g#_teldef_#_030893.fits

caldb/data/asca/gis/bcf

Unknown

Four files, with a naming scheme g$n$_teldef_$xxx$_030893.fits, one with each of:

• $n$ = 2, 3 applicable to GIS2 and GIS3 respectively
• $xxx$ = FLF indicating that the data was calculated using the Fast Lorentz Method ( FLF) method of centroiding the position of a IPMT event.
• $xxx$ = POW2 indicating that the data was calculated using the Power of 2 method of centroiding the position of a IPMT event.

Eric Gotthelf (NASA/GSFC ASCA GOF), keywords modified by Ron Zellar.

(No OGIP multi-mission standard)

See above

• 1993 Jun 07 (Eric Gotthelf, ASCA GOF, NASA/GSFC).
  • These extensions contain the GIS gain maps and a set of x, y position error maps created from the University of Tokyo GIS table calibration file data. These maps model the spatial gain and position distortions of the GIS.
  • The gain map gives, for any detector X, Y coordinate, the expected PHA for a given input energy and operating parameters. The gain map is produced by interpolating the gain values mea- sured over the face of the detector at uniformly spaced, but incompletly sampled intervals onto a finer square mesh at the full resolution of the detector electronic ADC.
  • The position distortions are given in terms of error maps, i.e, for a given measured X and Y, what is the value needed to add to this number to describe the physical location of this measur- ement on the face of the detector. Thus the error maps are used to determine the true detector location of a measured photon.
  • First, the measured positions are transformed by minimizing the mean deviation from their expected (physical) locations via a global least-square fit. The transformation coefficiencs are then used to rotate, translate, and scale the measured locations into detector coordinates. The residule errors are them inter- polated over the detector face in a similar manner as with the gain map. These error maps are then written out to this FITS file with the the transformation coefficiences and other scale information in the headers. A set of X, Y maps is created for each of the GIS position measurment algorithms.
  • For both the spatial gain and the position distortion, two sets of maps are available. One for which the data is interpolated onto physical space and the other onto the measured space.

  • The GIS position and gain linerization over the active area (r < 20 mm) is currently of the order of 1-2 percent. This should improve.

  • The region outside a radius of approx. 20 mm is considered unreliable.

  • A more optimal GIS detector plate scale may be used (currently 0.25 mm/pixel) to compliment the new anode offset settings.

  • The current GIS3 calibration file data does not match the GIS3 flight image, the cause needs to determined.