ICID 11 => LED_UNBINNED

Illumination:

  • LED.

Purpose:

  • Unbinned LED calibration measurement.
  • Monitoring of bad and dead detector pixels.

Location:

  • Eclipse side of the orbit.

Usage:

  • From launch onwards, once per day.
  • As a result of an anomaly in the Folding Mirror Mechanism (FMM) no ICID 11 measurements were performed from 27 February 2006 up to (including) 11 June 2006, with only one measurement at 6 June 2006. After this period the anomaly was resolved and the regular measurement schedule of one measurement per day was resumed.

Description:

LED unbinned calibration measurement. First a number of dark measurements are performed (ICID 10), then a number of light measurements. It takes 8*6=48 seconds to read out one complete image. These unbinned measurements are well suited to determine / monitor the unbinned detector bad and dead pixels. The LEDs turn out to be very stable within one measurement sequence (little drift with time, better than 0.1%) once switched on, but the output reproducibility from one switch-on to the next or over long time periods is not as good (e.g. 0.5%). This makes the LEDs well suited for accurate relative calibration measurements within one measurement sequence (e.g. within one orbit). The corresponding dark (background) measurements (ICID 10) are available for background correction in case this would be required. The background correction is also performed in the 0-1 data processor. The LED measurements are stored in the level-1b calibration data product.