  An optical imager that exploits off-center image rotation to encode both the
lateral and depth coordinates of point sources in a single snapshot can perform
3D localization and tracking of space debris. When actively illuminated,
unresolved space debris, which can be regarded as a swarm of point sources, can
scatter a fraction of laser irradiance back into the imaging sensor.
Determining the source locations and fluxes is a large-scale sparse 3D inverse
problem, for which we have developed efficient and effective algorithms based
on sparse recovery using non-convex optimization. Numerical simulations
illustrate the efficiency and stability of the algorithms.
