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Flight Status Report

Friday, 25 July 1997

As of today, less than seven weeks remain until arrival at Mars. Over the past two weeks, the flight team has spent the majority of their time preparing for this arrival by conducting operational simulations, finalizing operational plans, and modifying Surveyor's onboard flight software.

Two simulations were conducted on July 17th and July 24th. These exercises were designed to train flight team members and tracking antenna operators of the Deep Space Network to react to time-critical situations that will occur during aerobraking. In this phase of the mission, the flight team will lower the high point of Surveyor's orbit from 56,000 to 400 km by repeatedly flying the spacecraft through the upper Martian atmosphere. Each exercise provided an opportunity for the team to analyze spacecraft telemetry from a simulated atmospheric pass, and to use the analysis toward generating new commands for the next pass.

In addition to the operational simulations, the flight team made two different modifications to Surveyor's onboard flight software. The first one involved reprogramming the payload data subsystem to collect information packets from the science instruments at a slightly faster rate. This improvement in efficiency will allow the camera and Thermal Emission Spectrometer to increase their combined volume of scientific data transmission by about 10%.

The second of the two software modifications will allow Surveyor's flight computer to automatically activate gyroscope #2 in the unlikely event that an anomalous condition is detected in either the #1 or #3 gyros. Normally, all three gyroscopes are active during flight to help the spacecraft keep track of its pointing orientation in space. However, because only two gyroscopes are required at any one time, project management has decided to save the #2 gyro for use as a backup in emergency situations.

After a mission elapsed time of 260 days from launch, Surveyor is 201.83 million kilometers from the Earth, 11.76 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 21.77 kilometers per second. This orbit will intercept Mars 48 days from now, slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). The spacecraft is currently executing the C9 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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