washington & munich
France is considering taking part in a proposed US spacecraft expedition to collect samples of Martian rock and return them to Earth. France's participation, if it comes about, could greatly increase the scientific return of the mission, which is planned for the year 2005.
The idea of France launching the 2005 spacecraft on Europe's large Ariane 5 launcher in exchange for a significant role in the US Mars exploration programme has been discussed for several months by officials at the French Centre National d'Études Spatiales (CNES) and the US National Aeronautics and Space Administration (NASA). NASA's rules prevent it from buying a non-US launcher directly.
No agreement has been reached, but the NASA Administrator, Daniel Goldin, said last week that he is optimistic that the sample return mission would be collaborative. “It is my hope and expectation that we will do this with the French,” he told a meeting of the American Astronomical Society meeting in Washington, DC.
NASA intends to launch spacecraft to Mars at every available opportunity for the next decade or more, with launch windows occurring every 26 months. The current plan is to send landers equipped with rover vehicles to two different sites on the planet in 2001 and 2003.
Each rover would collect rock samples and ‘cache’ them for later retrieval. The 2005 lander would then be sent to the site deemed more scientifically interesting of the two, where it would pick up the cached samples and return them to Earth in 2008.
Because of NASA budget constraints, the 2005 spacecraft is scheduled to launch on a medium-size Atlas or Delta rocket. But the Ariane, with its much larger capacity, would almost double the amount of payload that could be delivered to Mars. France could decide to use this excess capacity to send a lander to the second sampling site, according to Daniel McCleese, chief scientist for Mars exploration at NASA's Jet Propulsion Laboratory in California.
A full Ariane 5 launch would cost CNES about Ecu150 million (US$160 million. Other, cheaper alternatives for France include providing the Mars-orbiting vehicle that receives samples from the surface.
The country could also add scientific instruments to the 2005 rover — currently designated to be a ‘dumb’ rover that simply fetches samples collected on earlier missions. Adding the ability to analyse and collect its own rocks would provide a backup in case the rover is unable to retrieve the cached samples, says McCleese.
Francis Rocard, who heads the Solar System exploration office at CNES, says that if France were to furnish an Ariane launch, it would want to be involved in “some key elements” of NASA's Mars programme in return. This would probably include participation in the 2001 and 2003 missions, as well as the 2005 sample return, he says.
NASA has already chosen the scientific payload for the 2001 mission, but French scientists could be added as co-investigators, says Rocard. The 2003 payload, which has yet to be selected, could also include French experiments.
CNES has asked Germany to join the collaboration should an agreement with NASA be signed. It is likely that German scientists would contribute to the instrumentation but Germany's space budget is currently too tight to make a large involvement likely.
CNES scientists have long had an interest in Mars. The agency sponsored several experiments on the Russian Mars 96 spacecraft that failed two years ago before reaching the planet. French investigators are especially strong in the areas of imaging spectroscopy and micro-seismometers for planetary surface studies, according to McCleese.
International participation would strengthen NASA's Mars programme, he says, and is of particular interest to Goldin. Working groups from CNES and JPL have been meeting regularly to identify technical opportunities for collaboration, while the French government is working out budgetary issues. Both McCleese and Rocard hope for agreement by this summer.
The discussions come at a time when the European Space Agency's own proposed Mars mission, called Mars Express, faces uncertain funding (see Nature, 390, 325; 1997). CNES has been encouraged by French research minister Claude Allègre — himself a geologist who took part in analysis of the moon rocks — to play a large and consistent role in the international Mars programme and to do so it is prepared to forge significant bilateral agreements. This is a situation that secretly worries the ESA considerably, since bilateral agreements inevitably compete for national funding with scientific instruments for ESA missions.
Mars Express, a lander/orbiter mission scheduled for launch in 2003, may also include international collaboration. ESA and NASA have been discussing an Italian idea whereby a communications link on the Mars Express spacecraft would be used for the US sample return mission in 2005. So far, however, no agreements have been signed.
CNES and NASA are farther along in discussing what McCleese calls joint “precursor mini-missions” to Mars, which would be piggybacked on Ariane 5 launches that deliver commercial satellites to high geostationary orbits. These missions, which would run in addition to NASA's already planned Mars programme, could deliver between 80 and 160 kg of payload to the Martian surface beginning as early as 2000.
France would provide the Ariane 5 piggyback ride and an upper stage rocket, while NASA would provide the spacecraft. The scientific instruments would be developed jointly. Each mission would cost between $25 million and $50 million, and would be able to land simple instruments such as small probes or penetrators on the surface of Mars.
McCleese says the mini-missions would be ideal for positioning networks of sensors that could collect seismological and meteorological data. “It's something We've been working on for 20 years,” he says.
US funding for these mini-missions would have to come out of NASA's existing Mars programme, which is budgeted at about $1 billion over 10 years. The missions might also be accommodated within the agency's Discovery line of small and inexpensive planetary missions. As with collaboration on the sample return, no agreement has been reached yet. But McCleese believes the mini-missions have “a very high probability of happening”.