Method for observing a region of the earth's surface, notably located at high latitudes; ground station and satellite system for implementing this method

• US 20160006950A1
• Filed: 07/02/2015
• Published: 01/07/2016
• Est. Priority Date: 07/04/2014
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: SAINCT, Herv, SOULIGNAC, Vincent
• Granted Patent: US 11,050,950 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B64G 1/1021 Earth observation satellites
• CPC Class Codes: B64G 1/1085 Swarms and constellations
• CPC Class Codes: B64G 1/242 Orbits and trajectories
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture
• CPC Class Codes: H04N 23/951 by using two or more images to influence resolution, frame rate or aspect ratio
• CPC Class Codes: H04N 5/28 Mobile studios

Abstract

A method for observing a region of the Earth'"'"'s surface, called region of interest, implementing a plurality of satellites spaced apart along at least one non-stationary orbit, the method comprises: the acquisition, by at least two of the satellites, during a same passage over the region of interest and in successive acquisition periods, of a plurality of images of the Earth'"'"'s surface, called partial images, each covering a portion of the region of interest; and the obtaining of an image covering all of the region of interest by the merging of at least two partial images, exhibiting a predefined time shift between their acquisition periods, for each of the at least two satellites. A satellite system for observing a region of the Earth'"'"'s surface for the implementation of such a method, and ground segment belonging to such a system is provided.

Claims

1. A method for observing a region of the Earth'"'"'s surface, called region of interest, using a plurality of satellites moving along at least one non-stationary orbit, said method comprising:

acquiring, by at least two of said satellites, during a same passage over said region of interest and in successive acquisition periods, a plurality of images of the Earth'"'"'s surface, called partial images, each covering a portion of said region of interest; and

obtaining an image covering all of said region of interest by the merging of at least two said partial images, exhibiting a predefined time shift between their acquisition periods, for each of said at least two satellites.

2. The method of claim 1 wherein partial images, called images of a same rank, are acquired at the same time by said satellites;

a number of said satellites, said or each said non-stationary orbit and said acquisition periods being chosen such that partial images of the same rank, taken in combination, ensure a partial coverage of said region of interest, exhibiting coverage gaps.

3. The method of claim 2 wherein said partial images are obtained by scanning and, upon acquisition of a first set of partial images of the same rank, said scanning begins in proximity to said coverage gaps, whereas, upon subsequent acquisition of a second set of partial images of the same rank, said scanning ends in proximity to said coverage gaps.

4. The method of claim 1 wherein each said partial image is obtained by scanning a respective observation region, determined such that it does not extend beyond said region of interest.

5. The method of claim 1 using exactly two satellites.

6. The method of claim 1 wherein said satellites are spaced apart along a same non-stationary orbit.

7. The method of claim 1 wherein said image covering all of said region of interest is obtained by merging exactly two said partial images for each of said satellites, acquired in successive acquisition periods.

8. The method of claim 1 said region of interest is in the form of a spherical cap.

9. The method according to one of the preceding claims of claim 1 wherein said or each said non-stationary orbit is an inclined highly elliptical orbit—

of HEO type—

and said region of interest consists of a portion of the Earth'"'"'s surface exhibiting a latitude greater than or equal to a limit value L, with L≧

50° and

preferably L≧

60°

.

10. The method according to one of the preceding claims of claim 1, also comprising an operation of assignment, to each pixel of each said partial image, of a set of information representative of an acquisition instant and of a point of the Earth'"'"'s surface corresponding to said pixel, and wherein said set of information is used in the merging of said partial images.

11. A ground segment comprising:

at least one satellite receiver configured to receive, from at least two satellites spaced apart along a same non-stationary orbit, signals representative of images of the Earth'"'"'s surface, called partial images, each covering a portion of a same region, called of interest, and acquired in successive acquisition periods during a same passage of said satellites over said region of interest; and

a data processor configured to merge at least two said partial images for each of said at least two satellites, said partial images received from each said satellite exhibiting a predefined time shift between their acquisition periods, in order to obtain an image covering all of said region of interest.

12. A satellite system for observing a region of the Earth'"'"'s surface, called region of interest, comprising:

a space segment comprising a plurality of satellites moving along at least one non-stationary orbit, configured to acquire, during a same passage over said region of interest and in successive acquisition periods, a plurality of images of the Earth'"'"'s surface, called partial images, each covering a portion of said region of interest, and to transmit said partial images to a ground segment; and

a ground segment comprising;

at least one satellite receiver configured to receive, from at least two satellites spaced apart along a same non-stationary orbit, signals representative of images of the Earth'"'"'s surface, called partial images, each covering a portion of a same region, called of interest, and acquired in successive acquisition periods during a same passage of said satellites over said region of interest; and

a data processor configured to merge at least two said partial images for each of said at least two satellites, said partial images received from each said satellite exhibiting a predefined time shift between their acquisition periods, in order to obtain an image covering all of said region of interest.

13. The satellite system of claim 12 wherein said or each said non-stationary orbit is a highly elliptical orbit—

of HEO type—

and said region of interest consists of all the points of the Earth'"'"'s surface exhibiting a latitude greater than or equal to a limit value L≧

50° and

preferably L≧

60°

.