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Flight Status Report

Friday, 28 August 1998

A major milestone was reached on August 18th as the flight team celebrated Surveyor's 500th orbit around Mars. As of today, the spacecraft has completed 520 orbits and continues to transmit nearly 500 megabits of science data per day back to the Earth. Since the beginning of the summer-long science collection period at the end of May, nearly 200 orbits worth of data have been collected by Surveyor's instruments.

August's science activities were highlighted by the successful observation of the Martian moon Phobos on two separate attempts earlier in the month. This tiny satellite orbits the red planet once every 7.7 hours and is a potato-shaped rock about the size of Manhattan. During close approaches just after the low points on orbits #476 and #501, the spacecraft was commanded to slew its science instruments across the moon in order to obtain detailed images.

Planning activities to ensure success of the operations were complicated by the fact that no observations of orbit determination quality had been made of Phobos for nearly a decade. This lack of current and precise position data significantly increased the difficulty of pointing Surveyor's instruments. However, once the images were successfully obtained, chief navigator Dr. Pat Esposito confirmed that Phobos was within one kilometer of its predicted position.

Images and scientific commentary from the previous two attempts and from a third observation attempt scheduled for Monday, August 31th will be available in a press release on September 10th. Images will be posted to the project's web site that day.

Currently, the flight team is busy preparing for the temporary suspension of science activities and the resumption of aerobraking. The first maneuver to lower the low point of the spacecraft's orbit into the upper fringes of the Martian atmosphere will occur early in the morning on September 14th. For the following five months, Surveyor will repeatedly fly through the upper Martian atmosphere and use air resistance to gradually shrink the size of the orbit. The goal is to reduce the period from its current value of 11.6 hours to just under two hours. Global mapping operations from this two-hour orbit are scheduled to begin in April of next year.

After a mission elapsed time of 659 days from launch, Surveyor is 223.34 million miles (359.43 million kilometers) from the Earth and in an orbit around Mars with a high point of 11,098 miles (17,861km), a low point of 108.0 miles (173.8 km), and a period of 11.6 hours. The spacecraft is currently executing the P517 command sequence, and all systems continue to perform as expected. The next status report will be released in mid-September.

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