Both the military and scientific imaging communities learned from the early foliage penetration (FOPEN) developmental RADAR systems operated in the late-1960 to mid-1970 time frame. Two important system realities affected the growth of the technology: foliage attenuation limited the systems to short-to-medium-range operation; and manned aircraft could not adequately be protected at these ranges. Remotely piloted vehicles (RPV; also known as unmanned air systems, or UAS, in today's vocabulary) were just starting to be developed. They would address the ability to collect data in hospitable environments. More importantly, the development of wideband data links would enable significant processing and image interpretation on the ground. By the late 1980s, the image collection community had determined that SAR could provide acceptable and useful detection and characterization forested regions. These SAR systems required small antennas and modest power; which was acceptable for experiments and might be possible on RPV installations. In 1988, the NASA Jet Propulsion Laboratory started the AIRSAR program and flew a multiple-frequency SAR platform until 2004. At approximately the same time, several research groups started experimental FOPEN SAR systems, notably Stanford Research Institute (SRI) and Sweden's Defence Research Agency (FOA).

Chapter Contents:

• 2.1 SAR Resolution
• 2.2 FOPEN SAR Systems
• 2.3 References

Inspec keywords: synthetic aperture radar; autonomous aerial vehicles; spaceborne radar; radar imaging

Other keywords: antenna; remotely piloted vehicle; image interpretation; manned aircraft; foliage penetration SAR collection system; scientific imaging; foliage penetration developmental radar system; unmanned air system; military imaging

Subjects: Optical, image and video signal processing; Radar equipment, systems and applications