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prf xray.xspatial



prf -- Description of the point response functions, PRF, for ROSAT and Einstein


This document describes the PRF (a.k.a. PSF) for the appropriate instruments and gives tables of in-orbit calibration images available to PROS.


The point response function, PRF, (aka point spread function, PSF) of
each detector/mirror combination describes the spatial distribution of
counts from an unresolved source.  On-axis, it is usually found to be
circularly symmetric except for radial spokes caused by the mirror
support ribs.  Off axis, the PRF gets distorted by coma and other
aberrations.  To first order, the PRF is a function of energy and
off-axis distance.  To second order, there will be variations from
relative position of detector wires and there also may be distortions
from imperfect corrections for gaps (HRI) or other algorithms used to
compensate for known hardware non-linear behavior.  In these
referenced memos, we will partially address only the first order

	We have included PRF information with the PROS release because
there are many applications and uses (e.g. an immodel future
enhancement will allow the convolution of a selected PRF with a chosen
model).  In the 4 mission+focal-plane-detector descriptions we provide
analytic approximations, usually restricted to on-axis characteristic
based on some set of observations with a limited number of energy
distributions.  We also describe the set of images supplied: both
actual observations of sources known or thought to be essentially
unresolved and data from ground calibrations (monochromatic).  These
two sorts are loosely described by the terms "Sky CALs" and "Ground

	There are four help files with the following names:

prfroshri	The Rosat HRI+mirror		data in directory xrcal$
prfrospspc	The Rosat PSPC + mirror		data in directory xrcal$
prfeoipc	The Einstein IPC + mirror	data in directory xecal$
prfeohri	The Einstein HRI + mirror	data in directory xecal$

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