Compton Observatory Science Report #142 Thursday, November 4, 1993 This will be my last Science Report, as I am leaving the project on Monday. Chris Shrader will be taking over as reports editor. - Eric Chipman Questions or comments can be sent to the Compton SSC. Phone 301/286-8434, e-mail SPAN GROSSC::SHRADER, Internet shrader@grossc.gsfc.nasa.gov. Normal operations continue. There was a maneuver on Tuesday, November 2, to the attitude of Viewing Period 306. The times for this maneuver were 1456Z to 1503Z. The maneuver angle was 5.06 degrees, and the HGA boom angle from the equator is now 16.53 degrees. The current reboost plan is to do the next phase in two parts, from Nov. 19-23 and from Dec. 15-17. This schedule may be affected by the Hubble Servicing Mission if that flight is delayed, so we are watching the situation. There is a strong desire from several sides to complete the reboost by the end of December. ARCHIVES -------- Archive contents- BATSE - Bursts and flares to trigger 1463, Four months of daily HER and SHER data (some problems with this data are being looked at) Additional HER and SHER data up to April 1992 has been received at the SSC and is being installed in the archive. Some high-level pulsar light curves have been received at the SSC COMPTEL - Periods 1,4,6,7,8,12 and 13 are in the archive. The remainder of periods 1-13 are at the SSC, being processed. EGRET - Periods 0.2-35 are available (Maps and photon lists) (33-35 are NEW this week) OSSE - Periods 1.0 - 17 are now in the archive (SDB data). (16 is NEW this week) (Note that due to target name mismatches, some data including most beyond period 9.5 is hard to access; users may wish to contact the SSC for assistance.) Some pulsar data is also available off-line. BATSE ----- The BATSE instrument is operating normally. As of November 1st, BATSE has detected 804 cosmic gamma-ray bursts out of a total of 2509 on-board triggers in 923 days of operation. There have been 683 triggers due to solar flares with emission above 60 keV. COMPTEL ------- The COMPTEL instrument continues routine observations. The COMPTEL operations group reports an increased incidence of incorrect predictions of SAA passage since the orbital reboost of the CGRO spacecraft last month. These occur typically in the higher portions of the orbit, above 400 km in altitude. To date, no ill effects on the instrument have been noted; rather, a continually varying background level due to the eccentricity of the present orbit is the more immediate concern. The team has recommended to the Flight Dynamics group at Goddard that a review of the SAA definition procedure be carried out. EGRET ----- EGRET operations were normal this week. The deep survey continued this week. The interaction with guest investigators remains at a healthy level. Now that the ground rules have been established, preparations are being made for the Phase 3 Guest Investigator program. Once again I should like to issue the challenge to astrophysicists to try not just to explain the high energy gamma radiation seen from AGN's in terms of high energy charged particles, but to explain how such tremendous numbers of high energy charged particles are accelerated in the first place. - Carl Fichtel OSSE ---- OSSE operations are normal. In viewing period 306, the Z-axis target is the Virgo sky survey region (Key project) centered at (l,b) = (278,+59), and the X-axis target is the galactic center region (PI team). The Sun is accessible along the OSSE scan plane, and the slewing response to BATSE solar flare triggers is enabled. 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. Previously, the ODS process could store up to about 22 minutes of data in the low spectral range (50 keV to 1.5 MeV). Now with compression, up to about 30 minutes of data can be stored. No high time-resolution data (i.e. pulsar data) are stored on board. At the reacquisition of TDRSS link, the stored data are telemetered in place of real-time pulsar data for approximately the first 100 seconds of the TDRSS contact. Once the ODS buffer is empty, real-time pulsar data transmission resumes. Data from viewing periods 18 and 19 will be delivered to the Compton GRO Science Support Center Archive today. The targets during vp 18 were M82, PSR 1929+10, and 4U1957+11. The targets during vp 19 were the galactic plane near 58 degrees longitude and Her X-1.