For a system with N instruments, there are N times N minus 1 over two values of this vector quantity, which twists as the Earth rotates. For 10 points each:
[10m] Name this quantity. Because angular resolution is proportional to wavelength over this quantity, large values of it are preferred in astronomical interferometry.
ANSWER: baseline [accept the distance between telescopes; reject “distance between observatories”]
[10e] Telescope arrays used in interferometry primarily collect signal from this region of the spectrum. The original name of quasars refers to their emission of this radiation.
ANSWER: radio waves [accept radio astronomy or quasi-stellar radio sources]
[10h] The projection of the baseline vector normal to the line of sight is the argument of this function. Radio telescope arrays convert a measured response function to this function, then use an inverse Fourier transform to infer the underlying brightness distribution.
ANSWER: visibility function
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