TO:  Future LASCO and EIT Science Planners
FROM:  C. St.Cyr, S. Stezelberger, E. Einfalt  (LASCO/EIT Operations)
DATE:  30 September 1996 
       Revised 25 Oct 1996
RE:  Considerations for LASCO/EIT Science Planning 


These are ground-rules that we have developed in working with LASCO
and EIT Science Planners over the past few months.  


(1) The completed science plan is due by 13:00 local (12:00 local 
on Fridays for the complete weekend plan).  We strive to have the 
daily command load prepared by 14:00 local.  This includes 
specification of all partial field-of-view coordinates.  



(2) We require at least a one hour break in the plan between 
11:00-16:00 (local) for the uplink of the load and any special 
operations.  The actual uplink of commands requires 20 to 40 minutes, 
and no observations can be executed during that time.

There are numerous ground system anomalies that can and do interrupt
our plans, so "flexibility" is required.  Examples of such
anomalies might include:  scheduled and unscheduled Radio Frequency
Interference (RFI) at the DSN stations; LASCO/EOF/CMS/POCC computer
problems (hardware and software); DSN tracking problems;
emergencies on other spacecraft that bump SOHO; etc..., etc...



(3) For purposes of testing new sequences and performing engineering
maintenance tasks, we may need several hours on at least one day each week
identified as "test time."  This time needs to be during local business 
hours.  Potential dates and durations of scheduled tests should be 
identified at the LASCO/EIT Weekly Planning Session, held at
14:00 (local) each Wednesday in the EAF.



(4)  An observational cadence more frequent than seven (7) minutes 
is generally restricted to a duration of one hour.  This is because 
operations are processed serially onboard, and we try to maintain
the C1 and C2 hourly cadence.  A cadence of less than 7 minutes 
effectively "locks out" observation by other telescopes.



(5)  Staff coverage on weekends and holidays is limited.  Someone does 
check the health and safety of the telescopes EVERY day, but we prefer 
to schedule complex activities during local business hours.



(6) EIT sector motor operations at high cadence (ie, more often than 
the synoptic) must be scheduled during real-time contacts.  If these are 
scheduled during contacts other than local business hours, then it 
will be the EIT Planner's responsibility to monitor telemetry.



(7) All new sequences and new partial field-of-view coordinates must 
be tested during real-time, before inclusion in a daily command load.



(8) Synoptic Programs

As of this writing LASCO's nominal synoptic program attempts to maintain 
the following cadences:

	C1 FeXIV online		one per 60 minutes
	C2 Orange equatorial	one per 60 minutes
	C3 Clear equatorial	one per 90 minutes

Also, we try to acquire our once-per-day C1, C2, C3 polarizer sequences 
during the MLSO observing window (17:00-22:00 UT).

	
The EIT nominal synoptic program includes:

  4-sector synoptic sequence [1024x1024] between 01:00-02:00 UT

  4-sector synoptic sequence [full-field 2x2 bin] at 07:00, 13:00, and 19:00 UT



(9)  If you are examining current observations or monitoring telemetry 
and you think something is not correct, PLEASE TELL SOMEONE IMMEDIATELY!  
We would prefer to answer a few false alarms than risk missing a chance 
to correct an anomalous condition.

If no LASCO/EIT operations person is immediately available, the
Flight Operations Team in the POCC knows that OCD #358 is their response
to a LASCO/EIT dangerous condition.  (This invokes a power cycle
and reboot of the onboard computer, so it should only be used in
an emergency.)



(10) Background

There are three resources the operations team must manage
to insure proper observations occur:  the command uplink; 
the LEB activity cycles; and the telemetry buffer downlink.

The command uplink is limited to 500 commands.  The current 
synoptic programs for LASCO and EIT account for about 120 commands.
Effectively each additional image requires one command, so if one
desires many small field images, then one must be sure not to
excede the command limit.

Prior to July 1996 we executed rather simple variations of a standard
synoptic program.  Our primary bottle-neck was the limit of
our telemetry allocation of 5.2 kbit/sec.  The LEB has an output 
buffer which holds about 55 minutes worth of data -- this is roughly 
the equivalent of two full-field, full-resolution images which have 
been Rice compressed.

But since August 1996 we have been using the new OBE onboard software 
and Scott Paswater's Planning Tool.  With the expanded capabilities
that these have offered we must now manage two onboard resources: 
the telemetry buffer and the LEB activities.

LEB activity can be quantified by the time required to acquire 
a single exposure: 

(Mechanism Movement)+(Exposure Duration)+(CCD ReadOut)+(Image Processing)

Mechanism Movement is about 25 seconds; CCD ReadOut is 20 seconds.
The Image Processing step varies according to the size of and detail 
in the image, but our experience has shown that the minimum time 
required to complete a small (eg., 5x5 block) image is about one minute.

At the end of this duration, the LEB is then available to begin
another image, but we must consider how many bits this exposure
has put into the telemetry buffer.

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