NASA likely to miss Curiosity Mars rover’s landing signal

London -  NASA’ most sophisticated Mars rover, Curiosity, is aiming for a deep depression known as Gale Crater to land on the red planet, but the US space agency might not be able to follow the progress of the rover all the way to the surface.

This is because the main satellite that is supposed to be tracking the descent may not now be in the correct place in the sky.

As Curiosity attempts to land on the planet on 6 August (GMT), engineers have been tackling a fault on the Odyssey satellite and it is no longer in the best observational orbit.

Unless it can be moved back in the next three weeks, NASA will lose signal to the rover just as it is about to touch down.

This will not affect the outcome of the landing because Curiosity’s descent manoeuvres are all performed autonomously, but it will give rise to some high anxiety as everyone awaits confirmation that the 2.5-bn-dollar mission is safely on the surface.

“Odyssey right now looks like it may not be in the same spot that we’d expected it to be,” the BBC quoted Doug McCuistion, the director of NASA’s Mars exploration programme as saying.

“There may be some changes in real-time communication. We’ll let you know as this develops; we still have more work to do. But keep in mind, there is no risk to [Curiosity] landing. It does not have an effect on that,” he added.

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 orientatation 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.

This would leave NASA blind for the final, nail-biting two minutes of the landing operation.

Antennas on Earth will be following the descent but they will lose contact as Curiosity hurtles into Gale, one of the deepest holes on Mars. The steep crater walls will block all direct radio transmission to the home planet not long after the supersonic parachute is opened.

The agency will have two other orbiters watching the descent - the Mars Reconnaissance Orbiter (MRO), and the Europeans’ Mars Express spacecraft - but these only have a “store and forward” capability, which puts a significant delay in their data return time to Earth.

MRO is the key satellite here. Its information will not be available to engineers on Earth for three to four hours after landing.

 â€œIf Odyssey is not able to be moved and it still remains late, that means it will fly over [Curiosity] after the spacecraft has landed, and we presumably will [then] be able to see transmissions from it. It would be somewhere between 22:35 and 22:40 PDT,” explained Pete Theisinger, the rover project manager at Nasa’s Jet Propulsion Laboratory in Pasadena, California.