SPIE June 25, The Details. SPIE June 25, Previous Focus Tracking Curves SPIE June 25, Previous Focus Tracking Curves SPIE June 25, 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 SPIE June 25, Structural Temperatures SPIE June 25, Focus Model Gravity SR-Primary VFA-Primary HFA BUS SPIE June 25, Elevation Model Gravity BUS HFA VFA Alidade SPIE June 25, Azimuth Model Gravity Alidade HFA BUS VFA SPIE June 25, Optimization Focus optimization using pseudo-inverse for LSE solution Coupled Az and El gravity models (AN, AW constraint) Gradient descent SPIE June 25, x 110 m section of a parent parabola 208 m in diameter Cantilevered feed arm is at focus of the parent parabola Unblocked Aperture SPIE June 25, Telescope Structure and Optics SPIE June 25, Development Phases Actual schedule: Phase I: ?? Phase IIa (26GHz) Spring 2003 SPIE June 25, High Frequency Environmental Envelope SPIE June 25, Pointing Accuracy, 5 C Gradient, 5 El SPIE June 25, Pointing SPIE June 25, Focus SPIE June 25, Data Quality Jack Scan Gaussian Fits (Az, El, Focus) Polarization (LCP RCP) Direction (Forward Backward) SPIE June 25, Data Quality: Pointing (LCP RCP) SPIE June 25, 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 SPIE June 25, Focus Model Tests Wind < 2.5 m/s 15 < elevation < 85 9/5 is NCP 11/20 is all-sky Excludes Graphs show thermal contributions only SPIE June 25, Elevation Model Test SPIE June 25, Elevation Model Test SPIE June 25, Azimuth Model TermCoefficientMin-MaxSignificanceParameter M1M Alidade M2M HFA M3M BUS M4M VFA M5M CA, d(0,0) M6M NPAE, b(0,1) M7M IA, d(0,1) M8M AW, b(1,1) M9M AN, a(1,1) SPIE June 25, Azimuth Model Estimation = 3.9 SPIE June 25, Azimuth Model Test SPIE June 25, Azimuth Model Test SPIE June 25, Holography Results Finite Element Model Predictions SPIE June 25, Efficiency and Beam Shape SPIE June 25, Requirements for high-frequency observing SPIE June 25, Requirements for high-frequency observing SPIE June 25, Pointing Accuracy, 6 m/s wind SPIE June 25, Architecture of current GBT Observing System SPIE June 25, Architecture of HFOS SPIE June 25, Architecture of PCS SPIE June 25, 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