European Space Agency Solar System Science Operations Division VENUS EXPRESS Mission Calendar VEX-SCIOPS-TN-050 Issue 1 31 March 2008 Written by: M. Barthelemy PSA Approved by: D. Heather PSA R. Hoofs VSOC CHANGE RECORD SHEET Issue Rev. Pages Date No. No. Affected Description/Authority CR No. 31-03-2008 Issue 1 all Created - DISTRIBUTION LIST Recipient Organisation Recipient Organisation D. Heather PSA R. Hoofs VSOC VEX P.I. N/A OPS-ONN TABLES OF CONTENTS 1. INTRODUCTION..........................................................................................6 1.1 Purpose .....................................................................................................................................................6 1.2 Reference documents..............................................................................................................................6 2. GENERAL DATA ON THE MISSION ..........................................................6 3. ECLIPSE PERIODS, OCCULTATIONS, CONJUNCTIONS ........................6 4. MISSION PHASES ......................................................................................7 4.1 LEOP.........................................................................................................................................................7 4.2 NECP.........................................................................................................................................................8 4.3 ICP.............................................................................................................................................................8 4.4 VOI ............................................................................................................................................................8 4.5 VOCP ........................................................................................................................................................8 4.6 NMP ..........................................................................................................................................................9 4.7 EMP...........................................................................................................................................................9 5. SPACECRAFT INCIDENT ...........................................................................9 5.1 Safe Modes ...............................................................................................................................................9 5.2 Other incidents ........................................................................................................................................9 6. ACRONYMS ..............................................................................................10 LIST OF TABLES Table 1: Mission timeline ...................................................................................................................................6 Table 2: Eclipse periods .....................................................................................................................................7 Table 3: Occultation periods..............................................................................................................................7 Table 4: Conjunction periods .............................................................................................................................7 Table 5: Safe Mode list from 4/06/06 to 31/03/08. ...........................................................................................9 Table 6: List of the spacecraft incidents other than Safe modes that has occurred from 4/06/06 to 31/03/08. ..............................................................................................................................................................9 1. INTRODUCTION 1.1 Purpose This document aims at providing information about the mission, its phases and some of the environmental conditions. It contains an overview of Venus Express mission phases. It gives the dates for the different mission phases from launch to extended mission. It presents the eclipse periods, occultations and conjunctions in the third section. It also gives the list of spacecraft incident that occurred until the writing of this document. 1.2 Reference documents [RD1] EVTF_FDLVMA_DA______________00001.VEX: Flight Dynamics Event File. th [RD2] VEX-RSSD-PO-001, VEX Science Overview, 8 January 2007. th [RD3] VEX-RSSD-PO-005, VEX Extended Overview, 6 February 2008. 2. GENERAL DATA ON THE MISSION In this section, Table 1 shows the different mission phase from launch until the end of the extended mission phase. The phases and acronyms are discussed in section 4. Phase Acronym Phase name Start Date End Date Duration (days) LEOP Launch and Early Orbit Phase 09/11/05 11/11/05 3 NECP Near Earth Commissioning Phase 12/11/05 16/12/05 21 ICP Interplanetary Cruise Phase 17/12/05 04/04/06 107 VOI Venus Orbit Insertion 05/04/06 21/04/06 16 VOCP Venus Orbit Commissioning Phase 22/04/06 03/06/06 42 NMP Nominal Mission Phase 04/06/06 02/10/07 486 EMP Extended Mission Phase 03/10/07 May 2009 Table 1: Mission timeline 3. Eclipse periods, occultations, conjunctions In this section, the eclipse seasons, the occultations and the conjunction seasons are given. th The dates are given from the 14 May 2006, which corresponds to the orbit number 23 and the first day of commissioning operations. For instance, the eclipse season may begin before the th 14 May 2006, but we give this starting date because this date was the first day of operations in orbit. Eclipses [RD1] [RD2][RD3]: Eclipse season # Dates 1 14/05/06-31/05/06 Orbit 23-40 2 05/08/06-13/09/06 Orbit 106-145 3 16/11/06-10/01/07 Orbit 209-264 4 17/03/07-26/04/07 Orbit 330-370 5 28/06/07-21/08/07 Orbit 433-487 6 27/10/07-08/12/07 Orbit 554-596 7 09/02/08-01/04/08 Orbit 659-711 8 06/06/08-22/07/08 Orbit 777-823 9 23/09/08-10/11/08 Orbit 886-934 10 16/01/09-28/02/09 Orbit 1001-1045 11 04/05/09-23/06/09 Orbit 1110-1160 12 28/09/09-11/10/09 Orbit 1226-1270 13 15/12/09-01/01/10 Orbit 1335-1360 Table 2: Eclipse periods Earth Occultations [RD1][RD2][RD3]: Occultation season # Dates 1 11/07/06-30/08/06 Orbit 81-131 2 22/11/06-31/01/07 Orbit 215-285 3 26/04/07-01/07/07 Orbit 370-436 4 04/09/07-18/09/07 Orbit 501-515 5 04/01/08-13/03/08 Orbit 623-692 6 05/06/08-01/08/08 Orbit 776-833 7 28/10/08-31/12/08 Orbit 921-985 8 01/07/09-06/09/09 Orbit 1168-1236 9 09/12/09-01/01/10 Orbit 1328-1360 Table 3: Occultation periods Conjunctions[RD2],[RD3]: Conjunction season # Dates 1 superior 17/10/06-08/11/06 Orbit 179-201 2 superior 29/05/08-19/06/08 Orbit 769-790 3 superior 08/12/09-30/12/09 Orbit 1328-1350 Table 4: Conjunction periods 4. Mission Phases In this section, the different mission phases are described. 4.1 LEOP This phase lasted 3 days from few hours before launch until the execution of the TCM-1. Once the separation of the spacecraft from the launch vehicle is completed, the control took over. 4.2 NECP The Near Earth Commissioning Phase lasted 3 weeks. It included the following activities for the spacecraft: - spacecraft commissioning. - deployment of the MAG Boom. - Payloads commissioning. 4.3 ICP The Interplanetary Cruise Phase started after the Near Earth Commissioning Phase and ended shortly before Venus Orbit Injection when the spacecraft enters the Venus approach phase. During the cruise, the SC was kept in a 3-axes stabilized attitude (solar arrays Sun facing, HGA-2 Earth pointing) and communications with the ground was established at each daily pass. Spacecraft monitoring was done with a frequency of one pass per day for routine monitoring and control activities. Payloads science operations were excluded from the cruise phase. 4.4 VOI The Venus Orbit Insertion Phase lasted a little bit more than 2 weeks. It started just before the Venus capture manoeuvre and ended when the satellite had reached the operational orbit. th At the end of NECP, on the 29 March, a final course adjustment was performed to fine tune the arrival hyperbola for the orbit insertion. The Venus Orbit Insertion 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 meters/second (~ 4500 kilometers/hour). The spacecraft initially 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 were necessary: Velocity Date Activity 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 4.5 VOCP The Venus Orbit Commissioning Phase started once the operational orbit was reached and ended when it was declared ready for science data acquisition and transmission to the Earth. An initial post-cruise checkout was performed and then the readiness of the SC (and payloads) and the ground segment capability to operate their operational scenarios and environment was verified. The operation of the payloads was carried out off-line via the on-board Mission Timeline. During this phase, the Commissioning timeline was followed and the use of the Mission Planning System will be gradually phased in. This phase was used as a transition from the pre-defined activity scheme used in all previous critical phase involving the payloads, to a more dynamic approach based on the use of the full MPS functionality. 4.6 NMP The Nominal Mission Phase started at the end of the VOCP and lasted two Venusian days (486 Earth days). The selected operational orbit was inertially fixed, so that coverage of all planetocentric longitudes was accomplished in one Venus sidereal day (243 Earth days). The Nominal Mission Phase consisted in science data acquisition from the payloads, data storage in the SSMM and data transmission to the Earth. Once Venus Express is in operational orbit, the orbit is divided into two periods: the Earth Pointing period and the Observation period. The Earth pointing periods were dedicated to communication with Earth and battery charging. It was used whenever the spacecraft is not in the observation period. In the Earth pointing periods, one of the two High Gain Antennas was oriented towards Earth. The antenna was selected according to the season, so that the spacecraft's cold face remained always protected from illumination by the Sun. The rotation angle around the Earth direction was optimised in order to avoid any entrance of Sun light on the side walls radiators. High rate communication was performed 8 hours per day in X-band, in order to transmit to Earth all science data stored in the SSMM. An average of 2 Gbits of science data was downlinked every day to the new ESA ground station of Cebreros, Spain. The observation periods consisted of several different modes of observation, depending on the payload configuration and spacecraft orientation: Nadir pointing, Limb observation, Star occultation, Radio Science. 4.7 EMP The Extended Mission Phase has started at the beginning of October 2007 and will end at the beginning of May 2009. 5. Spacecraft incident 5.1 Safe Modes Table 5 summarizes the Safe modes that has occurred from the first day of operations in orbit th (4 June 2006) to the writing date of this document (31 March 2008). Safe Mode number Start date End date Safe Mode 1 13/06/06 Orbit 53 13/06/2006 Orbit 53 Safe Mode 2 25/08/06 Orbit 126 25/08/2006 Orbit 126 Safe Mode 3 22/09/06 Orbit 184 22/09/2006 Orbit 184 Safe Mode 4 27/09/06 Orbit 159 27/09/06 Orbit 159 Safe Mode 5 09/10/06 Orbit 171 09/10/06 Orbit 171 Safe Mode 6 27/01/08 Orbit 620 28/01/08 Orbit 620 Table 5: Safe Mode list from 4/06/06 to 31/03/08. 5.2 Other incidents Table 6 lists the other incidents that have affected the spacecraft from 4/06/06 to 31/03/08. Incident Name Start date End date VIRTIS H shutdown due to 13/08/07 4/11/07 cooling motors VIRTIS M shutdown 13/08/07 31/08/07 Payload Off due to SADE-A 25/08/07 27/08/07 misalignment Table 6: List of the spacecraft incidents other than Safe modes that has occurred from 4/06/06 to 31/03/08. 6. Acronyms AOCS Attitude and Orbit Control System DMS Data Management System EMP Extended Mission Phase ICP Interplanetary Cruise Phase LEOP Launch and Early Orbit Phase MAG Magnetometer MPS Mission Planning System NECP Near Earth Commissioning Phase NMP Nominal Mission Phase SC Spacecraft SSMM Solid State Mass Memory TCM Trajectory Correction Manoeuvre VOCP Venus Orbit Commissioning Phase VOI Venus Orbit Insertion