SCIAMACHY Long Term Monitoring

Health and performance of the SCIAMACHY instrument are regularly monitored by the Sciamachy Operations Support Team (SOST).
Monitoring activities are essential to detect and possibly correct for the degradation of instrument components. Therefore long-term monitoring is a prerequisite for a high data product quality throughout the lifetime of SCIAMACHY.
One part of the long-term monitoring activities is the trend analysis of measurements with the internal White Light Source (WLS) and of observations of the unobscured Sun above the atmosphere. In order to monitor the different SCIAMACHY light paths solar measurements are taken in various viewing geometries: In limb/occultation geometry (via ASM and ESM mirrors), in nadir geometry (via the ESM mirror through the subsolar port), and via the so-called calibration light path involving the ASM mirror and the ESM diffuser.
SCIAMACHY long-term monitoring comprises a regular analysis of these measurements.

The plots displayed on this page show first results of these monitoring activities.
Note that the monitoring data presented here have been reprocessed using actual (Level 1b V6.x upwards) radiometric key data.

The displayed data have been produced in the following way:
All measured spectra have been divided by the corresponding measurement at a reference time; then for each channel a median of the ratio is computed, yielding an effective instrument throughput for the different light paths.
The reference spectra for all light paths are derived from measurements on 16 January 2003 (the time of the first monthly calibration performed with final flight settings). The resulting medians are then scaled to be 1 just after the first decontamination under (quasi-)nominal measurement conditions in August 2002. Therefore, the reference date for all data is in fact 2 August 2002.
Subsolar measurements before 30 November 2002 (about orbit 3922) did not consider the known yaw misalignment of SCIAMACHY on ENVISAT and thus may not be used for monitoring purposes. Therefore there are no subsolar data shown before December 2002.
Since no valid subsolar measurements are available for August 2002 the subsolar throughput data have been scaled to 2 August 2002 by using the same factor as for the limb light path.
Note that measurements performed during times of reduced instrument performance (e.g. switch-offs or decontamination periods) have been omitted.

The plots are updated on a daily basis, thus reflecting the current status of the instrument.

Monthly long-term monitoring plots are also available (click here).

PMD monitoring results can be found here.

Spectrally resolved throughput monitoring results (based on Level 0 data) can be found here.

A download of spectral data is also possible (click here).

Channel 1 (Click to Enlarge) Click to Enlarge

Channel 2 (Click to Enlarge) Click to Enlarge

Channel 3 (Click to Enlarge) Click to Enlarge

Channel 4 (Click to Enlarge) Click to Enlarge

Channel 5 (Click to Enlarge) Click to Enlarge

Channel 6 (Click to Enlarge) Click to Enlarge

Channel 7 (Click to Enlarge) Click to Enlarge

Channel 8 (Click to Enlarge) Click to Enlarge

As can be seen from the plots, the SCIAMACHY instrument is generally in good shape. However, to avoid misunderstanding, some features in the plots require additional explanation:


Stefan Noël (

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