Instrument Psfs

  The PSF system supplies the following instrument specific psfs,

• EXOLE The EXOSAT LE detector
  
• PWFC The ROSAT WFC (detector 2). The PWFC psf accesses the WFC online calibration database to construct the spatially varying psf. The psf is evaluated at a single energy which is taken to be the peak of the bandpass of the filter used. If the filter cannot be found from the dataset, then the AUX parameter is used to prompt for it.
  
• WFC As PWFC but for survey data. The WFC survey psf is a weighted supposition of the pointed response sampled at a large number of field positions. Note that EVPSS should not use this psf, even for survey data, as the detector position is known for every photon.
  
• XRT_HRI The ROSAT HRI detector. This psf combines the essentially constant detector response with a radial model of the off-axis telescope response. The latter effect is not significant due to the small field of view of this detector
  
• XRT_PSPC The ROSAT PSPC1 and 2 detectors. The current model is a simple gaussian, whose width is a function of both off-axis angle and photon energy. The AUX prompt controls an assumed mean photon energy for the dataset. The current model is rather poor outside the support ring, and even inside does not model the mirror scattering properly. A more accurate model should be avaliable soon (March 92), which will incorporate a 3 component model consisting of a gaussian core, a Lorentzian mirror scattering component and an exponential fit to the wings caused by the deeper penetration of the detector by high energy photons.