Basic definitions and sign conventions

This section is partially derived from “Basic definitions for the USNO and NRL Optical Interferometers” by D. Buscher.

A baseline vector $B_{12}$ is oriented from telescope 1 to telescope 2, i.e. the baseline coordinates are the coordinates of station 2 minus the coordinates from station 1. In the aperture plane, the $u$ coordinate increases to the East, and the $v$ coordinate increases to the North. (Remember though that $uv$ coverages are plotted in $\cal OYST\!ER\,$as seen on the sky, so that the source structure and visibility function can be easily superposed.)

In PEARL, a map on the sky is allocated with the $x$-coordinate corresponding to RA, which increases to the left (East). The relationship between visibility and map is then

$$V(u,v)=\int B(\xi,\eta) exp(-j2\pi [u\xi + v\eta ]) d\xi\,d\eta$$