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DEPLOYED ANTENNA SENDING STREAMS OF NEW MARS IMAGES

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  • Jeroen Kumeling
    NASA Headquarters, Washington, DC Jet Propulsion Laboratory, Pasadena, CA March 29, 1999 DEPLOYED ANTENNA SENDING STREAMS OF NEW MARS IMAGES A steady stream of
    Message 1 of 1 , Mar 30 2:25 PM
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      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
      communications antenna.

      "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
      antenna deployment.

      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
      second.

      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.
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