SAC-B Launch Date

SAC-B was launched at 17:08:56 GMT on 11/4/96

Satellite achieved nominal orbit but failed to separate from Pegasus

Status as of November 5, 1996:

SAC-B and HETE were launched by "Maggie" (a Pegasus XL rocket) on 11/04/96. Drop occurred at 17:08:56 GMT. Orbital insertion was about 10 minutes later. The Pegasus achieved a nominal orbit but failed to separate from the satellite due to a failure of the Pegasus transient power bus. The system is now flying with SAC-B, HETE and the Pegasus 3rd stage connected together as a single 650 kg spacecraft.

SAC-B deployed its solar panels successfully and operated for about 10 hours. The on-board software was modified to permit operation without a separation indication and the ACS system was placed in safe-hold mode in an attempt to gain control and point the solar panels to the sun. At about 10 pm local time last night, the SAC-B satellite was still operating but was losing power. It was tumbling with the Z axis (the solar axis) ranging from about 55 degrees to about 95 degrees to the sun. The Pegasus 3rd stage was shadowing part of the solar array at all times, and none of the solar panels were illuminated for portions of the oscillation. The average power was insufficient to recharge the batteries, even during the daylight part of the orbit. At the last contact yesterday, battery power continued to decrease, but we hoped that the ACS would torque the system far enough to begin recharging the batteries. It now appears that this did not happen. We have had four passes over Wallops this morning and are unable to acquire any signal from the satellite.

Because the spacecraft is now so long, it will eventually stabilize in a gravity-gradient capture mode, although it will probably take a long time for it to lose its existing angular momentum. It could be captured in either orientation: SAC-B up or SAC-B down. The consensus now is that we are unlikely to be able to regain control in any event.

NASA and OSC are launching investigations into the failure. Although we hoped yesterday that we might be able to control the satellite and operate at least some of the instruments, that seems extremely improbable now.

I'd like to take this opportunity to express my thanks to CONAE and INVAP for the excellent work they did on SAC-B. I had hoped that we would get some top-rate science from it, but that now appears unlikely. In its few hours of operation yesterday, SAC-B demonstrated that Argentina knows how to build a successful satellite. Unfortunately, we were never able to turn on the science instruments and demonstrate their capabilities. At the moment, CUBIC is just a very expensive memorial tribute to Mario Gulich, the original Argentine project manager, who died tragically two years ago. A plaque commemorating Mario's contributions to the creation of SAC-B now orbits aboard the CUBIC instrument.

David Burrows

Status as of October 30, 1996:

The SAC-B/HETE launch was aborted today at T-5 seconds due to a problem with the vehicle. The launch attempt was about 45 minutes late because of a pressure problem on the plane, which gave us only one chance to launch before the launch window closed. A few minutes before launch a pin holding the Pegasus rudder in place during the plane flight failed to retract when commanded to do so. Several attempts to retract this pin failed and the launch was aborted when the plane exited the allowed "launch box".

This same problem occurred several years ago on the STEP-1 launch, and several other Pegasus launches have experienced difficulty in retracting these pins. The fin battery must be replaced before another launch attempt, and this procedure takes 48 hours. In order to allow sufficient time to resolve the pin retraction problem, the launch has been until at least Monday, November 4, 1996.

At this point there is no plan to broadcast the next launch attempt via NASA Select, because funds for the uplink have been exhausted.

Status as of October 29, 1996:

The SAC-B/HETE launch has slipped by 24 hours to allow time to determine whether a problem encountered on the Minisat and SWAS rockets will affect our launch. At this time, the consensus is that our rocket is not affected and that our launch can continue as planned with a 24 hour delay. Launch time is now 12:09 pm EST on 10/30/96.

Status as of October 28, 1996:

Everything is GO for launch of SAC-B/HETE at 12:09 pm EST on October 29, 1996. The L-1011 aircraft will take off from the Wallops Flight Facility runway at about 11:10 am. Coverage on NASA Select TV begins at 10:00 am on 10/29/96 with a rebroadcast of a press science briefing followed by launch coverage at 11:00 - 1:00 pm.

Status as of October 17, 1996:

The SAC-B/HETE launch has now slipped to October 29, 1996 due to several small problems encountered during integration of the payloads to the vehicle. Both satellites are now mated to the Pegasus. The ferry flight to Wallops is now scheduled for October 25.

Status as of October 2, 1996:

The SAC-B launch has now slipped to October 21, 1996. The current schedule has:

Status as of September 16, 1996:

The SAC-B launch has now slipped to October 18, 1996. The solar panels have been integrated onto the satellite for the final time. The satellite is now undergoing ACS phasing tests to verify that the coarse sun sensors (attached to the solar panels) are connected correctly to the Attitude Control System. The HETE satellite arrived last Saturday, but HETE has requested a delay in integrating to the Pegasus, which will push the SAC-B installation back to roughly September 27.

Status as of September 10, 1996:

The SAC-B launch is now officially scheduled for October 16, 1996, between 12:00 noon and 1:00 pm Eastern time. SAC-B is at Vandenberg Air Force Base undergoing final testing before integration onto the Pegasus XL launch vehicle. HETE is being shipped to Goddard Space Flight Center this week for testing, and then will be sent to Vandenberg for integration onto the Pegasus. The current schedule calls for HETE installation on September 19-20, SAC-B installation on September 24-25, fairing installation on October 1-2, shipment to Wallops Flight Facility on October 9, and launch on October 16.

Status as of August 20, 1996:

The SAC-B launch is now dependent on the imminent launch of the FAST satellite and on the progress of the HETE piggyback satellite. A telemetry problem has delayed the launch of the FAST satellite until early tomorrow morning. Although the HETE satellite has now passed its thermal vacuum test, delays in the HETE schedule have unofficially pushed our launch date back to October 16, assuming a successful FAST launch.

Status as of July 15, 1996:

The SAC-B launch is now scheduled for October 8, 1996. With the successful launch of the TOMS satellite on a Pegasus XL a couple of weeks ago, the Pegasus launch queue continues to move forward on schedule. The forward jump in the SAC-B launch schedule was made possible by a slip in the Spanish Minisat-1 satellite launch, and now puts SAC-B/HETE second in the launch queue, behind only the FAST mission.

Status as of May 24, 1996:

The SAC-B launch is now scheduled for November 24, 1996. This actually represents the earliest possible launch date, assuming that the launches preceeding SAC-B/HETE do not encounter problems or delays. However, with the successful launch of the MSTI-3 satellite on a standard Pegasus last week, the Pegasus launch queue continues to move forward on schedule. The launches scheduled before SAC-B/HETE now include TOMS, FAST, and a Spanish satellite.

Status as of March 20, 1996:

The SAC-B launch is now scheduled for November 1, 1996. This was accomplished by switching SAC-B and SWAS in the Pegasus launch queue. November 1 actually represents the earliest possible launch date, assuming that the launches preceeding SAC-B/HETE do not encounter problems or delays.

Status as of March 11, 1996:

The Pegasus XL return-to-flight successfully launched the REX satellite into orbit on 3/8/96. This puts the Pegasus XL launch queue back into active status. The next Pegasus launch is a standard Pegasus scheduled for 4/19/96. The first NASA Pegasus XL launch is now TOMS (Total Ozone Mapper), scheduled for 6/1/96. The SAC-B launch is still scheduled for December 1996.

Status as of February 21, 1996:

The status is unchanged from the last report, except that the Pegasus XL return-to-flight is now scheduled for March 4, 1996.

Status as of February 5, 1996:

The CUBIC/SAC-B launch date is still unknown, due to continuing uncertainty in the status of the Pegasus XL launch vehicle, which is still awaiting its first successful flight. The current schedule calls for the Pegasus XL return-to-flight on 29 February 1996, but a slip appears to be likely. If this flight is successful, there are five missions ahead of SAC-B in the launch queue. It now appears likely that earliest possible SAC-B launch date is December 1, 1996.

Pegasus launch queue


Last updated November 5, 1996
Web page maintained by David Burrows ( burrows@astro.psu.edu )
Department of Astronomy and Astrophysics
Penn State University