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Astronomical Characterization and Improvements Spring 2005

This is intended to be the top-level page providing an overview, and links to work related to characterizing and improving the antenna via primarily astronomical observations. There is some overlap with instrumentation work via the use of temperature sensors, inclinometers, the Quadrant Dectector and other devices to improve and/or measure pointing and tracking performance.

• Goals
• Overview of work planned during Spring 2005
• Task List
• Commissioning Experiments
• Commissioning Time Dates

Goals

• Support the use of Q-band (40-50GHz) for astronomical observations for February 1 2005 through May 1 2005 inclusive. This primarily consists of:
  • Re-validating and applying the Spring 2004 rigging-angle OOF results
  • Measuring the resulting gain-efficiency curve
  • Ensuring visiting observers are well-supported in the areas of observing and calibration strategy
• Support the preliminary engineering commissioning of the Penn Array (86-94GHz) in April/May 2005.
• Prepare for production Q-band observing for Winter 2005/06 (by 1st October 2005).
• Prepare for commissioning and demonstration science observations with the Penn Array for Winter 2005/06 (by 1st October 2005).

This work fall into a number of areas:

• improve the surface efficiency, via a combination of out-of-focus (OOF, see OOFHolography) and traditional holography, and potentially "quick-tweak" measurements of e.g. coma and astigmatism (these may in the end become just a variant of the OOF technique).
• Continue to improve the pointing performance (in conjunction with instrumentation work).
• Develop techniques to fully characterize tracking performance.
• Develop improved scanning techniques (in collaboration with PAR efforts), including after-the-fact knowledge of beam position
• Potentially, address issues with antenna control both prior to, and during a scan (depends on software effort available).

Overview of work planned during Spring 2005

Initially, we had hoped to make a round of simple coma/astigmatism measurements, and OOF holography, prior to the start of Q-band observing. This has not been completed due to a combination of lack of staff effort, and poor weather. However, we have a set of surface adjustments which were made during Spring 2004, which we believe will certainly improve antenna performance.

Task List

• Revive OOF zernike coefficients, confirm these have correct signs, etc. (no reason to doubt this?)
• Perform definitive gain-elevation curve with OOF zernikes (and possibly without, for comparison purposes).
• Repeat simple astigmatism measurements with OOF enabled (may allow a simple elevation-dependent astigmatism removal).
• Common user scripts (config_tool / turtle) for applying OOF zernikes (possibly including elevation/astigmatism).
• Get Dana's existing notes into Project Note wiki page.
• PTCS Project Note describing definitive Q-band efficiency measurements.
• Complete Coma Project Note including contribution of tilt-removal to translation.
• Rationalize coma memo results with OOF results and pointing model.
• PTCS Project Note describing all geometry and optics conventions.
• PTCS Project Note / wiki page descringing Penn Array Requirements.
• Decide (simulation? experiment?) Ka-band OOF configuration.
• Decide (simlation? experiment?) Ka-band OOF scanning pattern.
• Investigate incorporation of QD or other beam-position measurements into off-line data flow.
• Perform Ka-band OOF experiments.
• Develop continuum GB FITS -> OOF data analysis path.
• PTCS Project Note describing tracking performance experiment.
• Perform tacking performance experiment, for appropriate scanning patterns.

Commissioning Experiments

Roughly in priority order, should do Q-band measurements as soon as weather is good enough:

• Excellent weather Q-band measurement of gain-elevation curve with Spring 2004 OOF geostationary satellite coefficients.
  • ideally ~12 hours on a single source horizon to zenith
  • 3C286 rises at ~11pm, transits around 5am, 3C48 transits around 7pm, sets 11pm (are these the best sources?)
• Excellent weather Q-band efficiency comparison with/without Spring 2004 OOF geostationary satellite coefficients, at a range of elevations. (a few hours?)
• Spot check of astigmatism technique at Q-band with OOF coefficients turned on, at a range of elevations (a few hours?)

• Start work on AntennaCharacterizationTrackingPerformanceSpring2005

• X-band test of "defocus" antenna with primary, compensate with subreflector, should see no net change (test of OOF software). An hour or so?

Commissioning Time Dates

Refer to http://wwwlocal.gb.nrao.edu/GBTopsdocs/GBTschedules/schedules.html, but currently:

• Sun 16th Jan daytime, Q-band project checkout

• Mon 17th Jan daytime, PTCS tests, flex scheduled
• Wed 17th Jan daytime, PTCS tests, flex scheduled
• Fri 17th Jan daytime, PTCS tests, flex scheduled
• Mon 24th Jan 16:30 to Tue 25th Jan 16:30 (24 hours), flex scheduled against
• Wed 26th Jan 16:30 to Thu 27th Jan 16:30
• Sat 29th Jan 21:00 to Sun 30th Jan 03:00 (6 hours), flex scheduled against
• Mon 31st Jan 21:00 to Tue 01st Feb 03:00

• Tue 1st Feb onwards GBT01A-005 "A High resolution spectral survey of TMC-1 at Q-band", Turner and Langston
• Tue 1st Feb onwards GBT04C-006 "Q-band search for high redshift carbon monoxide line emission", Vanden Bout et al.

-- RichardPrestage - 12 Jan 2005