NAME

diodemap -- Compute the diode response non-uniformities.

USAGE

diodemap input eetrailer diodemap setsize

DESCRIPTION

This task will compute the diode to diode response using observations of the internal GHRS flat field lamp. The typical input observations will be a PMAP of the photocathode (i.e., a Y-scan, or a vertical scan of the photocathode with the X-deflection held constant). The task will sum the lines from a number of different Y deflections to average out photocathode granularities. Low frequency photocathode variations and variations in the lamp intensity are then removed by fitting least squares cubic splines of a definable number of nodes through the data. To prevent large photocathode blemishes from affecting the computed responses, the input observations are divided into sets, and a response is computed for each set. An average of all sets is taken with the worst point for each diode being discarded.

The Routine Science Data Processing (RSDP) system corrects data by dividing the resulting output array by the response image. If comb-addition is used, then RSDP computes a response for each data point by averaging responses for all diodes used in obtaining the data point.

PARAMETERS

input [file name template]

Name of the input file template containing the photocathode Y-scan of the internal flat field lamp. Paired-pulse correction should already have been performed on these observations (calhrs calibration step, PPC_CORR.)

eetrailer [file name template]

File name template of the extracted engineering trailer images corresponding to the images specified in input. Engineering trailer images contain the values for the 12 special diodes.

diodemap [file name]

Name of the file created by diodemap containing the diode response image required by RSDP.

setsize = [integer, min=1, max=INDEF]

The number of observations in each set. Diode responses will be computed for each set of observations. The results of all sets will be averaged with the worst value for each diode not used.

(nodes = 15) [integer, min=3, max=30]

Number of equally spaced nodes in the least squares cubic splines used to fit each set of input data.

(niter = 10) [integer, min=1, max=INDEF]

Number of iterations of the Levenberg-Marquardt least squares algorithm used to fit the cubic spline.

(template = "hrs$templates/hrsdio.hhh") [file name]

Name of the template file used for creating the output diode response image specified by the diodemap parameter.

EXAMPLES

1. Compute the diode response using input data images ffmap1 through ffmap15 and the corresponding extracted engineering trailer images ffee1 through ffee15. Each images contains 7 groups (substep bins) giving 15 sets of diode responses to be averaged (the default is 7 responses per set). Results will be placed in the output image dmap.

hr> diodemap ffpmap*.hhh[*] ffee*.hhh[*] dmap

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