— NASA may call on its fleet of Martian probes including the twin rovers to come to the aid of its Mars Global Surveyor spacecraft, which has not called home in more than a week.
On 2 November, the 10-year-old Mars Global Surveyor (MGS) orbiter notified Earth that it had had trouble adjusting the position of one of its two solar panels. Then it went silent for two days. A very weak signal was detected on 5 November but nothing has been heard from the spacecraft since (see NASA struggles to contact lost Mars probe).
The spacecraft is programmed to try to contact Earth after going seven days without receiving commands. This would have fallen on either 9 or 11 November, depending on whether the spacecraft received commands NASA tried send it on 4 November. NASA listened on both days, but heard nothing.
Now, the agency plans to use another of its spacecraft, the Mars Reconnaissance Orbiter (MRO), to try to diagnose the problem. MRO arrived at Mars in March 2006.
Late on Wednesday, MRO will try to determine MGS's location by taking a picture with a low resolution camera. Using this information, MRO will take another image of MGS on Friday using its High Resolution Imaging Experiment (HiRISE) the most powerful camera ever sent to Mars.
The HiRISE image should be detailed enough to determine how MGS is oriented in space and how its solar arrays are positioned.
If one of the solar arrays is pointed too far away from the Sun, MGS may be slowly running out of power. Its power may have already dropped below the level needed to operate the spacecraft's transmitters, which would explain its silence.
If there is a slow decline in power and it cannot be stopped, the spacecraft would eventually die. "If we're gradually losing power we could lose the spacecraft," says MGS manager Thomas Thorpe of NASA's Jet Propulsion Laboratory in Pasadena, California, US.
If the MRO image confirms there is an improperly pointed solar panel, MGS's managers can try to command the entire spacecraft to turn so the faulty solar array receives more sunlight. If it is turned, the other solar array should be able to track the Sun because it has shown no signs of trouble.
If the MRO images do not help find and fix the problem, there is another option. Mission managers could command MGS to turn on an onboard radio beacon, which the Mars rovers Spirit and Opportunity may be able to hear.
The beacon signal would not contain any information, but its detection would at least indicate that the spacecraft is alive and able to respond to some commands. If the rovers heard the signal, they could notify another NASA orbiter, the Mars Odyssey spacecraft, which would in turn tell Earth.
"If next week we really don't have any other options, then we would do it," Thorpe told New Scientist.
Even though there are several other spacecraft now observing Mars, a revived MGS would be especially useful for tracking changes on Mars, Thorpe says, by comparison with observations MGS has made over the past nine years.
"When you're looking for changes, it's important to look with the same instruments and sensitivity to know that what you're seeing are really changes, and not due to a different instrument or sensitivity," he says.