Ionospheric range-rate effects in satellite-to-satellite tracking

Ionospheric range and range rate corrections in satellite-to-satellite tracking were investigated and the magnitude of errors that have to be considered for communications between satellites and related experiments was defined. The major causes of the sudden and sometimes large variations apparent in the ionospheric range and range rate corrections along the satellite arc are the geometric effects of the raypath and the curved ionosphere, and the localized perturbations in electron density along the satellite-to-satellite line of sight. Ionospheric tracking errors are greatly effected by the following parameters, whose influence was thoroughly investigated: satellite height, height of maximum electron density, localized ionospheric perturbations and gradients, and electron density variations with diurnal, day-to-day, seasonal, and solar cycle patterns. The results point to the need of using a sophisticated modeling approach incorporating daily solar data, and where possible actual ionospheric measurements as update information. Simulations were performed for satellites at various heights: Apollo, Geos, and Nimbus tracked by ATS-6; and in two different geometric configurations: coplanar and perpendicular orbits.