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Mars Global Surveyor Update - September 14, 1997

Mars Global Surveyor
Flight Status Report 
Sunday, 14 September 1997

	Today marked Surveyor's third full day of operations in orbit 
around the red planet. As of 11:59 p.m. PDT, the spacecraft has just 
passed the halfway point of its second revolution around Mars and is now 
falling back toward the low point of  its orbit. Surveyor will reach this 
point at 12:28 p.m. on Monday. 

	Currently, the spacecraft's velocity relative to the surface of 
Mars measures 1,271 m.p.h. (568 meters per second). By the time Surveyor 
reaches the bottom on Monday afternoon to start its third orbit, the 
velocity will have accelerated to nearly 10,515 m.p.h. (4,700 meters per 
second).

	Most of the day's activities were devoted toward configuring the 
spacecraft for orbital operations. The first of these occurred early in 
the morning when the onboard flight computer was commanded to switch its 
internal navigation system from an Earth-based coordinate frame to a 
Mars-based frame. Later in the afternoon, the computer loaded critical 
parameters into the software for the aerobraking phase of the mission 
that will begin Wednesday morning.

	Tomorrow afternoon, Surveyor will perform a rotation to point the 
science instruments directly at Mars during a 20-minute period centered 
on the point of closest approach of the third orbit. This opportunity 
will allow the laser altimeter and camera to collect science for the 
first time at Mars. The laser is currently powered off and will be 
activated about six hours prior to the start of orbit number 3.

	In addition, the Thermal Emission Spectrometer and Magnetometer 
science instruments will also utilize Monday's 20-minute opportunity to 
scan the red planet. However, these instruments have been collecting data 
on a continuous basis because they do not need to be pointed directly at 
Mars in order to operate. 

	After a mission elapsed time of 311 days from launch, Surveyor is 
159.49 million miles (256.67 million kilometers) from the Earth and in an 
orbit around Mars with a period of 45 hours. The spacecraft is currently 
executing the T2 command sequence, and all systems continue to be in 
excellent condition.

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Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
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