First Campaigns Evaluation
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
- Ref image: efr20001117.180530 2x2 binned exp: 10.4s (7.5+2.9s)
- Expected exp ratio: 68.6/41.6 = 1.65 or 68.6/30=2.28 (no shutter close time)
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 1 | 6m34s (= 5.8 images) or 7m50s (= 6.9 images) 5.3% of sequence |
|
Section 2 |
nb images= 38 + 2 wrong exposure |
cadence= 68.35s |
Interruption 2 | 6m26s (= 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 sequence | 45.6x66=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 |
|