Simulation chain
| Notebook | Content |
|---|---|
00_general.ipynb |
Project overview: goal of a VLB interferometer with an 11.5 km baseline (Wilhelmsburg–Michelbach), principle, key figures (resolution, delay, fringe rate, data rate), clock and timing requirements, sensitivity, road map |
01_sky_models.ipynb |
Sky models, file format, maps, own skies, visibilities, catalogue of known regions with selector |
02_instrument.ipynb |
Antenna types and primary beams, dish transfer function, B210 receiver and sensitivity, arrays and baselines, choice of the baseline length (Cyg A), selector |
03_signal_simulation.ipynb |
Generating SDR receiver signals (IQ samples of the B210 at each station) based on the sky model under variable baseline parameters: signal model, raw fringes, measured vs. model visibilities over the baseline length, clock errors (TCXO/GPSDO), quantisation, SigMF output, selector |
04_observation.ipynb |
Source tracking, geometric delay and fringe rate, uv-tracks by Earth rotation, visibilities over a track, transit (drift scan) of fixed antennas (Sun with two horns), asymmetry of a track, selector |
05_correlator.ipynb |
FX correlator on the simulated SDR signals: fractional delay, fringe stopping, delay/rate search and refinement, cross spectra, visibilities; station clock and LO offsets; selector |
06_imaging.ipynb |
Gridding, natural/uniform/Wiener weighting, dirty beam and dirty image: OH masers with the project baseline and three stations, Cygnus A, selector |
07_deconvolution.ipynb |
Högbom CLEAN, clean beam and restoration, Wiener filter (migrated from Appendix A): maser group with the project baseline, convergence and loop gain, Wiener against CLEAN, three stations, limits for Cygnus A, selector |
08_sun_first_target.ipynb |
The Sun with two horns on one B210 (migrated from Appendix B): signal strength, baseline choice, fringe rate over the year, raw-signal checks (covered horns, crosstalk, channel phase), transit with the solar day, radio diameter, procedure, selector |
09_spectral_lines.ipynb |
Spectral lines: channels and velocities, Doppler correction to the LSR, sky models with spectra, OH masers on the 11.5 km baseline (spectra towards a position, channel maps), effect of a missing Doppler correction, HI absorption against Cygnus A, planning of a line observation, selector |
Theory
| Notebook | Content |
|---|---|
A_fringes.ipynb |
Shows and explains how fringes evolve: fringe pattern on the sky, fringe rate from the Earth's rotation, effect of the source size (fringe contrast), fringes in a long track (Cygnus A with zooms of 5–20 min, natural and structure fringe rate), selector |
B_fourier.ipynb |
Explains the Fourier transformation and the correlation: transform pairs and convolution theorem, van Cittert–Zernike (numerical check against the analytic visibilities), one baseline = one Fourier component, the dish as low-pass filter, cross-correlation and cross spectrum (XF vs. FX, Wiener–Khinchin), the delay beam, selector |
C_sampling_iq.ipynb |
Sampling and complex baseband: Nyquist and aliasing, IQ mixing, IQ imbalance and DC offset, band edges, quantisation (efficiency, input level, Van Vleck), what the B210 delivers, selector |
D_noise_sensitivity.ipynb |
Radiometer equation, SEFD and antenna temperature, noise of a visibility (simulation check), S/N against integration time, bandwidth and baseline length for the project targets, coherence and clocks (random-walk phase, coherent vs. incoherent averaging), image noise, selector |
E_coordinates.ipynb |
Coordinate frames: equatorial (RA/Dec, hour angle, sidereal time), horizontal (azimuth/elevation, circumpolar sources, parallactic angle), WGS84/ECEF/ENU and the baseline vector, uvw and the uv-ellipse (checked against the classical formulas), delay and w, precession J2000 → date, selector |
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