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David Harland wrote:
<blockquote
cite="mid:3122dc4a634682143cc3adb9e9632275.squirrel@webmail.aoc.nrao.edu"
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<pre wrap="">On Fri, June 24, 2011 12:51 pm, Michael Rupen wrote:
</pre>
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<pre wrap="">...
* SDM Tables take their times from observation documents which give
the requested scan start times. The OPT produces scans in LST,
which unless you work hard are aligned on LST seconds.
</pre>
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<pre wrap=""><!---->
An amplification here for those less familiar w/ the OPT, and a question
regarding how the OST (dynamic scheduler) is used in practice:
The OPT allows users to choose from one of 6 types of timings for a scan.
Two axes:
1. Time definition: UT vs LST
2. Time type: scan-stop, on-source, total-duration
In order for all OPT scans to be aligned on integral LST seconds we'd need
to have all scans expressed as LST total-duration (which is, at least
currently, the norm) AND we'd need the model-to-script (m2s) algorithm to
be fed a start time that was an LST w/ no fractional seconds.
Question (for Keith): are the start times that the OST feeds to m2s
necessarily LSTs w/ no fractional seconds?
</pre>
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The OST does NOT schedule SBs to run on whole second intervals;
fractional seconds are usually included.<br>
Some rounding to the next whole second logic was recently added, but
this does not cover every case.<br>
-Keith<br>
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cite="mid:3122dc4a634682143cc3adb9e9632275.squirrel@webmail.aoc.nrao.edu"
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<pre wrap="">
Even if the above is answered in the affirmative, as we build the script
we're continually converting away from LST to UT in order to put scan
start MJDs in the script. I'd be quite surprised if we didn't accumulate
rounding error of at least fractions of a millisecond, and possibly more.
UT is the native time type for most, if not all, of our group's code. LST
is a convenience provided for the users.
</pre>
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<pre wrap=""> ..the requested scan interval will not in general contain an
integral number of 1sec UT integrations aligned on UT seconds...
</pre>
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<pre wrap=""><!---->
I've had a chat w/ more than one person about forcing scans to be integral
multiples of integration times. Nothing has been settled in this area
yet.
</pre>
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