DV02 Metrology System Issues and Tracking

TIP Last Update: JeffMangum - 11 September 2009

Issues Tracked

For in-depth discussion of all issues associated with DV02 metrology integration and commissioning see the DV02 Metrology Issues topic.

  • Replace T1
  • Update ACU metrology interface software
    • 2009-09-11: Waiting to schedule.
  • Recalibrate LS metrology sensors
    • 2009-09-14: Not properly installed. Waiting contractor readjustment.

Associated JIRA Tickets

  • Primary:
  • Secondary:
    • AIV-286: Perform OPT Verification Tests
    • AIV-833: Analysis of OPT Pointing Results From Acceptance Through AIV
    • AIV-743: Check Linear Sensor Metrology System Software

Metrology System Calibration Constants

Date Pad AN0 (arcsec) AW0 (arcsec) SA2 (arcsec) SA3 (arcsec) phi2 (deg) phi3 (deg) NPAE (arcsec) Comments
24 April 2009
Acceptance values
8 May 2009
AIV measurement
9 July 2009
AIV measurement
10 September 2009
AIV measurement

Tiltmeter Metrology System Calibration Offsets

Date Pad TiltXOffset (arcsec) TiltYOffset (arcsec) Tiltmeter Blanking Time (sec) Tiltmeter Filter Time (sec) Comments

Linear Sensor Metrology System Calibration Offsets

Antenna Pad LS Offset 1A (mm) LS Offset 1B (mm) LS Offset 2A (mm) LS Offset 2B (mm) Comment

Metrology Sensor Time and Temperature Dependence

In mid-September 2009 NickEmerson calculated, from various ACU reports, the LS dependence on local temperature and the time and local temperature dependence of the tiltmeter. Here is what he found:

  • LS Dependence on Temperature: I looked back through lots of DV02 data (going back to April acceptance tests) up until August 22nd, 59 runs altogether. From each of these I calculated the tiltmeter offsets, average temperatures, linear sensor output, etc. Anyway, attached are 3 plots. The first (DV02_LS_TempDependence.pdf) shows the linear sensor output (averaged over each pointing run) plotted as a function of the average temperature of the relevant yoke arm during that run. Not surprisingly there is a very good correlation between the total length of each linear sensor vs. temperature. FYI I calculate the expansion coefficient to be approximately 55um/C. You may remember that the total range of these sensors is about ±1mm. As you can see from the plots, at a temperature of about 5C we are reaching the limit of the range of the sensors. In fact there was one run (on July 22nd) where we reached the end of the travel range of the sensor, causing it to deliver bogus values. After talking with Lutz the conclusion is that we have to realign the linear sensors, basically to try and get them in the middle of the range when we are at 0C. That gives us just about enough range to operate within ±20C but we may experience problems beyond that. The alignment itself is very easy (maybe 1-2 hours total) though of course we have to be careful to consider ambient temperature at the time of alignment.
  • Tiltmeter Time Dependence: The next plot (DV02_Tilt_TimeDependence.pdf) shows the change of tiltmeter offsets as a function of time.
  • Tiltmeter Temperature Dependence: Finally the last plot (DV02_Tilt_TempDependence.pdf) shows the tiltmeter offsets as a function of the tiltmeter temperature (actually a sensor very near the tiltmeter, not the one inside the tiltmeter). This plot shows a very clear correlation between the temperature and tilt X offset, and some correlation between tilt Y offset and temp, though not so clear as with X.

-- JeffMangum - 2009-09-11
Topic revision: r7 - 2009-11-05, JeffMangum
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