Satellite problem may delay confirmation of Mars landing

Engineers are studying options for dealing with a glitch in a Mars-orbiting satellite that could delay receipt of telemetry confirming a successful August 6 landing by NASA's Mars Science Laboratory rover.

by William Harwood

July 16, 2012 3:23 PM PDT

Best-case scenario: An artist's rendering of Curiosity safely on Mars.

(Credit: NASA)

Unexpected problems with a NASA science satellite in orbit around Mars could briefly delay receipt of telemetry from the agency's $2.5 billion Mars Science Laboratory rover during the spacecraft's dramatic 7-minute descent to the surface August 6, officials said Monday.

While the issue with the orbiting Odyssey satellite will have no effect on the rover's ability to successfully execute its autonomous entry, descent, and landing sequence -- half jokingly dubbed "Seven Minutes of Terror" by project engineers -- it could mean an additional period of nail-biting before confirmation that the so-called "sky crane" landing technique actually worked.

Touchdown on the floor of Gale Crater is expected at 1:17 a.m. EDT (GMT-4) on August 6. Because of the distance between Earth and Mars on landing day -- 154 million miles -- the earliest possible confirmation of landing would come 13.8 minutes later, at 1:31 a.m. "Earth received time."

"Odyssey lost a reaction wheel a few weeks ago," Doug McCuistion, director of the Mars Exploration Program at NASA headquarters, told reporters. "That was totally unexpected. Reaction wheels are utilized to help manage spacecraft attitude and momentum in space. We haven't fully worked out the issue related to that loss yet, but we have plenty of backup systems."

To be clear, he said, "it won't have any impact on (the rover's) landing. It's all a communications issue."

The Mars Science Laboratory rover, named Curiosity, is one of the most expensive -- and technologically challenging -- planetary science missions ever attempted. Over the course of a two-year mission, the nuclear-powered rover will explore Gale Crater and attempt to climb up a 3-mile-high central mountain, using a suite of sophisticated instruments to help scientists understand the broad history of Mars and whether it ever hosted a habitable environment.

Tipping the scales at 1 ton, Curiosity is the size of a small car, too large to use the airbag landing system devised for NASA's Pathfinder and the long-lived Spirit and Curiosity rovers.

Faced with the challenge of getting a large rover off the top of a traditional rocket-powered lander, engineers came up with a novel approach known as the sky crane. Instead of putting the rover on top of a legged lander, they put the rover below it and did away with the legs altogether.

As the lander approaches the surface, descending under the power of eight rocket engines, Curiosity will be lowered on a long cable directly to the ground. Once its wheels make contact, the cable will be severed and the rocket-powered descent stage will fly off to a crash landing a safe distance away.

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