The Fall 2000 and Fall 2001 SOHO-Ulysses Quadratures

Abstract

SOHO-Ulysses quadrature occurs when their included angle with the Sun is 90°. At these times the same plasma leaving the Sun in the direction of Ulysses can first be remotely analyzed with SOHO and then later be sampled in situ at Ulysses. Quadratures in Fall 2000/2001 are of special interest because Ulysses will be near the south and north heliographic poles, respectively, and it will be near sunspot maximum. But, the quadrature geometry is complex — Ulysses is not in a true polar orbit and the orbital speed of Ulysses and SOHO about the Sun will be comparable. In neither case is true quadrature achieved, but this works to the observer’s advantage. Here we show plots of the relative positions of SOHO and Ulysses throughout the two quadrature intervals.