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Keyhole Planning with CDS

There are four keyhole periods during the SOHO year, and they arise because of a failure in the mechanism for the SOHO high gain antenna, which necessitates rolling the spacecraft by 180 degrees every half orbit. More details can be found through the SOHO webpage.

For a large part of the keyhole period, CDS is not able to observe for 24 hours/day and see we operate a much reduced science programme, consisting only of synoptic observations. No JOPs or campaigns are supported.

Below we give a prescription for filling the CDS timeline during the keyhole.

Prescription for filling up time-slots during keyhole

 

  • Confirm with the CDS operators about the time when they require each day’s plan to be ready by. Sometimes you may have to plan several days in advance as commanding periods are very limited.
  • Please consult the file http://sohowww.nascom.nasa.gov/soc/keyholes.html that contains the most up-to-date list of observing windows during the keyhole.
  • CDS science operations can be run as normal until the periods marked with SELECT VGMFL5 or SELECT VGM. These periods are referred to below as 'restricted'.
  • A restricted period ends with SELECT ALL.
  • During a restricted period, CDS observations should only be scheduled during the periods marked PASS D** in the keyhole file. If a pass is less than 1 hour long then it should not be used.
  • During a restricted period, CDS science operations should be started 15 mins after the start of the pass. E.g., if the pass starts at 12:00, then operations should be started at 12:15.
  • During a restricted period, data taken within the last 5 minutes of a pass may be lost, thus planners should attempt to complete studies before this point. However, for long studies (such as SYNOP) it is preferable that the study be run and a small amount of data lost, rather than the study not be run at all.
  • Science operations are not possible for at least 24 hours following the MANEUVER. The RAL team or GSFC operators will provide precise instructions on when the CDS science plan should be stopped and started before and after the MANEUVER.

 

Studies to be run during  restricted periods:

 

  • Try to run SYNOP each day and, if possible, try to run at around the same time each day. If a PASS lasts for 7 hours or more, then SYNOP_F/v4 (duration: 6hr 30min) should be run, otherwise SYNOP_G5/v1 (duration: 3hr 20min).
  • NIMCP/v1 should be run once per week.
  • ENG should be run every day if possible.
  • The quiet Sun NIS atlas (NISAT_S/v2) should be run once per week.
  • FULLCCD/v3 should be run once per week.
  • If a suitable PASS occurs on Tuesday, then the GIS meridian study (SPECT_4) should be performed.
  • If the 20th falls during the planning week, then the planner should try to perform the NIS spectral atlases (NISAT_S/v2) for an active region and coronal hole.
  • All other free slots should be filled with the coronal hole study STRE4W/v111.
  • If a mechanism lubrication is scheduled for the keyhole period then it is performed with the study ENG-AT/v3 which should be run inside of a PASS and not in a SELECT ALL period.
  • Whilst the CDS Doors are CLOSED, but not during the actual S/C MANEUVER the study FULLCCD/v3 should be run, repeat each run between 4 and 6 times, but only during a PASS. Make sure the CDS operators are aware that they need to load this plan.

 

Descriptions of the above studies are given below:

 

TITLE: SYNOPTIC SCAN
DATES:
Run ONCE PER DAY as near to 00:00 UT as possible
ACTIVITY: N-S scan in several lines running down central meridian.
CONTACTS: Richard Harrison - r.harrison@rl.ac.uk
STUDY TO BE RUN: SYNOP_F (Study ID 37, Var 4) [Assumes medium telemetry, i.e. 11.3 kbit/s. If high rate run SYNOP_HI, Study ID 37, Var. 2 instead].
On a day when USUN_4 is scheduled, run a shorter SYNOP_G5 (ID 219, var.1).
DURATION: 6.75 hours

 

TITLE: CONTAMINATION CHECK (QCM READING)
DATES:
Run ONCE PER DAY DURING NEAR-REAL TIME CONTACT
ACTIVITY: QCM reading.
CONTACTS: Jeff Payne - j.payne@rl.ac.uk
STUDY TO BE RUN: Acronym 'ENG' (and the title 'Run Anytime') in planning tool. Arrange timing with CDS Duty Engineer.

 

TITLE: NIS MCP SENSITIVITY MONITORING
DATES:
Run THREE TIMES PER WEEK on Quiet Sun
ACTIVITY: NIS wide/narrow slit comparison for mapping sensitivity of VDS. Pointing must be completely on the solar disk, in a featureless area of quiet Sun.
CONTACTS: Bill Thompson - thompson@orpheus.nascom.nasa.gov
STUDY TO BE RUN: NIMCP (Study ID 61, Var. 1)
DURATION: 17 min.

 

TITLE: NIS SPECTRAL ATLAS
DATES:
Run ONCE PER WEEK on Quiet Sun
ACTIVITY: NIS full spectral atlas on a quiet Sun region, for detailed spectral atlas and instrument monitoring.
CONTACTS: Richard Harrison - r.harrison@rl.ac.uk
STUDY TO BE RUN: NISAT_S (Study ID 17, Var. 2)
DURATION: 58m.

 

TITLE: NIS FULL CCD STUDY
DATES: Run ONCE PER WEEK on Quiet Sun
ACTIVITY: Full NIS CCD read out test activity
CONTACTS: Bill Thompson - thompson@orpheus.nascom.nasa.gov
STUDY TO BE RUN: FULLCCD (Study ID 15, Var. 3)
DURATION: 1m 40s.

TITLE: CORONAL HOLE STUDY
ACTIVITY: Run STRE4W/v111 at the north or south coronal hole. Modify the number of pointings according to the length of the DSN pass.
POINTING: If only one raster is possible, set the pointing to (X=0,Y=+1040) or (X=0,Y= -1040). If two rasters, then set pointings to (X=110,Y=+1040) and (X=-110,Y=+1040) at the North pole, or use Y=-1040 to point to the South pole. If three runs, then add an additional pointing at (X=0,Y=+880) for the North pole or Y= -1040 for the South pole.
DURATION: Each run of STRE4W/v111 lasts 1hr 43mins

Last revised on .