with Simon Mansfield
Surveyor Orbit Down to 19 Hours
JPL - February 1, 1998 - Last week, the flight team celebrated a mission milestone as Surveyor completed its 100th orbit around Mars. Afterward, flight operations manager Joe Beerer characterized aerobraking operations to reduce the size of the orbit as proceeding at a "very satisfying" pace. As of today, Surveyor is completing one revolution around Mars every 19.2 hours. This orbital period is nearly 75 minutes shorter than that predicted for this time prior to the winter holidays.
Aerobraking progress continues to be assisted by the relative calm state of the Martian atmosphere despite the continuance of the traditional dust storm season. A stable atmosphere allows the spacecraft to aerobrake at slightly lower altitudes in order to experience more air resistance. This increase in air resistance results in the size of the orbit shrinking at a faster rate.
In other news, the flight team has inserted spacecraft rotation commands to the list of tasks executed on every orbit. Normally, Surveyor spends the majority of its time with its high-gain antenna pointed directly at the Earth. The new commands occur twice per orbit and rotate the spacecraft so that different parts are better exposed to the Sun. These rotations are necessary to keep the temperatures on the Mars Orbiter Laser Altimeter science instrument from falling below its functional limit of 10 degrees Celsius. Current analysis shows that the laser will require these warming rotations until September of this year.
After a mission elapsed time of 449 days from launch, Surveyor is 207.12 million miles (333.33 million kilometers) from the Earth and in an orbit around Mars with a high point of 17,260 miles (27,777 km), a low point of 75.2 miles (121.0 km), and a period of 19.2 hours. The spacecraft is currently executing the P112 command sequence, and all systems continue to perform as expected. The next status report will be released on Friday, February 20th.
JPL Surveyor Page
EARTH INVADES MARS
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