Thermal Design and Thermal Behaviour of Radio Telescopes and their Enclosures

Transkript

1 Thermal Design and Thermal Behaviour of Radio Telescopes and their Enclosures Bearbeitet von Albert Greve, Michael Bremer 1. Auflage Buch. X, 420 S. Hardcover ISBN Format (B x L): 15,5 x 23,5 cm Gewicht: 795 g Weitere Fachgebiete > Physik, Astronomie > Astronomie: Allgemeines > Astronomische Beobachtung: Observatorien, Instrumente, Methoden Zu Leseprobe schnell und portofrei erhältlich bei Die Online-Fachbuchhandlung beck-shop.de ist spezialisiert auf Fachbücher, insbesondere Recht, Steuern und Wirtschaft. Im Sortiment finden Sie alle Medien (Bücher, Zeitschriften, CDs, ebooks, etc.) aller Verlage. Ergänzt wird das Programm durch Services wie Neuerscheinungsdienst oder Zusammenstellungen von Büchern zu Sonderpreisen. Der Shop führt mehr als 8 Millionen Produkte.

2 1 Radio Astronomy and Radio Telescopes Radio Wavelengths and Radio Telescopes Deep Space Network and Large Communication Antennas Radio Telescopes in Space Overview of Telescope Constructions Radio Telescope Constructions in View of Thermal Aspects Optical Configurations The Parabolic Reflector The Cassegrain and Gregory System Basic Telescope Constructions The Telescope with Alidade Support The Telescope with Pedestal Yoke Support The Telescope with Pedestal Fork Support Telescope Components Reflector Backup Structure (BUS) The Homologous BUS The Open and Closed, Ventilated and Climatised BUS Reflector Panels Active Reflector Surface The Quadripod and Subreflector The Secondary Focus Cabin The Thermal Design of Radio Telescopes Telescope Enclosures The Variable Thermal Environment The Environment and Observatory Sites The Ambient Air The Ambient Air Temperature Measured Ambient Air Temperatures xvii

3 xviii Approximation of the Daily Ambient Air Temperature Rate of Ambient Air Temperature Change Wind Speed and Wind Direction Measured Wind Speeds Wind Speed and Convective Heat Transfer Ground Temperature Measured Ground Temperatures Approximation of the Ground Temperature Humidity, Condensation, Icing Humidity and Sky Radiation Sky Temperature Measured Sky Temperature Calculation of the Sky Temperature Cloud Coverage Solar Radiation Measurements of Solar Radiation Meteorological Design Specifications Space Environment Calculation of Solar Illumination The Apparent Motion of the Sun The Plane Surface The Tube Surface The Parabolic Reflector Surface Borderline between Shadow and Sunshine Solar Illumination of the Reflector Surface The Open and Closed BUS The Box type Enclosure (Astrodome) The Cylindrical Enclosure (Astrodome) The Over Hemispherical Radome Manipulation of Insolation through Surface Finish Sun on Subreflector and Quadripod Temperature Measurements and FEM Thermal Deformation Calculations Electric Resistance Temperature Sensors Temperature Measurements by Infrared Radiation Temperature Sampling Rate Location of Temperature Sensors (InterpolationMatrixandInfluenceMatrix) Precision of Temperature Measurements Prediction of Temperature induced Deformations Empirical Relations Temperature related Measurements...120

4 xix 7 Heat Transfer Laws of Thermodynamics and Modes of Heat Transfer Amount of Heat transferred Heat Content Heat Transfer by Conduction Heat Transfer by Convection Heat Transfer by Conduction and Convection The Convective Heat Transfer Coefficient (h) Forced Convection Natural Convection Forced Convection and Ventilation Natural Convection and Ventilation Radiative Heat Transfer Heat Transfer by Conduction, Convection and Radiation Radiative Nodes and View Factors Radiative Nodes View Factor Relations Internal View Factors Energy/Heat Conservation The Steady and Non Steady Thermal State External Thermal Time Constant τ ext Internal Thermal Time Constant τ int (Conduction) Radiative Coupling towards Sky and Ground (External View Factor) Vertical and Horizontal Walls The Radome and Astrodome The Parabolic Reflector The Open and Closed BUS Measured Thermal Behaviour of Radio Telescopes Telescope Supports The Pedestal The Alidade The Fork Support Path Length Variations of Telescope Supports (forradiointerferometerandvlbiarrays) BUS Supports The (climatised) Yoke The Central Hub Backup Structures (BUS) The Open BUS The Closed BUS The Ventilated BUS Radial and Circular Ventilation...220

5 xx The Climatised BUS (IRAM 30 m Telescope) Thermal Deformations and Active Reflector Surfaces The Radome/Astrodome enclosed BUS Temperature Changes of the BUS and Focus Changes Panels Experimental Data of Panel Temperatures Panel Temperatures measured on Telescopes Thermal Panel Buckling Heated Panels, De icing of Panels Quadripod, Subreflector, Focus Cabins Quadripod Subreflector Focus Cabins Observations in the Direction of the Sun De icing of a Telescope Measured Temperature Uniformity of Radio Telescopes The measured Thermal Behaviour of Telescopes Temperature Monitoring and Trouble Shooting Other Thermal Effects Measured Thermal Behaviour of Enclosures Thermal Model Calculations Mechanical Models of Structural Components Static Thermal Calculations (TheUseofKnownTemperatureDistributions) Dynamic Thermal Model Calculations (TheDerivationofTemperatureDistributions) Node Structure of Thermal Models The Thermal Environment as Input Data Models of Panels Model of Telescope Supports Model of an Alidade Model of a Yoke Model of a Fork Support Model of a Backup Structure Model of an Open BUS Model of a Closed BUS with Natural Ventilation Model of a Closed BUS with Forced Ventilation Model of a Radome and Closed Astrodome Servo loop Controlled Ventilation/Heating/Cooling Model Calculations and Energy Balance Model Calculations for Operational Purposes Precision of Model Calculations Programmes for Model Calculations...304

6 xxi 12 Beam Formation and Beam Degradation Wave Propagation and Beam Formation The Perfect Radio Telescope The Beam Pattern of the Perfect Radio Telescope The Real Radio Telescope Systematic Wavefront Deformations Repetitive Wavefront Deformations (ThermalPanelBuckling) Random Wavefront Deformations Superposition of Random and Systematic (Thermal) Deformations Beam Deformations and Thermal Tolerances Thermal Tolerances Global Estimates of Temperature Influences Reflector Diameter Estimates Estimated Thermal Behaviour of a BUS Estimated Thermal Behaviour of an Alidade/Fork Support Estimated Thermal Behaviour of Panels System Alignment Tolerances Displacements and Tilts of Main Reflector and Subreflector Temperature induced Pointing Errors Alignment Errors: Temperature Tolerance Estimates Random Reflector Errors Design Specifications and Error Budget Optical Telescopes and Enclosures A Summary and Further Studies A Summary of the Present State Temperature Measurements and Dynamic Thermal Models Further Studies A Dynamic Thermal Error Budget for Design A Fundamental Investigation of Radio Telescope/Antenna Constructions Future Design A Units and Fundamental Constants B Average Value, Root Mean Square Value (rms) C Pointing Model D Zernike Polynomials Picture and Graphic Credits...369

7 xxii References Indices Historical Names Index Author Index Book Index Subject Index...389