Apparatus and method for controlling a satellite

Patent metadata

Field	Value
Publication number	US-10167093-B2
Application number	US-201715661698-A
Country	US
Kind code	B2
Filing date	Jul 27, 2017
Priority date	Sep 10, 2015
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

Abstract

Provided is an apparatus for controlling an orbiting satellite by sensing a change in a yaw angle of the orbiting satellite and calculating a ground sample distance (GSD) based on the yaw angle. The apparatus may include a sensor configured to sense a yaw angle corresponding to yaw steering of the orbiting satellite, and a processor configured to calculate, based on the yaw angle, a GSD corresponding to a length of a pixel projected onto a planetary surface scanned by the orbiting satellite.

First claim

What is claimed is:

1. An orbiting satellite comprising:
a movement controller configured to control an attitude of the orbiting satellite, the attitude comprising an orbital velocity, a roll angle, a pitch angle and a yaw angle of the orbiting satellite;
an image acquirer configured to scan a planetary surface in a scanning direction corresponding to the attitude; and
a calculator:
wherein the calculator is configured to:
calculate a major axis and a minor axis of an ellipse corresponding to a trace of a pixel projected onto the planetary surface based on a change in the yaw angle;
calculate a tilt angle between a direction vector and a line of sight (LOS) vector projected onto the planetary surface; and
calculate a ground sample distance (GSD) according to the following equation:
GSD=√{square root over ( a 2 cos(ψ+β) 2 +b 2 sin(ψ+β) 2 )}

wherein:
a is a length of the major axis;
ψ is the yaw angle;
β is the calculated tilt angle; and
b is a length of the minor axis.

2. The orbiting satellite of claim 1 , wherein the calculator is configured to project, onto a plane in which the yaw angle is measured, direction vector and the line of sight (LOS) vector of the image acquirer onto the planetary surface, and to calculate the tilt angle between the projected direction vector and the projected LOS vector when the yaw angle is set to “0”.

3. The orbiting satellite of claim 2 , wherein the calculator is configured to calculate the line rate based on the GSD and the orbital velocity.

4. The orbiting satellite of claim 1 , wherein the calculator is configured to calculate a line rate based on ground sample distance (GSD).

5. The orbiting satellite of claim 4 , wherein the calculator is configured to calculate a line rate based on the ground sample distance (GSD) and the orbital velocity of the satellite.

6. The orbiting satellite of claim 5 , wherein the calculator is configured to determine a scanning speed of the image acquirer based on the calculated line rate.

7. The orbiting satellite of claim 1 , wherein:
the movement controller is an actuator selected from the group consisting of: a magnetic torquer; a momentum wheel; a reaction wheel and a thruster; and/or
the image acquirer is a charge coupled device (CCD).

8. A method of controlling an orbiting satellite, wherein the orbiting satellite comprises a movement controller configured to control an attitude of the orbiting satellite and an image acquirer configured to scan a planetary surface in a scanning direction corresponding to the attitude, and wherein the method comprises:
sensing the attitude of the orbiting satellite, the attitude comprising a roll angle, a pitch angle and a yaw angle of the orbiting satellite;
calculating a major axis and a minor axis of an ellipse corresponding to a trace of a pixel projected onto the planetary surface by the orbiting satellite based on a change in the yaw angle;
calculating a tilt angle between a scanning direction vector and a line of sight (LOS) vector projected onto the planetary surface;
calculating a ground sample distance (GSD) according to the following equation:
GSD=√{square root over ( a 2 cos(ψ+β) 2 +b 2 sin(ψ+β) 2 )}

wherein:
a is a length of the major axis;
ψ is the yaw angle;
β is the calculated tilt angle; and
b is a length of the minor axis;
calculating a line rate corresponding to a scanning direction of the orbiting satellite based on the ground sample distance (GSD); and
adjusting the scanning speed of the orbiting satellite based on the line rate.

9. The method of claim 8 , wherein the length of the major axis and the length of the minor axis are calculated based on:
a radius of the planet;
an altitude from the planet to the orbiting satellite;
an angle at which a pixel is viewed from a scanning focal point of the orbiting satellite; and
an angle between a vertical vector from the orbiting satellite to the planet and a vector from the orbiting satellite to a scanning point at which the planet is scanned.

10. The method of claim 9 , wherein calculating comprises:
setting the yaw angle to “0”; and
projecting, onto a plane in which the yaw angle is measured, each of the scanning direction vector of the orbiting satellite and the line of sight (LOS) vector between the orbiting satellite and a scanned object onto the planetary surface; and
determining the tilt angle between the projected scanning direction vector and the projected LOS vector.

11. The method of claim 8 , wherein the length of the major axis and the length of the minor axis are calculated using the following equation:

a
=

c

cos
⁢

⁢

(
θ
)

⁢
cos
⁢

⁢

(
ϕ
)

,

b
=
c

where a denotes the length of the major axis, b denotes the length of the minor axis, ϕ denotes the roll angle, θ denotes the pitch angle, and c denotes the length of the pixel.

12. The method of claim 11 , wherein calculating the tilt angle comprises:
setting the yaw angle to “0”; and
projecting, onto a plane in which the yaw angle is measured, each of the scanning direction vector of the orbiting satellite and the line of sight (LOS) vector between the orbiting satellite and a scanned object onto the planetary surface; and
determining the tilt angle between the projected scanning direction vector and the projected LOS vector.

13. The method of claim 10 , wherein the tilt angle is calculated using the following equation:

β
=

tan

-
1

⁡

(

a
⁢

⁢

tan
⁡

(
ϕ
)

b
⁢

⁢

tan
⁡

(
θ
)

)

where β denotes the tilt angle, ϕ denotes the roll angl

Assignees

• Korea Aerospace Res Inst

Inventors

• Jeon Moon Jin
• Lee Sang Rok
• Kim Hui Kyung
• Kim Eung Hyun
• Lim Seong Bin
• Choi Seok Weon

Classifications

• G05D1/0883

  Physics · mapped topic

• B64G1/365 Primary

  using horizon or Earth sensors · CPC title

• G05D1/0094

  involving pointing a payload, e.g. camera, weapon, sensor, towards a fixed or moving target · CPC title

• B64G1/26

  using jets · CPC title

• B64G1/1021

  Earth observation satellites · CPC title