1 st post launch SCIAMACHY calibration & Verification Meeting L1b Astrium Friedrichshafen – Germany 24 July 2002 First level 1b Leakage current analysis

Content Related Verification Tasks What has been looked at so far Orbit and State specifics First results Conclusions

Related Verification Tasks L : Number of orbital regions for leakage current correction (and L ) L : Verification of deep space assumption L : Number of different dark current states sufficient to determine LC param. L : Range checking of newly calculated leakage current parameter

What has been looked at so far (1) L : Number of orbital regions for leakage current correction (and L ) L : Verification of deep space assumption L : Number of different dark current states sufficient to determine LC param. Has to be seen as “investigation started”!!

What has been looked at so far (2) L : 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

Orbit and state specifics States: State ID 46, 63, 67 beta flight states, I.e. no aperture, no ND filter Orbits 1614, 1657 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: S1S6 S2S7 S3S8 S4 S5 1657: S1S6 S2S7 S3S8 S4S9 S5

First Results (1) FPN of orbit All orbital positions (series 1 to 8) do show identical results. Results for orbit 1657 are not shown for similarity.

First Results (2) All orbital positions (series 1 to 8) have identical FPN!

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.

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.

First Results (5) Channels 6 behaves somewhat strange. Lower wavelength part (6) shows atmospheric variation, 6+ does not!

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.

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 1 st 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.

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)? Don’t we see atmospheric contribution in 6+, 7 and 8 due to contamination? Do we have other explanations for this?