ESA presentation

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1st post launch SCIAMACHY calibration
Verification Meeting L1b Astrium Friedrichshafen
Germany 24 July 2002 First level 1b Leakage
current analysis
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Content
Related Verification Tasks
What has been looked at so far
Orbit and State specifics
First results
Conclusions
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Related Verification Tasks
L1. 01.01 Number of orbital regions for leakage
current correction (and L1.06.02)
L1. 06.01 Verification of deep space assumption
L1. 06.03 Number of different dark current
states sufficient to determine LC param.
L1. 06.04 Range checking of newly calculated
leakage current parameter
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What has been looked at so far (1)

• L1. 01.01 Number of orbital regions for leakage
  current correction (and L1.06.02)

• L1. 06.01 Verification of deep space assumption

• L1. 06.03 Number of different dark current
  states sufficient to determine LC param.

• Has to be seen as investigation started!!

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What has been looked at so far (2)

• L1. 06.04 Range checking of newly calculated
  leakage current parameter

• ADS 1
• Start time first state
• Attachment flag
• Start time last state
• Orbit phase
• Temperatures (OBM, Science Channels, PMD)
• FPN
• Error FPN
• Leakage current channel 1 to 8
• Error on leakage current channel 1 to 8
• Mean noise per detector element
• PMD dark offset
• Error on PMD offset

• ADS 2
• Start time of state
• Attachment flag
• Average dark measurement
• Standard deviation of average dark
• PMD dark offset
• Error on PMD offset
• Solar straylight from azimuth (science channels)
• Error on solar straylight
• Straylight for PMD
• Error on straylight for PMD

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Orbit and state specifics
Orbits 1614, 1657
States State ID 46, 63, 67 beta flight states,
I.e. no aperture, no ND filter
Both orbits contain some measurements in the
South Atlantic Anomaly which has not filtered
out (yet)
Input values for following orbital positions (0.5
sunrise)
1614 S1 S6 S2 S7 S3 S8 S4 S5
1657 S1 S6 S2 S7 S3 S8 S4 S9 S5
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First Results (1)
FPN of orbit 1614. All orbital positions (series
1 to 8) do show identical results. Results for
orbit 1657 are not shown for similarity.
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First Results (2)
All orbital positions (series 1 to 8) have
identical FPN!
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First Results (3)
Average of all 8 plots of the previous type. All
this proves that the FPN is (as expected)
independent of orbital position.
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First Results (4)

• Channels 1 to 5 show a significant amount of
  atmospheric contribution to the leakage signal.
• Dark space (at 150 km tangent height) assumption
  could not be confirmed.
• Record 2 (as from eclipse) gives best results for
  all channels.
• Amount of straylight overestimated because only
  first, but not first 10 readouts has been
• disregarded from analysis.

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First Results (5)

• Channels 6 behaves somewhat strange.
• Lower wavelength part (6) shows atmospheric
  variation, 6 does not!

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First Results (6)

• Channels 7 8 seem to have no atmospheric
  straylight (no obvious differences for all
  regions)
• Dark space (at 150 km tangent height) assumption
  can be confirmed.
• Orbital dependence almost as expected.

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Conclusions
FPN behaves as expected
Leakage current shows large atmospheric
contributions (much larger than expected) This
holds only for channels 1 to 5 and partly 6.
Channels 7 8 are apparently less effected.
But they might not see it due to the ice
(contamination).
Proposal for 1st LC auxiliary data set from
in-flight data Take orbit 1614 or 1657 and take
the one data set from eclipse being
representative for all orbital regions. Errors
due to that approach are in the order of 0.5 in
channel 7 8 For channels 1 to 6 this number
still needs to be assessed because the
memory Effect was not correctly considered.
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Points for Discussion

• Different Leakage current for nadir and limb
  (last scan)
• Straylight handling
• Is harmonic analysis really necessary?
• Shall we try and find a better tangent height
  (with less stray light)?
• How many readouts shall be rejected from
  analysis (and why)?
• Dont we see atmospheric contribution in 6, 7
  and 8 due to contamination?
• Do we have other explanations for this?