Electronic Imaging in Astronomy

Transcription

1 Ian S, McLean Electronic Imaging in Astronomy Detectors and Instrumentation (Second Edition) j""v Published f udiisnea in association with witn fyj Springer Praxis PubUshing Publisl PR Chichester, UK

2 Contents About the author.. '..:...' xv Preface xvii List of figures. xxi List of tables.. xxix List of abbreviations and acronyms xxxi Introduction.... xxxvii 1 The development of electronic imaging in astronomy Observational astronomy Historical development ' What are the observables? : "1.2 From eyes to electronic sensors The eye Photography The photoelectric effect Photomultiplier tubes Electron-scanning devices The impact of solid-state imaging Invention of the CCD Electronic imaging across the spectrum The continuing growth of astronomical technology Bigger telescopes and better images^ Common-user instrumentation and automation Surveys and data archives; the virtual observatory... 27

3 vi Contents 1.5 Terminology of electronic imaging Image formation Detector performance Summary Exercises References 36 Web sites.. : Suggestions'for. additional reading...] Beating the atmosphere Atmospheric absorption and transmission : Atmospheric emission, thermal and non-thermal Turbulence......' Kolmogorov theory and origin of seeing Fried parameter Speckle interferometry Lucky imaging Adaptive optics Measuring the wavefront The isoplanatic patch Deformable mirrors Natural guide star systems Laser guide star systems Optical and IR interferometers...' Phase closure Space telescopes Summary Exercises References 74 Web sites Telescopes 77 ~" 3.1 Historical development Telescope designs Basic optical properties The astronomical (lens) telescope.."..' 87 3:2.3- Reflecting telescopes; the parabolic dish. : Correctors and hybrid telescopes Telescope mounts Automated telescopes and remote observing ' Remote observing Automated imaging telescopes Survey telescopes.... ". 101

4 Contents vii 3.4 Very Large Telescope design Segmented primaries Thin-meniscus mirrors Spin-cast honeycombs... ; Prospects for Extremely Large Telescopes Case study: design of a two-mirror telescope Ill 3.6 Summary Exercises References " 116 Web sites ' The discovery power of modern astronomical instruments 119 ' 4.1 Imaging the sky; more than pictures , Early surveys of the sky Digitized surveys Drift scanning and the Sloan Digital Sky Survey 129 ' The Two Micron All Sky Survey Deep imaging in selected fields, Diffraction-limited imaging Interferometers; expanding the baseline Spectroscopy; atomic fingerprints Introduction High resolution, from cosmic abundances to planet hunting Medium-resolution and low-resolution spectroscopy Multiobject spectroscopic surveys; 3-D maps of the (. j" Universe :5 Imaging spectroscopy; x, y, and A 150 " t r 4.3 Polarization; transverse waves Introduction Polarization maps and spectra Summary Exercises References 157 '" General astronomy texts referenced 159 Web sites Instrumentation and detectors * 5.1 Photometers and cameras Photoelectric photometers Camera systems Pixel sampling and matching to the plate scale

5 viii Contents " * ' Spectrometers....; Resolution and dispersion Diffraction gratings...: ' Prisms '. 175 :.' ' Grisms.., Polarimeters...' Modulators and polarizers The Stokes parameters...." :... : Mueller matrices.'..., Interferometers -...' The Fourier Transform Spectrometer (FTS) The Fabry-Perot etalon.. : Interference filters " Detectors...' ; Classification..-' Semiconductors.. : Photoconductors and photodiodes Thermal detectors._ Coherent detectors , Summary Exercises...; References and suggested further reading 197 Designing and building astronomical instruments Basic requirements Overall system layout. \ Optical design, First order to ray tracing Aberrations Wavefront errors Coatings and interference filters Mechanical design Materials and properties Mechanisms Cryogenics and vacuum methods Electronics design. ' Software Summary......! Exercises Special topic.... : : References and suggested further reading ) ' Web sites for optical software.;

6 Contents ix 7 Charge-coupled devices The early years :1 Invention and development The astronomical push "Basic principles, of CCDs,' Charge storage Charge-coupling and clocking CCD constructions Interline and frame-transfer CCDs CCD outputs...: Buried-channel CCDs Two-phase, four-phase, and virtual-phase CCDs , Backside-illuminated CCDs Multi-pinned phase CCDs Astronomical requirements : Slow-scanning, cooling, and optimization CCD mosaics.. r Drift scanning '...: ;266.\. 7.5 Special devices High-speed CCDs with on-chip gain Deep-depletion CCDs for no fringing... : Orthogonal transfer CCDs. 271?.5.4. Customized CCDs Summary Exercises References and suggestions for further reading Web sites 275 CCDs forcollege teaching -...' Practical operation of CCDs : Clock voltages and basic electrical factors., The analog signal chain CCD sequencers and clock drivers Dark current and cooling ' Cosmic rays and luminescence Bad pixels and charge transfer efficiency Noise sources! Signal processing and digitization Correlated double-sampling On-chip binning Overscanning and sub-arrays Uniformity of response UV flashing and QE pinning 307

7 x Contents 8.9 Summary... v Exercises References and suggested further reading. : 312. Web sites Characterization and calibration of array instruments From photons to microvolts : Quantum efficiency and DQE Photon transfer function Noise, bias, and dark current Flat-fielding strategies Fringes and sky emission Linearity Photometry : Spectroscopy Polarimetry Signal-to-noise calculations Summary Exercises References.., 351 Web sites " ; Image processing and analysis Computers.*....;.. " Data acquisition and data transfer Data file formats Data reduction and analysis systems The IRAF package The IDL package FITS Liberator Principles of image analysis and processing Displaying images Image enhancement.' Image restoration...: Summary Exercises References...;:. 383 Web sites Electronic imaging at infrared wavelengths : Introduction..-.. :.. :-...' Early history of infrared astronomy The beginning of modern infrared astronomy The launch of IRAS :

8 Contents xi 11.2 Infrared wavebands Atmospheric windows The high-background problem Chopping... : Infrared array detectors The infrared "array" revolution, dejd vu The hybrid structure Photovoltaicdevices Impurity band conduction devices Far-infrared arrays based on germanium Other forms of infrared arrays Practical operation of infrared arrays Linearity ~"" Dark current'and cooling Noise sources Quantum efficiency Multiple outputs Array controllers Readout modes Single-sampling Correlated double-sampling (CDS) Reset-read-read or Fowler sampling Sampling up the ramp (UTR) Infrared instruments General issues ' IR cameras Infrared spectrometers AO cameras and integral field spectroscopy The impact of infrared arrays Ground-based observing The Stratospheric Observatory for Infrared Astronomy IR astronomy in space Summary ;...' Exercises References 426 Web sites Electronic imaging at ultraviolet, X-ray, and gamma-ray, wavelengths Introduction..: Grazing incidence telescopes Coded mask telescopes Ultraviolet detectors and instruments UV-sensitive CCDs MicroChannel plates Electron-bombarded CCDs 445

9 xii Contents. : 12.3 X-ray detectors and instruments Introduction CCDs in the X-ray regime... ;., X-ray spectroscopy X-ray instruments: the Chandra X-ray Observatory (CXO), Gamma rays Detectors for high energy Gamma-ray observatories in space Ground-based gamma-ray observatories Summary Exercises References ; 463 Web sites....' Suggested further reading Electronic imaging at sub-millimeter and radio wavelengths Introduction to radio astronomy Radio telescopes ' Antennas \ Receivers Detectors/Mixers _, Interferometers and aperture synthesis The microwave background COBE and WMAP...: Sub-millimeter detectors and instruments Bolometers Thermal edge sensors!.:...-.: Microwave kinetic induction detectors : Summary :...' Exercises References and sugested further reading 498 Web sites..... ; Future developments...., Scientific challenges New ground-based telescopes Next-generation adaptive optics Next-generation instrumentation New space telescopes v.. :. : The future of electronic imaging Conclusion : References..:..., Web sites...:: 513

10 Contents xiii Answers to selected exercises 515 APPENDICES A Powers-of-10 notation B Units of measurement and useful conversions 523 C Physical and astronomical constants 527 D Astronomical magnitude scale and relation to lux 529 E Basic observational astronomy facts 531 F Useful statistics 535 Index :. 537