CSMM Gain Stability

Principal: dmkelly
Deputy: TBD
Data Monkey(s): Jerry for CSMM expertise, team Ge for data reduction and centroiding
Priority: Necessary
Downlink Priority: Normal
Analysis Time: 3 weeks
Last Updated:

Objective

Determine whether the gain of the scan mirror is stable. If not, decide how to change the scan mirror gain, scanpos table, and MIPS AORs to provide good pointing and to avoid bumping into the hardstops.

Description

MIPS-081 provided the baseline data for assessing the stability of the scan mirror gain. We duplicate very little of that test in normal operations; the exception is 70um NF imaging. In this test, we will look at where sources fall on the array during the 70um photometry AOT. If the positions are not consistent from one running of the AOT to the next, we will look for trends that suggest a change in CSMM gain. If we find evidence for a gain change, we will rerun mips-081 to confirm the gain change and then decide how to proceed. We will do two other things to study the CSMM gain and gain stability. One is to measure the centroids of stars in WF nominal mode and to calculate the CSMM gain. We will need to do this during the first 24um photometry AOTs, and we can repeat the measurement from time to time later during IOC. The second thing is to record the scan mirror current that corresponds to each of the 4 dark positions and to see if the currents are stable during a campaign and from one campaign to the next.

Data Collected

We need to scavenge all of the 70um NF imaging data taken during IOC/SV. We need to look at 24um WF nominal photometry. We need to look at telemetry channel I-0110 CSM_Current for scanpos 101,102,103,104 and maintain the results in a database. 





Data Reformatting Requirements



Array Data Desired:



     70um NF and WF photometry data




Data Reformatting Option:





Special Instructions:







Task Dependencies






Calibration Dependencies






Output and Deliverable Products

1) Centroids for each of the star positions in the 70um NF and WF maps.
2) Comparisons of these centroids from one campaign to the next.
3) Database showing the CSMM current for each of the dark positions
4) Evidence for or against a changing CSMM gain and a plan for
how to proceed.



Data Analysis


Step by step analysis:
1) Run mips_sloper and mips_caler on all of the data.  
2) Measure centroids for the star images in the 70um NF maps.
3) Measure centroids for the star images in 70um WF maps measured
   during the same campaigns as the NF data.
4) If the NF star positions are different from one execution of
   the test to the next, compare to the WF data and see if there
   is evidence for a gain change.  This will be very tough if
   different targets are used in WF and NF mode, as will usually
   be the case.
5) Examine CSMM current telemetry from the dark observations and
   make at least one entry into the database for each campaign






Software Requirements

mips_sloper, mips_caler, and a tool for measuring centroids.



Actions Following Analysis

If there is no evidence for a change in CSMM gain, do nothing.
If the gain appears to be changing, schedule another running of
mips-081 for confirmation.  Feed new gain measurements to Chad
so that he can recalculate the optimal scanmap parameters.



Failure Modes and Responses

If the CSMM gain changes, change the CSMM gain and perhaps also
the scanpos table and the MIPS AOTs so that we do not bump the 
scan mirror into the hardstops.



Additional Notes