NASA Headquarters, Washington, DC
Jet Propulsion Laboratory, Pasadena, CA
March 29, 1999
DEPLOYED ANTENNA SENDING STREAMS OF NEW MARS IMAGES
A steady stream of new data from Mars, including high- resolution images,
will begin arriving next week at Earth receiving stations following
yesterday's deployment of the Mars Global Surveyor's high-power
"Having a deployed, steerable high-gain antenna is like switching from a
garden hose to a fire hose in terms of data return from the spacecraft,"
said Joseph Beerer, flight operations manager for Mars Global Surveyor at
NASA's Jet Propulsion Laboratory.
"Up until now, we have been using the high-gain antenna in its stowed
position, so periodically during the first three weeks of our mapping
mission, we had to stop collecting science data and turn the entire
spacecraft to transmit data to Earth," Beerer explained. "Now that the
high-gain antenna is deployed and steerable, we have the ability to
simultaneously study Mars and communicate with Earth."
The antenna was deployed at about midnight EST, Sunday, March 28. It had
been stowed since launch in November 1996 to reduce its chances of being
contaminated by exhaust from the spacecraft's main engine, which was fired
periodically throughout the mission. The spacecraft entered orbit around
Mars in September 1997 and used a technique called aerobraking to gradually
lower the spacecraft's altitude to the desired orbit for mapping. The
mapping mission began March 9; full-scale mapping begins April 4.
Because engineers were uncertain that a device intended to dampen the force
of the deployment would work correctly, engineers used the antenna in its
stowed configuration for the first three weeks of mapping. This allowed the
team to meet the mission's minimum science objectives before risking the
Last night, the dish-shaped high-gain antenna, 5 feet in diameter, was
deployed on a 6.6-foot-long boom and was pushed outward from the spacecraft
by a powerful spring. The suspect dampening device worked as it should
have, cushioning the force of the spring and limiting the speed of the
deployment, similar to the automatic closer on a screen door. With the
antenna successfully deployed, Mars Global Surveyor will return a nearly
constant stream of observations of Mars for the next two years.
Information from the science instruments is recorded 24 hours a day on
solid state recorders on board the spacecraft. Once a day, during a 10-hour
tracking pass over a Deep Space Network antenna, the data are transmitted
to Earth. In addition, every third day a second tracking pass is used to
transmit data "live" at a very high rate directly to Earth without being
put on the recorder. These data, which will contain high-resolution images
of Mars, will be transmitted at rates between 40,000 and 80,000 bits per
Mars Global Surveyor is managed by the Jet Propulsion Laboratory for NASA's
Office of Space Science, Washington, DC. Lockheed Martin Astronautics of
Denver developed and operates the spacecraft. The Jet Propulsion Laboratory
is a division of the California Institute of Technology.