MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

       The Mars Global Surveyor flight team has begun using the spacecraft's high-gain antenna again for primary communications and returned the orbiter to its normal flight configuration, called "array normal spin."

       On Sunday, September 20 at 11 p.m. Pacific time, the spacecraft was successfully commanded to reestablish its inertial reference using its star scanning system. This step enabled the spacecraft to point its high-gain antenna directly at Earth at 8:30 p.m. on Monday, September 21.

       The spacecraft remains in excellent health. The ground software error which caused significant discharge of the spacecraft's batteries and, subsequently, sent the spacecraft into contingency mode last week, has been corrected. The corrected software has been used to build the first aerobraking drag pass sequence. This sequence will be radioed to the spacecraft later today.

       The aerobraking burn sequence to initiate the second phase of aerobraking will also be sent to the spacecraft by ground controllers today. The 13.6-second propulsive burn will begin tomorrow at 11 a.m. PDT, during the spacecraft's 573th orbit around the planet, and allow Global Surveyor to take its first "step" back into the upper layer of the Martian atmosphere approximately six hours later. Aerobraking will continue through mid-February 1999 and gradually shrink the spacecraft's current 11.6-hour period to the final, two-hour circular science mapping orbit.

       Currently, Mars Global Surveyor is about 350 million kilometers (216 million miles) from Earth, circling the planet at a closest approach of about 172 kilometers (107 miles) above the surface and about 17,854 kilometers (11,070 miles) at the farthest point in its elliptical orbit.