Distributed satellite missions and technologies - The TechSat 21 program

Spaceborne bi- and multistatic SAR: potential and challenges

“…4, left, see also [6][25] [26]) or by a fully active (Fig. 4 right, see also [7][8] [10]) satellite constellation. Fully active systems have in general a higher sensitivity and flexibility, are less prone to ambiguities, and enable easier phase synchronization like in a ping-pong mode with alternating transmitters or by a direct exchange of radar pulses.…”

“…Sparse aperture systems enable highly accurate velocity measurements of moving objects on the ground and may also overcome the problem of blindness against certain directions of target motion [34] [35]. Another opportunity is precise target localization [36] [7]. A coherent combination of multiple SAR images acquired from slightly different view angles can also improve the geometric resolution.…”

“…1 on the left. Examples for fully active systems are the multistatic TechSAT 21 constellation [7] and the bistatic Radarsat 2/3 tandem [8]. Semi-active systems combine an active illuminator with one or more passive receivers as shown in Figure 1 on the right.…”

Coordination Challenges for Autonomous Spacecraft

“…For instance, the mission concept motivating TechSat-21, a US Air Force mission [2], involves a set of clusters of spacecraft evenly distributed on a circular orbit (see Figure 5). Multiple spacecraft cluster together to improve signal separation for radar imaging and clusters break up to improve signal space coverage for enabling point-to-point communications.…”

“…While these reasons for having multiple platforms in a mission are not exclusive, they do have a major impact on how the resulting missions are formulated and managed. For instance, the Air Force's TechSat-21 mission concept [2] involves a distribution of clusters of platforms. Each cluster forms a synthetic aperture for radar sensing, and the number of clusters depends on the desired global coverage.…”