Flux Nonlinearity Calibration, Part 1, 70 & 160 µm

Principal: Karl Gordon
Deputy: Almudena Alonso, Karl Misselt
Data Monkey(s):
Priority: Normal
Downlink Priority: Normal
Analysis Time: 24
Last Updated:

Objective

The purpose of this task is to determine the calibration file necessary to remove the pixel-to-pixel differences in the flux nonlinearity for the 70 and 160 µm arrays.

Description

Point to a smooth, low-background sky position (internal dark position?). Take 10 cycles of 10 second DCEs where each calibration cycle consists of a normal stim flash, two backgrounds, the same stim flashed at a different level for 10 seconds, and two more backgrounds. Before the first cycle starts, a single background DCE is necessary.

The 10 cycles should be repeated 8 times with the middle stim flashed at a level which, on average, fills the well to 1/10, 1/4, 1/2, 3/4, full, 1 1/2, 2, and 4.

Data Collected

This task will produce 8 datasets with 61 DCEs in each dataset for each array.

Data Reformatting Requirements

Array Data Desired:

70 & 160 µm

Data Reformatting Option:

Special Instructions:
Each 61 DCE dataset should be packed into separate FITS files. This will result in 8 files for each array (16 total).

Task Dependencies

Calibration Dependencies

Output and Deliverable Products

The main output of this task will be two calibration files for mips_caler (one each for the 70 and 160 µm) arrays. These calibration files will give factors which correct a point source/stim flash ratio measured on a single pixel to an array average ratio. This calibration will remove the pixel-to-pixel variation in the flux nonlinearity and the final global flux nonlinearity will be determined from standard stars.

Data Analysis

Each dataset will be run through mips_sloper and mips_caler with the appropriate switches. The ten cycles at each stim ratio value will be averaged to produce a higher S/N measurement for each pixel. The average ratio across the array will be used to compute the correction factor for each pixel. This will be done at each stim ratio value and the resulting 8 measurements (minus saturating ratios) will give the correction values as a function of stim ratio.

Software Requirements

Actions Following Analysis

The accuracy of the flux nonlinearity correction files (part 1) will be tested by comparing the global flux nonlinearties measured from the different positions in photometry mode of standard stars.

Failure Modes and Responses

If this task fails often, then the reason of the failure needs to be determined, corrected, and the task rerun.

Additional Notes

This task will need to be done for other backgrounds post-IOC/SV.