DV01 Pointing System Issues and Tracking

TIP Last Update: JeffMangum - 23 November 2009

Issues Tracked

Resolved issues indicated with strike through.

  • AIV-521: Antenna #2 AIV - DV01: Radio Pointing Verification
    • Radiometric pointing verification at OSF (not entirely useful).
  • AIV-1469: Antenna #2 AIV - DV01 - AOS: Establish Radio Pointing Model
    • Radiometric pointing verification at AOS (immediately following move from OSF to AOS).
    • Clear from ACU report data taken just before and just after move that problems with large HASA and HASA2 terms (mainly) appeared immediately after antenna was moved.
    • According to NickEmerson the tiltmeter temperature sensor/correction problem (AIV-1586 - DV01 Has Developed Eratic Pointing) was resolved with an ACU software update on 2009-11-09. The metrology module was updated. Furthermore, NickEmerson points out that updating a module does not wipe nor change any of the saved parameters, so my concerns about the tiltmeter and linear sensor calibration values (and their possible adverse affects on the pointing performance) are likely unfounded.
    • Serious concerns about quality of ridges on AOS foundations.
      • NickEmerson has looked at the ridges on both the foundation upon which DV01 currently sits and the foundation to which DV02 was moved to on 2009-11-20. Before DV02 was set down NickEmerson made a quick measurement of the ridges, and found 2 of them to be grossly out of spec (one of them by a factor of 7), which doesn't instill much confidence in the foundations. The official measurement report of that pad describes it as slightly out of spec.
      • NickEmerson also made an inspection of the foundation to which DV01 was set, and saw that one of the ridges has a rather significant dent. NickEmerson took a photo of the ridge with the dent with feeler gauge partially inserted. It's not immediately clear that this dent could be causing our problems, but it would have taken quite a strong hit to make such a dent so it does make you wonder what other damage might have been caused to the underlying foundation insert which may not be visible.
      • NickEmerson also notes that the concrete around these ridges also looks slightly messy, but that may just be superficial and normal. Apparently the grout must be jack-hammered after curing to make it the correct height, then it is sealed again with some kind of epoxy or something.
      • NickEmerson asked Bill Johnson about the dent, and he said it was already there before they lowered the antenna onto the foundation.
  • AIV-1690: Obtain Tiltmeter Data From DV01
    • Trouble ticket associated with radiometric pointing problems found after move to AOS (AIV-521).
    • Tiltmeter measurement of the center of the foundation made by Bernard Lopez. Unfortunately, this is not what we are really concerned about. What we want to know is how the foundation is moving relative to the antenna at the radius of the azimuth bearing or at the feet.
  • AIV-639: DV01 and DV02 High Elevation Tracking Servo Oscillation
    • 2009-10-09: There has been a long-standing problem with DV01 and DV02 going into servo oscillation at high elevation. Vertex determined that it was a problem with their "observing mode guessing" code and have made some modifications. Klaus sent a new ACU software version (1.4.3) to the site on 2009-10-08 which contains a cure for the oscillation problem. The modified "submode detection" now also identifies transitions that do not exactly match the FS and OTF patterns in the spec. With the new software such transitions are no more handled in submode "tracking" and, thus, in a much smoother manner. This hopefully will close out the "high elevation servo oscillation issue".

Pointing Model Coefficients

All units arcsec.

Date Pad IA IE CA NPAE AN AW HECESorted ascending HESE
15 January 2009

15 January 2009

-- JeffMangum - 2009-09-11
Topic revision: r4 - 2009-11-23, JeffMangum
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