ISO cadences

[Rob Seaman]

Rick illuminates:

> FYFI: RTML does this via
>
> 	PhaseConstraint
> 		Description (a string)
> 		PhaseTime (an ISO dateTime)
> 		PhasePeriod (an ISO duration)
> 		PhaseStart (a double)
> 		PhaseEnd (a double)
> 		PhasePdot (a double)	
>
> if one thinks in phases and wants something between PhaseStart and  
> PhaseEnd or via
>
> 	SeriesConstraint
> 		Count (a positive integer)
> 		Description (a string)
> 		Interval (an ISO duration)
> 		Tolerance (an ISO duration)
>
> if one thinks in time and wants something at a time +/- a time  
> tolerance.

Interesting.  Presume these are typically expressed as something like  
"Newtonian" topocentric universal times.  Would you be able to  
construct an observing sequence where shutter open (or mid-exposure)  
occurs on an even barycentrically corrected cadence?  How about  
adjusting schedules for higher order effects like shutter corrections  
or differential airmass corrections for effective mid-exposure timings?

(No, I don't know anybody else who could do the latter either.)

The Gemini TCS was being designed about the time I implemented the  
barycentric (think I cheated and used only a heliocentric algorithm  
due to a favorable Jovian juxtaposition) cadencing for SONG.  Tried  
to interest them in implementing a general approach to exposure  
scheduling.  Not much interest there.

Rob