A key instrument aboard Europe鈥檚 Mars Express spacecraft has been resuscitated after mysteriously breaking down several months ago.
Investigators are still searching for the cause of the failure, which could affect a similar instrument on the Venus Express spacecraft, due to launch on 9 November.
The Planetary Fourier Spectrometer (PFS) measures the composition and distribution of atmospheric gases on Mars by analysing the sunlight they reflect. It has repeatedly made headlines since it began operating in January 2004 because of its detections of methane and formaldehyde 鈥� gases that may signal life on the Red Planet.
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But it began to operate sporadically in April 2005 and gradually failed more and more often until it could no longer collect data, in July. In September and October, mission officials began switching on back-up components to try to find the source of the problem.
Finally, the instrument began to work when its extra 鈥減endulum motor鈥� was turned on. This device drives a rotating mirror that continuously changes the distance that one of two beams of incoming light travels. The second beam of light is sent down another path, so that the two beams interfere in a detector and produce telltale patterns that reveal the composition of the atmospheric gases.
Proof in the pudding
Engineers are still tweaking the optical setup to operate with the auxiliary motor, but on 27 October the instrument passed a critical test when it booted up correctly while the spacecraft was swivelling in space. Operating the delicate instrument during such a 鈥渕echanical disturbance was the ultimate proof in the pudding鈥�, says Fred Jansen, the spacecraft鈥檚 mission manager.
He expects the instrument to resume data collection in mid-November and is chairing a panel investigating what caused the first pendulum motor to fail. 鈥淲e have to see what we can do to avoid the problem鈥� in the now-operational auxiliary motor, he says.
Finding the cause may also help mission managers plan how they will use a similar instrument on the Venus Express mission due to lift off from the Baikonur Cosmodrome in Kazakhstan on Wednesday. But Jansen emphasises that the PFS worked for its design lifetime of one Martian year, 鈥渟o there was no need to do anything drastic鈥� with the Venus mission.
鈥淚 feel great,鈥� says Jansen of the instrument鈥檚 new lease on life. He says the PFS will now be able to study how Mars鈥檚 atmosphere changes over a longer timescale and further observations will 鈥渇irm up鈥� its contentious detections of methane and formaldehyde: 鈥淢ethane in the atmosphere is still a lively debate topic today.鈥�
