pyoof 0.2.0

pyoof is a Python pacakge which performs out-of-focus (OOF) holography on astronomical beam maps for single-dish radio telescopes.

pyoof is a Python package which computes out-of-focus (OOF) holography for beam maps of a single-dish radio telescope. The OOF holography is a phase-retrieval holography procedure to find the aperture phase distribution (or simply phase error) and the associated errors on a radio telescope surface. The main advantage of the method, compared to the traditional with-phase holography, is the lack of extra equipment needed to perform observations and the wide range in elevation. These two allow the method to study gravitational deformations on the surface, the most well behaved and prominent source of deformations on a radio telescope surface. The method required the use of a compact source, with a good signal-to-noise (200) and rms noise (14 mJy). Then a set of continuum observations are required, two of them out-of-focus and one in-focus. The OOF observations are performed adding a known radial offset to the telescope’s sub-reflector. The aperture phase distribution, related to the power pattern (observed beam maps) can be expressed as a sum of polynomials times certain coefficients. The parametrization of the aperture phase distribution allows the construction of it by using a nonlinear least squares minimization, due to the highly nonlinear relation between the aperture distribution and power pattern (degenerated problem). The pyoof package takes as an input the observed beam maps and computed such coefficients to find the aperture phase distribution (on the primary reflector).