1. SPIE – June 25, 2004 1 The Details….

2. SPIE – June 25, 2004 2 Previous Focus Tracking Curves

3. SPIE – June 25, 2004 3 Previous Focus Tracking Curves

4. SPIE – June 25, 2004 4 Temperature Sensor Locations T SR T F1 T F4 T F5 T F3 T F2 T H2 T H3 T B2 T B1 T B3 T B5 T B4 T E1 T E2 T A3 T A1 T A2 T A4

5. SPIE – June 25, 2004 5 Structural Temperatures

6. SPIE – June 25, 2004 6 Focus Model Gravity SR-Primary VFA-Primary HFA BUS

7. SPIE – June 25, 2004 7 Elevation Model Gravity BUS HFA VFA Alidade

8. SPIE – June 25, 2004 8 Azimuth Model Gravity Alidade HFA BUS VFA

9. SPIE – June 25, 2004 9 Optimization Focus optimization using pseudo-inverse for LSE solution Coupled Az and El gravity models (AN, AW constraint) –Gradient descent

10. SPIE – June 25, 2004 10 100 x 110 m section of a parent parabola 208 m in diameter Cantilevered feed arm is at focus of the parent parabola Unblocked Aperture

11. SPIE – June 25, 2004 11 Telescope Structure and Optics

12. SPIE – June 25, 2004 12 Development Phases Actual schedule: Phase I: ?? Phase IIa (26GHz) Spring 2003

13. SPIE – June 25, 2004 13 High Frequency Environmental Envelope

14. SPIE – June 25, 2004 14 Pointing Accuracy, 5° C Gradient, 5° El

15. SPIE – June 25, 2004 15 Pointing

16. SPIE – June 25, 2004 16 Focus

17. SPIE – June 25, 2004 17 Data Quality Jack Scan Gaussian Fits (Az, El, Focus) Polarization (LCP – RCP) Direction (Forward – Backward)

18. SPIE – June 25, 2004 18 Data Quality: Pointing (LCP – RCP)

19. SPIE – June 25, 2004 19 Structural Temperature Sensors 19 locations, 0.2C interchangeable accuracy, 0.01C resolution, 1Hz, range –35 to 40C. (actual accuracy is ~0.1C, temp control of conversion elex) Design documentation: –PTCS Wiki (AntennaInstrumentation) –PTCS Project Note PTCS/PN12 Accuracy tested in lab: –Solar/convective loading –Selected unit-to-unit accuracy, repeatability –Electronics temperature range RFI mitigated, ESD protected Two thermistor failures, forensics with YSI Integrated into M&C First cut pointing, focus predictive algorithms tested

20. SPIE – June 25, 2004 20 Focus Model Tests Wind < 2.5 m/s 15° < elevation < 85° 9/5 is NCP 11/20 is all-sky Excludes 1000-1800 Graphs show thermal contributions only

21. SPIE – June 25, 2004 21 Elevation Model Test

22. SPIE – June 25, 2004 22 Elevation Model Test

23. SPIE – June 25, 2004 23 Azimuth Model TermCoefficientMin-MaxSignificanceParameter M1M1 5.58624.022.4 Alidade M2M2 -8.03312.721.3 HFA M3M3 -1.62892.43.8 BUS M4M4 1.36832.02.8 VFA M5M5 3.41240.0 CA, d(0,0) M6M6 1.32230.71.0 NPAE, b(0,1) M7M7 3.51520.93.0 IA, d(0,1) M8M8 -2.49601.94.8 AW, b(1,1) M9M9 -1.33601.82.5 AN, a(1,1)

24. SPIE – June 25, 2004 24 Azimuth Model Estimation  = 3.9

25. SPIE – June 25, 2004 25 Azimuth Model Test

26. SPIE – June 25, 2004 26 Azimuth Model Test

27. SPIE – June 25, 2004 27 Holography Results

28. Finite Element Model Predictions

29. SPIE – June 25, 2004 29 Efficiency and Beam Shape

30. SPIE – June 25, 2004 30 Requirements for high-frequency observing

31. SPIE – June 25, 2004 31 Requirements for high-frequency observing

32. SPIE – June 25, 2004 32 Pointing Accuracy, 6 m/s wind

33. SPIE – June 25, 2004 33 Architecture of current GBT Observing System

34. SPIE – June 25, 2004 34 Architecture of HFOS

35. SPIE – June 25, 2004 35 Architecture of PCS

36. SPIE – June 25, 2004 36 Telescope Structure and Optics Optics: 110 m x 100 m of a 208 m parent paraboloid Effective diameter: 100 m Offaxis feedarm Elevation Limit: 5  degrees Slew Rates: Azimuth – 40deg/min; Elevation – 20deg/min Main Reflector: 2209 actuated panels with 68  m rms. Total surface: rms 400  m FWHM Beamwidth: 740"/f(Ghz) Prime Focus: Retractable boom Gregorian Focus: 8-m subreflector with 6-degrees of freedom Rotating Turret with 8 receiver bays