Venus Express

Venus Express is the first Venus exploration mission of the European Space Agency. It is currently in orbit around Venus and collecting scientific data.

History

The mission was proposed in 2001 to reuse the design of the Mars Express mission. However, some mission characteristics led to design changes: primarily in the areas of thermal control, communications and electrical power. For example, since Mars is approximately twice as far from the Sun as Venus is, the radiant heating of the spacecraft will be four times greater for Venus Express than Mars Express. Also, the ionizing radiation environment will be harsher. On the other hand, the more intense illumination of the solar panels will result in more generated photovoltaic power. The Venus Express mission also uses some spare instruments developed for the Rosetta spacecraft. The mission was proposed by Jet Propulsion Laboratory's Kevin Baines, who also worked on Cassini and New Horizons, and co-investigator on Venus Express' VIRTIS instrument.

The launch window for Venus Express was open from 26 October to 23 November 2005, with the launch initially set for 04:43 UT on 26 October. However, problems with the insulation from the Fregat upper stage led to a two week launch delay to inspect and clear out the small insulation debris that migrated on the spacecraft. It was eventually launched by a Soyuz-Fregat rocket from the Baikonur Cosmodrome in Kazakhstan on 9 November 2005 at 03:33:34 UT into a parking Earth orbit and 1 h 36 min after launch put into its transfer orbit to Venus. A first trajectory correction maneuver was successfully performed on 11 November 2005. It arrived at Venus on April 11, 2006, after approximately 150 days of journey, and fired its main engine between 07:10 and 08:00 Universal Time (UT) to reduce its velocity so that it could be captured by Venusian gravity into a nine day orbit. The burn was monitored from ESA's Control Centre, ESOC, in Darmstadt, Germany.

Seven further orbit control maneuvers, two with the main engine and five with the thrusters, were required for Venus Express to reach its final operational 24-hour orbit on 7 May 2006.

Venus Express entered its target orbit at apocentre on 7 May 2006 at 13:31 UT, when the spacecraft was at 151 million kilometres from Earth. Now the spacecraft is running on an ellipse substantially closer to the planet than during the initial orbit. The orbit now ranges between 66 000 and 250 kilometres over the Venus and it is polar. The pericentre is located almost above the North pole (80º North latitude), and it takes 24 hours for the spacecraft to travel around the planet.

Venus Express will study the Venusian atmosphere and clouds in detail, the plasma environment and the surface characteristics of Venus from orbit. It will also make global maps of the Venusian surface temperatures. Its nominal mission is planned to last for 500 Earth days (approximately two Venusian years). On-board resources are sized for an additional 500 Earth days.

Instrumentation

Venus Express is the first mission to visit Venus since the 1989–1994 NASA Magellan mission. Unlike the Magellan probe, Venus Express will not be capable of imaging the surface of Venus with high spatial resolution by means of cloud-penetrating imaging radar. It is, however, fitted with several instruments designed to study Venus in new ways.

Venus Express is outfitted mostly with spare parts and designs from the Mars Express and Rosetta missions. The spacecraft has been adapted to cope with the high radiation and thermal environment surrounding Venus.

ASPERA-4: An acronym for "Analyzer of Space Plasmas and Energetic Atoms," ASPERA-4 will investigate the interaction between the solar 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 on Mars Express, but adapted for the harsher near-Venus environment.

MAG: The magnetometer is 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 will be able to map the magnetosheath, 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 for lightning). MAG is derived from the Rosetta lander's ROMAP instrument.

PFS: The "Planetary Fourier Spectrometer" operates in the infrared between the 0.9 µm and 45 µm wavelength range and is designed to perform vertical optical sounding of the Venus atmosphere. It will perform global, long-term monitoring of the three-dimensional temperature field in the lower atmosphere (cloud level up to 100 kilometers). Furthermore it will search for minor atmospheric constituents that may be present, but have not yet been detected, analyze atmospheric aerosols, and investigate surface to atmosphere exchange processes. The design is based on a spectrometer on Mars Express, but modified for optimal performance for the Venus Express mission.

SPICAV: Short for "Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus," SPICAV is an imaging spectrometer that will be used for analyzing radiation in the infrared and ultraviolet wavelengths. It is derived from the SPICAM instrument flown on Mars Express. However, SPICAV has an additional channel known as SOIR (Solar Occultation at Infrared) that will be used to observe the Sun through Venus's atmosphere in the infrared.

VeRa: Venus Radio Science is a radio sounding experiment that will transmit radio waves from the spacecraft and pass them through the atmosphere or reflect them off the surface. These radio waves will be received by a ground station on Earth for analysis of the ionosphere, atmosphere and surface of Venus. It is derived from the Radio Science Investigation instrument flown on Rosetta.

VIRTIS: VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) is an imaging spectrometer that observes in the near-ultraviolet, visible, and infrared parts of the electromagnetic spectrum. It will analyze all layers of the atmosphere, surface temperature and surface/atmosphere interaction phenomena.

VMC: The Venus Monitoring Camera is a wide-angle, multi-channel CCD. It will operate in the visible, ultraviolet, and near infrared spectral ranges. It will map surface brightness distribution and search for volcanic activity, monitor airglow, study distribution of unknown ultraviolet absorbing phenomenon at the cloud-tops, and other science observations. It will create images and movies as well. It is derived in part by the Mars Express High Resolution Stereo Camera (HRSC) and the Rosetta Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS).

Important events and discoveries

August 3 2005: Venus Express completed its final phase of testing at Astrium Intespace facility in Toulouse, France. It flew on a Antonov An-124 cargo aircraft via Moscow, before arriving at Baikonur on 7 August.
August 7 2005: Venus Express arrived at the airport of the Baikonur Cosmodrome.
August 16 2005: First flight verification test completed.
August 22 2005: Integrated System Test-3.
August 30 2005: Last Major System Test Successfully Started.
September 5 2005: Electrical Testing Successful.
September 21 2005: FRR (Fuelling Readiness Review) Ongoing.
October 12 2005: Mating to the Fregat upper stage completed.
October 21 2005: Contamination detected inside the fairing — launch on hold.
November 5 2005: Arrival at launch pad.
November 9 2005: Launch from Baikonur Cosmodrome at 3:33 UT.
November 11 2005: First trajectory correction maneuver successfully performed.
February 17 2006: The main engine is fired successfully in a dress rehearsal for the arrival maneuver.
February 24 2006: Second trajectory correction maneuver successfully performed.
March 29 2006: Third trajectory correction maneuver successfully performed - on target for April 11 orbit insertion.
April 7 2006: Command stack for orbit insertion maneuver is loaded on the spacecraft.
April 11 2006: The Venus Orbit Insertion (VOI) is completed successfully, according to the following timeline:

	spacecraft time (UT)	ground receive time (UT)
Liquid Settling Phase start	07:07:56	07:14:41
VOI main engine start	07:10:29	07:17:14
pericentre 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

Period of this orbit is nine days.

April 13 2006: First images of Venus from Venus Express released.
April 20 2006: Apocentre Lowering Manoeuvre #1 performed. Orbital period is now 40 hours.
April 23 2006: Apocentre Lowering Manoeuvre #2 performed. Orbital period is now approx 25 hours 43 minutes.
April 26 2006: Apocentre Lowering Manoeuvre #3 is slight fix to previous AML.
May 7 2006: Venus Express entered its target orbit at apocentre at 13:31 UT

References

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External links

ESA description of the Venus Express mission
extrasolar-planets.com — Venus Express
ESA Science & Technology - Venus Express page
Orbit Insertion - Scheduled events to shape orbit concluding May 6, 2006
Venus Express Official Page

ESA probes | Venus spacecraft

Gourt Home::Gourt :: Venus Express

History

Instrumentation

Important events and discoveries

References

External links