MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
Contact: Mary Hardin (818) 354-0344
FOR IMMEDIATE RELEASEMarch 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 last night's deployment of the Mars
Global Surveyor's high-power communications antenna.
"Having a deployed, or 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. "We now have a steady stream of data."
"Up until now, we have been using the high-gain antenna in
its stowed position, so during the first three weeks of our
mapping mission, we had to stop collecting science data and turn
the entire spacecraft periodically to transmit data to Earth,"
Beerer explained. "Now that the high-gain antenna is deployed
and steerable, we have the ability to simultaneously make
measurements of Mars and communicate with Earth without turning
The antenna was deployed about 9:30 p.m. Pacific time
Sunday, March 28. It had been stowed since launch in November
1996 to reduce the chances of it being contaminated by the
exhaust plume 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 antenna
Last night, the 1.5-meter-diameter (4.9-foot) dish-shaped
high-gain antenna was deployed on a 2-meter-long (6.6-foot) boom
and was pushed outward from the spacecraft by a powerful spring.
A damper mechanism cushioned the force of the spring and limited
the speed of the deployment, somewhat similar to the piston-like
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 are recorded 24
hours per day on solid-state recorders onboard the spacecraft.
Then the data are transmitted to Earth once a day, during a 10-
hour tracking pass over a Deep Space Network antenna. 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 spacecraft's onboard recorder. These
data, which will contain high-resolution images of Mars, will be
transmitted at rates between 40,000 and 80,000 bits per second.
Mars Global Surveyor is managed by JPL for NASA's Office of
Space Science, Washington, DC. JPL's industrial partner is
Lockheed Martin Astronautics, Denver, CO, which developed and
operates the spacecraft. JPL is a division of the California
Institute of Technology.
Further information about the mission is available on the