Spacecraft rolls

SOHO COMMISIONING PHASE TEST SHEET

1. TEST IDENTIFICATION
   Roll maneuver to checkout instruments.

2. TEST PURPOSE
   The purpose of this test is to determine the polarization and stray light characteristics of several instruments: CDS, EIT, GOLF, LASCO, MDI, SUMER. SWAN and VIRGO.

3. APPLICABLE PHASE
   Cruise.

4. SCHEDULED
   At any time after all of the instruments have completed enough commissioning procedures to participate. It must also be at a time when stars are in the fields of view of the LASCO C2 and C3 sensors.

5. TYPE OF MEASUREMENT
   The instruments perform solar measurements at a variety of roll angle positions. In this way the solar input rolls with respect to the instrument, but internal reflections/polarizations should stay constant.

6. SUCCESS CRITERIA AND/OR EXPECTED OUTPUT
   The expected output is a determination (off-line) for each instrument of the instrumental polarization and stray light characteristics.

7. METHOD / DURATION
   Seven roll maneuvers are performed with a dwell of 30 minutes at each one for a total of 3.5 hours, exclusive of the time to perform the roll.

8. PROCEDURE REFERENCE
   

   
   Roll spacecraft +30 degrees (to +30)
   Dwell 30 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   Roll spacecraft +30 degrees (to +60)
   Dwell 30 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   Roll spacecraft +30 degrees (to +90)
   Dwell 60 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   Roll spacecraft +45 degrees (to +135)
   Dwell 30 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   Roll spacecraft +45 degrees (to +180)
   Dwell 60 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   Roll spacecraft -180 degrees (to 0)
   Dwell 60 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   Roll spacecraft -90 degrees (to -90)
   Dwell 60 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   Roll spacecraft -90 degrees (to 0)
   Dwell 60 minutes
         EIT:        Image the corona in each sector position (4 images)
         LASCO:      Image the corona in clear + 3 polarizers for each
                     telescope (12 images).
   
   

9. CONSTRAINTS / PREREQUISITES
   The roll maneuver may not be performed using the gas jets.
   All instruments sufficiently operational.
   Stars in the fields of view of as many imaging instruments as possible.

   Required accuracy for maneuver is only a couple of degrees (e.g. a roll of 45 degrees may be anything between 42 to 48 degrees) but attitude determination after completion maneuver must be within normal SOHO range.

10. SPECIFIC REQUIREMENTS
    

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    Russ Howard
    Last modification: March 1, 1996