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lgaperloc stsdas.hst_calib.hsp



lgaperloc -- Perform aperture location calibration phase III for a large aperture.


lgaperloc intable outtable edge_level


Use data from four sets of different pointings to determine the edge of the circular aperture. These four sets of pointings are crossing the aperture edge at the four different quardrants. An additional observation is made at the approximate aperture center. The edge count level is then determined from the count rate obtained at the (approximate) aperture center, multiplied by a user- specified fraction (using the edge_level parameter). Coordinates corresponding to this edge count level are calculated for each set of pointings. Finally, the accurate center coordinate is obtained from these four edge points.

The input table can not have more than 2,500 points.


intable [file name]
Name of the input table; this table has the following columns:

'DOBJ'          Digital count rate (real).
'DOBJ_ERR'      Digital count rate's standard deviation (real).
'V2'            V2 coordinate of the pointing (real).
'V3'            V3 coordinate of the pointing (real).
'EPOCH'         Epoch of the observation (double).
outtable [file name]
Name of the output table produced by lgaperloc; this table will have the following columns:

'V2'            V2 coordinate of the aperture center (real).
'V3'            V3 coordinate of the aperture center (real).
'SIGMA_V2'      Standard error of V2 (real).
'SIGMA_V3'      Standard error of V3 (real).
edge_level = 0.[real, min = 0, max = 1]
Fraction of the count rate at center to be used to specify the edge count level.
(v2_key = "V2") [string]
Column name of the V2 coordinate in the input table.
(v3_key = "V3") [string]
Column name of the V3 coordinate in the input table.
(count_key = "DOBJ") [string]
Column name of the count rate in the input table.
(counterr_key = "DOBJ_ERR") [string]
Column name of the count rate's standard deviation in the input table.


1. Calculate the center coordinate of a large aperture from the input data table xlgaperloc$input and put results in the output table ylgaperloc$output. Edge points are assumed to have a count rate half of what the (approximate) aperture center has. The data type is digital.

hs> lgaperloc "xlgaperloc$input" "ylgaperloc$output" 0.5
               v2_key="V2" v3_key="V3" count_key="DOBJ" 




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