Principal: Chad Engelbracht
Deputy: Dean Hines, Dave Frayer, Susan Stolovy
Data Monkey(s): James Muzerolle, Kate Su, Casey Papovich
Priority: Necessary
Downlink Priority: Normal
Analysis Time: 72h
Last Updated:
The purpose of this task is to compare the output of the MIPS 24µm calibration stimulator (preferably the flat-field stimulator) to the output of a calibration star. It will also check the stimulator stability on short timescales.
Small field photometry AOT data on a standard star will be collected in a fashion identical to the routine 24µm flux calibration task, mips-920. These data will be interspersed with stim flashes recorded using the 24µm stim flash IER, MIPS-IER-120. The sequence is as follows: 1) Observe the star using the photometry AOT with 3 second integrations and small field dither (2 cycles). 2) Observe the stimulator (MIPS-IER-120). 3) Repeat 1 and 2 five times. The observation needs a S/N in photons of 100:1 in the stimulator and star so that the uncertainty is dominated by repeatability (4-5%).
The AOR listed here takes 349 seconds and the stim IER takes 71 seconds, so the total duration of this task is 5 * (349 + 71) / 60, or about 35 minutes. This is well within the 50 minutes allocated for this task. If we have to use a fainter star for calibration, we'll use 10-second DCEs, pushing the total time up to about the allocated 50 minutes.
The preferred target is HD 159330, which is the routine 24µm standard used in mips-920.
This task will generate 150 observations of the standard star, 35 observations of the stimulator, and 15 dark observations for a total of 200 DCEs. The stellar and stimulator observations will both be 3-second DCEs. The stimulator observations will be generated using the 24µm stimulator IER (MIPS-IER-120), while the standard star observations will be generated using the standard calibrator AOR used in mips-920.
Array Data Desired:
24 µm
Data Reformatting Option:
Special Instructions:
The main goal of the analysis is to determine the flux conversion factor for this campaign and to assess the repeatability of the stimulator on short timescales. It is similar to the standard 24um flux calibration (mips-920), but is repeated 5 times to improve S/N and to assess short-term variability of the stimulator. The stellar data will be reduced in a fashion identitical to mips-920, while the stimulator data will be run through mips_sloper and mips_caler using the default parameters.
To derive the flux conversion factor, photometry will be performed on the star in each of the 150 DCEs. The results will be averaged, rejecting any measurement greater than 3 standard deviations from the mean. The assumed flux of the star (from the tables on the MIPS IST web page) will be divided by the measured counts to compute the flux conversion factor.
A mosaic of the stellar images will be generated. This image will be examined visually for any obvious problems, such as poor matching of background levels between DCEs, missing data, asteroids in the field, etc. Photometry will also be performed on the stellar image and compared to the results derived above. If the flux conversion factors do not match within the errors, a more thorough investigation of the data will be required.
The processed stimulator images will be averaged for each of the 5 repeats of the measurement. If any image deviates by more than 3 standard deviations from the mean, the data will be investigated more thoroughly. The median value of the stimulator image will be computed for each of the repeats and examined for any trends or for greater-than-expected scatter. If the data are acceptable, the data will be averaged to form a single stimulator image and the flux conversion factor will be inserted in the header. The data will be archived and made available to the IT/IST.
If the standard anomaly response actions do result in usable data, the test must be repeated.