1st post launchSCIAMACHY calibration & Verification Meeting

L1bAstrium 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

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

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”!!

What has been looked at so far (2)L1. 06.04: Range checking of newly calculated leakage current parameter

ADS 1Start time first stateAttachment flagStart time last stateOrbit phaseTemperatures (OBM, Science Channels, PMD)FPN Error FPNLeakage current channel 1 to 8Error on leakage current channel 1 to 8Mean noise per detector elementPMD dark offset Error on PMD offset

ADS 2Start time of stateAttachment flagAverage dark measurementStandard deviation of average darkPMD dark offsetError on PMD offset Solar straylight from azimuth (science channels) Error on solar straylightStraylight for PMDError 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:S1 S6S2 S7S3 S8S4S5

1657:S1 S6S2 S7S3 S8S4 S9S5

First Results (1)FPN 1614

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FPN

Series1Series2Series3Series4Series5Series6Series7Series8

FPN of orbit 1614. 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!

Rel. difference of first FPN/orbit 1614 to its orbital average

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First Results (3)Average deviation from average FPN/orbit 1614

-2E-12

-1.5E-12

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Series1

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)

Channel 4

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3073 3201 3329 3457 3585 3713 3841 3969Pixel ID

Leak

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BU]

Rec 1 Rec 2 Rec 3 Rec 4 Rec 5 Rec 6 Rec 7 Rec 8 Rec 9

•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!

Channel 6

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5121 5249 5377 5505 5633 5761 5889 6017Pixel ID

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Rec 1 Rec 2 Rec 3 Rec 4 Rec 5 Rec 6 Rec 7 Rec 8 Rec 9

Channel 6+

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5888 6016 6144Pixel ID

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Rec 1 Rec 2 Rec 3 Rec 4 Rec 5 Rec 6 Rec 7 Rec 8 Rec 9

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.

Channel 8

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7171 7299 7427 7555 7683 7811 7939 8067Pixel ID

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Rec 1 Rec 2 Rec 3 Rec 4 Rec 5 Rec 6 Rec 7 Rec 8 Rec 9 selected pixel 7500

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oribit region

LC [B

.U. s

-1]

Series1

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 representativefor all orbital regions. Errors due to that approach are in the order of 0.5 in channel 7 & 8For 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?