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General :
Observations :
Operations :

Procedure :
 Measure of the Linearity
Author :
  SOFI team
Release :
09/11/00 : update 
 21/01/00 : creation

The linearity of SOFI detector is checked every other month since November 2000. This is done with the template SOFI_img_tec_Linearity.obd.  The last MIDAS images are saved in /home/sofi/midwork on wsofi.

  • Make sure MIDAS for PCO is running on wsofi.
  • Make sure SUSI M4 mirror is in position SOFI.
  • Load the template SOFI_img_tec_Linearity.obd from /data/SOFI/SYSTEM/COMMON/OBD/CALIB into Bob and run it. Move in the calibration unit. You will be asked to switch the calibration lamp on, set the light intensity to have an average of about 1000 ADU in the illuminated part of the array when the DIT is 2 (default value for the first image). To get consistent results it is CRUCIAL  to use the  HALOGEN LAMP with the CALIBRATION UNIT.  An intensity around 16 is usually suitable to obtain the desired level.
  • The lamp will be automatically switched off at the end of the template and the calibration unit put out.
  • The value of the deviation to the linearity will be displayed in the bottom part of the BOB window at the end of the template. It takes about 30 minutes to run the template with the default parameters.
  • A plot of ADU/integration_time versus integration_time (i.e. versus flux received on the detector) will be displayed in a MIDAS graphic window and also printed. Show the plot to the support astronomer and discuss with him/her the results, then archive the plot in the Insrument Calibration Folder under SOFI linearity..
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    Last Update: January 14, 2001 (Malvina Billeres)