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## NAME

deadtimez -- Compute GHRS paired pulse coefficients.

## USAGE

`deadtimez observed expected table pptab`

## DESCRIPTION

This routines computes the paired pulse, or deadtime coefficient, for the equation:

y = (1 - exp(-tx)) / t where: y - observed count rate, x - true count rate, and t - time coefficient.The value of "t" is computed using a least squares fit to an input set of observed count rates, x, versus expected count rates, y. The Levenberg-Marquardt iterative method is used to compute the least squares value of t by minimizing chi-squared.

## PARAMETERS:

- observed [file name template]
- File names of the images of observed count rates. The maximum total number of data points in all input images is 50,000.

- expected [file name template]
- File names of the images of expected count rates corresponding
the the observed count rates in
`observed`.

- table = "deadtimez" [file name]
- Output table of fit results. This table will have the following columns:
'EXPECTED' - Expected count rates (real). 'OBSERVED' - Observed count rates (real). 'OBS_FIT' - Fitted values of the observed count rates (real). 'RESIDUAL' - Residuals of the fit (real).

- pptab = "pptab" [file name]
- Name of the output paired pulse table created by
`deadtimez`(for use by the Routine Science Data Processing (RSDP) system). (Table columns`EPSILON`,`Q0`,`Q1`,`F`, and`ITERATIVE`are not used by the`deadtimez`task.) The table has the following columns:'INSTRUMENT' - Set to "HRS" (character*3). 'DETECTOR' - Detector number (1 or 2) (integer). 'TAU1' - Set to the computed time coefficient (double). 'EPSILON' - Set to "0.0" (real). 'THRESHOLD' - Set to the value of the 'threshold' input parameter (double). 'Q0' - Set to "0.0" (real). 'Q1' - Set to "0.0" (real). 'F' - Set to "0.0" (real). 'ITERATIONS' - Set to "1" (integer).

- (tau= 10.2e-6) [real]
- Initial guess for the time coefficient.

- (niter = 10) [integer]
- Number of iterations of the Levenberg-Marquardt least squares method.

- (threshold = 1.0) [real]
- Value of the threshold used by RSDP to decide if a correction to the input observed count rate is needed. This parameter is simply copied from the input table to the output table.

- (detector=0) [integer, min=0, max=2]
- Detector number for which this calibration is to be used. If set
to "0" (for both detectors), the output table,
`pptab`, will have two rows (one per detector). Otherwise, the output table,`pptab`, will have one row corresponding to the specified detector.

## EXAMPLES

1. Compute the paired pulse coefficients using the data images
`obs` and `exp`.

cl> deadtimez obs exp fittab pptab

## BUGS

## REFERENCES

## HELP

For assistance using this or any other tasks, please contact help@stsci.edu or call the help desk at 410-338-1082.

## SEE ALSO