Solving the polarization problem in ALMA-VLBI observations
Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2014

The Atacama Large mm-submm Array (ALMA) is, by far, the most sensitive mm/submm telescope in the World. The ALMA Phasing Project (APP) will allow us to phase-up all the ALMA antennas and use them as one single VLBI station. This will be a key component of the Event Horizon Telescope (EHT), a Global VLBI array at millimeter wavelengths. A problem in the APP is the calibration and conversion of the polarization channels. Most VLBI stations record their signals in a circular basis, but the ALMA receivers record in a linear basis. The strategy that will be followed in the phased-ALMA VLBI observations will be to correlate in a “mixed” basis (i.e., linear versus circular) and convert the visibilities to a pure circular basis after the correlation. We have developed an algorithm to perform such a polarization conversion of the VLBI visibilities. In these proceedings, we present the basics of this algorithm and discuss on the polarization conversion in the general case where single dishes (besides phased arrays) record with linear receivers in VLBI observations. We show some results of our algorithm applied to realistic simulations, as well as a test with real VLBI observations at 86 GHz between the Onsala radiotelescope (recording in linear basis) and the Effelsberg radiotelescope (recording in circular basis).

Författare

Ivan Marti-Vidal

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

John Conway

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

Michael Lindqvist

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

A. Roy

Max Planck-institutet

W. Alef

Max Planck-institutet

A.J. Zensus

Max Planck-institutet

Proceedings of Science

18248039 (eISSN)

Vol. Part F113821 Artno: 034- 034

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

Infrastruktur

Onsala rymdobservatorium