Compton Observatory Science Report #144 Friday, November 19,1993 
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


                          Coming Soon:

Starting on December 2 (there will be no weekly report next week
due to the Thanksgiving Holiday), the CGRO weekly report will be
distributed via the "HEASARC Listserver" mailer utility. For most
current subscribers, the change should be transparent. Listserv
provides some added capabilities, such as subscribing or
unsubscribing (to this or similar services for Goddard supported
missions such as ROSAT and ASCA), and communicating with other
members of the CGRO community. For general information on
listserv, send e-mail to listserv@athena.gsfc.nasa.gov, with the
word "help" as the text of your message (no Subject item is
necessary).


                       Spacecraft Status:


The second phase of the CGRO reboost operation was begun this
morning (11/19/93), with a one-minute burn of the two B-side
orbit adjust thrusters (OATs). Preliminary conclusions from the
real-time data indicate that this reboost operation worked
successfully. As in previous orbit reboost burns, the B2 and B3
attitude control thrusters fired during the OATs burn to minimize
the disturbance torques and position error. The current reboost
activities are scheduled to continue through 11/23, with the next
series of reboosts occurring on 12/15-17/93. The December burns
could be affected by any slips in the Shuttle HST servicing
mission, but our current plan is to try for 12/15-17/93 even if
the Shuttle is up. (Quite aside from this, all of us involved
with the CGRO mission wish the best of luck to everyone involved
for a successful HST repair mission!).

Current plans are for the F1 TDRS to be drifted over Australia by
early February, 1994, which will greatly improve our data
transmission efficiency. Subsequent to 02/94, we expect average
efficiencies upwards of 83% .



                    Instrument Team Reports:

                              BATSE


During viewing period 308 BATSE folded-on-board pulsar data is
being collected for the Crab pulsar, PSR J0437-471, PSR 1259-63,
Cen X-3, and Her X-1. 

As of November 17th, BATSE has detected 821 cosmic gamma-ray
bursts out of a total of 2534 on-board triggers in 934 days of
operation. There have been 688 triggers due to solar flares with
emission above 60 keV.


                              OSSE

OSSE operations are normal.

In viewing period 308, the Z-axis target is the Virgo sky survey
region (Key project) centered at (l,b) = (283,+75), and the
X-axis target is the galactic plane near (337,0) (Key project).
When neither target is available, i.e. when both are occulted by
the Earth, the targets are Mrk 421 and NGC 7213. The Sun is not
accessible along the OSSE scan plane, and the slewing response to
BATSE solar flare triggers is disabled.

The OSSE Mission Operations team is preparing for the upcoming
reboost interval. During the portion of each day that reboost
operations are in progress, OSSE will be in a low-power mode. For
the remainder of each day, the instrument will be in full-power
Science/Engineering mode, and we will perform a number of
engineering tests.

Data from viewing periods 20 and 21 will be delivered to the
Compton GRO Science Support Center Archive today. The targets
during vp 20 were the galactic plane near (l,b) = (40,0), SS433,
NGC 253, and EF Eri. The targets during vp 21 were NGC 1068 and
the galactic center region. 


                              EGRET

EGRET operations were normal this week, with the deep survey
continuing. This survey will be interrupted by the next phase of
the reboost beginning on November 19, 1993. The guest
investigator program remains active. Work is progressing on the
several scientific papers related to the EGRET data from the
whole sky. When they are finished, the high energy gamma-ray
results for the entire sky will be available in the form of
scientific articles.

                             COMPTEL


The COMPTEL instrument is performing well and is carrying out
routine observations. Deep-exposure observations of the Virgo
region continue. Preparations are complete for the next sequence
of reboost maneuvers of the spacecraft, scheduled to begin on
November 19.