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