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,
Another subdirectory of the Process directory is calibs.
Here you will find files containing calibration information for these
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
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, omc1nw.in 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
Last updated March 2, 1998. Contact email@example.com