Scattered Light Background Monitor

Principal: James Muzerolle
Deputy: Karl Gordon, Dave Frayer, Nanyao
Data Monkey(s):
Priority: Necessary
Downlink Priority: Normal
Analysis Time: 24 hours
Last Updated:

Objective

Monitor background counts at 24, 70, and 160 µm from a set of darks during each campaign, tracking the cool-down of the telescope.

Description

Telescope should be pointed at the default dark position 2 (CVZ-south, 6:16:40 -60:48:59 2000). Acquire dark measurements for 24, 70, and 160 µm using the standard dark IERs.

Data Collected

Darks will be obtained using the standard dark IERs. For the 24 and 160 µm arrays, 35 DCEs will be acquired at 10 second exposure times. A total of 70 DCEs will be acquired for the 70 µm array, 35 at each of the two dark positions.

Data Reformatting Requirements

Array Data Desired:

All 3 arrays.

Data Reformatting Option:

Special Instructions:
All DCEs in one cycle of each dark IER must be packed into one fits file with extensions, for a total of four files corresponding to the 3 arrays (2 files for 70).

Task Dependencies

Calibration Dependencies

Output and Deliverable Products

The final product will be a single dark calibration image for each array.

Data Analysis

The data will be processed with the DAT: mips_sloper without dark subtraction (-b), mips_caler without flat fielding (no flag; here, this step is necessary only for proper input into mips_enhancer), and mips_enhancer (with -f to specify the input *.cal.fits file with extensions) to combine multiple DCEs generated by the dark IER into a dark current calibration image. The IDL script "get_rdnoise.pro", which is contained in the DAT distribution, can be used to measure and compare the counts in these images. This script will output both the dark current (i.e., the signal on the array, in e/s; it will not be truly dark until the spacecraft has cooled to <5 K!) and the read noise (not important here). Note that the boost frames will appear to have lower counts than the rest. Trends over multiple campaigns will be analyzed and compared to the expected spacecraft cooling curve. Note that 24 µm should saturate until the telescope reaches ~45-50 K (by about campaign C-D1) (**but will difference images be saturated???**), 70 µm saturates until ~17 K (about campaign F), and 160 µm saturates until ~9 K (about campaign G-H). Predicted telescope cooldown curve
Predicted 24um backgrounds (Note: expected point source saturation level has changed to 5.6 Jy)
Predicted 70um backgrounds (Note: expected point source saturation level has changed to 5.3 Jy)
Predicted 160um backgrounds (Note: expected point source saturation level has changed to 8 Jy)

Software Requirements

Actions Following Analysis

Tracking of dark counts in each campaign needs to be cataloged in the appropriate place (web site?).

Failure Modes and Responses

If the data are unusable (missing data, excessive noise, saturation) in a particular campaign, it is probably not worth trying to redo the observation unless multiple campaigns have failed and inadequate time sampling becomes a problem.

Additional Notes