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side1_offset stsdas.hst_calib.hrs.z_calib


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NAME

side1_offset -- Apply the offset to side 1 carrousel position parameters.

USAGE

side1_offset input output colname offset

DESCRIPTION

After the Hubble Space Telescope Servicing Mission in December, 1993, side 1 of the Goddard High Resolution Spectrograph (GHRS) again became available for science observations. However, because of an earlier failure in the GHRS, the grating carrousel could not reliably be controlled from the side 1 electronics. Hence, a flight software change enabled controlling of the carrousel from side 2 regardless of which side of the instrument was in use for observation.

The consequence is that carrousel positions are always in reference to the side 2 position. This required some minor changes to calhrs. However, major changes are required for any reference table which uses carrousel position to determine which rows of the table to use. Up to this point, 1 January 1994, all reference tables had carrousel positions based on side 1 carrousel readings for the side 1 gratings, ECH-A, G140M, and G140L. Thus, the carrousel values and related parameters must be modified to account for side 1 gratings to use side 2 carrousel positions. This task handles these modifications for the following reference tables: CCR5, CCR6, CCR8, CCR9, and CCRA. Reference table CCRC also needs modifications, but this is performed by the task "side1_offset_rc".

In the future, when new calibrations are performed, the calibrations will be based on side 2 carrousel positions, hence this task will no longer be necessary. This task is mainly used to update old reference tables in leu of new calibration tables.

This routine adds a value (specified in the "offset" parameter) to a column (specified by the "colname" parameter). However, the only rows affected are those rows whose value in the "grating" column is one of the side 1 gratings: ECH-A, G140L, or G140M. Any other row is not affected. The a new table is created with the modified column.

The offset is nominally the value that satisfies the following equation:

	side2_carpos = side1_carpos + offset

where

	side2_carpos = Carrousel position as read from the side 2
			encoder.
	side1_carpos = Carrousel position as read from the side 1
			encoder. 
	offset       = Offset in carrousel encoder units.

See the examples for how each of the GHRS reference tables would be modified using this task.

PARAMETERS

input [file name]
Name of the GHRS reference table to be modified. If blank, no action will occur.
output [file name]
Name of the modified table.
column [string]
Name of the column to add the offset to.
offset = [real]
Offset to apply to the column values.
(verbose = yes) [boolean]
YES to write out informational messages.

EXAMPLES

The following examples show how to modify the CCR5, CCR6, CCR8, CCR9, and CCRA GHRS reference tables. The main parameter to look for is the "column" parameter. The different tables require different columns to be modified. The only other reference table that needs modification is the CCRC table. A task specific to CCRC is required; see "side1_offset_rc".

1. Modify the table representing the CZCCR5R relation for the side 1 offset. The default offset will be specified.

	cl> side1_offset ccr5_old.tab ccr5_new.tab cap_c 10936

2. Modify the table representing the CZCCR6R relation for the side 1 offset. The default offset will be specified.

	cl> side1_offset ccr6_old.tab ccr6_new.tab carpos 10936

3. Modify the table representing the CZCCR8R relation for the side 1 offset. The default offset will be specified.

	cl> side1_offset ccr8_old.tab ccr8_new.tab carpos 10936

4. Modify the table representing the CZCCR9R relation for the side 1 offset. The default offset will be specified.

	cl> side1_offset ccr9_old.tab ccr9_new.tab carpos 10936

5. Modify the table representing the CZCCRAR relation for the side 1 offset. The default offset will be specified.

	cl> side1_offset ccra_old.tab ccra_new.tab r0 10936

BUGS

REFERENCES

Jonathan Eisenhamer, STSDAS

Code based on information provided by Don Lindler.

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

side1_offset_all, side1_offset_rc, calhrs


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