`get_fiducial` - Flat field and fiducial set¶

This script lives in analysis.fp_fit. Its purpose is to analyze peak heights from fp_fit operations, calibrated to pW, and determine the average relative optical couplings (proportional to uK / pW) for the detectors in an array.

The code also allows the user to identify a subset of the detectors as “fiducial”, meaning that their relative optical calibration seems to be stable enough to act as an anchor for absolute calibration purposes.

Running an analysis¶

First pass¶

Use a configuration file like the example, here: :get_fiducial.in.

Before running the code, update at least these settings:

fpfit_reduced: The pattern for the path to reduced fp_fit results for each observation; for example: '../200423/fp_output1/reduced/{tod_id}_fp.fits'
tod_list: The path to an ascii file listing the observations you want to include (with tod_id in the first column).

We will update the cut parameters after looking at the preliminary output. So go ahead and run:

mkdir depot
moby2 get_fiducial get_fiducial.in

On the first pass, the code will write calibration results (copied from the IV) into depot/. This calibration will be re-used on subsequent runs. The flat field numbers will be relative to this baseline calibration.

Iteration: set the rms_cut¶

To iterate, first see if you want to adjust the “rms_cut” setting. Look at the “10_rms_hist” plots, and adjust rms_cut in the parameter file to exclude things above the cut line.

Iteration: set the fiducial_selection¶

We mark detectors as fiducial if they lie within some bounded region in the plane of average flatfield correction (“amp”) and scatter (or fractional rms, “frms”). The plots “{tag}_20_{fcode}.png” show each detector’s position in this plane, and dashed lines that cut out a rectangle in this space. The boundaries of the rectangle are set in the parameter file under “fiducial_selection”, which is a dictionary index by fcode. A typical entry looks like this:

{'fcode': 'f039',
 'amp': (0.001, 0.200),
 'frms': (0.001, 0.10),
}

Outputs¶

Once you have converged on a reasonable bounding box, look at the textual output from the program and assess whether the number of fiducial / flatfielded detectors are acceptable.

Configuration options¶

All configuration options are members of a block called get_fid. In most cases these are well-documented in the example configuration file provided above.

get_fiducial - Flat field and fiducial set¶