Status: Operational 2005. First Launch: 2005-11-09. Last Launch: 2005-11-09. Number: 1 .
Payloads carried included:
NASA NSSDC Master Catalog Description
Venus Express was a European Space Agency (ESA) mission to study the atmosphere and plasma environment of Venus from orbit. The main goal of the mission was to conduct a comprehensive study of the atmosphere of Venus and to examine the plasma environment and the interaction between the upper atmosphere and the solar wind. Aspects of the surface and surface-atmosphere interaction were also studied. It primarily investigated: the role played by the greenhouse effect in creation of the atmosphere; the behavior and characteristics of cloud and haze formation at different altitudes; processes at work in atmospheric escape and its interaction with solar winds; and the mechanism behind the super rotation in the upper atmosphere. It was also designed to study the weak Venus' magnetic field, the UV absorption features at 80 km altitude, the high radio wave reflectivity areas on the surface, the atmosphere-surface interaction, and the possibility of volcanic or seismic activity.
The Venus Express spacecraft is based on the Mars Express satellite bus and has a launch mass of 1240 kg, which includes 93 kg of payload and 570 kg of fuel. The main bus is a rectangular box with dimensions of 1.65 x 1.7 x 1.4 meters. The core structure within the box is composed of an aluminum launch vehicle adapter ring, 90 cm in diameter and 20 cm high, two aluminum beams embedded in the ring, aluminum braces, two upper floors to hold the propellant tanks, an upper floor and three shearwalls to provide stiffness. The floor and wall panels are made of honeycomb bonded to aluminum face sheets. Propulsion and reaction control are provided by a bipropellant system comprising a 415-N main engine mounted under the lower floor and eight 10-N thrusters located at the four lower corners of the spacecraft. The two 267-liter propellant tanks, one containing nitrogen tetroxide and one containing mono-methyll hydrazine, are mounted in the center of the core structure. A 35.5 liter tank contains helium for use as a pressurant. Spacecraft attitude knowledge is provided by two star trackers, two sun sensors, and two inertial measurement units comprised of gyros and accelerometers. Reaction wheels are used for attitude maintenance.
Power of 1100 W at 28 volts DC at Venus orbit is supplied by two symmetric rotatable wings of 1056 gallium arsenide triple junction (GaInP2/GaAs/Ge) solar cells with a total area of 11.4 square meters interlaced with aluminum strips to minimize heating. Each wing has a mass of 20.7 kg. Power is stored in three 24-Ah lithium-ion batteries. Communications are via redundant dual band transponders which contain two duplicate transmit/receive chains, each with an X-band transmitter (8419 MHz) and receiver (7166 MHz) and an S-band transmitter (2296 MHz) and receiver (2100 MHz). The system uses a 1.3 meter high gain S- and X-band antenna, a smaller secondary high-gain X-band antenna, and two low-gain omnidirectional S-band antennas. It also uses two 65-W travelling wavetube amplifiers, a radio frequency distribution unit, and a waveguide interface unit. Downlink rates of up to 262,000 kpps are possible. Passive thermal control is achieved through the use of radiators, Kapton multi-layer insulation, heat pipes, optical solar reflecting covers and sulphuric anodisation coatings.
Data is stored in a 12 gigabit solid state mass memory and run by a control and data management unit. The scientific instruments are based on instruments on Mars Express and Rosetta. They are: the Venus Monitoring Camera, a wide angle imager; ASPERA, a combined energetic neutral atom imager, ion, and electron spectrometer, and magnetometer; PFS, an IR Fourier spectrometer; SPICAV/SOIR, a UV/IR spectrometer; VIRTIS, a UV, visible, IR imaging spectrometer; MAG, a suite of two magnetometers, and VeRa, a radio science experiment.
Venus Express launched successfully on 9 November 2005 at 03:33 UT (8 November 10:33 p.m. EST) on a Soyuz-Fregat booster from the Baikonur Cosmodrome in Kazakhstan. The original launch was to have taken place on 26 October 2005 but was postponed due to contamination of the launch fairing, After launch the spacecraft went directly to a Venus transfer trajectory. Cruise to Venus took 153 days and covered a distance of roughly 400 million km. Arrival at Venus and orbit insertion began on 11 April 2006 with the LSP start at 7:14:44 UT (3:14:44 EDT - Earth received time, one way transmission time is about 7 minutes) and main engine start at 7:17:14 UT (3:17 a.m. EST). The burn ended at 8:07:28 UT (4:07 a.m. EDT) after imparting a delta-V of 1246.28 m/s. The initial orbit was 400 x 350 000 km with a period of about 9 days, a sequence of seven maneuvers culminating on 6 May on orbit 16 brought it into an elliptical 24 hour, 250 x 66000 km polar orbit with the periapsis centered initially over 78 N latitude. The nominal mission started on 4 June 2006 and was originally planned to last roughly two Venus sidereal days (486 Earth days), but has been extended and is still operational. The nominal orbit is still a 24 hour polar orbit, with a periapsis altitude of 170 to 270 km and apoapsis altitude of 66000 km. The pericenter has drifted northward at roughly 3 degrees per year, reaching the north pole in October 2009. It now continues southward at the same rate. Staus of the spacecraft has been nominal except that the PFS instrument has not been operational since launch due to a malfunction, a decrease in S-band signal level occurred at the end of 2006, and the VIRTIS-M cryocooler failed in October 2008 disabling the VIRTIS-M infrared channel. Routine science operations ended on 15 May 2014, and the spacecraft periapse was allowed to drop to 130-135 km to study atmospheric density and aerobraking effects, with the core part of the study lasting from 18 June to 11 July. The periapse was raised again to 460 km and the mission entered a reduced science phase. The fuel was assumed to be depleted by late November and contact was lost with Venus Express on 28 November 2014.
Total budget for the mission was 220 million euros ($262 million U.S. 2005) of which 82.4 million euros is for satellite construction and instrument integration and 37 million euros is for the launch.
Credit: Manufacturer Image
Launch delayed from October 26. The Soyuz placed the probe and Fregat upper stage into a 30 km x 190 km x 51.6 deg orbit around the earth. At apogee the Fregat stage made a 50 m/s maneuver to circularize the orbit. At the appropriate moment in this parking orbit, the Fregat fired again, then separated from the now Venus-bound probe at 05:11 GMT. Venus Express passed lunar orbit on November 10 at 10:10 GMT and went into a 0.702 AU x 0.993 AU x 0.26 deg inclination solar orbit. It was to brake itself into a 250 km x 326,550 km x 89.7 deg orbit around Venus on 11 April 2006 at 08:40 GMT. Two maneuvers would put in its final 24-hour Venus orbit of 282 x 66,911 km x 90.0 deg on 30 April. This was selected to synchronise the satellite with tracking stations on earth, while the planet slowly revolves below its perigee point over the following several months.