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Flight Status Report

Friday, 19 September 1997

This morning at 6:28 PDT, Surveyor reached the low point and start of its fifth orbit around Mars. For a time period of 24 seconds centered around this point in the orbit, the spacecraft performed its second aerobraking pass of the mission by skimming through the upper Martian atmosphere at an altitude of 79.5 miles (128 km). During the pass, air resistance caused a 10 degree increase in temperature on the solar panels. This rise was well within allowable limits.

According to Surveyor's atmospheric science team, the thickness of the atmosphere during today's pass was more than twice the expected value as predicted by current models. However, because the air at the current aerobraking altitude is extremely thin, this increased thickness posed no threat to the spacecraft.

Based on today's new data about the thickness of the upper Martian atmosphere, the flight team has decided to lower the altitude of next aerobraking pass to 75 miles (121 km). In the original plan, the altitude of the next pass occurred at 72.7 miles (117 km). This new altitude is slightly higher in order to offset the increase in atmospheric thickness as compared to the model value. Over the next week, the flight team will continue to lower the aerobraking altitude until the spacecraft encounters enough air resistance to slow down by an appreciable amount on every orbit.

As of 11:59 p.m. PDT, Surveyor is climbing toward the top of its fifth orbit around the red planet. Currently, the spacecraft is at an altitude of 32,930 miles (53,000 km) and is moving with a velocity of 805 m.p.h. (360 meters per second) with respect to the planet. The next aerobraking pass through the atmosphere will take place early Sunday morning at the low point and start of the sixth orbit.

After a mission elapsed time of 316 days from launch, Surveyor is 161.76 million miles (260.33 million kilometers) from the Earth and in an orbit around Mars with a period of just under 45 hours. The spacecraft is currently executing the P5 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