Sample Data Analysis - Hertz

The concepts behind the analysis process are very similar for Hertz. Integ and stokes are used for the initial steps of the analysis process. Rough is the functional equivalent of rougher and rough-sp. [An additional analysis step, bigift, which solves for the instrument and telescope polarization (rather than assuming them) is made possible by the use of an instrument rotator. However, since there are no plans to ever rotate SPARO, I mention bigfit only for completeness.]

Since there are currently no sparo data files, I have set up a sample analysis using Hertz files. The sample files can be found in

Underneath the Process and Data directories there are subdirectories for each object. In this case, there is only one object, omc1.

Calibration Information

Another subdirectory of the Process directory is calibs. Here you will find files containing calibration information for these observations.

rgm - Contains the relative gain matrix. This file allows integ to normalize signals from different bolometers properly to account for differing sensitivities.

qu.bigfit - Contains reduced stokes parameters (q,u) for the instrument and telescope contributions. This file is used by rough to subtract out the instrument and telescope polarization.


All of the calls to the analysis programs are found in cshell scripts. Specifically look at:

The script files can be run with
csh do.integ
source do.integ

This shell script looks over the data files (eg. omc1nw.0708) and calls integ.cnoise3 for each file. The output files are named for the extension of the data file, for example 0708. The -dc option tells integ to deglitch the data using Chauvenaut's criteria (see Taylor's book on statisitics). The -r option specifies the relative gain matrix.


The shell script which executes the stokes program is do.stokes. The input file to stokes, first specifies how many data files we want to include, and then lists the name of each file. The format of this file is critical. The output file, omc1nw.stk, first contains some information on how the file has been generated. The body of the file contains a pair of lines for each polarization measurement made at each sky position. The value in the stokesP column for the first line of each pair is q, the value in the second line is u. The x,y = 0,0 position corresponds to the boresight. When the array is square on the sky, x increases to the right, and y increases down. This is a slightly screwy coordinate system - a useful memory device is that both x and y increase with increasing pixel number. The orientation of these coordinate axes with the sky is specified by alpha - gamma (the sky rotation minus the rotation of the dewar) and by gamma0 (the gamma at which the array is up and down). The options specified in this shell are -e 5 which specifies that the errors on the polarization signal should be reset to the median error, if the calculated error is smaller. The option -a 41 specifies what alpha-gamma to use.


The shell script which calls rough is do.rough. The input file is the *.stk file which was output by stokes. The output file, omc1nw.r contains the polarization, direction, signal and errors for every position measured on the sky. These results have been obtained by subtracting out the specified instrument contributions and averaging the results for each sky position. The -t filename option specifies the file containing the stokes parameters of the telescope and instrument contributions. The -pv omc1nw.pv option specifies the file to write out the results in a format expected by the polplot program. Polplot takes this output and creates a mongo macro. Since we don't have mongo and Northwestern, I have not installed this program. The -x 21 option specifies the zero angle of the halfwave plate to be 21 degrees.
Last updated March 2, 1998. Contact