Space-Based Synthetic Aperture Radar (SAR)


Old technology: : ERS-1 SAR during deployment

Introduction

SARs are used in environmental monitoring, earth-resource mapping and military systems; images can be acquired in inclement weather or during night-time. The larger the SAR the greater the imaging detail that can be acquired. There is interest in developing large SARs that can be operated from small satellites.

A new concept:

The standard design for a space-based SAR (shown above) is based on rigid surfaces deployed by motorised hinges. This leads to structures that are heavy and do not package compactly.

Recent research at NASA JPL has concentrated on developing membrane SARs that are deployed by inflatable tubes. However, the use of inflatables in space involves high risks.

Instead, we have developed a scheme in which the membrane is supported by a frame of solid bars connected by self-locking hinges. This allows us to put on a spacecraft a SAR with 4.5 times the area of the old design, but without the risks of inflatables

Some details:

SARs generally have an aspect ratio of 5:1. In camSat1 this shape is made from a solid square in the center and two deployable 2:1 rectangles on either side. Each rectangle is a frame with six hinges. It is not a perfect mechanism and some of its members have to twist during deployment. Computer simulations of the 3D kinematics were used to predict the maximum amount of twist required during deployment, reducing uncertainty in model design.

The self-locking hinges developed in this project have many other applications and are currently being patented.

[ Cambridge University | CUED | Structures | Deployable Structures ]

Last updated on the 25 May 2004

rcb@eng.cam.ac.uk / E. Kebadze - ek235@eng.cam.ac.uk