file: ~dd/text/caldb_axafcal.txt, v0.3 1999-07-16 dd

AXAF Calibration Products Architecture: "$CALDBaxafcal" 
===============================================================

Related Documents
-----------------
1. Calibration Products and Process
http://space.mit.edu/HETG/cal_overview.html

2. AXAF CALDB Architecture
http://hea-www.harvard.edu/~arots/asc/fits/caldb.txt

3. HETG Calibration Products Architecture: "$CALDBhetgcal"
http://space.mit.edu/HETG/caldb/cal/hetg/docs/caldb_hetgcal.txt


Introduction
------------

The CALDB standard provides for the organization of calibration
FITS-file Data ("pcf" = primary calibration files) and the final
calibration files ("analysis reference data" ARD in ASC terminology)
used by simulation and analysis software ("bcf" and "cpf" in specified
FITS formats).  This CALDB file structure is being applied to the AXAF
observatory by the ASC (Joy Nichols and Arnold Rots); their
architecture is summarized in the next section.

For AXAF there can be a large gap (that is, much processing) between
the ground or flight data ("pcf") and the final calibration files that
describe the components properties, the bcf FITS files. (Note that the
cpf files will generally be created from the bcf files with software in
CALDB/software/axaf.)  In order to fill in this gap, especially for
grating spectrometer calibration, a local axaf calibration directory
is added to contain the intermediate data, processing software, and
technical memos to fully document the calibration process.


Summary of AXAF CALDB Architecture (Presented here for Reference)
-----------------------------------------------------------------
 from http://hea-www.harvard.edu/~arots/asc/fits/caldb.txt

$CALDB/docs/axaf/

$CALDB/software/axaf/

$CALDB/data/axaf/ pcf/     acis/               pcf = calibration Data in
                           hrc/                      FITS format (lab, XRCF,
                           hrma/                     flight, etc.)
                           grating/ letg/
                                    hetg/
                  acis/    index/
                           bcf/     grade/     bcf = "basic cal. file",
                                     ... etc.        ARD in FITS format,
                           cpf/     detmap/          generally specific to
                                     ... etc.        a single component,
                  hrc/     index/                    e.g., detector QE.
                           bcf/     badpix/
                                     ... etc.
                           cpf/     detmap/    cpf = "cal. product file",
                                     ... etc.        ARD in FITS format,
                  hrma/    index/                    generally composite
                           bcf/     effarea/         property of several
                                     ... etc.        components, e.g., 
                           cpf/     wpsf/            PSF.
                                     ... etc.
                  grating/ index/
                           letg/    bcf/     greff/
                                    cpf/     lsf/
                                              ... etc.
                           hetg/    bcf/     greff/
                                    cpf/     lsf/
                                              ... etc.

All of the above directories and their contents will be official
products produced by ASC for the community.  Note that the pcf
branch is not generally supplied to the user, nor is its data
routinely used by analysis software.


Overview of the AXAF Calibration Directories
--------------------------------------------

The following directory structure is added to the CALDB to accomodate
the AXAF calibration process needs.  For each instrument appropriate
subdirectories are defined and maintained, and at a minimum "docs" and
"cip" are required.  The contents of the cip directories are calibration
products directly relevant to ARD creation.

$CALDB/local/axaf/ cal/    acis/             Responsible:   TBD
                                    /docs
                                    /cip
                         aspect/             Responsible:   rac/CXC
                                    /docs
                                    /cip
                                    /OTHER_DIRS
                          focus/             Responsible:   lpd/CXC
                                    /docs
                                    /cip
                           hetg/             Responsible:   dd/HETG
                                    /docs
                                    /cip
                            hrc/             Responsible:   TBD
                                    /docs
                                    /cip
                           hrma/             Responsible:   TBD
                                    /docs
                                    /cip
                           letg/             Responsible:   TBD
                                    /docs
                                    /cip
                        optaxis/             Responsible:   lpd/CXC
                                    /docs
                                    /cip
                     platescale/             Responsible:   lpd/CXC
                                    /docs
                                    /cip
                           xrcf/             Responsible:   TBD
                                    /docs
                                    /cip


Directory Environment Variables
-------------------------------

In order to allow flexibility in the location of these AXAF calibration
directories, it is recommented that software make use of the following
environment variables which may then be modified for a given installation
or to allow swapping in test or prototype directories:

       variable_name      nominal_ASC_installation_definition
       -------------      -----------------------------------
setenv CALDB              /data/aus1/caldb                (at ASC/SAO)
                          /nfs/wiwaxia/d4/ASC/data/caldb  (at ASC/MIT)
                          TBD                   (at user installation)

setenv CALDBaxafdata      $CALDB/data/axaf
setenv CALDBaxafdocs      $CALDB/docs/axaf
setenv CALDBaxafpcf       $CALDB/data/axaf/pcf
setenv CALDBaxafsw        $CALDB/software/axaf

setenv CALDBaxafcal       $CALDB/local/axaf/cal

setenv CALDBaspectcal     $CALDB/local/axaf/cal/aspect
setenv CALDBaciscal       $CALDB/local/axaf/cal/acis
setenv CALDBhetgcal       $CALDB/local/axaf/cal/hetg
setenv CALDBhrccal        $CALDB/local/axaf/cal/hrc
setenv CALDBhrmacal       $CALDB/local/axaf/cal/hrma
setenv CALDBletgcal       $CALDB/local/axaf/cal/letg
setenv CALDBxrcfcal       $CALDB/local/axaf/cal/xrcf

Thus, for example, software would look for HRMA cips in
$CALDBhrmacal/cip/ .

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