Aerospace Helps Bring Gamma Ray Observatory Down Safely

EL SEGUNDO, Calif. (7/24/00) -- The Aerospace Corporation was acknowledged at a press conference June 4 by Al Diaz, director of the NASA Goddard Space Flight Center, for the company's role in safely bringing down a giant.

The giant was the Compton Gamma Ray Observatory, which reentered Earth's atmosphere June 4 and plunged into the Pacific Ocean some 2,000 miles southeast of Hawaii at 2:30 a.m. EDT. At 17 tons the spacecraft is one of the largest ever launched by NASA.

Technical experts from The Aerospace Corporation's Vehicle Systems Division (VSD), the Reconnaissance Systems Division (RSD), Center for Orbital and Reentry Debris Studies (CORDS), and the Civil and Commercial Division were instrumental in helping to design and execute the successful splashdown.

NASA began deliberating the probability of uncontrolled reentry after one of the observatory's three attitude-control gyros failed in December 1999. Given the spacecraft's size, scientists felt it likely several large masses of the observatory would survive reentry after breakup.

NASA enlisted The Aerospace Corporation's assistance, and in January the Civil and Commercial Division arranged for two company experts to perform technical reviews on the state of the remaining gyros and the likelihood of uncontrolled reentry.

Dr. William Ailor, CORDS, and Dr. Ken Hagen, RSD, participated in a NASA "red team" review to provide a recommendation to program management at NASA headquarters.

NASA decided in February to deorbit the giant observatory using a series of thruster firings to lower the perigee of the orbit until it was within the atmosphere, causing sufficient drag to break up the spacecraft and cause reentry.

Aerospace VSD and RSD personnel participated in developing the deorbit operation plan with the Goddard Space Flight Center operations team. Dr. Wayne Hallman and Benjamin Mains of VSD assisted in designing the deorbit plan and contingency plans.

Mains, during the critical four-day period between the first thruster firing and reentry, verified each thruster maneuver and its resultant effect on the impact area in the Pacific. Observation of the spacecraft's successful reentry and impact was provided by U.S. Space Command.

The observatory spent nine years on orbit studying gamma-ray emissions in space.