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Mars Global Surveyor Update - September 12, 1997

Mars Global Surveyor
Flight Status Report 
Friday, 12 September 1997

	The Mars Global Surveyor spacecraft continues to perform flawlessly 
24 hours after entering orbit around the red planet. As of 11:59 p.m. 
PDT, the spacecraft has completed half of its first revolution around 
Mars by reaching the high point of the orbit. This point lies at an 
altitude of 33,570 miles (54,026 km) above the planet. The spacecraft is 
now falling back toward Mars, and will reach the low point and start its 
second orbit at 3:28 p.m. PDT on Saturday.

	Today, the navigation team released a preliminary solution of the 
spacecraft's orbit following yesterday's successful Mars orbit insertion 
burn. "We targeted for a 45-hour orbit period and achieved an orbit of 44 
hours, 59 minutes, and 34 seconds," said chief navigator Dr. Pat 
Esposito. "That's what I call a precision maneuver," he added.

	Data transmitted to Earth from Surveyor corroborates Esposito's 
assessment of a precision maneuver. This data was collected by the 
spacecraft's accelerometers and shows that that the orbit insertion burn 
slowed the spacecraft by 2,176.61 m.p.h. (973.03 meters per second). This 
value differs from the expected value of 2,176.58 m.p.h. by less than 
one-thousandth of one percent.

	Lead propulsion engineer Sam Dominick reports that the burn 
consumed 621.15 pounds (281.75 kg) of Surveyor's propellant supply. As 
expected, this value amounts to most of the spacecraft's total capacity. 
Currently, the hydrazine fuel tanks are only 31% full, and the nitrogen 
tetroxide oxidizer tank contains just over 9% of its original supply.

	Saturday evening, the flight team will activate Surveyor's science 
instruments two hours after the start of the second orbit. This 
activation will allow the Magnetometer and Thermal Emission Spectrometer 
science instruments to collect data on a continuous basis. However, the 
Mars Orbiter Camera and Mars Orbiter Laser Altimeter instruments need to 
be pointed directly at Mars to collect data. The first opportunity for 
these two instruments will occur during a 15-minute time period centered 
on the start of third orbit on Monday at 12:28 p.m. PDT. Additional 
science data will be acquired during the forthcoming aerobraking phase of 
the mission. The actual start of mapping operations will not begin until 
March 1998.

	After a mission elapsed time of 309 days from launch, Surveyor is 
158.18 million miles (254.56 million kilometers) from the Earth and in an 
orbit around Mars with a period of 45 hours. The spacecraft is currently 
executing the T1 command sequence, and all systems continue to be in 
excellent condition.

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