Problem Resolution Key to Milstar Mission Success

EL SEGUNDO, Calif. (3/19/01) -- Personnel from The Aerospace Corporation joined Air Force and contractor team members in the successful launch of a Milstar Block II satellite, Flight 4, aboard a Titan IVB rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station Feb. 27, resolving a number of problems along the way.

"This will begin a new era of secure communications for the nation's warfighters," said Dr. Wanda Austin, general manager of the corporation's MILSATCOM Division.

An Aerospace Milstar team led by Austin was at the Cape to support the launch. Aerospace team members evaluated data in real time and provided "go, no-go" recommendations to the Air Force throughout the launch processes.

Schriever Team

Another Aerospace team was at Schriever Air Force Base in Colorado during post-Centaur separation and early-orbit operation.

The Aerospace team worked with Air Force and contractor personnel to evaluate the satellite's health during ascent and Centaur separation. Following separation the joint team performed satellite command and control functions, solar-array deployment, payload wing deployment, and activation of the communication payload.

Prelaunch Challenges

Engineers faced prelaunch difficulties when anomalous electrical readings on the Stage 1 Automatic Destruct System were received two days before launch. Engineers determined that the fault was a short in a piece of ground test equipment. This was verified by test, and the Automatic Destruct System was cleared for flight.

During the countdown change-over to gaseous nitrogen an anomaly team was formed to address loss of nitrogen flow to the payload fairing. After a thorough analysis of winds and payload fairing pressures during the anomaly, it was determined that there was no possibility of contamination having entered the payload fairing vents, and the countdown continued.

A second major countdown problem encountered was an "input error" received while trying to download constants from the Guidance Control Unit. An anomaly team verified that flight software had not been disturbed and that the launch countdown could continue.

Acceleration Examined

After launch, just as the Titan Centaur upper stage finished its third and final burn, telemetry data indicated the possibility of a small, residual vehicle acceleration. A separation-inhibit command was issued from Schriever Air Force Base to allow time for an assessment. After it was determined that the issue was not a true acceleration but normal noise in an accelerometer, the separation command was sent and executed with success.

Austin said her team was prepared, having rehearsed this exact scenario.

"Inhibiting the separation was the lowest-risk decision, given the data in hand," she said. "Once we determined that there was no risk in proceeding with the separation, the mission director and spacecraft contractor agreed with having Schriever issue the separation command."

Preparations Pay Off

Titan mission manager Ed Vierzba congratulated the launch team and commented that "It takes more than a year to perform all the mission-unique analyses to support a launch. The proof is in a six-hour ride to geosynchronous orbit."