On the solution of the polarisation gain terms for VLBI data collected with antennas having Nasmyth or E-W mounts

TL;DR

This paper introduces new code in AIPS to support polarisation analysis for VLBI antennas with Nasmyth and E-W mounts, enabling better data processing for these increasingly common configurations.

Contribution

The paper develops and demonstrates new AIPS support for Nasmyth and E-W antenna mounts in VLBI polarisation analysis, addressing a gap for these mount types.

Findings

Effective corrections for Nasmyth and E-W mounts demonstrated

Support for multi-band and high-slew-rate antennas enabled

Application shown on GMVA and LBA data

Abstract

I report on the development of new code to support the Nasmyth and E-W antenna mount types in AIPS which will allow polarisation analysis of observations made using these uncommon antenna configurations. These mount types may become more widely spread as they have several advantages, particularly for geodetic observatories. Multi-band observations, with multiple receivers, can only be fitted into telescopes with Nasmyth feeds. These are the requirements for the new generation of geodetic arrays as discussed in IVS2010. Further more the next generation of antennae will also be required to have very high slew rates, and these can be achieved with the E-W mount. The mount type affects the differential phase between the left and the right hand circular polarisations (LHC and RHC) for different points on the sky. The target antennae for the project was the Yebes 40m telescope, but as that was still under construction the data used as a demonstration was from the Pico Veleta antenna as part of the Global Millimeter VLBI Array (GMVA). For the E-W mount type there are suitable data from the Australian LBA array. I demonstrate the effectiveness of the changes made and that the Nasmyth and E-W corrections can be applied.