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CGRO biweekly Status Report

   Compton Observatory Science Report #162, Friday July 2, 1994
     Chris Shrader, Compton Observatory Science Support Center

        Questions or comments can be sent to the CGRO 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 function nearly flawlessly.

                 Science Support Center Activities

A draft version of the Cycle-4 timeline was formulated last week
and is now undergoing detailed constraint checking by the Goddard
Flight Dynamics branch. The timline development was a collaborative
effort between representatives from the PI Teams, the Guest
Investigator community and the CGRO-SSC.

The CGRO-SSC can now support the use of the XSPEC program for
spectral analysis of EGRET data. XSPEC spectral fitting program
used widely within the X-ray astronomy community, which offers many
spectral models. It is also possible to develop new models to use
with XSPEC.

Congratulations to BATSE Principal Investigator, Dr. Gerald
Fishman, who was among a small group of distinguished NASA
scientists invited the White House this week as part of a 25'th
Anniversary celebration of the Apollo moon landing. 

                        Instrument Reports


EGRET operations were normal this biweekly period. Delivery of data
to the CGRO-SSC is on schedule. Interaction with Guest
Investigators has slowed a bit due to their summer vacations, but

Several major papers are nearing completion and others have
recently been submitted to scientific journals. Hence, if all goes
well, with typical review cycles there should be a number of new
papers, or at least preprints, available by the end of the year,
with some interesting general conclusions worthy of consideration. 

OSSE operations are normal.

In viewing period 335.0 (12-18 July), the Z-axis target was PSR
J0437-47 (Guest Investigator M. Bailes) and the X-axis target was
Geminga (PI team). When both targets were occulted, OSSE observed
SMC X-1 and QSO 0954+658. The Sun was not available on the OSSE
scan plane.

In viewing period 334 (18-25 July), the Z-axis target is the
galactic plane (Key project) near (l,b) = (15,0), and the X-axis
target is Her X-1 (Guest Investigator M. Kunz). When both targets
are occulted, OSSE observes QSO 0954+658. The Sun is not available
on the OSSE scan plane.

A small contingent from the OSSE team is attending the 30th COSPAR
meeting in Hamburg this week. Highlights of recent results are
being presented, in particular, the interesting spectral behavior
of A0535+26, Cyg X-1, and Seyfert galaxies.

Data from viewing periods 214, 215, and 216 were delivered to the
Compton GRO Science Support Center archive this week. The targets
during period 214 were 1E 1740.7-2942 and MCG-2-58-22. The targets
during period 215 were Cen A, GRO J1317-44, SN 1987A, and PSR
0540-69. The targets during period 216 were SN 1993J and M31.


A revision to the BATSE flight software was loaded on July 19. The
most significant change is that the solar flare trigger signal now
encodes the burst elevation angle. This will allow OSSE to slew to
bursts automatically. 

The BATSE data is being search for hard x-ray and gamma-ray
emission due to the Shoemaker-Levy impacts on Jupiter, but so far
no emission has been detected.  

Over the last week the BATSE pulsed source monitor has detected
pulsed flux from Her X-1, 4U 1626-67, OAO 1657-415, Vela X-1 and GX
301-2. BATSE folded-on-board data is currently being collected for
the Crab Pulsar, Her X-1, and PSR J0437-471. 

As of July 18th, BATSE has detected 1058 cosmic gamma-ray bursts
out of a total of 2985 on-board triggers in 1182 days of operation.
There have been 734 triggers due to solar flares with emission
above 60 keV.  


The COMPTEL instrument is performing well and continues routine

A cosmic gamma-ray burst was recorded within the field of view of
COMPTEL on 8 July. The position of the burst was determined within
a few hours of occurrence, and this information distributed via the
BATSE/COMPTEL/NMSU rapid-response network. The details for this
particular event follow:

NOTICE_DATE: Sat Jul  9 01:16:32 GMT 1994
ORIG_SENDER: burst@comptel.unh.edu
BURST_DATE :  9541 TJD;  8-JUL-1994
BURST_TIME : 74526.00 SEC; 20:42: 6 UT
BURST_SCZEN:   6.0 Deg.
BURST_SCAZI: 139.0 Deg.
BURST_CLASS: Weak  (Approx  37 events)
COORD_J2000: [RAsc     Decl]   [RAsc            Decl]
============ ===============   ======================
MAXLIK_POS : [300.2d  22.3d] = [20h 0m40s  22d15m11s]
ERRBOX1_POS: [299.0d  22.9d] = [19h55m49s  22d51m12s]
ERRBOX2_POS: [300.5d  23.5d] = [20h 2m 1s  23d27m15s]
ERRBOX3_POS: [301.4d  21.5d] = [20h 5m26s  21d32m45s]
ERRBOX4_POS: [299.8d  21.0d] = [19h59m17s  20d57m15s]
COORD_B1950: [RAsc     Decl]   [RAsc            Decl]
============ ===============   ======================
MAXLIK_POS : [299.7d  22.1d] = [19h58m38s  22d 6m29s]
ERRBOX1_POS: [298.5d  22.7d] = [19h53m49s  22d42m49s]
ERRBOX2_POS: [300.0d  23.3d] = [20h 0m 1s  23d18m27s]
ERRBOX3_POS: [300.8d  21.4d] = [20h 3m23s  21d23m44s]
ERRBOX4_POS: [299.3d  20.8d] = [19h57m14s  20d48m38s]

There will be a general team meeting of the collaboration next week
in Leiden, The Netherlands.

Finally, while hopes for an all-COMPTEL final in the World Cup were
never fully realized, recent events elsewhere in the Solar System
have helped place those results in the proper perspective (though
there are still some dissenting opinions within the team).