NASA Engineers Fix Orbiter Millions Of Miles Away
June 28, 2012

NASA Engineers Fix Orbiter Millions Of Miles Away

Lee Rannals for - Your Universe Online

NASA's Mars Odyssey orbiter is back in business after the spacecraft found itself placed into "safe" mode earlier this month.

The spacecraft's flight team returned the orbiter back to full service this week after a two-week sequence of activities to recover Odyssey from safe mode.

The orbiter switched itself to safe mode when one of the three primary reaction wheels used for altitude control stuck for a few minutes on June 8.

NASA engineers determined that the sticking wheel was unreliable, so they switched the spacecraft to a spare one that had been unused since the mission's April 7, 2001 launch.

"Odyssey is now back in full, nominal operation mode using the replacement wheel," Steve Sanders, lead engineer for the Odyssey team at Lockheed Martin Space Systems, said in a press release.

Observations with Odyssey's Thermal Emission Imaging System and its Gamma Ray Spectrometer resumed on the Red Planet on Monday. The orbiter also acts as a Mar's rover relay for NASA.

The space agency said that it received data from its Mars Exploration Rover Opportunity on Wednesday, showing that Odyssey's relaying capabilities are up and going.

Odyssey will soon be serving as a communication relay for NASA's new Mars Science Laboratory mission once the spacecraft lands in August.

As of Wednesday, the Mars Science Laboratory has traveled about 307 million miles of its 352-million-mile route to Mars, according to NASA.

MSL, which is carrying the one-ton rover Curiosity, is expected to arrive at the Red Planet on August 5, 2012, after venturing through space towards Mars since its November 26, 2011 launch.

In order to communicate Mars rovers to Earth, Odyssey uses a set of three reaction wheels to control which way it is facing relative to the Sun, Earth or Mars.

Increasing the rotation rate of a reaction wheel on Odyssey causes the orbiter to rotate in the opposite direction. The spacecraft's configuration in use from launch up until this month combined the effects of three wheels at right angles to each other to provide control in all directions, according to NASA.

The replacement wheel engineers just recently installed is skewed at angles to all three of the others so that it can be used as a substitute for any one of them, NASA said.

Odyssey is also capable of using thrusters for directing its orientation, but this method requires the orbiter to use its limited supply of propellant, rather than the electricity it gains from the Sun.