OGIP Calibration Memo CAL/CSB/95-005

COS-B
CALIBRATION FILES
IN THE OGIP CALDB

COS-B CALIBRATION FILES IN THE OGIP CALDB






edited by:
Paul Barret, Brendan Perry, http://legacy.gsfc.nasa.gov/docs/bios/imgeorge.html & Ron S Zellar
HEASARC
Codes 664 & 668,
NASA/GSFC,
Greenbelt, MD20771
Last Update: 1995 Feb 24
(by IMG)





SUMMARY

The COS-B calibration datasets currently in the OGIP caldb are described.
Intended audience: HEASARC Support Scientists, OGIP programmers and authors of data analysis s/w.

LOG OF SIGNIFICANT CHANGES


Release Sections Changed Brief Notes
Date
1995 Feb 23 All First Public Version

Chapter 1
INTRODUCTION

1.1  Overview

This document is intended to provide notes on the origin, format, limitations etc of all COS-B calibration datasets within the http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/caldb_intro.html.
In the rest of this chapter, the location and structure of the http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/caldb_intro.html at http://www.gsfc.nasa.gov/GSFC_homepage.html at is briefly described, along with references to other relevant documentation.
All COS-B Spark Chamber (SC) and Proportional Counter (PC) datasets within the caldb at NASA/GSFC are then summarized in Chapters  & respectfully, with non-instrument specific datasets summarized in Chapter .

1.2  The OGIP Caldb at NASA/GSFC

The location, organization and contents of the http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/caldb_intro.html on-line at http://www.gsfc.nasa.gov/GSFC_homepage.html is summarized in OGIP Calibration Memo CAL/GEN/93-006 (available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/memos/cal_gen_93_006/cal_gen_93_006.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/memos/cal_gen_93_006/cal_gen_93_006.html versions).

1.2.1  Location

The http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/caldb_intro.html OGIP calibration database (caldb) is physically located on the (ultrix) legacy machine within the http://heasarc.gsfc.nasa.gov/docs/lhea/homepg_lhea.html at http://www.gsfc.nasa.gov/GSFC_homepage.html within the caldb directory tree The entire caldb directory tree is available to remote users via ftp://legacy.gsfc.nasa.gov/caldb or gopher://legacy.gsfc.nasa.gov/11/caldb Within the OGIP, the caldb has been remote mounted on all other machines and the symbolic links /caldb & /CALDB created to point to the above top level directory. An identical copy of some sections of the caldb is also available on the (VMS) LHEA vax cluster at NASA/GSFC (see CAL/GEN/93-006, available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/memos/cal_gen_93_006/cal_gen_93_006.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/memos/cal_gen_93_006/cal_gen_93_006.html versions).

1.2.2  Basic Structure

The contents of the /caldb area is sub-divided between the following sub-directory trees: Here we only consider the data tree. It should be noted that access to certain caldb directory trees is also available from other areas of the legacy anonymous ftp account via symbolic links (see CAL/GEN/93-006, available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/memos/cal_gen_93_006/cal_gen_93_006.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/memos/cal_gen_93_006/cal_gen_93_006.html versions).

1.2.3  Calibration Data File Classes

The OGIP caldb classifies files as `Primary Calibration Files', `Basic Calibration Files' and `Calibration Product Files' (PCFs, BCFs & CPFs respectively; see also CAL/GEN/91-001, available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/memos/cal_gen_91_001/cal_gen_91_001.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/memos/cal_gen_91_001/cal_gen_91_001.html versions). PCFs are 'raw' ground and in-orbit calibration datasets not of immediate interest to most users as they are not directly required for (all but the most specialized) scientific data analysis tasks. These dataset are not considered here. BCFs contain the lowest level calibration datasets potentially required by downstrem software, and can be considered the `atomic units' of the instrument calibration. CPFs contain `convolutions' of the information stored within BCFs customized for a specific analysis task and/or scientific observation.
All BCF & CPF calibration files are organized using the scheme
/caldb/data/mission/inst
where mission & inst are the OGIP-standard names for the mission and instrument. For internal management purposes, a further division into inst/bcf and inst/cpf sub-directories is made in most cases. Non-instrument specific calibration datasets, including general spacecraft housekeeping information etc, can be found in the /caldb/data/mission/mis sub-directory.

1.3  Conventions used within this Document

Throughout this document, the hash (#) symbol is used as a wild-card in filenames to indicate several files are available with slightly different names. In all cases the detailed naming scheme, along with the characters which can be used to replace the # are described in the detailed description of the file set.

1.4  Acknowledgments

The information within this document is based upon that in Appendix A of versions of the COS-B Calibration Guide prior to 1994 Feb 23. The COS-B Calibration Guide was written by Paul Barrett, Brenadan Perry & Ian M George, and is available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/cosb/cosb_calguide/cosb_calguide.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/cosb/cosb_calguide/cosb_calguide.html versions. Appendix A has been removed from the COS-B Calibration Guide and is effectively replaced by this document.

Chapter 2
COS-B SC CALIBRATION FILES

2.1  Summary of Available Files

The SC calibration files available under the
/caldb/data/cosb/sc/type
directory tree are listed in Table . In many cases the actually files will be stored in sub-directories under this tree, as detailed in the corresponding detailed description.
Table 2.1: Summary of COS-B SC calibration files available within the OGIP Caldb

Filename Description Section
Basic Calibration Files (type = bcf)
None
Calibration Product Files (type = cpf)
ebounds.rmf EBOUNDS dataset
effarea#.ear Effective Area Datasets
redist#.rmf Redistribution Matrices
rpsf_051993.fits Point Spread Function

2.2  CPF: SC Detector Redistribution Matrices

2.2.1  redist#.rmf

Location

ftp://legacy.gsfc.nasa.gov/caldb/data/cosb/sc/cpf
Summary of Files

The COS-B redistribution matrix file is in the standard redistribution matrix FITS format for X-ray astronomy (see the document CAL/GEN/92-002). There are 115 input and output energy channels. The channels are based on a logarithmic scale and span the energy range from 37.63 MeV to 7818.17 MeV, though the COS-B team recommends that events below 50 MeV not be used, and very few events are detected above 5000 MeV.
Unlike most X-ray detectors where the redistribution matrix does not depend on its position in the detector, the redistribution matrix for a spark-chamber does, thus seven files for different ranges of zenith angles are given.
Delivered to CALDB by:

Brenden Perry (HEASARC)
File Format

HDUDOC/VERS = CAL/GEN/92-002/1.0.0
(see CAL/GEN/92-002, available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/memos/cal_gen_92_002/cal_gen_92_002.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/memos/cal_gen_92_002/cal_gen_92_002.html versions).
Input Datasets, Assumptions, etc

No information supllied to the CALDB other than that above.
Points to Note

2.3  CPF: SC Effective Areas

2.3.1  effarea#.ear

Location

ftp://legacy.gsfc.nasa.gov/caldb/data/cosb/sc/cpf
Summary of Files

The COS-B effective area matrix file is in the standard effective area matrix FITS format for X-ray astronomy (see the document CAL/GEN/92-019). The effective area is given for 115 energy channels and out to an zenith angle of 30 degrees in 0.5 degree increments.
To accommodate the sensitivity of the spark-chamber to e-pair angle selection, seven files have been made for pair angles less than 4, 6, 8, 10, 12, 20, and 90 degrees.
Delivered to CALDB by:

Brenden Perry (HEASARC)
File Format

HDUDOC/VERS = CAL/GEN/92-019/1.0.0
(see CAL/GEN/92-019, available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/memos/cal_gen_92_019/cal_gen_92_019.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/memos/cal_gen_92_019/cal_gen_92_019.html versions).
Input Datasets, Assumptions, etc

No information supllied to the CALDB other than that above.
Points to Note

2.4  CPF: SC Point Spread Functions

2.4.1  rpsf_051993.fits

Location

ftp://legacy.gsfc.nasa.gov/caldb/data/cosb/sc/cpf
Summary of Files

The COS-B psf file is in the standard psf FITS format for X-ray astronomy (see the document CAL/GEN/92-018). Columns 1, 2, and 5 have the same meaning as in that document. The exception is columns 3 and 4. Though the column names (RAD_LO and RAD_HI) are the same, their meaning differs significantly from that of X-ray imaging detectors where the X-ray event is given as a position on a 2-dimensional grid. For the detection of high energy g-rays where a spark-chamber is used, such a grid does not exist and therefore the concept of radial distance does not exist. Instead the zenith and azimuth angles of the event with respect to the telescope's z-axis is recorded and therefore the probability of detecting an event depends upon zenith angle.
The psf of spark-chambers depends strongly on energy. Since high energy electrons and positrons are less affected by multiple Coulomb scattering, their direction is more accurately know. Thus the psf is given for three energy ranges and a maximum zenith angle of 20 degrees in 0.2 degree increments.
Delivered to CALDB by:

Brenden Perry (HEASARC)
File Format

HDUDOC/VERS = CAL/GEN/92-018/1.0.0
(see CAL/GEN/92-018).
Input Datasets, Assumptions, etc

No information supllied to the CALDB other than that above.
Points to Note

2.5  CPF: SC EBOUNDS dataset

2.5.1  ebound.rmf

Location

ftp://legacy.gsfc.nasa.gov/caldb/data/cosb/sc/cpf
Summary of Files

The COS-B energy bounds matrix file is in the standard energy bounds matrix FITS format for X-ray astronomy (see the document CAL/GEN/92-002). There are 115 energy channels.
Delivered to CALDB by:

Brenden Perry (HEASARC)
File Format

HDUDOC/VERS = CAL/GEN/92-002/1.0.0
(see CAL/GEN/92-002, available on-line as ftp://legacy.gsfc.nasa.gov/caldb/docs/memos/cal_gen_92_002/cal_gen_92_002.ps and http://legacy.gsfc.nasa.gov/docs/heasarc/caldb/docs/memos/cal_gen_92_002/cal_gen_92_002.html versions).
Input Datasets, Assumptions, etc

No information supllied to the CALDB other than that above.
Points to Note

Chapter 3
COS-B PC CALIBRATION FILES

3.1  Summary of Available Files

The PC calibration files available under the
/caldb/data/cosb/pc/type
directory tree are listed in Table . In many cases the actually files will be stored in sub-directories under this tree, as detailed in the corresponding detailed description.
Table 3.1: Summary of COS-B PC calibration files available within the OGIP Caldb

Filename Description Section
Basic Calibration Files (type = bcf)
None
Calibration Product Files (type = cpf)
None

Chapter 4
COS-B MISCELLANEOUS CALIBRATION FILES

4.1  Summary of Available Files

The miscellaneous non-instrument specific & s/c-related calibration files available under the
/caldb/data/cosb/mis/type
directory tree are listed in Table . In many cases the actually files will be stored in sub-directories under this tree, as detailed in the corresponding detailed description.
Table 4.1: Summary of COS-B MIS calibration files available within the OGIP Caldb

Filename Description Section
Basic Calibration Files (type = bcf)
None
Calibration Product Files (type = cpf)
None

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