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    Volume 2, Number 2                          July 13, 1992

+ EUVE calibration phase continues--15 EUV sources observed so far
+ Two potential new EUV sources under study
+ Two EUVE sources show evidence for variability
+ UV leak calibration carried out--no problems found
+ Initial daytime data test carried out
+ Geomagnetic storm caused enhanced background in some detectors
+ Occasional large burst events being analyzed--probably not cosmic
+ AAVSO program begins: interested observers urged to contact EUVE
+ EUVE Public Archive opens for business
+ Sky Survey phase to start on schedule July 23


Instrument Stellar Calibration
The EUVE in-orbit calibration phase  continued  without  a  hitch
this week. The EUV stars that have now been observed and detected
include: WD 1254 +223, WD 1620 -391, AR Lac,  WD  1845  +019,  WD
0050 -332, WD 2111 +498, AT Mic, MCT 2020 -4234, Her X-1, RE 1938
-461.  These have been used to calibrate the  boresights  of  all
the  instruments  and also to carry out an initial calibration of
the spectrometer channels. The final calibrations  will  conclude
this week. The sky survey phase will start on schedule July 23.

Her X-1 was observed  to  attempt  a  GMT-versus-spacecraft  time
calibration.  Initial  indications  are  that the data  may allow
this to be done successfully.

Initial analysis indicates that some of the  calibration  targets
have  been  observed  in  the  EUVE Long Wavelength Filter (tin).
These targets will be good candidates for the long term  calibra-
tion  monitoring program. We plan to re-observe a small sample of
sources detected at all EUV wavelengths on  a  monthly  basis  to
search for any evidence of instrument degradation.

UV Leak Calibration
Initial analysis of the bright B stars observed does not indicate
any significant UV leaks in the EUVE filters.

Initial Daytime Operations Test
An initial test of operation in the daytime was carried out  with
the  short  wavelength  scanners. The count rates observed in the
aluminum filter were low and indicate that daytime data  will  be
feasible. Count rates in the lexan filter rose significantly dur-
ing the scan, which crossed the sunlit  earth.   Detected  counts
are  attributed  to the residual UV transmission longward of 2000
angstroms at a level of 10(-10). Variability in the observed flux
is  either due to variations in reflected UV from cloud cover, or
to  ozone band  emission variations. Further  daytime  tests  are
planned once EUVE begins sky survey mode July 23, including tests
of the spectrometer channels.

Geomagnetic storm
During last week a geomagnetic storm storm was detected  in  some
of  the filters. Count rates rose as high as 600 c/s. The data is
being analyzed to understand the source of the emissions.

South Atlantic Anomaly
The boundaries of the South Atlantic Anomaly are being mapped  to
determine the relevant charged particle contours for data quality

Large Bursts
About 16 large count-rate bursts have been detected in  the  EUVE
detectors.  Count  rates  go  as high as 8000 c/s for time scales
less than a few seconds. The source of these bursts is not under-
stood.  The co-aligned telescopes do not see bursts simultaneous-
ly; however, the pulse height of the burst counts is not as  high
as would be expected for large charged particle events.


Potential Sources Scrutinized
At the marathon EUVE science team meeting last Friday, two poten-
tial  new  EUV sources were presented. Potential optical counter-
parts of these new EUVE sources include a white dwarf and a  cool
star.  These two sources are the ones that have survived scrutiny
by the Data Analysis Team so far. A number of other potential new
sources  did  not survive detailed scrutiny, others potential new
sources are still being checked   carefully.  The  two  new  EUVE
sources  have  now  been  assigned to EUVE scientists for further
checking, optical counterpart verification and publication.

All 15 sources detected so far are being checked for any evidence
of  variability.  At  the science team meeting Friday, scientists
presented evidence of variability for two of the sources  in  the
EUVE  catalogue.  These sources have also been assigned to scien-
tists for further checking and scientific publication.

AAVSO and Optical Monitoring Program
The AAVSO is initiating a program to provide contemporaneous  ob-
servations of variable stars during the periods when they will be
observed by EUVE during the sky survey. Any observers  interested
in  being  involved  in  this  program  should contact Dr. Robert
Patterer at rjp@cea.berkeley.edu. Observers will receive informa-
tion  on  the  planned  dates  for which individual stars will be
visible to EUVE.

EUVE Public Archive
The EUVE Public Data Archive is opening for business  next  week.
The  first data that will be made publicly available includes the
first-light images. Each issue of this electronic newsletter will
contain  announcements  of  data that is being released publicly.
If you wish to obtain publicly available EUVE data, or a  listing
of  what  is  available,  please  contact  Dr.  Jeremy  Drake  at
The  EUVE  Electronic  Newsletter  is  issued  by  the Center for  
Extreme  Ultraviolet  Astrophysics,   University  of  California, 
Berkeley. The opinions expressed  are those of the authors.
         Publishers: Roger F. Malina, C. Stuart Bowyer
              Managing Editor: Camille Trentacoste
       Funded by NASA Contracts NAS5-30180 and NAS5-29298
Send newsletter correspondence to: pub@cea.berkeley.edu (Internet)
The EUVE Project is managed by NASA's Goddard Space Flight Center
in  Greenbelt, MD.  The EUVE Project Manager at GSFC is Mr. Frank
Volpe, the GSFC Project Scientist for EUVE is Dr. Yoji Kondo, the
Deputy Project Scientist is Dr. Ronald Oliversen. The NASA  Head-
quarters EUVE Program Scientist is Dr. Robert Stachnik, the Depu-
ty  Program  Scientist is Dr. Derek Buzasi, the NASA Headquarters
EUVE Program Manager is Mr. John  Lintott.   Information  on  the
EUVE Guest Observer Program is available from:
     Dr. Yoji Kondo, Mail Code 684 GSFC, Greenbelt, MD 20771
           (301) 286-6247 -  euve@stars.SPAN.NASA.GOV

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