PNEU-SCAN - A NOVEL, LIGHTWEIGHT TWO-AXIS TELEMETRY TRACKING SYSTEM

Abstract

Over a decade ago the author developed a unique conically scanning tracking antenna feed (RADSCAN) with only one moving part and extremely high reliability. While the system had many advantages over single-channel monopulse (SCM), there were two disadvantages: one was weight due to the drive motor; the other was the fact that the scan speed was constant. EMP is just completing the development of a conscan tracking feed which is pneumatically driven (Pneu-Scan) - thus eliminating the heavy electric drive motor. Since most telemetry tracking antennas require a dehydrator/pressurizer for environmental reasons, no additional drive power is required to scan the feed since the pressurized air from the dehydrator system is used to drive the feed. In addition, the scan speed is proportional to the continuously varying pressure. If increased reliability is required, then redundant dehydrators can be used. The feed system has only one moving part constructed from graphite fiber that weighs less than an ounce. The feed is driven by a small lightweight impeller. An S-band tracking feed of this design is less than five inches in diameter - as compared to 12 inches for an SCM feed. It is also considerably lighter than an SCM feed. Decreased aperture blocking - by more than a factor of two enhances sidelobe levels and maximizes gain. The new feed illuminates a lightweight 5-foot diameter graphite-epoxy constructed paraboloidal reflector positioned by an elevation-over-azimuth pedestal. Both the elevation and azimuth assemblies of the pedestal are constructed of graphite fiber composite material - which greatly reduces both weight and cost as compared with the conventional steel or aluminum construction. An inflatable rotodome surrounds the elevation assembly and rotates with azimuth. The rotating sphere has minimum wind induced torque thereby minimizing the required drive power. The weight of the entire system is less than 135 pounds - yielding an extremely light weight, low cost, versatile two-axis telemetry tracking system.