Chandra X-ray Observatory

Update: 99-148

The Chandra X-ray Observatory is flying free of the Space Shuttle and is on its way to its operational orbit. Controllers at the Chandra Operations Control Center in Cambridge, Mass., report that the observatory is performing beautifully.

Chandra was deployed from Columbia's cargo bay at 7:47 a.m. EDT today. An hour later, Chandra's two-stage Inertial Upper Stage (IUS) propelled the observatory into a transfer orbit of 205 by 44,759 miles in altitude. The first stage motor ignited at 8:48 a.m. EDT for 125 seconds then separated and the second stage ignited at 8:51 a.m. EDT for 117 seconds.

Following the second burn, Chandra's solar arrays were deployed and the IUS separated from the observatory at 9:50 a.m. as planned. The arrays are generating approximately 2 kilowatts of electrical power for Chandra's heaters, science instruments, computers and transmitters.

Following separation from the IUS, controllers in Cambridge activated Chandra's Pointing Control and Aspect Determination (PCAD) system and its Momentum Unloading Propulsion System (MUPS). The PCAD system includes the rate gyros, reaction wheels and the onboard computer. It allows controllers to maneuver and point the observatory. MUPS includes small thrusters that fire to unload the reaction wheels once they become saturated with momentum.

Chandra responded as expected to a series of routine commands controlling its attitude. The primary maneuver called a Coarse Attitude Adjustment, moved Chandra through approximately 33 degrees of pitch rotation to calibrate the spacecraft attitude sensors.

The Flight Operations Team also activated the AXAF Charge Coupled Device Imaging Spectrometer (ACIS) small vent valve to ensure that no ice would form on the charge-coupled device (CCD.) ACIS will be activated today to make sure the temperature doesn't get too cold for the primary components. ACIS is made up of 10 charge-coupled device (CCD) arrays and is capable of recording not only the position, but also the color, or energy, of x-rays. These detectors are similar to those used in home video recorders and digital cameras, but are designed to detect x-rays.

Over the next several days, Chandra's own integral propulsion system will move the observatory to its operating orbit of approximately 6,800 miles by 86,966 miles or 10,000 kilometers by 140,000 kilometers. In preparation for the first firing of Chandra's engines, controllers in Cambridge began activating the hydrazine fuel system.

During the next 12 hours Chandra will go through a series of maneuvers to prepare for the first firing of its Integral Propulsion System.

The team will activate Chandra's High Resolution Camera (HRC). This science instrument will be a primary tool in studying x-rays.

Editor's Note: NASA's Marshall Space Flight Center in Huntsville, Alabama manages the Chandra X-ray Observatory for NASA's Office of Space Science, NASA Headquarters, Washington, D.C.. The Smithsonian Astrophysical Observatory in Cambridge, Mass., manages the Chandra science program and controls the observatory for NASA. TRW Space and Electronics Group of Redondo Beach, Calif., leads the contractor team that built Chandra.