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INFORMAL ELECTRONIC NEWSLETTER FOR THE EUVE SCIENCE PAYLOAD
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Volume 2, Number 2 July 13, 1992
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NEWS SUMMARY:
+ 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
CALIBRATION AND CHECK-OUT PROGRAM:
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
flags.
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.
SCIENCE PROGRAM:
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
archive@cea.berkeley.edu
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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
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Send newsletter correspondence to: pub@cea.berkeley.edu (Internet)
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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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