NAME

pcabackest -- Creates an estimated PCA background spectrum for a specific observation from the background model created by the PCA instrument team.

USAGE

        pcabackest infile outfile modelfile(s) filterfile modeltype 
          interval propane layers
          gaincorr gcorrfile fullspec interp syserr maxmodels

DESCRIPTION

The background spectrum in the XTE Proportional Counter Array is modelled based upon measured rates which are recorded in the Standard Mode 2 data file. The PCA instrument team provides file(s) for one or more background models, which are interpreted by pcabackest (see "modelfile" parameter, below). pcabackest reads a Standard Mode 2 FITS file and produces a background spectrum for each PCU for each record in the Standard Mode 2 file. The output of pcabackest can be further processed by saextrct to generate background spectra or light curves appropriate to a given observation.

PARAMETERS

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 some of the values of the parameters upon which the model is based.

outfile [filename]

Name for output file containing the background estimate created by pcabackest.

modelfile [filename or @list-of-files-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. At this time, model files are being improved with great rapidity, so the PCA TEAM DOES *NOT* RECOMMEND USE OF THE "CALDB" OPTION. Instead, users should select appropriate model files from the RXTE GOF anonymous-FTP area (ftp://legacy.gsfc.nasa.gov/xte/calib_data/pca_bkgd) The PCA team produces models as separate files for each model component. Users should download the model components appropriate for their work and input them at the modelfile prompt, either giving the full path name of the model file(s) or the name of an ascii file listing the full path name of each model to be used, one model file per line.

filterfile [filename]

The name of the filterfile created by xtefilt which contains additional parameters required by the models to estimate the background. If all the parameters required are available in the Standard mode 2 file then the value "none" can be used instead of a file name. However, as of FTOOLS v4.2, a filter file is required for all recommended models.

(modeltype=both) [INTERNAL, EXTERNAL, BOTH]

For older models *ONLY* (eg., "Q6"), this parameter can be used to specify construction of internal background only, external, or both. For the new models (eg., "faint" or "sky" models), this parameter MUST BE SET TO "BOTH" - these models combine external and internal background features in a single file. Specification of "internal" or "external" with these models will cause pcabackest to reject them.

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 longer intervals may be specified for output, and will be created by integration. Shorter values may not be specified at this time.

(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. Note: If you explicitly specify a gain correction file you should specify the extension of this file you wish to use. By default, pcabackest will use the first extension and does no checking of the validity of the extension it uses for the data being analyzed.

fullspec=no [boolean]

By default, pcabackest produces a 129 channel background spectrum which correspond to the 129 channels of Standard Mode 2. Setting fullspec=yes will cause pcabackest to produce a 256 channel background spectrum. This flag is automatically set when gaincorr is set.

saahfile=none [filename]

The name of the file containing information about the particle dose from each passage through the South Atlantic Anomaly (SAA). This file is needed for models based upon an exponential decay of activation caused by passage through the SAA. The special value "caldb" will search the calibration database for the appropriate file (note: SAA history files will not be in the CALDB for this release). This file will be periodically updated by the PCA team as the XTE mission continues. Check the URL listed under the "modelfile" parameter for the location of the latest SAA history file.

(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=no) [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. Work is still underway to determine the best methods for analysis of these errors; users are encouraged to consult the PCA team page (http://lheawww.gsfc.nasa.gov/docs/xray/xte/pca/) before using using this parameter.

(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. Note: The number of "models" is not the number of model files. Each model file usually contains 30 models. You should only change this value if pcabackest tells you that it must be larger.

(timeslop=32) [integer]

The number of seconds by which the filter file is allowed to be shorter than the input file. Data beyond the ends of the filter file will not be very intelligently extrapolated but the program will run.

(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.

BUGS

Systematic error estimates are still mostly meaningless and in any case they are output in a format such that there is only one person on this Earth who knows what they mean.

SEE ALSO

saextrct, seextrct

CATEGORY