TerraSAR-X/TanDEM-X Formation Acquisition - Analysis and Flight Results

Kurzfassung

This paper summarizes the work performed in the fields of TanDEM-X (TDX) launch injection collision assessment, target orbit acquisition analysis and in-flight realization of the formation acquisition with the already flying TerraSARX (TSX). The first two topics were essential in the process of TDX launch day selection in order to minimize both the risk of collision and the maneuver budget. Here risk of collision refers to the danger of close approach between TSX and the newly injected Dnepr upper-stage, the gas dynamic shield, and the TDX. Furthermore, the analytical approach to estimate the TDX total velocity increment required for the acquisition of the formation with TSX is discussed including a presentation of the results that characterize the maneuver budget as a function of launch day and launch injection accuracy. The formation acquisition strategy was numerically estimated for the confirmed launch date considering operational constraints and recent TSX orbit evolution. After TDX launch only minor changes to the pre-launch maneuver sequence became necessary especially due to unforeseen space debris avoidance maneuvers within the first days of the mission. Besides the description of the formation acquisition process, this paper also depicts the formation reconfiguration process from wide into narrow formation performed in October 2010. The successful acquisition of the close formation was the start of the common TSX / TDX instrument operation for purpose of bi-static commissioning.