files follow the same filenaming convention with the .LBL and _QL.PNG extension respectively. Geometry files =============== N/A for CRUISE phase Geometry files provided by the SPICAV team will have the following name: SPIV_YYT_nnnnApp_M_vv_GOXww.TXT Where: X 1 letter describing the content of the file. The value of this letter can be L for a light version of the geometry file (only some main parameters) and F for a full version ww version number of the software generating the geometry file Calibration ============= Calibration is in constant evolution. A CALIB directory is present within the dataset, and contains the Spicav UV calibration technical note (SPICAV_NT_UVCALIB_V1.PDF). The UV Gain Curve values and the UV efficient area values are also provided. SOFTWARE: ========= The team provide a SOFTWARE directory which contains routines able to read the Venus Express SPICAV-UV PDS data and label files under Windows. The main routine readSBN_UV.pro has been developed by the SPICAV team and calls the readPDS set of IDL procedures developed at the SBN. A fuller description of the content of the SOFTWARE directory is given in the SPICAV_READPSD43.LBL file, and a description of the software itself is given in the SPICAV_READPDS_README.TXT file in the /SPICAV_READPSD43 directory. Ancillary Data ============== SPICE files produced by VSOC/ESTEC in collaboration with NAIF/JPL from the VENUS Express orbit files generated by ESOC are used in our data processing chain, in particular to generate geometry files. |
| Mission Description |
Mission Overview ================ Venus Express is ESAs 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 ESAs 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 countdown sequence. During this period the Venus Express Mission Operations Centre (VMOC) at ESOC performs its final simulation programme including the validation of the Flight Operations Plan (FOP) and the final mission control system. mission phase start time : UNK mission phase stop time : 2005-11-09 LAUNCH AND EARLY ORBIT PHASE (LEOP) ----------------------------------- The Venus Express spacecraft was launched on a Soyouz-Fregat rocket from the Baikonur Cosmodrome at 3:33:34 UT on 9 November 2005. The three-stage Soyuz launcher lifted the Fregat autonomous upper stage (fourth stage) with Venus Express mounted on it into a sub-orbital trajectory. After separation from the Soyuz third stage, a Fregat main engine burn (at an altitude of about 200 kilometres) for around 20 seconds placed the Fregat-Venus Express composite into an almost circular parking orbit. After a coast phase of about 70 minutes in the low Earth orbit, a second Fregat engine burn, lasting 16 minutes, moved the combined craft from the parking orbit onto an escape trajectory, after which the Fregat stage and Venus Express separated. Duration : 3 days mission phase start time : 2005-11-09 mission phase stop time : 2005-11-11 After separation, Venus Express spent approximately 150 days in an interplanetary transfer orbit. During this phase, trajectory corrections were performed using the spacecrafts own thrusters. NEAR EARTH COMMISSIONING PHASE (NECP) ------------------------------------- It includes the following activities for the spacecraft: - spacecraft commissioning. - deployment of the MAG Boom. - Payloads commissioning. Duration : 3 weeks mission phase start time : 2005-11-12 mission phase stop time : 2005-12-16 INTERPLANETARY CRUISE PHASE --------------------------- The Interplanetary Cruise Phase finishes about one month before Venus capture. During this 3 months phase, the spacecraft in on the Sun-centred ballistic orbit to Venus. Most of this phase is not dedicated to any specific activity, except the cruise orbit determination and correction. Duration : 107 days mission phase start time : 2005-12-17 mission phase stop time : 2006-04-04 VENUS ORBIT INSERTION PHASE (VOI) --------------------------- The Venus Orbit Insertion (VOI) phase is the period of transition between the Interplanetary Cruise phase and the final operational orbit around Venus. It starts before the Venus capture manoeuvre and ends when the satellite has reached the operational orbit. The duration of this phase is about 2 weeks. A final course adjustment was performed on 29 March to fine tune the arrival hyperbola for Venus Orbit Insertion. The VOI manoeuvre took place on 11 April 2006. To enable capture of the spacecraft, it was first slewed such that the main engine was aligned to the direction of travel. The main engine burn lasted around 50 minutes and decelerated the spacecraft by approximately 1251 ms-1 (~ 4500 kmh-1). The spacecraft intially entered a highly elliptical polar orbit with a pericentre of 400 km, an apocentre of 350 000 km and a period of 9 days. To achieve the final operational orbit a series of correction manoeuvres are necessary: Date Activity Velocity Change (m/s) 15 April 2006 Pericentre Control Manoeuvre #1 5.8 20 April 2006 Apocentre Lowering Manoeuvre #1 199.9 23 April 2006 Apocentre Lowering Manoeuvre #2 105.3 26 April 2006 Apocentre Lowering Manoeuvre #3 9.2 29 April 2006 Apocentre Lowering Manoeuvre #4 8.0 2 May 2006 Apocentre Trim 2.0 6 May 2006 Pericentre Control Manoeuvre #2 3.1 Duration : 16 days mission phase start time : 2006-04-05 venus capture manoeuvre : 2006-04-11 mission phase stop time : 2006-04-21 VENUS ORBIT COMMISSIONING PHASE --------------------------------- The Venus Payload Commissioning phase starts when the spacecraft has reached the operational orbit and ends when it is declared ready for science data acquisition and transmission to the Earth. It is dedicated to spacecraft commissioning activities, payloads commissioning and demonstration activities prior to operational science operations. The duration of the Payload Commissioning phase around Venus is about 1 month. The operations to be performed during the phase are the following: - S/C in-orbit commissioning, - Payloads in-orbit commissioning, - Isolation of the Propulsion system. Duration : 42 days mission phase start time : 2006-04-22 mission phase stop time : 2006-06-03 ROUTINE OPERATIONS PHASE ------------------------ The selected operational orbit is inertially fixed, so that coverage of all planetocentric longitudes will be accomplished in one Venus sidereal day (243 Earth days). The nominal mission orbital lifetime is two Venus sidereal days (486 Earth days). It consists in science data acquisition from the payloads, data storage in the SSMM and data transmission to the Earth. There are two different phases of operations for Venus Express once it is in operational orbit: the Earth Pointing phase and the Observation phase. The Earth pointing phase is dedicated to communication with Earth and battery charging. It is used whenever the spacecraft is not in the observation phase. In the Earth pointing phase, one of the two High Gain Antennas is oriented towards Earth. The antenna is selected according to the season, so that the spacecrafts cold face remains always protected from illumination by the Sun. The rotation angle around the Earth direction is optimised in order to avoid any entrance of Sun light on the side walls radiators. High rate communication will be performed 8 hours per day in X-band, in order to transmit to Earth all science data stored in the Solid State Mass Memory. An average of 2 Gbits of science data will be downlinked every day to the new ESA ground station of Cebreros, Spain. The observation phase consists of several different modes of observation, depending on the payload configuration and spacecraft orientation: Nadir pointing, Limb observation, Star occultation, Radio science. During observation, the Sun can illuminate under transient conditions any spacecraft face, except for the cold face. The duration of observation is therefore limited by thermal constraints and by battery discharge. The maximum duration of an observation period depends on the Sun direction with respect to the orbit plane, which varies along the mission. Duration : 486 days mission phase start time : 2006-06-04 mission phase stop time : 2007-10-02 EXTENDED OPERATIONS PHASE ------------------------- mission phase start time : 2007-10-03 mission phase stop time : May 2009 Science Subphase ---------------- For the purpose of structuring further the payload operations planning, the mission phases are further divided into science subphases. Phase number Date Orbit CRUISE 2005-11-09 -1 VOI 2006-04-11 0 PHASE 0 2006-05-14 23 PHASE 1 2006-06-04 44 PHASE 2 2006-07-11 82 PHASE 3 2006-09-14 146 PHASE 4 2006-11-16 209 PHASE 5 2007-02-01 286 PHASE 6 2007-03-16 330 PHASE 7 2007-04-25 370 PHASE 8 2007-06-30 436 PHASE 9 2007-08-21 488 PHASE 10 2007-10-04 531 PHASE 11 2007-10-27 554 PHASE 12 2008-01-04 623 PHASE 13 2008-04-01 711 PHASE 14 2008-06-05 776 PHASE 15 2008-08-01 833 PHASE 16 2008-09-23 886 PHASE 17 2008-12-31 985 VOI and Phase 0 ------- This initial phase is devoted to the spacecraft and payload checkout and in orbit commissioning. The phase will consist of: - experiments commissioning (until 14/05/2006, orb 23). - Science case commissioning (16-27 May 2006, Orb 23-36). - Extended case commissioning (May 28-June 3, Orb 37-43). This one will also occupy the first half of phase 1. VOI --- Dates : April 11 - May 13 2006 Orbits : 1-23 Phase 0 ------- Dates : May 14 - June 03, 2006 Orbits : 23-43 MTP : 1 Phase 1 ------- Phase 1 is favorable for observations of the evening terminator vicinity. Dates : June 4 - July 10, 2006 Orbits : 44-81 Phase duration : 37 days MTP : 2-3 Phase 2 ------- Phase 2 provides favorable conditions for the earth and solar occultation, and for the nadir observations of the night side. Dates : July 11 - September 13 2006 Orbits : 81 - 145 Phase duration : 64 days MTP : 3-5 Phase 3 ------- The Venus dark side could be observed in the beginning of Phase 3. Phase 3 will also have conditions for systematic observations of the morning/evening terminator and for solar corona studies. Dates : September 14, 2006 - November 15, 2006 Orbits : 146 - 208 Phase duration : 62 days MTP : 5-7 Phase 4 ------- Phase 4 will have solar occultation, dayside off-pericenter observations, and earth radio occultation as first priority. Dates : November 16, 2006 - January 31, 2007. Orbits : 209-285 Phase duration : 76 days MTP : 7-10 Phase 5 ------- Phase 5 has favorable conditions for observations of the evening terminator. Dates : February 1 - March 15, 2007. Orbits : 286-329 Phase duration : 43 days MTP : 10-12 Phase 6 ------- Phase 6 provides good conditions for observations of the noight side and atmospheric sounding in solar occultation geometry (eclips season 3). Dates : March 16 - April 24, 2007. Orbits : 330 - 369 Phase duration : 39 days MTP : 12-13 Phase 7 ------- Phase 7 includes Earth occultation season. Proximity to the Earth creates excellent conditions for bi-static sounding and radio-occultation experiment that can reach maximum sounding depth. Avantage of this phase is that it has maximum downlink data rate. So it will be used to study the atmosphere with high spatial resolution. As earlier in phases 1, 3, 5 the terminator sector of the planet will be available for observations in this phase. Dates : April 25 - June 29, 2007. Orbits : 370 - 435 Phase duration : 65 days MTP :13-15 Phase 8 ------- Phase 8 contains eclipse season #4. Thus significant portion of orbits will be devoted to solar occultation observations. This phase is favourable for investigation of dayside dynamics especially in the end of the phase when the downlink data rate reaches its maximum. Proximity to the Earth provides good conditions for solar corona studies and bi-static sounding. Dates : June 30 - August 20, 2007. Orbits : 436 - 487 Phase duration : 51 days MTP : 16-17 Phase 9 ------- Phase 9 is favourable for observations of the vicinity of evening terminator. By the end of this season conditions for the off- pericentre night side observations will be fulfilled. Main scientific focus of this phase is to provide observations of the evening terminator. Dates : August 21 - October 3, 2007. Orbits : 488- 530 Phase duration : 42 days MTP : 17-19 Phase 10 -------- Phase 10 has no eclipse or occultation seasons. A routine sequence of off-pericenter observations followed by Nadir, limb or stellar occultations will be carried out. Dates : October 4 - October 26, 2007. Orbits : 531- 553 Phase duration : 22 days MTP : 19-20 Phase 11 -------- During phase 11, the Eclipse season starts from orbit 554 to 597. However, solar occultations will be only possible from orbit 576 to 596 because of the temperature conditions due to the sun position. VIRTIS will perform some airglow campaign in nadir and limb geometry. VMC will observe the surface on the night side. The observation targets are Asteria Regio, Hinemoa, Gunda and Kawelu Planitia, Beta Regio (Rheja and Theja Mons) and Phoebe Regio. SPICAV will observe stars at large distance, later in the phase. Two spot pointings will be performed in orbit 561 and 571. Gravity measurements will be performed over Atalanta Planita in orbits 615, 617, 619, 621. Dates : October 27, 2007- January 3, 2008. Orbits : 554- 622 Phase duration : 68 days MTP : 20-22 Phase 12 -------- Earth occultation season begins in orbit 623 and ends in orbit 692. VeRa will have the priority for pericentre observations of the Southern Hemisphere. VIRTIS near-IR will do temperature sounding in the same region. Then cross-correlation on results will be made possible. Pendulum observations or science case number 2b will be performed during all this phase. From orbit 659 to orbit 680, three periods overlap: Earth occultations, Eclipse season, solar opposition. The solar opposition is favorable for apocentre mosaics by VIRTIS. Science cas number 6 and number 2b (pendulum observations) will be mainly performed at the end of the phase (from orbit 690). The surface targets for this phase are Atahensik and Zimina Coronae, Atla Regio (Ozza Mons) and East from it and Atalanta Planitia. Dates : January 3 - March 31, 2008. Orbits : 623- 710 Phase duration : 87 days MTP : 22-25 Phase 13 -------- There is no specific season during most of phase 13. The science cases performed will be case number 1, 5 and 7 at pericentre and case 2 off pericentre. At the end of the phase 13, in orbit 769, the mission enters superior conjunction phase and telecommunication outage period (orbit 769 to 790) during which all science operations will be suspended. Dates : April 1 - June 4, 2008. Orbits : 711- 775 Phase duration : 64 days MTP : 25-28 Phase 14 -------- During Phase 14, the eclipse and Earth occultation season overlap (orbit 777-821). The Earth occultation period lasts longer up to orbit 832. VMC will perform surface observations before pericentre and wind tracking after pericentre. SPICAV will do solar occultations, night limbs before pericentre and UV observations of the exosphere on the day side. Stellar occultations may be performed in coordination with VeRa. At pericenter they will observe dayglow. Possibly sub-solar point tracking may be performed by SOIR. VIRTIS will perform night limbs monitoring on ascending branch together with SPICAV. They will also do surface imaging before pericentre with VMC. The VeRa Earth occultation experiments begins in orbit 817. The targets for the surface observations are East flank of Atla Regio, Ozza Mons, Zevana and Paga Chasma. Dates : June 5 - July 31 , 2008. Orbits : 776- 832 Phase duration : 56 days MTP : 28-30 Phase 15 -------- There is no specific season during phase 15. At the beginning of the phase, SPICAV will perform night limbs before pericenter, plane limbs after pericenter and stellar occultations with VeRa. Later in the phase, SPICAV will perform day side limbs before and after pericenter. VMC will perform wind tracking after pericenter (day side). VIRTIS will do night side and terminator monitoring and limb observations together with SPICAV at the beginning of the phase. Later in the phase, day side and terminator monitoring will be performed. Dates : August 1 - September 22 , 2008. Orbits : 833- 885 Phase duration : 52 days MTP : 30-32 Phase 16 -------- This phase will start with Eclipse season (orbit 866 - 934). During phase 16, there is also Mosaic season (orbit 903 - 969) and Earth occultation season (orbit 921 - 985) SPICAV will perform solar occultation after pericentre and limb observations. VMC will perform monitoring and wind tracking on the day side. Later on the mission they will be able to do surface imaging after pericenter. Around orbit 967, they will perform night side imaging of Aphrodite Terra. VIRTIS will perform day side monitoring before pericentre and limb observations together with SPICAV. Later in the phase, VIRTIS will also perform Mosaic at apocentre. VeRa will perform radio occultations. Dates : September 23 - December 31 , 2008. Orbits : 886- 985 Phase duration : 99 days MTP : 32-35 |
