Contact with Curiosity may be lost during its descent to the Martian surface

As NASA prepares for the August 6 landing of the Curiosity rover on Mars, its scientists have made the disturbing realization that communication will likely be lost during its harrowing seven minute descent to the surface. Engineers attribute the fault to a critical support satellite, Odyssey, which is currently stationed in orbit around the red planet. But despite the setback, NASA is assuring the public that it won't affect the landing.

The problem has to do with the positioning of Odyssey during the time of the descent. Unless they can reposition the satellite in the next three weeks, NASA will lose the signal to the rover literally one minute before making its historic landing.

Contact with Curiosity may be lost during its descent to the Martian surface

NASA attributes the glitch to adjustments made on July 11 when working on Odyssey's attitude control systems. The satellite moved slightly in its orbit and then put itself into a temporary safe mode. By July 13, NASA had sent commands to the satellite, taking it out of its self-imposed hibernation and reorienting it to point downward at Mars.

But now, NASA may have to wait an excruciating 1.5 to 2 hours before Odyssey makes a pass over the Curiosity landing site.

The rover, which weighs 900kg, will hit the top of the Martian atmosphere at 20,000km/h (13,000mph) and quickly slow down to a rate of one meter per second prior to making a soft touchdown. The system is completely autonomous and no external interventions are required; the satellite glitch should have no impact on the landing itself, merely in how the data gets sent back to Earth and how timely that data is.

That said, NASA could stand to lose critical data from the descending spacecraft. Writing in the BBC, Jonathan Amos explains:

Engineers have built a complex EDL system that includes a supersonic parachute and a rocket-powered crane. Everything must work on cue and in sequence.

It was expected that the Odyssey orbiter would track the whole descent, relaying UHF signals from the rover right up to the landing and for a few minutes beyond.

But the spacecraft recently experienced a reaction wheel failure.

This device is used to manage the satellite's orientation and momentum in space, and because engineers have been investigating the issue they have not as yet moved Odyssey back into the correct orbit to see the full landing sequence - and they may not do so.

But all is not lost as far as tracking data is concerned. According to Popular Science, the "aging" Mars Odyssey is one of two other spacecraft NASA plans on using to track Curiosity's descent, namely the Europeans' Mars Express satellite (which will also be in a poor position), and NASA's other satellite, the Mars Reconnaissance Orbiter (MRO). However, the MRO is only capable of "store and forward" capability, which means that it'll transmit data to Earth about three to four hours after the descent.

All this said, NASA is still holding out for Odyssey. They may be able to tweak its orbit in time for the descent. Hmm, as if the seven minutes of terror isn't going to be nail-biting enough.

Sources: NASA, BBC, Popular Science, Discovery News.

Images via EDL-Odyssey/NASA/JPL.