.jpg) Venus Express in orbit | |
| Mission type | Venus orbiter |
|---|---|
| Operator | European Space Agency |
| COSPAR ID | 2005-045A |
| SATCATno. | 28901 |
| Website | www |
| Mission duration | Planned: 2 years Final: 9 years, 2 months, 9 days |
| Spacecraft properties | |
| Manufacturer | EADS Astrium |
| Launch mass | 1,270 kg (2,800 lb)[1] |
| Dry mass | 700 kg (1,500 lb)[1] |
| Payload mass | 93 kg (205 lb)[1] |
| Dimensions | 1.5 × 1.8 × 1.4 m (4.9 × 5.9 × 4.6 ft)[1] |
| Power | 1,100 watts[1] |
| Start of mission | |
| Launch date | 9 November 2005, 03:33:34 (2005-11-09UTC03:33:34) UTC[2] |
| Rocket | Soyuz-FG/Fregat |
| Launch site | Baikonur31/6 |
| Contractor | Starsem |
| End of mission | |
| Disposal | Deorbited |
| Last contact | 18 January 2015, 15:01:55 (2015-01-18UTC15:01:56) UTC[3] |
| Decay date | January / February 2015 |
| Orbital parameters | |
| Reference system | Cytherocentric |
| Pericytherion altitude | 460 km (290 mi)[4] |
| Apocytherion altitude | 63,000 km (39,000 mi)[4] |
| Inclination | 90 degrees[5] |
| Period | 24 hours[5] |
| Venus orbiter | |
| Orbital insertion | 11 April 2006 |
 ESA Solar System insignia for theVenus Express mission | |
Venus Express (VEX) was the firstVenus exploration mission of theEuropean Space Agency (ESA). Launched in November 2005, it arrived at Venus in April 2006 and began continuously sending back science data from its polar orbit around Venus. Equipped with seven scientific instruments, the main objective of the mission was the long term observation of theVenusian atmosphere. The observation over such long periods of time had never been done in previous missions to Venus, and was key to a better understanding of the atmospheric dynamics. ESA concluded the mission in December 2014.[6][7][8][9]
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Starting out in the early planetary system with similar sizes and chemical compositions, the histories ofVenus andEarth have diverged in spectacular fashion. TheVenus Express data were intended to contribute not only to in-depth understanding of how theVenusian atmosphere is structured today, but also to understanding of the changes that led to the currentgreenhouse atmospheric conditions. Such investigations contribute to the study ofclimate change on Earth.[10][11][12][13]
ASPERA-4: An acronym for "Analyzer ofSpacePlasmas andEnergeticAtoms," ASPERA-4 investigated the interaction between thesolar wind and the Venusian atmosphere, determine the impact of plasma processes on the atmosphere, determine global distribution of plasma and neutral gas, study energetic neutral atoms, ions and electrons, and analyze other aspects of the near Venus environment. ASPERA-4 is a re-use of the ASPERA-3 design used onMars Express, but adapted for the harsher near-Venus environment.[14][15]
MAG: Themagnetometer was designed to measure the strength of Venus's magnetic field and the direction of it as affected by the solar wind and Venus itself. It mapped themagnetosheath,magnetotail,ionosphere, and magnetic barrier in high resolution in three-dimensions, aid ASPERA-4 in the study of the interaction of the solar wind with the atmosphere of Venus, identify the boundaries between plasma regions, and carry planetary observations as well (such as the search for and characterization of Venus lightning). MAG was derived from theRosetta lander's ROMAP instrument.[16][17]
One measuring device was placed on the body of the craft. The identical second of the pair was placed the necessary distance away from the body by unfolding a 1 m-long (3.3 ft) boom (carbon composite tube). Two redundant pyrotechnical cutters cut one loop of thin rope to free the power of metal springs. The driven knee lever rotated the boom perpendicularly outwards and latched it in place. Only the use of a pair of sensors together with the rotation of the probe allowed the spacecraft to resolve the small natural magnetic field beneath the disturbing fields of the probe itself.[16][17]
The measurements to identify the fields produced by the craft took place on the route from Earth to Venus.[18][19] The lack of magnetic cleanness was due to the reuse of theMars Express spacecraft bus, which did not carry a magnetometer.[19] By combining the data from two-point simultaneous measurements and using software to identify and remove interference generated byVenus Express itself, it was possible to obtain results of a quality comparable to those produced by a magnetically clean craft.[19]
VMC: TheVenusMonitoringCamera is a wide-angle, multi-channelCCD. The VMC is designed for global imaging of the planet.[20] It operated in the visible (VIS), ultraviolet (UV), and near infrared (NIR1 and NIR2) spectral ranges, and maps surface brightness distribution searching for volcanic activity, monitoringairglow, studying the distribution of unknown ultraviolet absorbing phenomenon at the cloud-tops, and making other science observations.[21][22][23]
It was derived in part from theMars ExpressHigh Resolution Stereo Camera (HRSC) and theRosettaOptical, Spectroscopic and Infrared Remote Imaging System (OSIRIS). The camera is based on a Kodak KAI-1010 Series, 1024 x 1024 pixel interline CCD, and included anFPGA to pre-process image data, reducing the amount transmitted to Earth.[24][25]
The consortium of institutions responsible for the VMC included theMax Planck Institute for Solar System Research, the Institute of Planetary Research at theGerman Aerospace Center and the Institute of Computer and Communication Network Engineering atTechnische Universität Braunschweig.[26] It is not to be confused withVisual Monitoring Camera mounted onMars Express, of which it is an evolution.[24][27]
| VMC Channel | Central Wavelength | Spectral Range |
|---|---|---|
| VIS | 513 nm | 503 – 523 nm |
| NIR1 | 935 nm | 900 – 970 nm |
| NIR2 | 1.01 μm | 990 – 1030 nm |
| UV | 365 nm | 345 – 385 nm |
PFS: The "PlanetaryFourierSpectrometer" (PFS) should have operated in theinfrared between the 0.9 μm and 45 μm wavelength range and was designed to perform vertical optical sounding of the Venus atmosphere. It should have performed global, long-term monitoring of the three-dimensional temperature field in the lower atmosphere (cloud level up to 100 kilometers).[28]
Furthermore, it should have searched for minor atmospheric constituents that may be present, but had not yet been detected, analyzed atmosphericaerosols, and investigated surface to atmosphere exchange processes. The design was based on aspectrometer onMars Express, but modified for optimal performance for theVenus Express mission. However PFS failed during its deployment and no useful data was transmitted.[29]
SPICAV: The "SPectroscopy forInvestigation ofCharacteristics of theAtmosphere ofVenus" (SPICAV) is animaging spectrometer that was used for analyzing radiation in the infrared and ultraviolet wavelengths. It was derived from theSPICAM instrument flown onMars Express. However, SPICAV had an additionalchannel known asSOIR (SolarOccultation atInfrared) that was used to observe the Sun through Venus's atmosphere in the infrared.[30][31]
VIRTIS: The "Visible andInfraredThermalImagingSpectrometer" (VIRTIS) was animaging spectrometer that observed in the near-ultraviolet, visible, andinfrared parts of theelectromagnetic spectrum. It analyzed all layers of the atmosphere, surface temperature and surface/atmosphere interaction phenomena.[32][33][34]
VeRa:VenusRadio Science was a radio sounding experiment that transmitted radio waves from the spacecraft and passed them through the atmosphere or reflected them off the surface. These radio waves were received by a ground station on Earth for analysis of theionosphere, atmosphere and surface of Venus. It was derived from the Radio Science Investigation instrument flown onRosetta.[35][36]
The mission was proposed in 2001 to reuse the design of theMars Express mission. However, some mission characteristics led todesign changes: primarily in the areas of thermal control, communications and electrical power. For example, sinceMars is approximately twice as far from theSun as Venus, the radiant heating of the spacecraft was four times greater forVenus Express thanMars Express. Also, theionizing radiation environment was harsher. On the other hand, the more intense illumination of thesolar panels resulted in more generatedphotovoltaic power. TheVenus Express mission also used some spare instruments developed for theRosetta spacecraft. The mission was proposed by a consortium led by D. Titov (Germany), E. Lellouch (France), and F. Taylor (United Kingdom).[37]
Venus Express completed its final phase of testing atAstrium Intespace facility inToulouse, France on 3 August 2005 and arrived at the airport of theBaikonur Cosmodrome on 7 August 2005. First flight verification test was completed on 16 August 2005. Integrated System Test-3 was completed on 22 August 2005. Last major system test successfully started on 30 August 2005. Electrical testing was completed on 5 September 2005. The Fuelling Readiness Review was completed on 21 September 2005. The spacecraft was mated to theFregat upper stage on 12 October 2005.[38]
Thelaunch window forVenus Express was open from 26 October to 23 November 2005, with the launch initially set for 26 October 4:43UTC. However, problems with the insulation from the Fregat upper stage (detected on 21 October 2005) led to a two-week launch delay to inspect and clear out the small insulation debris that migrated on the spacecraft.[39] The spacecarft arrived at launch pad on 5 November 2005 and it was launched by aSoyuz-FG/Fregat rocket on 9 November 2005 at 03:33:34 UTC into a parking Earth orbit and 1 h 36 min after launch put into its transfer orbit to Venus.[40][41][42]
Three trajectory correction maneuvers were successfully performed on 11 November 2005, 24 February 2006, and 29 March 2006. The main engine was fired successfully on 17 February 2006 in a dress rehearsal for the arrival maneuver.[43] The command stack for orbit insertion maneuver was loaded on the spacecraft on 7 April 2006. The spacecraft arrived at Venus on 11 April 2006, after 153 days of journey, and fired its main engine between 07:10:29 and 08:00:42UTCSCET to reduce its velocity so that it could be captured by Venusiangravity into an orbit of 400 by 330,000 kilometres (250 by 205,050 mi).[44] The burn was monitored from ESA's Control CentreESOC inDarmstadt, Germany. Period of this initial orbit was nine days.[44]
| Event | Spacecraft event time (UTC) | Ground receive time (UTC) |
|---|---|---|
| Liquid Settling Phase start | 07:07:56 | 07:14:41 |
| VOI main engine start | 07:10:29 | 07:17:14 |
| periapsis passage | 07:36:35 | |
| eclipse start | 07:37:46 | |
| occultation start | 07:38:30 | 07:45:15 |
| occultation end | 07:48:29 | 07:55:14 |
| eclipse end | 07:55:11 | |
| VOI burn end | 08:00:42 | 08:07:28 |
Seven further orbit control maneuvers, two with the main engine and five with the thrusters, were required forVenus Express to reach its final operational 24-hour orbit around Venus.[44] First images of Venus fromVenus Express were released on 13 April 2006.[46]
| Time | Event | Result |
|---|---|---|
| 20 April 2006 | Apoapsis Lowering Manoeuvre #1 | Orbital period changed to 40 hours |
| 23 April 2006 | Apoapsis Lowering Manoeuvre #2 | Orbital period changed to 25 hours 43 minutes |
| 26 April 2006 | Apoapsis Lowering Manoeuvre #3 | slight fix to previous ALM |
Venus Express entered its target orbit at apoapsis on 7 May 2006 at 13:31 UTC, when the spacecraft was 151,000,000 kilometres (94,000,000 mi) from Earth. At this point the spacecraft was running on anellipse substantially closer to the planet than during the initial orbit. The polar orbit ranged between 250 and 66,000 kilometres (160 and 41,010 mi) over Venus. Theperiapsis was located almost above the North pole (80° North latitude), and it took 24 hours for the spacecraft to travel around the planet.[47]
Venus Express studied theVenusian atmosphere and clouds in detail, theplasma environment and the surface characteristics of Venus from orbit. It also made global maps of the Venusian surface temperatures. Its nominal mission was originally planned to last for 500 Earth days (approximately two Venusian sidereal days) until 19 September 2007, but the mission was extended five times: first on 28 February 2007 until early May 2009; then on 4 February 2009 until 31 December 2009; and then on 7 October 2009 until 31 December 2012.[48] On 22 November 2010, the mission was extended to 2014.[49] On 20 June 2013, the mission was extended a final time until 2015.[50] Between 18 June and 11 July 2014, the spacecraft performed successfulaerobraking experiments[51] with multiple passes at 131 to 135 km altitude.[52][53]
On 28 November 2014, mission control lost contact withVenus Express. Intermittent contact was reestablished on 3 December 2014, though there was no control over the spacecraft, likely due to exhaustion of propellant.[54] On 16 December 2014, ESA announced that theVenus Express mission had ended.[6] Acarrier signal was still being received from the vehicle, but no data was being transmitted. Mission manager Patrick Martin expected the spacecraft would fall below 150 kilometres (93 mi) in early January 2015, with destruction occurring in late January or early February.[55] The spacecraft's carrier signal was last detected by ESA on 18 January 2015.[3]
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