PROCEDURE: 23h

TITLE: HRC QEH test

CATEGORY: 

PURPOSE: Determine if HRC suffers from Quantum Efficiency Hysterises

FREQUENCY: Run once with F250W, if an effect is seen, run again using
F435W, and F814W. 

DETECTOR: HRC

PREREQUISITES: For each run, start HRC at a fairly warm Temp (e.g. off
state, at room Temp), then cool down to TEC = -83C.

HARDWARE REQUIREMENTS: RAS/CAL or STUFF + pinhole

SOFTWARE REQUIREMENTS: 

COMMAND MODE: PSTOL

PROCEDURE/EXPOSURES:
     HRC GAIN = 1, TEC = -83C
     All exposures taken with the same filter (F250W, F435W, F814W)

     a. RAS/CAL version:
      --  Configure RAS/CAL with 6mm aperture, 
      --  RAS/CAL lamp either:
           + D2 lamp on for F250W, or 
           + tungsten for F435W or F814W
      --  If possible have an approx matching filter in front of the
	  RAS/CAL lamp so that only the appropriate filters reach the
	  RAS/CAL PMT.
      --  set lamp-current or ND for HRC count rate ~10^4 e/s/pixel
      --  Take RAS/CAL PMT measurement
      --  PMT out of light path
       1. bias frame
       2. 600s dark
     3,4. 2 x  1s external exposure
     5,6. 2 x 10s external exposure (1.0x full well)
     7,8. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
       9. 600s dark
   10,11. 2 x  1s external exposure
   12,13. 2 x 100s external exposure (10x full well)
   14,15. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
      16. 600s dark
   17,18. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
      19. 600s dark
   20,21. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
      22. 600s dark
   23,24. 2 x  1s external exposure
   25,26. 2 x 1000s external exposure (100x full well)
   27,28. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
      29. 600s dark
   30,31. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
      32. 600s dark
   33,34. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
      35. 600s dark
   36,37. 2 x  1s external exposure
      --  Put PMT in light path, take RAS/CAL PMT measurement
      --  remove PMT from light path
      38. bias

     b. Local QEH only with RAS/CAL:
        as above, but omit PMT measurements

VARAIANTS: a: RAS/CAL version
           b: RAS/CAL local QEH only
	   c: STUFF version

TOTAL EXPOSURES: 38

TOTAL TIME: ~4.7 hrs
  assume 10 minutes startup
          4 minutes overhead per exposure

ANALYSIS:
     combine image pairs to remove CRs

     QE = const * HRC count rate / RASCAL count rate  
	  take const = 1 (i.e. arbitrary normalization)
          HRC count rate can be global or local (we will look at both)
	    => QE(global) - one number derived from bias subtracted image.
	       QE(local) - combined 1s image pairs, bias subtracted

     Look at QE(global) for each 1s pair.  Hysteresis will show as elevated
     QE after longer exposures.  Want to see if there is a global
     effect, and whether it decays with time (hence the long darks).

     To look for relative QE(local) changes, divide reduced 1s image pairs
     by first image pair.  The relative QE(local) change we are most
     likely to see is higher QE(local) at trap sites (the dark blobs in
     normal flats).  

     Darks - examine these for residual images, particular after the
     2x100s exposures (about 10x full well each).