Concern that the antenna might be damaged during its deployment prompted the Mars Global Surveyor team to complete three weeks of mapping with the antenna in its stowed position. Data was transmitted during that period, but with the antenna deployed the rate of transmission has grown dramatically, a NASA scientist said. The 2-meter antenna boom swung out a short distance before a damper in the deployment hinge kicked in, which slowed the antenna for a smooth, controlled deployment. It could have been worse. The flight team had been concerned that the damper aboard the spacecraft, which has been in space since 1996, would not perform as designed.
Scientists believe such damper devices are altered during prolonged exposure in a vacuum.
Trouble for the 1,060-kilogram Mars Global Surveyor spacecraft began shortly after its November 1996 launch when one of the explorer's solar arrays failed to deploy to its proper position, said Charles Whetsel, chief engineer for Mars Global Surveyor from 1996 to 1999. The flight team surmised that a piece of a damper device installed to cushion the mechanical shock of the array's deployment had broken off and become wedged in the hinge joint connecting the solar panel to the Lockheed Martin Astronautics-built spacecraft. The misaligned solar array would delay the start of the primary mapping mission by one year, until March 1999, but the flight team made the most of the delay by making close fly-by observations of the planet that otherwise would not have been possible, said Arden Albee, project scientist for Mars surveyor operations. They theorized that prolonged exposure to space could degrade the device's ability to slow, or dampen, the momentum of a deployable item such as the antenna, Whetsel said. In April 1998, a mock-up of the Mars Global Surveyor deployment hinge and damper device were placed in a vacuum chamber for three months.