Protection of the Radarsat Spacecraft from the Low Earth Orbit Environment

Abstract

RadarSat, the first Canadian Earth observation spacecraft, was successfully launched in November, 1995. RadarSat employs a powerful synthetic aperture radar (SAR) to view the Earth’s surface through any weather condition in daylight or darkness to provide high resolution imagery of the ground.

A unique feature is the very flexible, variable imaging radar beam mode which can be selected from any one of the 20 pre-established beam mode parameter sets stored in the on-board computer. Also, additional beam mode parameters can be programmed from the ground. RadarSat was designed as an operational satellite capable of providing imagery on demand to users for over five years in orbit.

In order to provide almost complete ground coverage of the Earth with the required resolution, RadarSat orbits the Earth in a nearly polar orbit at an altitude of approximately 800 km. This places the spacecraft directly in the harsh Low Earth Orbit (LEO) environment with accompanying effects of atomic oxygen, trapped charged particle radiation and orbital debris, among other perils.

In order to successfully complete the challenging five-year mission and ensure a constant source of data, RadarSat incorporated unique design features to defeat the deleterious effects of the harsh LEO environment. These include protection of polymeric materials against atomic oxygen, orbital debris shielding of sensitive components and radiation considerations. These design features will be discussed in the paper.