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Current GBT Performance

Current GBT Performance. Systematic Focus Errors. Axial Focus Offset: air temperature versus elevation. Gravitational & Temperature Focus Effects. Temperature Effect. Gravitational Effect. Measure focus over short time period. NCP source 0117+8928. Systematic Pointing Errors.

zachary-mccoy
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Current GBT Performance

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  1. Current GBT Performance

  2. Systematic Focus Errors Axial Focus Offset: air temperature versus elevation

  3. Gravitational & Temperature Focus Effects Temperature Effect Gravitational Effect Measure focus over short time period NCP source 0117+8928

  4. Systematic Pointing Errors

  5. Plan of Attack • Rationalize data acquisition • Rationalize data analysis • Implement temperature sensor system • Concentrate efforts on pointing and focus • Characterize performance with X-band (8 -10 GHz)

  6. Data Quality Gaussian Fits (Az, El, Focus) Polarization (LCP – RCP) Direction (Forward – Backward) Jack Scan

  7. Data Quality: Pointing (LCP – RCP)

  8. Data Quality: Pointing (LCP – RCP) Flux (9 GHz) > 0.08 Jy RMS < 2.5 arcsec < 0.03 HPBW

  9. Data Quality: Focus (LCP – RCP) Flux (9 GHz) > 0.08 Jy RMS < 3.8 mm << focus beamwidth

  10. Data Quality: Pointing (F – B)

  11. Data Quality: Wind

  12. Observational Strategy • NCP source to probe temperature effects • Up-down sources at night to probe gravity effects • All-sky for a combination

  13. Initial Results • All-sky (Az, El) pointing • Removed systematic pointing residuals • Simultaneous fits to gravity and temperature • Separate two effects • Refine focus and pointing models

  14. Current Performance • Model: • Simultaneous solution to temperature and gravity effects • Datasets: • All-sky pointing run (2003 Nov 20) • Half-power tracking (2003 Nov 20) • Metrics • Blind pointing • Offset pointing • Continuous Tracking

  15. Blind Pointing: Azimuth

  16. Blind Pointing: Elevation

  17. Blind Focus

  18. Offset Pointing: Azimuth and Elevation

  19. Offset Focus

  20. Tracking: Ku-band (14 GHz) El half-power track

  21. Current Performance: (NO temperature corrections) Benign Conditions: (1) Exclude 10:00  18:00 (2) Wind < 2.5 m/s Blind Pointing: (1 point/focus) Offset Pointing: (90 min) Continuous Tracking: (30 min)

  22. Supplemental Material

  23. Blind Focus

  24. Blind Pointing: residuals versus (A, Z)

  25. Blind Pointing: residuals versus time

  26. Blind Pointing: 2-D RMS Raw Residuals One PEAK at the start of the evening

  27. Blind Pointing: Azimuth

  28. Blind Pointing: Elevation

  29. Blind Focus

  30. Tracking: Ku-band (14 GHz) El half-power track

  31. Tracking: Ku-band (14 GHz) El half-power track

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