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Brief Calibration History

Table 1 gives a summary of principal changes in the ASCA calibration and dates. Details of all these can be found in the ASCA GOF calibration pages.

Table 1

Significant ASCA Calibration Milestones

    Date

    Detector

    Software

    Description

    12/20/93

    SIS

    sisrmg v0.4

    Release of v0.4 SIS matrices e.g. s0c1g0234p40e1_512.rmf

    04/19/94

    XRT

    ascaarf v2.02

    Thermal shield was included twice; corrected.

    06/20/94

    SIS

    sisrmg v0.6

    Release of v0.6 SIS matrices e.g. s0c1g0234p40e1_512v0_6.rmf

    06/28/94

    XRT

    ascaarf v2.30

    Gaussian fudge in XRT effective area introduced.

    11/09/94

    SIS

    sisrmg v0.8

    Release of v0.8 SIS matrices s0c1g0234p40e1_512v0_8i.rmf

    -

    -

    -

    These use PI channels for the first time and include major QE change.

    09/05/95

    XRT

    ascaarf v2.50

    Updated XRT effective area and PSF files to v1.1 of Nagoya ray-tracing code.

    09/05/95

    GIS

    ascaarf v2.50

    Uses updated version of GIS response (v4.0)

    11/22/95

    XRT

    ascaarf v2.51

    Bug fix: Gaussian fudge was always ON.

    02/26/96

    XRT

    ascaarf v2.53

    Updated XRT effective area and PSF files to v2.0 of Nagoya ray-tracing code.

    02/29/96

    SIS

    sispi

    PH2PI file sisph2pi_290296.fits released.

    04/10/96

    XRT

    ascaarf v2.60

    arffilter fudge to XRT effective area added.

    05/06/96

    XRT

    ascaarf v2.61

    Slight changes to relative norms of arffilter fudges.

    July 1996

    XRT

    ascaarf v2.62

    OFFICIAL release of XRT v2.0 EA and PSF files.

    03/11/97

    SIS

    sispi

    PH2PI file sisph2pi_110397.fits released.

    April 1997

    SIS

    sisrmg v1.1

    No major changes to sisrmg after v1.1, until 2001.

    -

    -

    -

    Various changes since v0.8, including RDD model, updated

    -

    -

    -

    echo corrections, non-uniform CTI, updated event threshold

    -

    -

    -

We identify three major phases of calibration characterized by the differences which have the most significant effects on model parameters derived from fitting data. All other changes in calibration have much less effect than these. The three phases are as follows.

OLD Calibration. In this phase, SIS response matrices (rmf files) are used which were released on November 9, 1994 and correspond to v0.8 of the SIS response matrix generator, sisrmg. By definition, for this phase, sisrmg itself was not used to create a custom response matrix (which therefore does not include any time-dependent corrections). In this phase, the XRT response function was based on v1.1 or lower of the Nagoya ray-tracing code (in this memo we use v1.1). Finally, the ancilary response function (ARF) was generated without the two fudge factors (i.e. fudge=no and arffil=no, or else these fudge factors did not exist at the time). The SIS PH to PI file used is sisph2pi_290296.fits or earlier version. Note that later versions of this file are back-compatible. This phase of calibration was used in many early ASCA papers, even as late as 1997 (for example, Nandra et al. 1997, ApJ, 477, 602; hereafter N97).

CURRENT Calibration. This phase of calibration is characterized by (1) the use of the SIS response matrix generator, sisrmg, to generate customized response matrices for a given observation, (2) the use of the Nagoya XRT ray-tracing code version 2.0, and (3) both fudge factors in the ARF turned on (i.e. fudge=yes and arffil=yes). The SIS PH to PI file used is sisph2pi_110397.fits. This phase of calibration is the one universally used now (as of June 2001) and has been available for public use since July 1996 (apart from the PH to PI file, which was released 11 March 1997). For example, the Tartarus AGN database uses this version of the calibration. In a particular science paper, the reader should check to find out whch calibration set was used, especially in the publications years 1995-1997.

NEW Calibration. As yet this only exists in an experimental form and is planned for release by the end of 2001. It will include many changes to the SIS response which have resulted from cumulative radiation damage. Other changes include corrections to the GIS response, bringing the energy scale into alignment with the SIS; use of a new ray-tracing code which uses corrected optical constants for Gold; and revised optical axes for all four instruments. Both fudges in the ARF will be removed. We will not be saying much about this phase of calibration in this report since the details are yet to be finalized.

Next: Effects on Power-Law Slope and Absorbing Column
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This file was last modified on Tuesday, 12-Oct-2021 11:22:04 EDT
Curator: Michael Arida (SP Sys); arida@milkyway.gsfc.nasa.gov
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This file was last modified on Tuesday, 12-Oct-2021 11:22:04 EDT

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