Today, at 8:15 a.m. PDT, Surveyor's onboard computer commanded the firing of a pyrotechnic device to open valve #11 in the propulsion system. The firing physically connected the nitrogen tetroxide oxidizer tank with the rest of the propulsion system. About one hour later, the computer opened a latch valve to allow high-pressure helium to flow from its storage tank into Surveyor's propellant tanks. This helium provides pressure to expel the propellant from the spacecraft's rocket nozzle during engine firings.

Several minutes after the opening the helium valve, propulsion engineer Sam Dominick announced that the pressure in the propellant tanks had reached the required value of 270 pounds per square inch. With the completion of this crucial pressurization event, Surveyor's propulsion system is now ready to perform Thursday's Mars orbit insertion burn.

As of today, only two days remain until Surveyor completes its 10- month voyage to reach the red planet. Currently, the spacecraft is less than 600,000 km from Mars and is closing that gap at a rate of 251,000 km per day.

After a mission elapsed time of 306 days from launch, Surveyor is 252.52 million kilometers from the Earth and is moving in an orbit around the Sun with a velocity of 22.10 kilometers per second. This orbit will intercept Mars two days from now, at 6:31 p.m. PDT on September 11th (01:31 UTC, September 12th). The spacecraft is currently executing the T1 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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