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1. Radio Antennas
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Contents
Contents
1. Radio Antennas
1.1 Introduction
1.2 Basic Principles
1.3 The perfect Single-Dish antenna
1.4 The real Single-Dish Antenna
1.4.1 Sytematic Deformations: Defocus, Coma, Astigmatism
1.4.2 Random Errors
1.5 Radiometric Relations
2. The interferometer principles
2.1 Basic principle
2.2 The Heterodyne Interferometer
2.2.1 Source Size Effects
2.2.2 Finite Bandwidth
2.3 Delay Tracking and Frequency Conversion
2.4 Fringe Stopping and Complex Correlator
2.5 Fourier Transform and Related Approximations
2.6 Array Geometry & Baseline Measurements
3. Receivers : an overview for non-specialists
3.1 Introduction
3.2 Coupling optics
3.3 Why we need heterodyne receivers
3.4 Local oscillator system
3.5 Local oscillator injection
3.6 Photon-assisted tunneling
3.7 Mixer
3.8 Cryostat
3.9 Actual receivers
4. Cross Correlators
4.1 Introduction
4.2 Basic Theory
4.3 The Correlator in Practice
4.3.1 Digitization of the input signal and clipping correction
4.3.2 Time lag windows and spectral resolution
4.3.3 Main limitations
4.4 The correlator on Plateau de Bure
4.4.1 The current system
4.4.2 Future improvements
4.5 Appendix
4.5.1 Summary of definitions
4.5.2 Clipping correction for 4-level quantization
5. LO System and Signal Transport
5.1 An Heterodyne Interferometer
5.1.1 The simple interferometer
5.1.2 The heterodyne interferometer
5.1.3 Frequency conversion
5.1.4 Signal phase
5.2 Delay lines requirements
5.2.1 Single side band processing in a finite bandwidth
5.2.2 Double side band system
5.3 Side band separation
5.3.1 Fringe rate method
5.3.2 Phase switching method
5.4 The PdB Signal and LO transport system
5.4.1 Signal path
5.4.2 LO generation
5.4.3 Further signal processing
5.4.4 Phase stability requirements
5.4.5 Cable electrical length control
5.5 Next generation instruments
6. The Plateau de Bure Interferometer
6.1 History
6.2 Description
6.3 Array operation
6.3.1 Array calibration
6.3.2 Array observations
6.4 Proposal submission and contact people
7. Band pass and Phase Calibration
7.1 Definitions and formalism
7.1.1 Baseline based vs antenna based gains
7.1.2 Gain corrections
7.2 Bandpass calibration
7.2.1 Bandpass measurement
7.2.2 IF passband calibration
7.2.3 RF bandpass calibration
7.2.4 Side band calibration
7.3 Phase calibration
7.3.1 Phase referencing by a nearby point source
7.3.2 Phase referencing by a point source in the primary beam
7.3.3 Phase referencing using another band or another frequency
8. Atmospheric Absorption
8.1 The Atmosphere
8.1.1 Constituents of the atmosphere
8.1.2 Thermodynamics of the air
8.1.3 Hydrostatic equilibrium
8.1.4 Water
8.1.5 Photodissociation products
8.2 Spectroscopy of H
2
O, O
2
, O
3
8.2.1 Water vapor
8.2.2 Molecular oxygen
8.2.3 Ozone
8.3 Propagation of a wave in the atmosphere - Line shapes
8.4 The atmospheric absorption spectrum at millimeter wavelengths, ATM
8.5 Correction for atmospheric absorption,
T
A
*
8.5.1 Simplest case
8.5.2 More realistic case
8.5.3 General case
9. Atmospheric Fluctuations
9.1 Introduction
9.2 Hydrodynamical basics of turbulent motion
9.3 Statistical properties of turbulence
9.4 Remote sounding techniques
9.5 Current phase correction at IRAM
9.6 Phase correction during off-line data reduction
9.7 Frequently asked questions
10. Amplitude and Flux Calibration
10.1 Definition and Formalism
10.2 Single-dish Calibration of the Amplitude
10.2.1 Low opacity approximation and implication for
T
cal
10.2.2 Absolute errors on
T
cal
due to instrumental parameters
10.2.3 Relative errors or errors on
T
cal
L
/
T
cal
U
10.2.4 Estimate of the thermal noise
10.3 Flux Calibration (visitor's nightmare)
10.3.1 Introduction
10.3.2 Calibration procedure at Bure
10.3.3 Determining the absolute flux scale on a project
10.3.4 Possible biases and remedies
10.3.5 The program FLUX
10.4 Interferometric Calibration of the Amplitude
10.4.1 Correction for the antenna gain
10.4.2 Estimate of the atmospheric decorrelation factor
f
10.4.3 Fitting Splines: the last step
10.4.4 A few final checks
11. Calibration in Practice
11.1 Introduction
11.1.1 Contents of the account
11.1.2 Before starting the data reduction
11.1.3 Activating the CLIC environment
11.2 The ``First Look'' procedure
11.3 The ``Standard Calibration (2-receivers)'' procedure
11.3.1 Inputs
11.3.2 Actions or Outputs
11.3.3 Results of the calibration
12.
UV
Plane Analysis
12.1
uv
tables
12.1.1
uv
table contents
12.1.2 How to create a
uv
Table
12.2
uv
data plots
12.3 Data editing
12.4 Position shift
12.5 Averaging
12.5.1 Data compression
12.5.2 Circular averaging
12.6 Model fitting
12.6.1 Position measurement
12.7 Continuum source subtraction
12.8 Self calibration by a point source
13. The Imaging Principles
13.1 Fourier Transform
13.1.1 Direct Fourier Transform
13.1.2 Fast Fourier Transform
13.1.3 Gridding Process
13.2 Sampling & Aliasing
13.3 Convolution and Aliasing
13.4 Error Analysis
13.5 Weighing and Tapering
13.6 The GILDAS implementation
13.7 Deconvolution
13.7.1 The CLEAN method
13.7.2 Interpretation of CLEAN
13.7.3 The CLEAN variants
13.7.4 The GILDAS implementation
14. Advanced Imaging Methods: WIPE
14.1 Introduction
14.2 Object space
14.3 Experimental data space
14.4 Image reconstruction process
14.4.1 Synthesized aperture
14.4.2 Synthetic beam
14.4.3 Regularization frequency list
14.4.4 Data space
14.4.5 Object representation space
14.4.6 Objective functional
14.4.7 Uniqueness and robustness
14.5 Implementation of WIPE at IRAM
15. Mosaicing
15.1 Introduction
15.2 Image formation in a mosaic
15.3 Mosaicing in practice
15.4 A CLEAN-based algorithm for mosaic deconvolution
15.5 Artifacts and instrumental effects
15.6 Concluding remarks
16. Imaging in Practice
16.1 Visualisation
16.2 Photometry
16.2.1 From Flux density to Brightness temperature
16.2.2 Accuracy of Flux density estimates
16.3 Short Spacings
16.3.1 UV_SINGLE
16.4 Dirty Tricks
16.4.1 MOMENTS
16.4.2 Continuum Subtraction
17. Basic Principles of Radio Astrometry
17.1 Introduction and Basic Formalism
17.2 The Phase Equation
17.3 Determination of Source Coordinates and Errors
17.4 Accurate Position Measurements with the IRAM Interferometer
17.4.1 Absolute positions
17.4.2 Relative Positions and Self-calibration Techniques
Bibliography
S.Guilloteau
2000-01-19
