polpav -- Calibrate the polarization position angle offset.
polpav intable outtable type refpol pol_eff
This task calculates the polarization position angle offset for up to four filters. The position angle offset is determined from the reference position angle of the observed standard star in the equatorial coordinate system, the position angle of the same standard star as measured in the HSP coordinate system, and the (predicted) position angle of the V3 axis in the equatorial coordinate system. The resulting offset is therefore the angle from V3 to the transmission axis of the 0 degree polarizer. If the predicted position angle of V3 differs from the real position angle, the calculated offset will also have a corresponding error. More than one measurement may be taken at the same aperture. For the same filter, there should be at least one measurement at each of the four apertures. Each of these measurements must have the same target, the same roll angle, and must be obtained at roughly the same temperature and epoch. In this task, observed targets should be polarized standard stars. The maximum number of input data points is 2,000.
Before actually performing the calculation, the raw digital count rates must be corrected for dark signal, pre-amp noise, high voltage factor, and dead time according to the following equation:
scaled digital count rate = (raw digital count rate / (1. - raw digital count rate * dead time) - dark signal - pre-amplifier noise) / (high voltage factor * relative sensitivity)If analog data are used, then the raw data is corrected as follows:
scaled analog count rate = ((raw analog DN - CVC offset) / gain factor - pre-amplifier noise - dark signal) / (high voltage factor * relative sensitivity)
- intable [file name]
- Name of the input table. The following columns are needed:
'DETECTOB' Object detector ID (int). 'APERTOBJ' Object aperture name (char*10). 'VOLTAGE' High voltage setting (real). 'VGAIND' Gain setting (real). 'THRESH' Discriminator setting (real). 'DET_TEMP' Detector temperature (real). 'DEA_TEMP' DEA temperature (real). 'EPOCH' Epoch of observation (double). 'PTSRCFLG' Point source flag (char*1). For digital data, the following columns are also needed: 'DOBJ' Digital count rate (real). 'DOBJ_ERR' Mean error of digital count rate (real). For analog data, the following columns are also needed: 'AOBJ' Analog reading (real). 'AOBJ_ERR' Mean error of analog reading (real). This task also needs the following columns: 'PA_APER' Position angle of the paerture (real). 'TRGTNAME' Target name (char*20).
- outtable [file name]
- Name of the output table produced by polpav; this table has
the following columns:
'FILTER_NAME' Filter name (char*4). 'POLARIZATION' Observed polarization in percent (real). 'ANGLE_OFFSET' Position angle offset in degrees (real). 'INTENSITY' Intensity of the target (real). 'TEMPAVE' Average temperature (real). 'EPOCHAVE' Average epoch (double). 'TRGTNAME' Target name (char*20).
- type = "digital" [string, allowed values = analog | digital]
- Input data type.
- refpol [file name]
- Name of the standard polarization target table; this table
has the following columns:
'OBJ_NAME_i' Name(s) of the object, where "i" is an integer between 1 and 5 (char*20). 'FILTER_NAME' Filter name, e.g., F551 (char*4). 'P' Polarization of the target in PERCENT (real). 'P_ERR' Error in P, in PERCENT (real). 'THETA' Polarization position angle of the target in equatorial system, and in degrees (real). 'THETA_ERR' Error in THETA, in degrees (real).
- (pol_eff) [file name]
- Name of the polarization efficiency calibration table; this table
has the following columns:
'APER_NAME' Aperture name (char*10). 'PEFF' Polarization efficiency (real). 'PEFF_ERR' Error of PEFF (real).
- (cal_tables = "") [string]
- Pset name for calibration file parameters. Parameters can be individually changed from the command line or can be edited as a group using :e from eparam or from the cl, eparam cal_tables or simply cal_tables. Details about these parameters are available by typing "help cal_tables".
- (save = no) [boolean]
- Save the scratch table containing intermediate
If save = yes, a message will be sent to the terminal and the logfile indicating the name of the file.
- (temp_key = "DET_TEMP") [string]
- Column name for temperature data in the input table.
1. Calculate the polarization position angle offset from the input data table xpolpav$input and put the results in the output table ypolpav$output while saving the intermediate result in another local table whose name will be announced to the user. The data type is digital. The reference polarization target table to be used is xpoleffv$refpol, the polarization efficiency table is xpolpav$pol_eff.
hs> polpav "xpolpav$input" "ypolpav$output" "digital" "xpoleffv$refpol" "xpolpav$pol_eff" save=yes