The first Venus mission in 15 years–and the only one planned this decade–is off on a five-month journey to our nearest planet following a successful launch last week.
The 1.2-metric-ton Venus Express, built by EADS Astrium and Alcatel Alenia Space, blasted off from the Baikonur Cosmodrome in Kazakhstan on Nov. 9 atop a Starsem Soyuz-Fregat booster. Immediate indications were that all systems were functioning normally.
The Fregat upper stage ignited a first time 9 min. into the flight, maneuvering the spacecraft into a low Earth parking orbit. A second firing, 1 hr., 22 min. later, boosted the probe into its interplanetary trajectory.
It was the year’s second Starsem mission, after PanAmSat’s Galaxy 14 in August.
The launch had initially been set for Oct. 26, but was delayed because of a thermal protection separation problem on the Soyuz upper stage. However, Gerhard Schwehm, head of planetary missions at the European Space Agency, which funded the mission, said that Nov. 9, near the middle of the month-long launch window, actually provided more favorable mission conditions. That, together with near-perfect Earth escape trajectory, will allow the mission to last up to 4.5 years. The nominal mission is two Venusian days (486 Earth days).
Venus Express was built in record time–five years from inception to launch–and at a relatively low cost of 220 million euros ($257 million), including instrumentation and two years of operation. This was made possible by borrowing heavily from its sister mission, Mars Express, currently in orbit, and the Rosetta spacecraft hurtling toward a 2014 comet rendezvous.
Nevertheless, Venus Express features breakthrough technologies in the thermal protection system and the solar panels, necessary to protect the spacecraft and its instruments from the harsh Venusian environment (AW&ST Aug. 1, p. 52). These technologies will serve as a basis for future forays into the inner solar system, including BepiColombo, said Michel Bouffard, Earth observation and science manager at Astrium.
THE SEVEN INSTRUMENTS on board will be commissioned in two steps, in the vicinity of Earth and then in the vicinity of Venus. Arrival in Venus orbit is set for Apr. 11, where Venus’s strong gravity–7.6 times that of Mars–is expected to present much tougher conditions for correct orbital insertion than Mars Express. First scientific results are expected in July.
Speaking at ESA’s space control center here, Director General Jean-Jacques Dordain noted that the agency is now in a position to study both Venus and Mars, the two planets most resembling Earth, at the same time, after visiting Titan, another body with terrestrial-like processes, at the beginning of the year. ESA also has a probe in orbit around the Moon, and is building one to explore Mercury to be launched in 2013.
Despite the wealth of information and 3D imagery provided by Mars Express, scientists think the impact of its Venus sistership will be even greater, if only because of the dearth of data currently available. Since the U.S. Pioneer Venus missions in 1978-92, scientists’ attentions have been focused on Mars and the outer solar system, and the search for life.
Indeed, the European mission is to be followed around 2010 by a Japanese probe, Planet-C, and there is talk of an ESA follow-on to Venus Express as well.
The main focus of Venus Express will be to gather data relative to the structure, chemistry and dynamics of the Venusian atmosphere, particularly the lower layers, about which virtually nothing is known. The goal is to obtain a “big-picture snapshot” explaining the reasons for the extremely high temperature and atmospheric pressure levels and huge greenhouse effect reigning on Venus, perhaps shedding light on climate changes currently perceived on Earth (AW&ST Oct. 24, p. 29). The only atmospheric data available now date back to Pioneer Venus.
Instruments on Venus Express include:
*A Planetary Fourier Spectrometer (IFSI-INAF, Italy) will measure atmospheric temperature and composition at varying altitudes, and provide a surface temperature map. Mission planners said they had made no changes following problems with a similar PFS on Mars Express, preferring to rely on the same redundancy features that permitted recovery of the Martian instrument (see p. 15).
*An infrared/ultraviolet spectrometer, Spicav/Soir (CNRS Aeronomy Service, France; Institute for Space Aeronomy, Belgium; IKI, Russia) will search for traces of water, oxygen and sulfur compounds thought to be present in the atmosphere. It will also measure density, temperature and pressure in the upper atmosphere (50-112 mi.).
*VeRa, a radio science experiment (Universitaet der Bundeswehr, Munich), will take atmospheric density, temperature and pressure readings between 35-100 km. altitude, and measure roughness and electrical properties on the planet surface. An ultra-stable clock will ensure a steady emitting frequency for optimum readings.
*Virtis, a UV/visible/near-IR spectrometer (CNR-IASF, Italy; Observatoire de Paris, France), will map the various layers of the atmosphere and study atmospheric dynamics.
*A magnetometer, MAG (IMF, Graz, Austria), and a plasma analyzer, Aspera (Institute of Space Physics, Sweden), will observe the interaction between the upper atmosphere and the solar wind, and analyze how the absence of a magnetic field affects this interaction; study the magnetic field generated by the plasma; and measure the rate at which water vapor and other molecules are escaping from the atmosphere.
Venus Express will also carry a high-resolution camera, developed by MPS of Katlenburg-Lindau, Germany. Operating in near-infrared, ultraviolet and visible wavelengths, the Venus Monitoring Camera is expected to send back views of the planet surface much clearer than the radar images taken by the American Magellan mission in 1990-94.
Among the targets, said Lucia Marinangeli, from IRSPS of Pescara, Italy, are the planet’s mountain belts–the first discovered beyond Earth, and an indicator of tectonic activity. Venus’s many volcanos, some of which may still be active, will also be in the camera sights. The VMC will try to exploit the “infrared windows” revealed during a flyby by the U.S. Galileo probe in 1990 on its way to Jupiter, which make it possible to penetrate cloud cover through to the surface.
Colin Wilson, an Oxford University scientist on the Virtis team, remarked that the capture orbit, which should last about six days at the mission’s outset, will provide particularly favorable conditions, because the probe will be hanging over the South Pole with the full planet in view. Thereafter, no more than a third of the planet will be visible at one time. Wilson said that VMC will also be used to monitor dynamic atmospheric phenomena such as the polar vortices and superrotation, along with weather activity suggested by Galileo imagery.
A new deep space antenna in Spain–ESA’s second–will help speed the reception and distribution of data.