SoHO ROLL
				---------

The primary observable for this activity is the full-disk computed
continuum in order to measure the solar limb. In addition, dopplergrams
and magnetograms are highly desirable during the role for instrument
calibration purposes. 

One complete roll will be performed in increments of 30 degrees with a 25
minute dwell at each 30 degree delta stop.  The spacecraft will make a
"negative" roll about the +X axis i.e. the spacecraft will roll 
counterclockwise and the sun will appear to move clockwise.

The MDI instrument should operate with the Image Stabilization System
closed loop for the entire roll period.


Observing sequence:

  The observing program is Dynamics mode with continuum intensity as the 
  second observable.

  The magnetograms will be brought down as direct downlink with a repeat of 
  2 magnetograms and a cadence of 24 minutes. 


  The difference between the Dynamics mode that has been typically run
  and the Dynamics mode proposed for this activity is detailed below.
  The disadvantage of the Direct Magnetogram Dynamics mode is that there
  is one minute each Alt period with no high rate telemetry data
  product.  The advantage is that all the continuum images are taken
  with 60 second observations.

        Minute  Obs             Standard        Direct Mag
        N       P60             V60/I60         V60/I60
        0       Head/P30/A30    V30/I30         M30
        1       Alt30           V30/I30         M30
        2       P30/Tail        V30/I30         (nothing)
        3       P60             V60/M30half     V60/I60
        4       P60             V60/M30half     V60/I60
        5       P60             V60/I60         V60/I60
        ...
        N       P60             V60/I60         V60/I60

  Data products observed during the first roll:

        Full disk dopplergrams sampled over 60 seconds - cropped
        
        Full disk computed intensity (Ic) sampled over 60 seconds
           - cropped and square root compressed
        
        Full disk magnetograms sampled over 30 seconds - cropped


Operations steps:

  MDI should be put into the Dynamics mode by turning off the campaign flag. 
  In addition, the continuum intensity should set as the second variable; 
  the direct magnetogram downlink enabled, and the Alt repeat set to 2.

        Using seq_options_v09 set the following flags/registers:
          "Dynamics Options" to "D/L Continuum"           
                * sets IP register 1683 to 0

          "Dynamics Options" to "D/L Mag in 160K"
                * this sets DEP register 5 to 2 (magtelm flag) and 
                * brings down magnetograms directly in high rate

  In order to obtain magnetograms at each roll position, the Alt cadence 
  must be set to take magnetograms more often. It is recommended that the
  Alt cadence be set to 24 which will insure a magnetogram pair during
  each roll dwell. 

  The "Alt Cadence" should be set approximately 5 to 10 minutes after
  the start of an Alt period in order to maintain the same Alt phase.
  The control file seq_options, should be used to set the "Alt Cadence"
  when the interval counter (Register R2) should be between 5 and 15. It
  is recommended that this adjustment take place immediately after the
  Alt observation that takes place at 17:36 UT.

        "ALT Options" then 
        "Change Alt Cadence" and set Alt cadence to 24 

        "ALT Options" then 
        "Change Alt Repeat Count" and set Alt repeat count to 2

  Verify that the ISS loop is closed.
  
  Monitor the PZT's during the roll using rtplot. In /md80/tmp/pzt is the 
  list of commands to type (monitor multxave,multyave,multxmax,multymax).


Activities after the completion of the roll:

  After the completion of the roll sequence and returning to nominal
  pointing, the structure/dynamics framelists need to be reloaded.  To
  revert back to the standard 30/60 framelists (with the new MTM tuning
  values):

        perf q_reset_v05
        perf q_runstr_v28