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CGRO Biweekly Status Report

Compton Observatory Science Report #155 Friday, April 15, 1994
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 Observatory, scientific instruments and all spacecraft
subsystems continue to performing normally, except for one anomaly
ionvolving the BATSE instruments which is described in detail

                    Science Support Center News

The interest in CGRO science from the astrophysics community is
quite healthy - a total of 234 CGRO Cycle 4 were received! The
proposals have been logged in, and are currently being sorted by 
the SSC staff. A peer-review meeting will take place in late June, 
followed promptly by time line development. Final results should
be announced during July. 

As noted in the COMPTEL report, there are now plans to establish
the SSC as an additional "COMPASS" site - this will allow guest
investigators full access to low-level COMPTEL data.

                        Instrument Reports


EGRET operations were normal this biweekly period. The average
percentage of possible data recovered remains about 80% or above.
Interactions with guest investigators remains at a good level.

At present EGRET is in the middle of the Mkn 421 observation. This
source is of interest because it is the only AGN seen by EGRET that
has also been seen at TeV energies. Several other quasars of
interest to EGRET are also in the field of view.

As noted two weeks ago, several papers related to EGRET results
will be presented at the APS meeting next week including ones on
galactic sources, the diffuse radiation, the search for microsecond
bursts, and AGNs. Of particular interest will be a paper presented
on the February 18, 1994 burst wherein two characteristics
suspected from an earlier burst were confirmed. They place
significant constraints on theories trying to explain these bursts;
in fact several theories are simply not consistent with the


OSSE operations are normal.

In viewing period 322 (5-19 Apr), the Z-axis target is QSO 1028+313
(Guest Investigator M. Maisack), and the X-axis target is the
blazar PKS 0528+134 (Key project).  In the portion of each orbit in
which neither target is above the horizon, the lower detectors are
testing a mapping strategy in the region of (l,b) = (175,-75).  The
Sun is not available for slewing on the OSSE scan plane.

Data from the following viewing periods have been sent to the
Compton GRO Science Support Center archive in the last two weeks.

  period       targets
   202         Her X-1, galactic plane near (l,b) = (355,0)
   203.0       Cyg X-1, galactic center region, GX301-2
   203.3       Cyg X-1, Cyg X-3, galactic center region, GX301-2
   203.6       Cyg X-1, galactic center region, GX301-2
   206         3C273, 3C279, galactic plane near (l,b) = (355,0)


The monolithic time to charge convertor (MQT) for LAD 3 experienced
a latch-up event on March 30th, and again on April 5th. Both events
resulted in the loss of all analyzed count spectra from the
detector.  The first event lasted for 31 hours, and the second for
7 hours. In both cases normal operation was restored by cycling
power to the module. Similar events have occurred before with this

As of April 12, BATSE has detected 955 cosmic gamma-ray bursts out
of a total of 2817 on-board triggers in 1085 days of operation.
There have been 729 triggers due to solar flares with emission
above 60 keV.


The COMPTEL instrument is performing well and continues routine

Following a decision taken at a recent team meeting, the COMPTEL
collaboration is pleased to announce its intention to release the
COMPASS data-analysis software package to the CGRO Science Support
Center, for use by Guest Investigators at the SSC.  This analysis
software will complement the COMPTEL data already being delivered
to the CGRO archive at the SSC, and is intended to facilitate and
foster increased use of COMPTEL flight data for scientific programs
by investigators outside the COMPTEL team.  The installation and
verification of COMPASS at the CGRO SSC will necessarily require
some period of time prior to public availability, but initial
discussions regarding the details of the implementation are already
underway between the COMPTEL team and members of the SSC technical