April 8, 2004

GP-B

Status   (processing notes)

The launch of the Gravity Probe B spacecraft has been postponed to no earlier than Monday, April 19. The additional time is necessary to allow engineers to troubleshoot an apparent short in launch pad ground support equipment. It is associated with a spacecraft battery monitoring circuit. Without this circuit, the battery voltage on the spacecraft cannot be remotely monitored from the pad during certain essential operations. The launch time for Monday, April 19 is 10:01:20 PDT. Should the launch be postponed 24 hours for any reason, the launch time is 9:57:24 a.m. PDT.

The spacecraft was moved from the payload processing facility to Space Launch Complex 2 on Thursday, April 1 and mated to the Boeing Delta II rocket. A spacecraft state-of-health check was successfully performed. The next major test is the Flight Program Verification to be conducted on Friday, April 9. This is an integrated test of the Delta II vehicle and the Gravity Probe B spacecraft. The two-day operation to install the two halves of the payload fairing around the spacecraft will follow on April 12 and is the final major spacecraft associated activity to be performed before launch.

Two days of major activities remain to be performed. On April 16, the loading of the second stage with its complement of hypergolic propellants is scheduled. On April 17, Flight Slews, which are launch vehicle engine steering checks, will be performed. Also, the final Range Safety beacon checks are scheduled.

Retraction of the mobile service tower, the gantry surrounding the Delta II, is scheduled to occur at 11:30 p.m. on Sunday, April 18. Loading of RP-1, a highly refined kerosene fuel, aboard the first stage, is scheduled to begin at approximately 7:30 a.m. on Monday, April 19. Loading of the cryogenic liquid oxygen into the first stage will begin approximately an hour later.

The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it).

Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precise manner for tiny changes in the spin axis direction. Gravity Probe B will be launched into a 400-nautical-mile-high polar orbit for a 16-month mission.

Government oversight of launch preparations and the countdown management on launch day is the responsibility of the NASA Launch Services Program based at John F. Kennedy Space Center. The launch service is provided to NASA by Boeing Launch Services.

MESSENGER

Status   (processing notes)

MESSENGER is at the Astrotech Space Operations facilities near Kennedy Space Center where it is undergoing prelaunch testing. Testing of the spacecraft’s radio system uplink and downlinks through the KSC/JPL interface with the Deep Space Network (MIL-71) continues. Autonomy testing is also continuing. This verifies MESSENGER’s ability to operate on its own when not in direct contact with Earth. Installation of thermal blankets continues.

On April 13, the spacecraft will be moved from its current location in the hazardous processing facility, where it has been since arrival, to an adjacent non-hazardous payload processing facility. The remainder of its final assembly and testing will be completed there. The spacecraft will return to the hazardous processing facility when ready for fueling, spin balance testing and mating to the upper stage.

MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Aura

Status   (processing notes)

NASA’s Aura spacecraft, the latest in the Earth Observing System (EOS) series, arrived at Vandenberg Air Force Base, Calif., on April 1 to begin launch preparations. Packed in a special shipping container, Aura was transported from Northrop Grumman Space Technology (NGST) in Redondo Beach, Calif.

This week the Spacecraft Aliveness Test is under way. This test verifies the spacecraft’s state of health after its trip from Redondo Beach. Next week the Spacecraft Comprehensive Performance Test will begin. This is a test of Aura’s instruments and onboard systems.

Aura’s four state-of-the-art instruments will study the dynamics of chemistry occurring in the atmosphere. The spacecraft will provide data to help scientists better understand the Earth ozone, air quality and climate change.

The EOS Aura satellite, instruments and science investigations are managed by NASA’s Goddard Space Flight Center in Greenbelt, Md.

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