pcabackest is written as a standard ftool. Here we list the parameters required for use with version 1.4f by presenting the part of the help page for pcabackest. Additional comments of modelfile and filterfile follow.
infile [filename]
The name of the Standard Mode 2 file for which the
corresponding background model will be created. This file is
also the source of the values of the parameters upon which the
model is based.
outfile [filename]
The name to use for the file containing the background estimate
created by pcabackest.
modelfile [filename]
The name of the file(s) containing the model created by the PCA
instrument team. This may be a list of model files containing
different model components or "caldb" to select the appropriate
model files from the calibration database. Normally, only
models which are valid at the time of the observation will be
used. This restriction can be overridden by specifying model
files and extensions explicitly.
modeltype=both [INTERNAL, EXTERNAL, BOTH]
Selects the type of background models to be included in the
estimate. The user may elect to include only internal, only
external (Diffuse X-ray) or all background. If this parameter
is set to "internal" or "external" then the background will
only include contributions from models containing a "BGSRC"
keyword which is set to "INTERNAL" or "EXTERNAL" respectively.
(interval=16) [integer]
The interval between successive background estimates in the
output file. The Standard mode 2 file contains data for every
16 seconds but the interval in the output can be made either
shorter (by interpolating) or longer (by integrating).
(propane=no) [boolean]
Setting propane=yes will cause pcabackest to generate
background estimates for the propane layer of each PCU. (Note:
there are no model files to support this feature.)
(layers=no) [boolean]
Normally, pcabackest computes the overall background spectrum
for each PCU. Setting layers=yes will cause pcabackest to
produce a separate background estimate for each anode of each
layer of each PCU.
(gaincorr=no) [boolean]
Setting gaincorr=yes will cause pcabackest to perform the gain
and offset correction to the background which the EDS applies
to data in modes where the data from multiple PCUs are
combined. Setting this flag forces the output spectrum to
contain 256 channels
gcorrfile [filename]
The name of the file containing the EDS gain and offset
corrections. The default value of "caldb" causes pcabackest to
search the calibration database for the correct file to apply.
(fullspec=no) [boolean]
By default, pcabackest produces 129 channel background spectrum
which correspond to the 129 channels of Standard Mode 2.
Setting fullspec=yes will cause pcabackest to produce 256
channel background spectrum. This flag is automatically set
when gaincorr is set.
(interp=yes) [boolean]
Some models contain a small number of bins in the modelled
parameter(s) but contain additional information so that
intermediate values can be obtained by interpolation. Setting
this parameter to "no" inhibits this interpolation but setting
it to "yes" does not cause models without the additional
information to be interpolated.
syserr=yes [boolean]
Forces the detailed computation of the estimated systematic
error in the background. Setting this parameter to "no" causes
pcabackest to execute much faster. It is likely that the
systematic error for a particular PCA background spectrum can
be determined without performing the detailed calculation.
Setting this parameter to "yes" causes pcabackest to create
additional spectral columns in its output which contain
information related to the systematic error estimate. This
information must be extracted using saextrct and manipulated
further in a way to be described later to be useful.
(maxmodels=256) [integer]
The limit on the number of background models that can be
processed at one time. If a background estimate involves many
different model components then this may have to be larger but
that is unlikely.
(clobber=yes) [boolean]
If set to "yes" then pcabackest will overwrite any existing
file with the same name as the background estimate file being
created.
The modelfile is either the name of a model file, the name of a file which itself contains the names of several modelfiles (using the ftools @filename convention), or CALDB which will cause pcabackest to search the CALDB for appropriate models. As of 27 November 1996, three models are available although only one is installed in the most recent CALDB (associated with the release of ftools v3.6). Information on obtaining the latest models is available from the http://lheawww.gsfc.nasa.gov/users/stark/pca/pcabackest.html. The three models are discussed below; the three models represent different components of the total background, and are intended to be used together.
The filterfile gives the name of the XTE filter file which is required for processing the activation model. Note that the standard processing (as of November 1996) creates a filter file in the stdprod subdirectory; however, for pcabackest to run properly, two additional parameters (BKGD_THETA and BKGD_PHI) are required. These can be obtained by rerunning xtefilt using updated tools available from the pcabackest page. These parameters are described below.