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The following list provides a brief summary of each of the MPE technical memos available at Goddard. These memos are mainly informal, sometimes in note form and many are pre-launch documents which will have been rendered obsolete by in-orbit work. Thus, these notes have not been circulated as preprints by MPE. Due to user demand, however, we will provide these on request. This list is intended to provide users with an idea of what information is available, the date relates to the MPE internal release date and gives some guidance as to which are pre-launch calibrations.
[Hasinger and Snowden1990]
This document gives a summary of all calibration corrections to be performed on individual PSPC events, starting out with the raw detector co-ordinates and the event amplitude. The correction algorithms detailed are:
This documents the position dependant gain corrections applied to the data during SASS processing. The position-dependant gain variations in the PSPC, which amount to 3-5%, can be corrected by a position and energy dependant function, yielding residual systematic gain errors of order 1% over the whole sensitive area of the counter.
A brief note describing the ROSAT PSPC effective collecting area as a function of energy and off-axis angle. These plots are based on in-orbit data, and here the effective area is defined as including all sources of obstruction within the XRT mirror assembly except the PSPC window support.
It is found that the PSPC dead time per event is energy dependant and changes with incident count rate. There are also differences between the two PSPCs. It is concluded that for most of the time the PSPC dead time will be dominated by vetoed particle background events. This pre-launch document describes how the necessary calibrations can be performed in-orbit.
The vignetting function is discussed. In particular, the effects of the various hardware components between the mirror assembly rear exit plane and the focal plane are discussed. These are: the magnetic deflector; the apertures of the focal plane housing ( which are holes in the sandwich plate and the carousel) and the efficiency of the focal plane detector both on-and off-axis.
[Plucinsky and Snowden1991]
A discussion of the particle background, now superseded by Snowden et al. (1992) and Plucinsky et al. (1993), Astrophysical Journal papers (see items #8 and #9).
[Snowden et al.1992]
A detailed description of the ROSAT PSPC particle induced background. The PSPC rejection efficiency for these spurious events is exceptionally high with a residual count rate of roughly counts s arcmin keV . About 77% of events enter through the detector while the remainder enter through the counter window. During typical conditions the count rate of the residual counts is well correlated with the Master Veto rate. The spectrum of residual events consists of a flat component, a soft power-law, and an Al K line at 1.5 keV. Typically the ratio between the power-law and flat components remains constant to % while the relative Al K contribution increases with increasing MV count rate. The distribution of counts over the field is uniform except for a slight radial dependance and shadowing caused by blockage of the externally producedcomponent by the window support structure.
[Plucinsky et al.1993]
An update of the 1992 Snowden et al. paper. Includes the post gain change calibration.
[Pfeffermann et al.1987]
The reference to the published paper is 1987: Proc. SPIE Int. Soc. Opt. Eng., 733, 519. The published paper should be sought directly rather than via the GOF.
[Briel et al.1988]
The ground calibration measuring the differential spatial non-linearities caused by the digitizing effects of the anode and cathode grids are discussed. In addition, the bulging of the thin PSPC entrance window and the position dependant gain of the counter are detailed. From those measurements MPE derive tables used to correct individual events in position and pulse height. Presented are the calibration methods and performance achieved for the PSPC.
In this memo the Polya model function (for the spectral response) is discussed, and compared to the empirical model of
[Jahoda and McCammon1988]
[Briel et al.1989]
Describes the pre-launch measurements of the anode pulse heights of the PSPC as a function of X-ray energy.
[Hasinger and Aschenbach1989]
Reports an update of the focal plane determination procedure compared to a 1989 July write-up.
[Schmitt and Snowden1990]
The transmissions of the entrance windows in the four PSPCs are discussed, plus the boron filters. A physical model is constructed for all known window components.
[Kürster and Hasinger1992a]
The boresight corrections, i.e., the systematic zero point shifts encountered between the measured and known object positions when expressed in detector co-ordinates, are discussed.
[Kürster and Hasinger1993b]
Time correction of the spacecraft clock.
On-axis point spread function, this is now written up in full, see #20.
[Hasinger et al.1992]
The components of the ROSAT PSPC on-axis point spread function PSF are discussed, and a direct comparison made between the predicted PSF from ground calibration measurements and in-flight data obtained during the early part of the mission.
The relationship between ROSAT coordinate systems and celestial coordinates are discussed.
[George and Turner1993]
A precursor to this document.
[Mendenhall et al.1992]
The importance of energy dependant exposure maps for the analysis of ROSAT PSPC data is demonstrated. Although current SASS generated exposure maps, based on a single, band-limited instrument map, are reasonably valid for central energies of the ROSAT bandpass, analysis of softer bands(<0.20 keV) are strongly affected by ``ghost'' images. Correction for such effects is critical for studies of extended objects and the diffuse X-ray background, and may also affect the identification of soft point sources. The authors present a method of generating energy dependant exposure maps (7 bands) for any PSPC pointed observation. These maps are based on instrument maps generated from all-sky survey data (similar to the currently used instrument map except for dividing the total PSPC bandpass into additional energy bands). Application of these maps will allow for accurate analysis over the entire PSPC bandpass.
[Snowden et al.1994]
A Here there be dragons paper for those interested in reducing PSPC observations in order to study extended objects of the SXRB.
[Snowden and Freyberg1993]
This APJ paper models the scattered solar X-ray background as seen by the ROSAT PSPC. The temporal and geometric variation of this background component is modeled and well reproduces the observed light curves. The spectral distribution is also modeled with good results.
Outline of planned calibration of the engineering model at the PANTER facility in late 1993.
[Hasinger et al.1993]
The authors compare the ROSAT PSPC on-axis point spread function PSF with the best signal-to-noise data obtained to date for a point source. They confirm that the parameterization detailed in CAL/ROS/92-001 does satisfactorily describe the observed PSF at energies keV.
[Hasinger et al.1994]
This memo details the extension of the description of the point spread function of the ROSAT PSPC to include off-axis effects. The authors present the off-axis PSF algorithm and compare the model to in-flight data. The limitations of the parameterization are discussed with respect to data analysis.
The ROSAT PSPC data processing software SASS gain corrects the pulse height analyser spectral data (PHA) to pulse invariant (PI) data. This study note tests the accuracy of those corrections by making a simple ratio comparison between spectra of a constant X-ray source, N132D taken at different epochs. The analysis shows evidence for variations in the N132D spectra which are interpreted as uncalibrated variations in the detector response.
The mission planning activities for the ROSAT project are discussed.
[Kürster and Hasinger1992b]
The possible connection between difficulties in boresight determination and the star tracker pixel calibration is discussed.
[Snowden and Schmitt1988a]
A pre-launch document discussing the possible orbital inclinations available One of a series of studies aimed at reducing the planned orbital inclination from , eventually was chosen.
[Snowden and Schmitt1988b]
A pre-launch document summarizing a series of studies aimed at reducing the planned orbital inclination from , eventually was chosen.
The expected oxygen particle flux in the XRT focal plane was investigated in order to study the possible degradation of the PSPC detector entrance window due to erosion by neutral oxygen atoms.
Discusses the on-board particle-background vetoing schemes for the PSPC.
This memo is intended to remind Guest Investigators of the importance of the effect related to ghost imaging in spectra extracted under certain criteria.
[Kürster and Hasinger1993a]
Now App. D.
A comparison of the two different sets of attitude solutions derived from the WFC and XRT star trackers is made for a suitable selection of time intervals of steady state pointing. To make it possible to substitute WFC for XRT attitude in cases where the XRT solution is either non-existent or of poor quality, the stability of the relative alignment of the two star trackers (as inferred from the comparison of the two data sets) is examined.
[Prieto et al.1994]
A review of the systematic shifts in the PSPC spectral response.
[Snowden et al.1995b]
The SASS PSPC data processing software corrects for time and spatial variations in the detector gain as part of the conversion from detected pulse height to pulse invariant channels. Analysis of the in-flight Al K calibration data has shown that there is an error in the spatial gain correction currently applied in SASS, and also that there are uncalibrated effects which need to be considered, requiring some additional correction based on the detector coordinates and arrival time of each event.
[Turner et al.1995]
This document gives a summary of all the calibration corrections applied to individual PSPC events during their conversion from their arrival position and pulse height channel (PHA) to their corrected coordinate and pulse-invariant (PI) channel. This memo is essentially a copy of the original MPE memo TN-ROS-ME-ZA00/027 (see item #1 - [Hasinger and Snowden1990]), but updated and expanded to refer to the FITS versions of the calibration files available from the HEASARC.
[David et al.1996]
Identical with Chap. 5 of this handbook.