[AAVSO-HEN] Swift

[Arne Henden]

Dan Kaiser wrote:
> The press release states Swift has a large field of view.  How large, as
> a percentage of the sky?
> 
The Burst Alert Telescope (BAT) is the primary gamma-ray instrument.
It covers 1.4 steradians (about 1/9 of the entire sky) and has a
localization accuracy of about 17 arcmin, amazingly good for a
gamma-ray telescope.  Once a burst has been localized by the BAT,
then the satellite slews to the localization and trains an X-Ray
Telescope (XRT) and a UV/Optical Telescope (UVOT) on the burst.
These cover the BAT localization error box and can provide
18arcsec (XRT) and 1arcsec (UVOT) localizations if an afterglow
is detected.  However, since the spacecraft has to slew, settle,
etc., the BAT localization will be in real-time but the other
localizations will be delayed by a minute or two.
   The next satellite that will cover the entire sky with its
gamma-ray detectors will be GLAST, not due to launch for a few
years.  So until then, we will have three working satellites
with similar gamma-ray fields of view.  Hopefully they can be
coordinated and point in different directions!
Arne