Data Quality - Thermal Performance

During routine SCIAMACHY operations there are certain TC/ATC related thermal activities which will degrade the performance of the detectors and/or the OBM. Such activities include

• TC Heater Power (trim heaters) readjustment
• ATC Temperature Setpoints readjustment
• transition to Heater-Refuse mode
• transition to Standby mode
• warm-up and operation in Nominal Decontamination
• warm-up and operation in Non-Nominal Decontamination

The infrared detectors suffer most from such a disturbance. Therefore these detectors take longest to reach thermal equilibrium again. The table below summarizes the stabilization times for each of these events.

1. stabilization times apply to a maximum downtime; shorter downtimes lead to shorter stabilization times (details provided in the IOM); the stabilization times are estimated from the start of the associated transition
2. stabilization times are estimated from the start of the cool-down phase

As long as the OBM and detector temperature stability has not been achieved, measurement data are of degraded quality. Detector temperatures and OBM temperatures are monitored on a weekly basis.

Data Quality History - Thermal

The columns labelled ’ABS_ORB Start’ and ’ABS_ORB Stop’ indicate orbit number of the event. The columns ’UTC - Start’ and ’UTC - Stop’ indicate the UTC times of the period with degraded performance. Note that these times can be approximations only. In case of detector temperatures the stop time is taken from the weekly monitoring plots for channel 1 indicating the orbit when a stable temperature level has been reached (not when the temperature is within the specified limits). Channels 7 & 8 require longer to reach a stable status. The OBM temperatures reaches thermal stability earlier (see page Data Quality).

The table below lists events affecting thermal stability from the start of routine operations onwards, i.e. January 2003. Quasi-routine measurements began in the Commissioning Phase in orbit 2204 (August 2^nd, 2002) with TC and ATC settings as of orbit 1454 (June 10^th, 2002 - see page Thermal History). No permanent TC or ATC adjustments had occurred between August 2002 and January 2003. A non-nominal decontamination in November 2002 did not affect data quality since SCIAMACHY had been transferred to OFF-SAFE as a safety measure in response to the Leonid meteor shower .

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