![]() |
||||||
The WATCH instrument was sensitive to 6-150 keV photons. The total field of
view covered 1/4 of the celestial sphere. During its 11 month lifetime,
EURECA tracked the Sun and WATCH gradually scanned across the entire sky.
The WATCH instrument was developed at the Danish Space Research Institute
and also flown on the Russian Granat mission. WATCH is a wide field monitor
based on the Rotation Modulation Collimator principle. It has a circular
field of view with a radius of about 65 degrees. There are 2 interleaved
detectors which create a phoswich of alternating strips of NaI(Tl) and CsI(Na).
Each strip is 5 mm wide by 2 mm thick The diameter of the phoswich is 110
mm and it is viewed across a 10 mm air gap by a single 125 mm
photomultiplier. The effective area of the NaI and CsI scintillators if about
45 cm2. The sensitivity is about 100 mCrab in 1 day. The effective
observation time for the 318 day mission was 120 days. The minimum time
resolution was 64 microseconds. |
If words seem to be missing from the articles, please read this. Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center. The Imagine Team |