Compton Observatory Science Report #143 Friday, November 12,1993 Chris Shrader, Compton Observatory Science Support Center Questions or comments can be sent to the Compton SSC. Phone: 301/286-8434 e-mail: NSI_DECnet: GROSSC::SHRADER Internet: shrader@grossc.gsfc.nasa.gov Spacecraft Status: ------------------ The Compton Gamma Ray Observatory remains in good health and is functioning normally. On 2 November the Z-axis of GRO was maneuvered to target 306, Virgo 278+58. The high gain antenna boom angle with respect to the equator is 16.53 degrees. As of November 4, 1993 the Compton GRO orbit had an apogee of 448.1KM and a perigee of 346.0 KM. Plans are continuing for Nov. 19-23 and Dec. 15-17 reboost activities, which would complete the process of placing CGRO in the desired 450-km near circular orbit. The reboost dates are shown on the latest viewing plan (revised on November 3) which is available on GRONEWS. If the space shuttle mission to repair the Hubble Space Telescope, currently set for December 1, is delayed, the second set of reboost activities might have to be rescheduled (available TDRSS support could not simultaneously handle both a shuttle mission and the needed commanding throughput for the CGRO reboost). The Australian TDRS ground station is essentially complete now. It is called the GRO Remote Terminal System (GRTS). The TDRS spacecraft called F1 will be drifted to Australia from November 22 to February 4. CGRO will be able to use F1 as it drifts and will have an increasing data transmission efficiency during this time. November 22 through December 27 will mainly be dedicated to testing. After that we should start to see the data transmission efficiency climb to 82% minimum by February. Instrument Team Reports ----------------------- BATSE ----- During viewing period 307 BATSE folded-on-board pulsar data is being collected for the Crab pulsar, PSR 0611+22, PSR 0628-28, and PSR 1259-63. In addition the pulsar hardware is being used to collect 31 ms resolution single sweep data from LAD 1 for pulsar searches. As of November 7, BATSE has detected 813 cosmic gamma-ray bursts out of a total of 2515 on-board triggers in 929 days of operation. There have been 683 triggers due to solar flares with emission above 60 keV. OSSE ---- OSSE operations are normal. In viewing period 307, the Z-axis target is the Virgo sky survey region (Key project) centered at (l,b) = (269,+69), and the X-axis target is the radio pulsar PSR 1800-21 (GI: J. Cordes). As part of the command load for viewing period 306, we modified OSSE flight software to compress the on-board storage (ODS) of data accumulated during times when TDRSS contacts are not available. With compression, spectral data in the low range (50 keV to 1.5 MeV) could be retrieved from about 90% of the orbit in vp 306. When the Australian TDRSS ground station becomes available, coverage of spectral data from the medium and high ranges and high time-resolution data will increase significantly. COMPTEL ------- The COMPTEL instrument is performing well and continues routine observations. Deep-exposure observations of the Virgo region are currently underway, and are approximately half-complete. EGRET ----- EGRET operations were normal this week, as the deep survey continued. The interaction with guest investigators remains at a healthy level. Dr. Reshmi Mukherjee ia an USRA scientist who joined us recently and is now working on EGRET data. The scientific paper on normal galaxies, on which Dr. P. Skreekumar was the first author, has been accepted by the Astrophysical Journal. The EGRET Compton Symposium papers will be available in preprint form in a few weeks.