Mars Surveyor Scientists Working on Balky Antenna
The main communications antenna on NASA’s Mars Global Surveyor spacecraft has become stuck and unable to automatically point toward Earth, a problem that could slow collection of data but shouldn’t put the mission at risk.
A hinge on the high-gain antenna stopped moving late last week, and flight controllers were unable to solve the problem over the weekend, Jet Propulsion Laboratory spokeswoman Mary Hardin said Monday.
The spacecraft put itself into a so-called contingency mode when the problem occurred, shutting down all science instruments and shifting communication with flight controllers to its smaller, low-gain antenna.
On Monday, engineers commanded the spacecraft to transmit recorded data that they hope will reveal what was happening on the spacecraft at the time the hinge stopped moving. Engineers did not expect to know what caused the problem until late Monday night or early this morning.
The hinge is one of two at the end of a boom on which the antenna is mounted. One hinge allows the antenna to move from side to side. The other hinge, which moves the antenna up and down, is the one that became stuck.
The hinges were designed to allow the high-gain antenna to keep pointing at Earth during communications sessions while the orbiting spacecraft keeps its instruments pointed at Mars to collect a continuous stream of images and data for mapping.
Engineers do not believe the problem is related to the March 28 deployment of the boom because the hinge had functioned properly since then.
Engineers have been concerned about deploying the boom from the folded position it had been in since launch because of worries that a device to cushion the force of the movement would malfunction.
The high-gain antenna can still be used even if the hinge doesn’t work. But that requires periodically halting the collection of science data and turning the entire spacecraft to point the antenna at Earth.
The $250-million probe is designed to photograph and map the surface of Mars at a much higher resolution than was possible with earlier spacecraft. The Global Surveyor is scheduled to photograph Mars for 687 days--a full Martian year. The start of photography was delayed for months because of problems with the hinge on a solar panel--the same sort of hinge that is on the antenna.
