Nodding the subreflector allows observers to switch between two beams of a high frequency receiver more rapidly than is possible with a standard nod. This has two possible benefits. First, it allows the observer to remove the effects of gain variations or atmospheric temperature or opacity variations on short time scales. This is particularly relevant when the weather conditions are unstable. Second, it has the potential for drastically lowering the observing overhead as compared to the standard nod.
Currently, subreflector nodding tests have involved configuring the subreflector nod in Astrid while running the actual scan via the Scan Coordinator or Antenna Manager in CLEO. This MR is to prevent Turtle from clearing the subreflector state at the beginning of a scan
so that an observer does not need to interact with CLEO to observe while nodding the subreflector. This makes nodding a more user-friendly experience and reduces lost time when the observer forgets to start or stop subreflector nodding while swapping between observing and pointing and focus scans.
Turtle clears subreflector settings before and after each scan to insure the user is not observing
with the subreflector in an unexpected state. A circumstance which is difficult to detect during
observing and can be missed during analysis. The only subreflector movements currently being
handled by turtle are for focus tracking; observer-initiated movements
have been specified at the script level using SetValues() or custom python scripts.
The reseting of the subreflector at the end of a scan was implemented because commanded
subreflector axes offsets were an exceptional case which needed to be confined to targeted scans procedures.
The implementation adjusted the antenna's subreflector axes to 0, but did not activate the parameter
allowing for the settings to be invocated at the next scan. This approach allowed a script to modify
the parameter without an intervening, unneeded subreflector movement.
The reseting of the subreflector at the start of a scan was implemented later as the result
of early PTCS work which involved setting the subreflector by cleo and glish scripts. Apparently,
it was felt that guaranteeing the subreflector started in a production-observing-mode state was imperative.
The result is that any subreflector settings set prior to a scan, either within
or outside turtle, are erased at the start of each scan.
Prevent turtle from clearing (setting to 0) all subreflector axes at the beginning of each
scan thus allowing that script-initiated settings are efficacious.
Remove the resetting of the subreflector axes to 0 at the start of a new scan. This consists
of removing one line. In addition, the clearing of the Y axis at the end of each scan needs
to be expanded to the other five axes, i.e., X, Z, XTilt, YTilt, and ZTilt.
Implementing this required having the AntennaConnection monitor Antenna state changes
to ensure that regardless of the means that a scan completes the axes are cleared.
Scans run on the telescope simulator with just the offending line in turtle removed displayed expected behavior
for the Y axis.
In all cases the subreflector parameters were cleared at the end of the scan.
This behavior satisfies the MR's requirement while still resetting the subreflector at the end of a scan
and allowing focus scans full control of the subreflector.
Normal sparrow install and release procedures should suffice. Since control of the subreflector is
not a production feature, I believe there is no end-user, or even internal documentation that needs
to be updated.
This is one of those changes where testing the targeted action is straightforward. Repeating
the above tests on the simulator should be sufficient. The concern is the existence of a
script or methodology that depends on the current feature (bug?). As in the past, we depend
on regression testing for exposing such deficiencies.
It is expected this change will have a broad repetitive effect on the unit tests since an
action that previously occurred on every scan is being removed. New unit tests will be
written to show setting of the subreflector parameter is not being overridden.
As part of the testing, verify that the subreflector segments are zeroed out (as expected) in the case of an abort during a Focus scan.
The simulator tests and the standard unit, regression and integration tests should be sufficient.
All that is required for integration is to confirm that a modification of the subreflector parameter
set prior to a non-focus scan is retained during the scan by either using CLEO, or a SetValues()
such as:
SetValues("Antenna", {"xyzSubrSegments,1,Y,pos" : 50})
Since subreflector movement is not part of our production observing except for focus scans, the
current set of regression tests are appropriate.
APPROVED: I acknowledge that my request is fully contained in this MR, and if the SDD delivers exactly what I specified, I will be happy.
ACCEPTED: I acknowledge that I have validated the completed code according to the acceptance tests, and I am happy with the results.
| Written |  - MarkClark - 18 Jul 2007 |
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| Checked | - MikeMcCarty - 18 Jul 2007 |
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| Approved by Sponsor | - D.J. Pisano - 18 Jul 2007 |
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| Approved by CCC | - AmyShelton - 20 Jul 2007 |
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| Accepted/Delivered by Sponsor | - RonMaddalena - 09 Aug 2007 |
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CCC Discussion Area
Revision r1.11 - 09 Aug 2007 - 14:30 GMT - AmyShelton
Parents: PlanOfRecordC52007
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