ASCA Glossary
- AO
- Announcement of Opportunity -- A particular round of guest observer
proposals. "AO data" means data gathered after the initial PV phase.
- ASCA
- Advanced Satellite for Cosmology and Astrophysics -- the lastest
Japanese X-ray satellite.
- BRIGHT mode
- A mode for the SIS detectors which groups the nine pixels around an
event together. On-board software rejects some spurious events
based on the pattern of excited pixels.
- BRIGHT2 mode
- A format for the SIS data in which FAINT mode
data is converted to BRIGHT mode with an additional correction for
dark frame error. This is done on the ground.
- dark frame error
- An error in SIS BRIGHT mode data due to fluctuations in the zero-level
calibration of the CCDs.
- dead time
- The short time after an event when a detector cannot process another
event.
- detector coordinates
- The coordinates of an event with respect to the GIS detector itself.
Detector coordinates are useful for correcting for vignetting effects.
- Euler angles
- A set of three angles specifying the spacecraft's orientation.
- FAINT mode
- A mode for the SIS detectors which sends data from individual CCD pixels
to the ground.
- FITS
- Flexible Image Transport System -- The standard file format used in
astronomy. FITS files are machine independent and self-documenting.
- FRF
- First Reduction File -- The files containing raw information from
the spacecraft in a format much like the one in which the information
was sent to the ground. These are the initial files as received from
Japan.
- GIF
- Graphics Interchange Format -- A bit map graphics file format which is in
wide use.
- GIS
- Gas Imaging Spectrometer -- One of two types of detectors on-board ASCA.
There are two of these referred to as "GIS2" and "GIS3".
- hot and flickering pixels
- Bad pixels in the SIS CCDs. Hot pixels give a constant false signal.
Flickering pixels give false signals intermittently.
- MPC mode
- A mode for the GIS which optimizes timing information but discards
event position information except for a simple on target/off target
mask. Since the detector gain is position dependent, there is as
yet no good way to analyze data taken in this mode.
- PH mode
- The usual observing mode of the GIS. In this mode, the position of
each possibly valid event is telemetered to the ground.
- PV
- Performance Verification -- The initial data gathering phase
of the mission where data was gathered to test the spacecraft's
capabilities.
- roll angle
- The additional "twisting" degree of freedom for the spacecraft
pointing in a particular direction.
- SIS
- Solid-state Imaging Spectrometer -- One of two types of detector
on-board ASCA. This one uses CCDs to detect X-ray photons. There are two
such detectors referred to as "SIS0" and "SIS1".
- superframe
- A unit of raw telemetered data from the spacecraft.