The Role of Physics in Overhead Imaging

Basic physics has profound implications for overhead imaging. This presentation will examine
illustrative surveillance concepts for defense applications using unmanned and space-based
platforms. We focus on two topics where physics plays a crucial role: 1) wide-area drone
surveillance, and 2) low-earth orbit (LEO) imaging. To accommodate drone limitations, sensor
concepts minimizing size and weight while maximizing scene coverage and resolution are
preferred. One intriguing concept uses composite focal plane arrays (CFPA). CPFAs apply
multiple discrete FPAs on a flat surface behind a single optical path. For this technology, we
discuss trade-offs for field-of-view and resolution and describe a number of engineering
challenges addressed for a realizable system. Given CFPA ‘big-data’ acquisition, physical
principles are invoked to facilitate a key capability – automated object tracking. Here, traditional
kinematics permits the tracking of moving entities from a moving platform over a large area.
Cheaper and frequent rocket launches have resulted in a burgeoning ‘small satellite’ market. This
has motivated desire for small earth-observing payloads. We discuss critical trade-space drivers
including LEO’s high velocity and stringent platform volume bounds. The space environment
also presents challenges for analysis using traditional electronics. We discuss the trade-off of
cost and reliability that defines LEO operation by examining the impact of the physical radiation
environment.