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Mars Global Surveyor Update - September 16, 1997

Mars Global Surveyor
Flight Status Report 
Tuesday, 16 September 1997

     Five days after entering orbit around the red planet, performance 
from the Mars Global Surveyor spacecraft continues to be outstanding. At 
10:58 a.m. this morning, the spacecraft reached the top of its third 
orbit and performed a five-second rocket engine firing. According to 
navigator Eric Graat, this small burn slowed Surveyor by 9.8 m.p.h. (4.4 
meters per second) and altered the tilt of the orbit with respect to the 
Martian north pole by 0.05 degrees. 

     Today's maneuver lowered the altitude of the orbit's low point from 
its current value of 163 miles (263 km) down into the upper fringes of 
the Martian atmosphere at 93 miles (150 km). Surveyor is currently 
falling back toward Mars and will reach this low point at 9:22 a.m. on 
Wednesday morning. At that time, the onboard flight computer will 
configure the spacecraft for its first pass through the Martian 
atmosphere.

     Over the next four months, the spacecraft will lose momentum as it 
passes through the upper atmosphere during the low point of every orbit. 
This aerobraking technique will be used to lower the high point of 
Surveyor's orbit from its current altitude of 33,555 miles (54,002 km) to 
less than 280 miles (450 km).

     After a mission elapsed time of 313 days from launch, Surveyor is 
160.41 million miles (258.15 million kilometers) from the Earth and in an 
orbit around Mars with a period of 45 hours. The spacecraft is currently 
executing the P3 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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