Beagle to begin 'frequent calls'

If Beagle is alive, it will call more frequently

British-built Mars probe Beagle 2 was due to switch into a communications mode on Wednesday that increases the chances of contact being made with it.

If Beagle is intact on the Martian surface, it will automatically begin "calling" Earth more frequently.

Two further attempts were made on Tuesday to contact Beagle with the Mars Odyssey craft in orbit around the Red Planet, but with no positive result.

Mars Express, Beagle's mothership, will try to reach the lander in January.

Mars Odyssey carried out another flyby of Beagle's landing site on Wednesday, but again the craft received no signal from Beagle.

Beagle's onboard timer should tell it when 10 "passes", or attempts to contact it via Mars Odyssey and the radio telescope at Jodrell Bank, have been made.

Beagle should have taken the lack of contact after the tenth pass as its cue to start hailing Earth more frequently. This mode is known as communications search mode 1 (CSM 1). In this mode, Beagle tries to send a signal twice a day.

Timer reset

On 5 January, Beagle switches to communications search mode 2 (CSM 2). In this mode, Beagle will begin transmitting its pulse code continuously throughout the Martian day.

In this mode, Beagle tries to communicate once every 10 minutes.

Scientists had thought Beagle 2's onboard timer might have been reset during or after its descent to the Martian surface. This would mean the lander was working out of sync with the attempts made to contact it.

A hardware reset is now considered unlikely, but a software reset of stored contact times has not been completely eliminated.

Mars Express could begin searching for Beagle 2 by 5 January. Scientists now think this is their best chance of contacting the lander.

Mike McKay, flight operations director at the European Space Agency's (Esa) Space Operations Centre in Darmstadt, Germany, said he believed Mars Express would be in the best position above Mars to pick up a signal from Beagle from 7 January.