First Campaigns Evaluation

Contents
  • 304A test sequence: 17/11/2000
  • First true 304A sequence: 19/11/2000
  • 195A initial test 2000
  • back to Shutterless main page



    304A test sequence: 17/11/2000

    Sequence timing and telemetry
    Measured cadence 68.55 s
    Measured duration 12m 34s (11 intervals) 13m 42.6s (12intervals)
    True processing overhead 60 s (compression ratio ~ 1.95?)
    processing 13x13/1.95x0.25 = 21.7s
    compression 13x13/1024/1.95*455 = 38.5s
    Total 60.2s
    True total effective exposure 60 + 8.6 = 68.6 s
    Fraction of drifted exposure 8.6/60 = 0.1427
    Estimated background 250DN (disk QS)/*0.14*0.8 = 29 DN
    Data flux 147.92 blocks/min
    Buffer level at the end 8.8% (134 blocks)
    Estimated total number of blocks: 13.71x66+134 = 904.9 + 134 = 1038.86 blocks
    (12x13x13 blocks = 2028 actual blocks) ---> compression ratio = 1.952
    or assuming a 2.5 compression ratio, ---> buffer end level = -6.1 % (-94 blocks)

    Exposure determination

    Region Shutless Normal Ratio
    corner 60 30 2.00
    CH 140 70 2.00
    QS 260 120 2.08
    limb 250 110 2.27
    AR 1250 500 2.5
    AR max 3500 1700 2.05
    Max histo 3000 1500 2.00

    NB:

  • on average, the smeared background due to readout is estimated at only 12% of the average disk intensity! It is in fact difficult to measure it without taking the ratio with a normal image.
  • The brightest areas only reach about 5000DN, while the average disk brightness is 250DN. Thus, no overexposure.


    First true 304A sequence: 19/11/2000

    Parameters
    Passband 304 A
    Compression Rice
    Binning no
    CCD clears no
    Commanded exposure 0s
    Number of images 3 x 40
    Subfield size 13 x 13 blocks
    Timing free-running mode (as fast as possible)
    Compression ratio 2.5 (measured)

    Target subfield

    [P1_X:P2_X,P1_Y:P2_Y]

    Quadrant SW (lower right): [ 513: 928, 564: 979] <------
    Nominal SW quadrant is then: [512:927,96:511] (upper left corner = CCD center)
    Shifted 1 block NE is then: [480:895,128:543]

    Sequence timing and telemetry
    Section 1 nb images = 37 + 2 wrong exposure + 1 missing file (1609...) cadence = 68.32s
    Interruption 16m34s (= 5.8 images) or 7m50s (= 6.9 images) 5.3% of sequence
    Section 2 nb images= 38 + 2 wrong exposure cadence= 68.35s
    Interruption 26m26s (= 5.6 images) or 7m42s (= 6.8 images) 5.3% of sequence
    Section 3 nb images= 38 + 2 wrong exposure (174951 is abnormal) cadence=68.7s

    Total duration: 2h26m52s = 146m52s

    Cadence 68.35 s (8.3 readout + 60.0 processing)
    True total effective exposure 60 + (2x8.6)*0.5 = 68.6 s
    True processing overhead 60.2 s (compression ratio ~ 1.95?)
    processing 13x13/1.95x0.25 = 21.7s
    compression 13x13/1024/1.95*455 = 38.5s
    Total 60.2s
    Fraction of drifted exposure 8.6/60= 0.1427
    Estimated background 250DN (disk QS)*0.14*0.8= 29 DN
    Data flux 148.35 blocks/min (uncompressed) > 59.34 blocks/min (compressed 2.5)
    Buffer level at the end empty!
    Total number of blocks transferable over 40 image sequence45.6x66=3007 blocks
    Total actual blocks 40x13x13= 6760 blocks (uncompressed) = 2704 blocks (compressed 2.5)
    --> 10% below telemetry rate

    Exposure determination

  • Ref image: efr20001219.154032 exp: 32.6s and efr20001219.184324 exp: 32.6s
  • Expected exp ratio: 68.6/32.6 = 2.10 or 68.6/30=2.28 (no shutter close time)

    Region Shutless Normal Ratio
    corner 60 30 2.00
    CH 170 75 2.27
    QS 250 110 2.27
    limb 250 100 2.50
    AR 800 400 2.00
    AR max 2200 1300 1.69
    Max histo 1700 1300 1.31

    NB: a 20% sensitivity loss occured between 2000/11/17 and 2000/12/19.



    195A initial test 2000

    Parameters
    Passband 195 A
    Compression no
    Binning no
    CCD clears 1 clear
    Commanded exposure 30s

    Initial estimates
    Cadence 53.82s (30s expos + 5.1 readout + 18.7 processing)
    Estimated processing time 18.7 s (compression ratio ~ 2.67?)
    0.260s/block, or 231 blocks/min
    True total effective exposure 30 + 5.1*0.5= 32.5 s
    Fraction of drifted exposure 2.5/30= 0.08
    Estimated background 350DN (disk QS)/*0.08*0.45 = 13 DN
    Data flux 80.27 blocks/min
    Estimated total number of blocks 10.76x66+301 = 710.4 + 301= 1011.4 blocks
    (12x8x9 blocks=864 actual blocks)
    --> buffer end level= 10% (154 blocks)
    Buffer level at the end 301 blocks (19.75%)

    Exposure determination

    • Ref image: efr20001117.191427 exp: 12.6s
    • Expected exp ratio: 32.5/12.6= 2.57 or 32.5/10=3.25 (no shutter close)

    Region Shutless Normal Ratio
    CH 200 60 3.33
    QS 350 125 2.80
    AR 1800 650 2.77
    AR max 4200 1700 2.47
    Max histo 3500 1300 2.69