Communication with the stranded Phobos-Grunt Martian probe is coming and going, following a first successful contact on Tuesday.
ESA's tracking station in Australia again managed to contact Russia's Phobos–Grunt spacecraft during the night of 23–24 November.
However, while the first pass delivered a clear signal, giving valuable information on the status and health of the spacecraft's systems, subsequent attempts to contact the probe failed.
"The first pass was successful in that the spacecraft's radio downlink was commanded to switch on and telemetry was received," says Wolfgang Hell, ESA's service manager for Phobos–Grunt.
"The signals received from Phobos–Grunt were much stronger than those initially received on 22 November, in part due to having better knowledge of the spacecraft's orbital position."
The second pass was short, and so was used only to uplink commands – no receipt of signal was expected.
However, on the following three passes early yesterday morning no signal was received.
The Russian mission controllers and ESA engineers believe that the reason's probably the orientation of the probe's communications system. During the first two passes, one of its two low-gain antennas was, due to the spacecraft's orbital position, oriented toward Perth, and communications worked.
During the three later passes, the spacecraft's orbital position changed, and the second, opposing, antenna was used – but to no avail.
"Our Russian colleagues will use this result for troubleshooting and to plan their commands for us to send tonight," says Manfred Warhaut, ESA’s Head of Mission Operations.
ESA engineers are now working to provide advice and assistance on how best to keep communication going. More attempts are planned.
It's still just about possible that Phobos-Grunt could continue with its planned mission to collect samples from the Martian moon. Even if that turns out not to be the case, it might be possible to give it a new target, such as an asteroid.