# US 2015/0102173 A1 · Method of solar occultation

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- Number: US 2015/0102173 A1
- Document ID: US20150102173A1
- Status: Published application
- Kind: A1
- Application number: 14/386,403
- Filed: 2013-02-25
- Published: 2015-04-16
- Earliest claimed: 2012-03-20
- Assignees: Airbus Defence and Space GmbH
- Applicants: Airbus Defence and Space Limited
- Inventors: Steve Evkersley; Stephen Kemble
- Web page: https://patentgrep.com/patent/US20150102173A1

## CPC

- B64G 1/105: {Space science}
- B64G 1/1085: {Swarms and constellations}
- B64G 1/242: {Orbits and trajectories}
- B64G 1/1064: {specifically adapted for interplanetary, solar or interstellar exploration}
- B64G: COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR

## Abstract

A method of solar occultation, and in particular solar coronagraphy, employing a spacecraft 200 is disclosed. The spacecraft is controlled to achieve a position within a target zone relative to a celestial body, such as the Moon, such that the celestial body occults the Sun, allowing observations of the Sun or the space around the Sun, and in particular the Sun's corona, to be made from the spacecraft. The spacecraft has an orbit 40 around the Earth in a plane S, which like the Moon's orbit 20 in plane M, is inclined relative to the ecliptic plane E. Once inside the target zone, the spacecraft's orbit is controlled such that it remains in the target zone for longer than it would otherwise. This is achieved through the orbit within the target zone being at least partly non-Keplerian, when the orbit is under the influence of spacecraft translational thrust for example. The invention also extends to a method of controlling a spacecraft, to a spacecraft, and to a solar coronagraph comprising a spacecraft and a celestial body.

## Claims

### Claim 1

A method of solar occultation employing a spacecraft, the method comprising:
controlling the spacecraft to achieve a position within a target zone relative to a celestial body such that the celestial body occults the Sun; and
observing the Sun or the space around the Sun from the spacecraft,
wherein the spacecraft is controlled to have an orbit within the target zone which is at least partly non-Keplerian or approximating non-Keplerian via a discrete set of frequent manoeuvres.

### Claim 2 (depends on 1)

The method of claim 1, in which the Sun's corona is observed from the spacecraft.

### Claim 3 (depends on 1)

The method of claim 1, wherein the Sun, as observed from the spacecraft, has a radius Rs and the target zone is defined as the zone within which, when observed from the spacecraft, the celestial body occults an area bounded by the entire circumference of the effective occulting disc formed by the celestial body, in which the area has a radius of at least 1.00 Rs.

### Claim 4 (depends on 3)

The method of claim 3, wherein the target zone is further defined as the zone within which, when observed from the spacecraft, the celestial body occults the Sun to an extent no greater than an area having a radius of 1.05 Rs at at least one point on the circumference of the effective occulting disc formed by the celestial body.

### Claim 5 (depends on 3)

The method of claim 3, wherein the target zone is further defined as the zone within which, when observed from the spacecraft, the celestial body occults the Sun to an extent no greater than an area having a radius of 1.05 Rs around the entire circumference of the effective occulting disc formed by the celestial body.

### Claim 6 (depends on 4)

The method of claim 4, wherein in which the celestial body occults the Sun to an extent no greater than an area having a radius of 1.02 Rs.

### Claim 7 (depends on 1)

The method of claim 1, wherein the celestial body is the Moon.

### Claim 8 (depends on 7)

The method of claim 7, wherein the spacecraft is controlled to orbit the Earth with an elliptical, parabolic or hyperbolic orbit such that, at perigee, the spacecraft is positioned within the target zone.

### Claim 9 (depends on 8)

The method of claim 8, wherein the line between the Moon and the Sun is defined as the x-direction and in which the spacecraft (200) is controlled to remain within the target zone for a predetermined period by controlling the motion of the spacecraft in a y-direction which is perpendicular to the x-direction and parallel to the ecliptic plane of the Earth.

### Claim 10 (depends on 9)

The method of claim 9, wherein the spacecraft is further controlled to remain within the target zone for a predetermined period by controlling the motion of the spacecraft in a z-direction which is perpendicular to both the x- and y-directions.

### Claim 11

A spacecraft configured to achieve a position within a target zone relative to a celestial body to enable observation from the spacecraft of the Sun or the space around the Sun by occultation of the Sun by the celestial body,
wherein the spacecraft is arranged to be controlled to have an orbit within the target zone which is at least partly non-Keplerian or approximating non-Keplerian via a discrete set of frequent manoeuvres.