Friday, 21 March 1997
On Wednesday, the flight team transmitted the C6 sequence to Surveyor. This sequence contains commands that will control the spacecraft for the next four weeks. C6 became active on Thursday at 6:00 a.m. PST.
The first major event in C6 occurred at 10:00 a.m. PST on Thursday. At that time, the onboard flight computer commanded the spacecraft's main rocket engine to fire for six seconds in order to make minor corrections to Surveyor's flight path. During this trajectory correction maneuver, the main engine burned a propellant combination of hydrazine fuel and nitrogen tetroxide oxidizer. In total, the spacecraft expended approximately 1.4 kilograms of propellant.
Immediately before the six-second burn was performed, Surveyor ignited eight of its 12 attitude-control thrusters for 20 seconds. These tiny thruster rockets are normally used to stabilize the spacecraft during main engine firings. The initial, 20-second thruster firing settled the liquid in the spacecraft's tanks to ensure a smooth flow of propellant to the more powerful main rocket engine that was used to perform the correction maneuver.
At this time, the navigation team is busy analyzing the accuracy of yesterday's trajectory correction maneuver. However, preliminary results from the accelerometer onboard the spacecraft show that the engine firing provided a velocity change of 3.875 meters per second. This value was within 0.5% of the predicted change of 3.857 meters per second.
Yesterday's maneuver was the second in a series of four trajectory correction maneuvers that are designed to refine the spacecraft's flight path to Mars. The first maneuver occurred shortly after launch last November. The third and fourth are currently scheduled for April 21st and August 25th, respectively.
After a mission elapsed time of 134 days from launch, Surveyor is 47.69 million kilometers from the Earth, 63.84 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 26.27 kilometers per second. This orbit will intercept Mars on September 12th, 1997. The spacecraft is currently executing the C6 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
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