Compton Observatory Science Report #134 Thursday, August 26, 1993 Eric Chipman, Compton Observatory Science Support Center Questions or comments can be sent to the Compton SSC. Phone 301/286-7764, e-mail SPAN GROSSC::CHIPMAN, Internet chipman@grossc.gsfc.nasa.gov. Science operations are continuing. There was a maneuver on Thursday, August 26, to improve the angle of the Sun on the solar arrays. The times were 0444Z to 0455Z, with a maneuver angle of 8.92 degrees. The HGA boom angle wrt the equator is 41.81 degrees. The new attitude is: Period 232.5 8/26/94 - 9/07/94 z-axis : l2 = 347.500, b2 = 0.000 x-axis : l2 = 257.500, b2 = 75.388 z-axis : RA = 258.019, DEC = -39.349 J2000 x-axis : RA = 182.057, DEC = 16.479 J2000 TARGETS SUMMARY TARG 1 RA = 258.019, DEC = -39.349 J2000 GPLANE 347.5 TARG 2 RA = 186.444, DEC = 12.661 J2000 NGC 4388 TARG 3 RA = 187.710, DEC = 12.390 J2000 M 87 Options for the reboost scenario are being studied intensively. In all options, the reboost will not occur before October. We hope to have a firm schedule by the end of next week. BATSE ----- The policy of disabling the BATSE burst trigger over western Australia is being reinstituted. This is due to an increase in the number of triggers caused by electron precipitation events over this area. These events are believed to be induced by the North West Cape VLF transmitter. During viewing period 232 BATSE folded-on-board pulsar data is being collected for the Crab pulsar, the Vela pulsar, Cen X-3, Her X-1, and PSR 1642-03. The pulsar hardware is also begin used to collect single sweep 31 ms resolution data for pulsar searches using LAD 6. As of August 23rd, BATSE has detected 746 cosmic gamma-ray bursts out of a total of 2397 on-board triggers in 831 days of operation. There have been 664 triggers due to solar flares with emission above 60 keV. COMPTEL ------- The COMPTEL instrument is performing well and continues routine observations. The collaboration has recently forwarded to the Science Support Center at Goddard a major delivery of COMPTEL flight data for insertion into the GRO public archive. These data include low-level (e.g, event lists, binned event matrices) and initial high-level (e.g., instrument response, exposure information) processed data, through GRO viewing period 13. Some conversion of these binary datasets into "GRO-standard" FITS formats by the technical staff of the SSC will be required before they become publically available on-line at the Science Support Center. EGRET ----- EGRET operations were normal this week. Work continues on the Second Compton Symposium to occur on September 20-22, 1003. Interaction with guest investigators and other scientists with whom we are working continues at a good level. Several analyses have already been completed now. We are planning for the interaction with other scientists in Phase 3 wherein the procedures will be somewhat different. OSSE ---- OSSE operations are normal. For viewing period 232.5, the Z-axis target is the Galactic plane near 347.5 degrees longitude (PI team). The X-axis targets for detectors 1 and 2 are NGC 4388 and M87 (PI team), while detectors 3 and 4 perform a trial mapping strategy for the sky survey of the Virgo region in Phase 3. When neither target is above the Earth's limb, engineering data are being collected to improve our calibration of the neutron v. gamma-ray pulse-shape discrimination efficiency. The Sun is not available on the OSSE scan plane, so the slewing response to BATSE solar flare triggers is disabled. There have been no slews to the Sun since the last report. Data from viewing periods 2.5 and 11 have been delivered to the Compton Science Support Center Archive. The targets during period 2.5 were the Sun, Cyg X-1, Cyg X-3, PSR 0114+58, and 4U0115+634; these data have now been reprocessed to the same degree as the subsequent viewing periods already delivered to the archive. The targets during period 11 were 3C273, SN 1991T, and the Galactic Center region.