MIPS 70um Dark Position Test

Principal: dmkelly
Deputy: cengelbracht
Data Monkey(s): One of the monkeys from team geranium
Priority: Necessary
Downlink Priority: Normal
Analysis Time: 24h
Last Updated:

Objective

Determine the optimum scan mirror positions for collecting 70um darks.

Description

While pointing at a region of very bright sky, collect a set of 10 3s DCEs, with stim flashes on the second and last DCEs. Then point to the 70um primary dark position, set relpos to 1568, and take a set of 10 10s DCEs with stim flashes on the second and last DCEs. Increment relpos by 160 counts and repeat this set of 10 DCEs. Repeat another 5 times, up to a final relpos value of 2528. Repeat at the 70um secondary dark position.

Data Collected

mips_sur_C0F2N1--| |---- (x15) mips_sur_C0F2N9--|


mips_mobs_phot
CESCANPOS '1,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CEGERSTCON '10,127,4,"MIPS"'
CESCANCON '"CHOP","REV",0,2048,2048,0,511,"MIPS"'
# sky brightness measurement, 10x3s DCEs, flashes on 2nd and 10th
CEMIPSUR '0x0,0x0,0,"NO_COADD",2,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,1,"NO_COADD",2,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
# stepping across primary dark position, 10s DCEs
CESCANPOS '102,"MIPS"'
CESCANCON '"CHOP","REV",0,1568,1568,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,2,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,3,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,1728,1728,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,4,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,5,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,1888,1888,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,6,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,7,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2048,2048,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,8,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,9,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2208,2208,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,10,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,11,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2368,2368,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,12,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,13,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2528,2528,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,14,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,15,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
# stepping across secondary dark position, 10s DCEs
CESCANPOS '103,"MIPS"'
CESCANCON '"CHOP","REV",0,1568,1568,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,16,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,17,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,1728,1728,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,18,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,19,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,1888,1888,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,20,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,21,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2048,2048,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,22,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,23,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2208,2208,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,24,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,25,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2368,2368,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,26,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,27,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
CESCANCON '"CHOP","REV",0,2528,2528,0,511,"MIPS"'
CEMIPSUR '0x0,0x0,28,"NO_COADD",9,1,"MIPS"'
CEGESTIM '"AUTO",8,"BOTHOFF","AON","BOTHOFF",10,10,"MIPS"'
CEMIPSUR '0x0,0x0,29,"NO_COADD",9,9,"MIPS"'
CEGESTIM '"AUTO",63,"BOTHOFF","BOTHOFF","BOTHOFF",10,10,"MIPS"'
mips_backto_mobs

Data Reformatting Requirements

Array Data Desired:

All Arrays

Data Reformatting Option:

SPECIAL

Special Instructions:
Each set of 10 DCEs should go in a separate file.

Task Dependencies

None (we need a working scan mirror and 70um flood stim)

Calibration Dependencies

70um WF illumination correction

Output and Deliverable Products

Stim-calibrated background level for each module for each relpos position. Plot of background level vs scan mirror angle. Scattered light level for each module. Determination of scan mirror positions that give the darkest backgrounds for each half of the array. Verification that all pixels are in the dark in one of the two dark positions.

Data Analysis

Step by step analysis:
1) Run mips_sloper and mips_caler on all of the data.  The output should
   be stim-calibrated images.  Keep in mind that this approach is not
   ideal for calibrating the background.  Retain information on stim
   brightnesses.
2) Use IDL or some other array handling tool.  If stim latents are handled
   correctly, average the 8 non-stim DCEs in each observation, otherwise
   skip the first three DCEs after the stim flash and average the other
   four.  Calculate median fluxes for each module.
3) Plot mean flux vs scan mirror position for each module and determine
   the darkest positions.  If the statistics are not good enough this way,
   average the four modules on a side of the array before plotting versus
   scan mirror position.  The IDL routine   mean_slope_70modules.pro  has
   been written for this purpose.  It calculates means, standard deviations,
   and maximum slopes for each module and array-side and for the full array.
   It works from mips_sloper output, on *.red.fits files, and it lets you 
   select how many DCEs to reject at the start and end of each set of DCEs.
4) Either based on a module-by-module assessment or by an average of the
   four modules on the dark side of the array, decide which scan mirror
   position is darkest.  Once the two dark positions are selected, compare
   the images to see if all pixels are in the dark in at least one of the
   two images.
5) Gather together some dark data measured on the ground in the Brutus
   chamber.  Reduce the data to produce a dark image.  Compare the stim
   brightnesses with the brightnesses measured during this test and scale
   the dark image to match responsivities.  Subtract the dark from the
   two darkest images to produce scattered light images.  Divide by the
   sky image and multiply by 100 to convert from brightnesses to percentages.
   Coadd columns to produce 1x32 images.  Fit a profile to these scattered
   light images.  One side of the array ought to be vignetted and the other
   not, so it might make sense to do a fit just to the dark side of the array.
6) Looking at the scattered light data, reexamine the selection of darkest
   positions and see if they are still thought to be the best choice.
7) Investigate whether it is reasonable to use a sky brightness measurement
   to correct for the scattered light contribution in dark data.  If so,
   provide information to the SSC that they can use to make this correction.

Software Requirements

mips_sloper, mips_caler, and an array manipulation tool (probably IDL). The tool mean_slope_70modules.pro has been written for calculating mean slopes for each module and array side. This tool makes use of two other IDL routines: kplot.pro and comp_std.pro

Actions Following Analysis

Determine the best primary and secondary 70um dark positions, and make an update to the scanpos table. If the changes are significant enough, push for an upload of a new scanpos table. Otherwise decide whether new values should be uploaded during the next CE FSW upload. If possible, introduce a scattered light correction into the dark handling software at the SSC.

Failure Modes and Responses

If the task is not run, continue to use the 70um dark positions determined on the ground. It should still be possible to calculate a scattered light image for the primary and secondary dark positions using the approach outlined above. If part of the array is in the light for both dark positions, compare to ground data and see if an approach can be developed for estimating the dark current on those pixels.

Additional Notes

The LBTC stray light survey analysis can be found on rincon:
Stray light survey