Data Quality

During routine SCIAMACHY operations there are certain activities/events which will degrade the quality of the measurement data, such that these data shall not be used. Reasons for degraded measurement data can be

1) Thermal imbalance of the detectors and/or the OBM

The thermal behaviour is disturbed by

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.

Event Item Stabilization Time
ATC/TC readjustment
TC Heater Power Det 5 & 6 27
Det 7 & 8 48
ATC Temperature Setpoints OBM 19
Recovery from a)
(max. downtime > 15 hrs)
OBM 19
Det 1 - 6 42.5
Det 7 & 8 58.5
(max. downtime > 6 hrs)
OBM 20
Det 1 - 6 43.5
Det 7 & 8 59.5
Cool-down in b)
Nominal Decontamination OBM 20
Det 1 - 8 58
Non-Nominal Decontamination OBM 20
Det 1 - 6 48
Det 7 & 8 56
  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.

2) Single Event Upset (SEU) of the PMD/SF ADC

Whenever the PMD ADC has suffered from a SEU, the PMD measurement data may be correpted afterwards. They shall not be used until a PMD/ADC_SF calibration has been executed. This calibration is triggered by monitoring specific PMD parameters.

3) Spacecraft manoeuvres

During manoeuvres of the spacecraft, the attitude control mode differs from that in nominal operations. Thus the pointing of the instrument will be disturbed. Whether pointing performance degradation has to be taken into account depends on the type of manoeuvre.

The entry in the Data_Quality_History table occurs manually.

Page generated 12 March 2003; last update: 30 July 2008