Tim Furniss/LONDON

The Mars Polar Lander (MPL) will not lose its science-gathering capability as a result of the loss of the Mars Climate Orbiter on 23 September, says NASA's Jet Propulsion Laboratory. The MPL is set to land on the edge of the Martian south pole on 6 December.

Initially, the Orbiter was to have acted as the prime relay station for the Lander before proceeding with its own science mission. Back-up systems will be used "to meet all the Polar Lander mission's requirements", says NASA. The statement is intended to counter claims by observers that the science goals of the MPL would be compromised as a result of the loss, despite the fact that the Mars Global Surveyor (MGS), in orbit around the planet, will be used as the primary relay station for the Lander.

The Surveyor had been assigned the job of collecting data from the two Deep Space 2 penetrator probes to be ejected from the MPL as it approaches the planet.

While the Surveyor can be used to relay transmissions from the MPL, the Lander could transmit direct to the NASA Deep Space Network tracking system. In this case, however, there will be a loss of science data, particularly as the transmission capability of the Lander is 15 times less than that of the lost Orbiter.

The Surveyor will be used as a relay station as well as relaying its own science data. Some science work, however, may be lost from the Surveyor since NASA will need antenna time to support communications with the Lander, as well as to continue the MGS science work.

NASA will not know whether the Surveyor relay will work until four days after the Lander arrives. If there is a problem, communications could be switched via the MGS's Mars Orbiter Camera, but the data will go straight to the science team and will have to be decoded and compressed before being sent to Jet Propulsion Laboratory's mission control.

A course-correction manoeuvre for the Lander has been set for 20 October after the mission controllers worked out how to reconfigure the communications commands and send new data to the spacecraft to allow it to communicate directly with the earth rather than via the MGS.

• ABC TV reports that 10 days before the Orbiter loss , the navigation team warned that the craft was coming in too close to Mars and a course adjustment was necessary. The requests were "repeatedly turned down", say sources.

Source: Flight International