1. December 3-4, Green Bank GBT PTCS In Progress Review Thermal Focus and Pointing Corrections K. Constantikes

2. GBT PTCS In Progress Review – December 3-4, 2003 2 Status New thermal model, new gravity model parameters –Uses 19 structural temperature sensors –Linear thermal, tradional gravity –Focus peformance ~< 3 mm (excludes midday) during ~30 mm thermal focus shift –Elevation performance ~<3” 1 , <1”/hour (excludes midday) during ~ 30” thermal pointing shift –Azimuth performance ~<3” 1 , <1”/hour (excludes midday) –Unanticipated dominance of horizontal feed arm influence PTCS/PN/25 “Thermally-Neutral Traditional Pointing Models and Thermal Corrections to Pointing and Focus” Test of real-time focus corrections (Balser and Prestage,11/20/03)

3. GBT PTCS In Progress Review – December 3-4, 2003 3 Structural Temperature 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

4. GBT PTCS In Progress Review – December 3-4, 2003 4 Structural Temperature

5. GBT PTCS In Progress Review – December 3-4, 2003 5 Structural Temperature

6. GBT PTCS In Progress Review – December 3-4, 2003 6 Algorithms Use existing GBT gravity pointing and focus models Structure is linear: Thermal effects superpose Temperature effect on focus, pointing assumed linear in temperatures No dependence on air or bulk temps, just differences Simultaneously estimate gravity and temperature model coefs Estimate coefs using 9/11, 10/2, 11/10 data Test models using 9/5, 11/20 data

7. GBT PTCS In Progress Review – December 3-4, 2003 7 Focus Model TermCoefficientMin-MaxSignificanceParameter M1M1 1.08613.114.3 SR-Pri M2M2 -0.6976.2-4.3 VFA-Pri M3M3 3.98115.662.0 HFA M4M4 -7.3260.9-6.8 BUS V1 M5M5 -0.68812.1-8.3 BUS V2 M6M6 -2.57612.1-31.2 BUS F M7M7 -180.6300.0 Offset M8M8 66.189.743.1 sin term M9M9 196.9490.6110.8 cos term

8. GBT PTCS In Progress Review – December 3-4, 2003 8 Focus Model Estimation

9. GBT PTCS In Progress Review – December 3-4, 2003 9 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

10. GBT PTCS In Progress Review – December 3-4, 2003 10 Focus Model Tests

11. GBT PTCS In Progress Review – December 3-4, 2003 11 Elevation Model TermCoefficientMin-MaxSignificanceParameter M1M1 -4.64551.2-5.3 BUS M2M2 1.783015.6-27.8 HFA M3M3 4.44885.926.4 VFA M4M4 -8.44771.6-14.0 Alidade M5M5 62.22180.0+0.000 -IE,d(0,0) M6M6 -55.86240.7-62.792 HZCZ,b(0,1) M7M7 -22.82680.9-38.216 HZSZ,d(0,1) M8M8 2.49602.0+2.169 -AW,c(1,0) M9M9 -1.33602.0-1.750 AN,d(1,0)

12. GBT PTCS In Progress Review – December 3-4, 2003 12 Elevation Model Estimation  = 3.6

13. GBT PTCS In Progress Review – December 3-4, 2003 13 Elevation Model Test

14. GBT PTCS In Progress Review – December 3-4, 2003 14 Elevation Model Test

15. GBT PTCS In Progress Review – December 3-4, 2003 15 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)

16. GBT PTCS In Progress Review – December 3-4, 2003 16 Azimuth Model Estimation  = 3.9

17. GBT PTCS In Progress Review – December 3-4, 2003 17 Azimuth Model Test

18. GBT PTCS In Progress Review – December 3-4, 2003 18 Azimuth Model Test

19. GBT PTCS In Progress Review – December 3-4, 2003 19 Why does it work? Didn’t for 140’ (von Hoerner), why should GBT? –Thermal diffusivity? –Time constants? –Characteristic length of perturbations? –Surface area of structural supports? –Better temperature measurement technology ! –Better homology?

20. GBT PTCS In Progress Review – December 3-4, 2003 20 Conclusions Focus and elevation greatly improved with thermally- neutral traditional model and temperature corrections Azimuth performance improvement marginal (but it’s already pretty good) Use of thermal imaging to improve locations Add sensors to HFA, BUS Work on graceful degradations Production implementation Further tests for confidence Thermal stability model

21. GBT PTCS In Progress Review – December 3-4, 2003 21 The Details….

22. GBT PTCS In Progress Review – December 3-4, 2003 22 Previous Focus Tracking Curves

23. GBT PTCS In Progress Review – December 3-4, 2003 23 Previous Focus Tracking Curves

24. GBT PTCS In Progress Review – December 3-4, 2003 24 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

25. GBT PTCS In Progress Review – December 3-4, 2003 25 Focus Model Gravity SR-Primary VFA-Primary HFA BUS

26. GBT PTCS In Progress Review – December 3-4, 2003 26 Elevation Model Gravity BUS HFA VFA Alidade

27. GBT PTCS In Progress Review – December 3-4, 2003 27 Azimuth Model Gravity Alidade HFA BUS VFA

28. GBT PTCS In Progress Review – December 3-4, 2003 28 Optimization Focus optimization using pseudo-inverse for LSE solution Coupled Az and El gravity models (AN, AW constraint) –Gradient descent