Scientific Operations
 Front Page
 Scientific Ops
  » Plans
  » Pointings
  » Report
  » Requests
  » Log
  » Notes
  » Tech Info
Notes for Planners
Important tips/rules for CDS planners
Latest revision: .

This page will be maintained as an up to date record of recent and/or important information for CDS planners. There is already a wealth of documented help for planners (eg see CDS software note #42, A guide for the visiting scientist.) However, with the weekly rota system useful bits of information often get overlooked and so all planners must familiarize themselves with the contents of this page prior to starting the week's plan. Any planners who come across information they think could be usefully recorded in here should contact
John Rainnie or Andrzej Fludra.

S/C Roll: The planner should not take account of any roll of the s/c when using Mk_plan or Image_tool. The cpt program will automatically apply any necessary offsets.


In the CDS operations room in the EOF, the telephone numbers of key operations staff are clearly posted, including home numbers. Minor problems can be dealt with locally - e.g. questions about running the planning tools, questions about operations procedures.
  • For scientific questions, contact Andrzej Fludra
  • For operational issues contact Chris Maroney or Ron Yurow.
  • For software and data questions contact John Rainnie.
  • Major questions about the scientific programme should be addressed to Andrzej Fludra
    Such questions might include priorities for major schedule clashes, the question of support for unannounced JOPs etc...
  • Major questions about instrumental issues should be addressed to Andrzej Fludra, Ron Yurow and Chris Maroney
If in doubt, speak to someone, at anytime of the day or night !

Feature Tracking

We have recently had more incidents with a request for 'feature tracking' not producing the expected effect. Please read software note #45 and remember the feature tracking option cannot be relied on to give stable pointing at the 2" level. Remember also the difference between feature tracking and rotation compensation.
  1. The minimum E-W movement is approx 2 arcsec.
  2. The actual movement may often be 2 +/-2 arcsec with the result that the effect may be 'worse than doing nothing' depending on what effect was intended.
  3. The default interval for updating the pointing is 600 secs. If an individual raster duration is less than this, no correction will ever occur (since the timer is reset at raster start), even if the raster is repeated indefinitely.
If in any doubt, resist requests to use the feature tracking option. Note that the rotation compensation option has been tidied in MK_PLAN to try and avoid unrealistic pointing changes.

Emergency Study

A few things to remember about the use of the Emergency Study (ES) option in XCPT in MK_PLAN.
  1. This option must be enabled (ie switch it ON) at all times when planning This now includes during the weekend plans (ie planning through to Monday on Friday)

  2. This option automatically adds entries in the Deferred Command Store (DCS) starting at 01:00 UT on the day following the last study planned. The DCS entries added "yesterday" will be automatically deleted when "today's" plan is loaded. HOWEVER be very careful if you plan a day in more than one chunk (ie you run XCPT more than once per day) with this option switched on. The reason is that every time you run XCPT with this option on, entries will be appended to the DCS for a suitably later time, and since the DCS does not allow overwriting of identical entries, you can end up with identical, multiple commands in the DCS and only one of these entries will be automatically deleted when "tomorrow's" plan is processed. In short if you use multiple runs of XCPT to plan a 24 hr period (or indeed if you RE-plan part of a day) make sure that the ES option is switched on for ONLY ONE of these runs.

The 5% rule

Don't forget the 5% rule when planning. Until further notice do not append studies to run for more than 4-5 hours in a single block, and then leave a 5% margin in time before starting the next time-tagged group. This does not apply to studies following the daily synoptic study whose duration is pretty well known by now.

Science Plan entries

The CDS science_plan can never be blank - there is always something happening even if it's nothing. Please ensure that something is always recorded in the science plan

Use of mirror/slit steps instead of OPS in XCPT

This option is not to be used lightly !

Because the effect of OPS movement is uncertain at the few arcseconds level, there is an option in XCPT (within MK_PLAN) which allows the planner to request that the pointing changes between rasters be catered for by changes in the mirror and/or slit positioning rather than by OPS movement. Since the mirror and slit have limited ranges, it is not always possible to accede to this request. For instance in an NIS raster that covers 240" in Solar X, there is no further mirror range to allow off-pointing of the raster centre. In such cases the request will be ignored and the OPS used as normal. On the other hand, for smaller NIS rasters it will be possible to offset the raster centre without using the OPS.

However, please note that NO movement of the slit location is permitted for NIS rasters. Therefore, if a request is made to relocate in Solar Y with this option switched on (eg if a series of rasters is moved to compensate for solar rotation, and a small delta Y is calculated) then the Solar X motion may well be achieved by offsetting the mirror but the Solar Y motion will be achieved by moving the OPS (the only permitted mechanism). Experience has shown that that will more than likely mess up the X pointing as well.

Therefore, if the requirement is for accurate off-pointing in Solar-X, it is encumbent upon the planner to ensure that NO change in Solar Y location is requested (possibly by resetting to zero the delta-Y pointing calculated in the 'rotate' option).

The option to repoint by moving the scan mirror rather than the OPS is obviously limited by the scan range of the mirror, but if the requested pointing is within range, taking due account of the raster size, this option will work for the following types of planned study.
  1. The mirror may be used to repoint when the number of 'Pointings' in MK_PLAN is greater than one. The individual (X,Y) locations for each pointing can be entered in MK_PLAN. Note this also works for studies containing more than one deferred pointing raster - but only the move between 'pointings' uses the mirror - all rasters within a pointing will be at the same location.
  2. The mirror option may be used when a study contains more than one raster and those rasters have 'fixed' or 'offset' pointing
To avoid confusion in the plan, it is advised to XCPT separately the portion of the day for which this option is required rather than XCPTing the whole day with this option and assuming most rasters will use the OPS because the movement is out of range or the plan does not fulfil one of the above criteria.

As MK_PLAN is not aware of the choice to use the mirror/slit for pointings (XCPT is called after MK_PLAN !) it cannot accurately allow for the time it takes to move the mechanisms between rasters, especially for GIS studies. For GIS studies The Planner MUST leave a larger time gap AFTER each group of tagged studies where this option is used. (Obeying the 5% rule is not sufficient) As a rule of thumb allow at least an extra 60 secs per raster. Failure to do this will cause STUDY ABORTS and data loss it may also crash the CDS processors !

Telemetry Submode Changes

As telemetry submode changes become more frequent it is the planners and ops staffs duty to be aware of when these changes are to occur. It is especially important if CDS is to be switched out of Medium, Low or Hi rate. Please consult the CDS SCIENCE OPERATIONS PLAN and the SOHO Calender for details of all submode changes.

Whenever telemtry rate submode changes are scheduled then the CDS instrument MUST NOT be running any science studies.

Medium rate is the normal mode of operation of CDS. In low rates CDS can only perform limited science and only studies approved for that rate should be run. In Hi rate CDS has studies available that are optimised to this rate, but most medium rate studies can still be run, though they may not benefit fully from the HI telemetry rate.

Real Time Operations

There are three ways of using CDS to make scientific observations -
  1. Standard pre-planned operations focused on monthly, weekly and daily planning activities,
  2. Real-time operations where commanding from the EOF is required to achieve certain scientific goals
  3. Inter-instrument flag operations where targets are identified on board and a pre-set sequence is run automatically.

We have not used the inter-instrument flags (yet). CDS has raised the question of their use at two recent PI meetings, but the other instruments were reluctant to use them. The standard pre-planned operations activity is the way we have proceeded so far, and for most scientific observations this is fine. Indeed, there are few scientific questions which require the rapid sequence/pointing alterations which can be made using items (ii) and (iii), above.
With CDS we are not running a random scientific operation; we take in requests for observations and plan and execute operations accordingly. The way we operate is governed by the incoming requests, i.e. by the user community. Thus, there are TWO golden rules concerning real time operation and these have been stated before:

  1. There must be a good case for using RT commanding of CDS and it has to be approved by the CDS management team.
    i.e. the use of RT commanding must be necessary in order to achieve the observation required. If the observation in question can easily be done in the normal way then we will not 'risk' the instrument.
  2. The request to make the observation must go through the normal CDS request/planning channels.
    i.e. as with any CDS observation, a request to use CDS should be made through the PI. As always, this should include details of what you want to do; a complete observing plan should be suggested.
None of this should be a surprise to anyone it reflects the way we have always worked.
Please note that REAL TIME OPERATIONS OF THIS KIND WILL BE RARE, it is not something which we will take lightly.


The observation of flares raises another set of questions. Given the upturn of the solar cycle and observations of active regions we are going to see flares at times whether we like it or not.

Given the nature of our detector systems we rejected any thoughts of observing flares for the first year and a half of scientific operation. Discussions in October 1997 concerning the NIS detector system in particular paved the way to a series of e-mail discussions between the RAL team and the NIS and GIS detector people.

One output of this discussion was the guideline for observing active regions when considering the predicted flare probabilities. THIS GUIDELINE IS ALWAYS WRITTEN INTO THE WEEKLY PLANNING NOTE AND SHOULD BE TAKEN SERIOUSLY.

The discussions culminated in a relaxing of the blanket 'no' to flare observations.

Observing flares is an activity which involves careful planning and some special actions in order to 'prepare' the operation. It is also something which can be detrimental to aspects of the detector system. So, it is something we do not do lightly.
Given the relaxed position with regard to flares, we responded to a request which was subsequently run at the end of April with the first 'official' flare observation with CDS. NOTE THAT THE REQUEST WENT THROUGH THE NORMAL PLANNING CHANNELS AND WAS ACCOMPANIED BY A WELL THOUGHT OUT OBSERVATION SCENARIO AND OBSERVING SEQUENCE.

CDS will not become a flare hunting device (in any case it is the PI's opinion that flares are really rather boring!). All CDS requests will be dealt with in a non-biased manner - as has always been the case. If you want to observe flares (or anything else for that matter), you must follow the usual course of action - i.e. plan out the observing sequence and make a request to the PI.

An active region may be observed using CDS regardless of the flare probabilities given by NOAA. If the planned Study is with the NIS, the GIS should be at a parked voltage. If a flare is seen, the NIMCP Study (see above) should be run as soon afterwards as is possible. In any case WIDE SLIT (90"x240") STUDIES ON ACTIVE REGIONS ARE NOT PERMITTED!!!

When performing flare studies where there is a good potential for seeing a flare, it is best if the rastering is not done over a small area. This is to avoid just sitting on a flare, without moving off it.

If an active region Study is to be run, and it is not aimed at the study of flares, it is best to avoid active regions with very high chances of large (M or X) class flares. Check the NOAA forecast on
Alternately use the CDS current conditions page that contains all the necessary references.
OPS Pointing via DCS

It is possible to update OPS pointing values that have already been loaded into the DCS without the necessity of replanning and reloading the plan via (IDL) MK_PLAN and (Perl script) LOADPLAN. This means that under favourable circumstances some studies can have their pointing updated only a matter of minutes before they are due to run. The operations staff will run the necessary software after receiving a request from the planner, and judging whether it is prudent to attempt the update (bearing in mind commanding constraints etc.).

Pointing commands are only put into the DCS if the study is time-tagged and the pointing is different from the previous study. If either of these does not apply then you will still have to go the MK_PLAN route to change anything. Note: that only the initial pointing of a series of pointings of the same study (eg for rotation compensation) is put into the DCS and hence this technique should not be used on those plan entries.

To use this new option the operators run the IDL procedure NEW_DCS_OPS (only master has the correct setup to allow this). This displays in a widget list the details of the last DCS dump that was sent. That dump usually originates from the last running of the Perl script LOADPLAN. The display is the same as in the DCS editing program DCS_EDIT, but the user interaction is slightly different.

To change an OPS pointing, highlight with the cursor either (not both) of the OPS left/right pointing command lines. A widget will appear that prompts the user for the new solar (X,Y) values to be uplinked in place of the highlighted pair. Enter these as decimal values separated by a space or comma. Multiple pointing commands may be edited anywhere in the DCS list. If you edit the same pair of commands more than once only the last entered edit will be saved.

Hit the 'Done' button when finished. A summary of the commands to be uplinked is given in the IDL session. These instructions are saved in files which the Perl script NEW_DCS_OPS will use as input. When ready the operations staff will run the script


At the end of the script a new dump of the DCS is made. You can therefore check if the edits have been successful by inspecting this dump either from the STM options menu or in the planning IDL session using either the NEW_DCS_OPS or DCS_EDIT widget based routines or (more quickly) using SHOW_DCS for a quick screen listing.

Three points to bear in mind.
  1. If you change the pointing in this way the new values will not be in the archived planning database (but this applies to other realtime pointing changes as well). The catalogues and FITS files of course will still contain the true observed values.
  2. The timings of commands in the DCS are calculated to allow enough, but not excessive, time for the mechanisms to move the distance the original plan calls for. If the new pointing is a long way from that in the original plan, not enough time may be allowed for the movement to the following study and a mechanism could still be moving when the next raster starts. This mode of operation should therefore not be abused, for example by loading the day's plan with all pointings at sun centre and with the intention of loading all the final pointings via NEW_DCS_OPS. Not only would this almost inevitably mess up the timings in the plan, it wouldn't work anyway because of the caveats mentioned earlier!
  3. If it is necessary to utilize untagged studies, the pointing coordinates for the untagged studies must match EXACTLY to the pointing coordinates for its parent timetagged study. If the coordinates do not match, then the untagged study will have internal commands to send the OPS to the undesired position.

Spatial offset between NIS and GIS

  • There is also an offset between the imaging of NIS and GIS. GIS images appear approximately 21.5" (was listed as 13") south of their NIS equivalents. Specific (X,Y) pointings for GIS should therefore be 21.5" (old value used was 13" south of the values determined by the software (image_tool for instance).

  • Last revised on .