Synthetic aperture radar assembly and a method of creating a radar image of a planet surface using such an assembly

• US 5,051,749 A
• Filed: 03/08/1990
• Issued: 09/24/1991
• Est. Priority Date: 03/21/1989
• Status: Expired due to Fees

• Current Assignee: British Aerospace, Inc.
• Original Assignee: British Aerospace, Inc.
• Inventors: Stoyle, Peter N. R.
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US07/489,185
• Time in Patent Office: 565 Days
• Field of Search: 342/25, 342/137
• US Class Current: 342/25.00A
• CPC Class Codes: G01S 13/222 using random or pseudorandom pulse repetition frequency
• CPC Class Codes: G01S 13/904 SAR modes

Abstract

A synthetic aperture radar assembly (1) locatable on a satellite (2) for radar imaging of a planet surface (3) in swaths, including means (8) for transmitting pulses (4) of electromagnetic radiation towards the planet surface (3) to be imaged, means (8) for receiving echoes of said pulses (4) returned by said planet surface (3), means for creating an image of a swath (5) of said planet surface (3) from said returned echoes and means for randomly varying the frequency of transmission of said pulses (4) to increase the width (11) of swath (5) imagable.

Claims

1. A synthetic aperture radar assembly locatable on a satellite for radar imaging of a planet surface in swaths, comprising:

means for transmitting pulses of electromagnetic radiation towards the planet surface to be imaged in widths of swaths to be imaged,

timing means, coupled to said transmitting means, for randomly varying the frequency of transmission of said pulses to increase the width of swath imageable;

means for receiving echoes of said pulses returned by said planet surface, and

means for creating an image of a swath of said planet surface from said returned echoes.

2. As assembly according to claim 1, further comprising means for scanning the transmitted pulses over the planet surface in a direction along a track of said swath and in a direction across the width of the swath transverse to the track.

5. An assembly as in claim 1 wherein said width of said swaths to be imaged is wider than an ambiguity limited swath width.

6. An assembly as in claim 5 wherein said image creating means includes means for summing a plurality of said echoes to average ambiguities to below noise level.

7. An assembly as in claim 1 wherein said timing means uses a random varying PRF such that a mean PRF remains constant.

3. A method of creating a radar image of a planet surface in swaths, comprising the steps of:

transmitting pulses of electromagnetic radiation from a satellite towards the planet surface to be imaged in widths of swaths to be imaged,

randomly varying the frequency of transmission of said pulses to increase the width of swath imageable,

receiving echoes of said pulses returned by said planet surface, and

creating an image of a swath of said planet surface from the returned echoes.

4. A method according to claim 3, further comprising the step of scanning the transmitted pulses over the planet surface in a direction along a track of said swath and in a direction across the width of the swath transverse to the track.

8. A method as in claim 3 wherein said width of said swaths to be imaged is wider than an ambiguity limited swath width.

9. A method as in claim 8 wherein said image creating step includes the step of summing a plurality of said echoes to average ambiguities to below noise level.

10. A method as in claim 3 wherein said timing means uses a random varying PRF such that a mean PRF remains constant.