After two failed Mars missions, the Odyssey craft will pave the way for future exploration of the red planet

NASA's $297 million Mars Odyssey spacecraft entered an initial orbit around the red planet after a 20min engine firing on 24 October. The successful orbiting boosted confidence in NASA's Mars exploration plans following the dual failures of the Mars Climate Orbiter (MCO) and Mars Polar Lander (MPL) in 1999.

The MCO failure, which resulted in the craft plunging into the Martian atmosphere, was due to confusion between NASA and prime contractor Lockheed Martin over the use of imperial and metric values, while the Lockheed Martin-built MPL's descent engine probably failed and the craft crashed on the surface after the landing leg deployment resulted in spurious signals to the engine due to bad wiring.

The 725kg (1,600lb) Lockheed Martin-built Mars Odyssey, which will study the geology and chemical composition of the planet, has completed a 200-day, 460 million km (285 million mile) journey since its launch in April. The initial, highly elliptical 19h Martian orbit is due to be reduced to a shorter, 2h circular orbit of approximately 400km altitude, performed by a series of aerobraking manoeuvres over the next 70 days. These manoeuvres use the atmospheric drag against the craft to slow its speed as the spacecraft reaches the low point of its orbit, slowly circularising the elliptical path.

The 917-day Mars Odyssey science mission will be performed by three science instruments - a thermal infrared imaging system, a gamma ray spectrometer and a radiation environment experiment.

The craft will also serve as a communications relay station for a series of US and international Mars missions planned in 2003-04 and will continue to be available in this mode for future missions.

NASA's Jet Propulsion Laboratory (JPL) Mars Exploration Rover team, meanwhile, has selected four prime candidate target landing sites for the two spacecraft which are planned to be launched in 2003. Two other sites have been selected as back-ups.

Each target area will be evaluated in detail using images from the Mars Global Survey, the Mars Odyssey orbiter and archived coverage from previous spacecraft. The prime sites are Hematite in Terra Meridiani, Melas Chasma in Valles Marineris, Athabasca Vallis in Elysium Planitia and the Gusev crater, with Isidis Planitia and Eos Chasma as back-up sites.

JPL, which is working on the designs of potential miniature, 3.6kg surface and sub-surface vehicles for exploring the planets and their moons, has proposed the use of bulldozers on Mars. The lightweight bulldozer rover, equipped with the latest artificial intelligence techniques could be used to investigate sites of potential hot springs, layers of ice or groundwater reservoirs identified from orbit.

Source: Flight International