EP3117260A1

EP3117260A1 - Optical method for detecting spatial moving objects and systems of telescopes for detecting spatial moving objects

Info

Publication number: EP3117260A1
Application number: EP15712284.7A
Authority: EP
Inventors: Michel BOËR
Original assignee: Universite De Nice (uns); Centre National de la Recherche Scientifique CNRS; Observatoire de la Cote dAzur
Current assignee: Universite De Nice (uns); Centre National de la Recherche Scientifique CNRS; Observatoire de la Cote dAzur
Priority date: 2014-03-14
Filing date: 2015-03-13
Publication date: 2017-01-18
Also published as: FR3018612B1; FR3018612A1; WO2015136102A1

Abstract

The method for detecting a moving object comprises: generating a plurality of fields of view (Z_kp) by means of a first telescope array (T_ij), the set of fields (FOV_ij) of each telescope (T_ij) having a spatial distribution inscribed in a conical crown (CC) of a defined spatial plane (P_O) called the optical plane, said optical plane being nonparallel to at least one of the optical axes (A_O(T_ij)) of a telescope (T_ij) and said conical crown (CC) having a diameter defining a large detection field; detecting at least one trace of a moving object (M₁) in the field (FOV_ij) of at least one telescope (T_ij) using an electronic detector (T_ij), the integration time of the electronic detector being defined so that the trace extends over a plurality of pixels for a given maximum orbital speed (V_M) of the moving object and a minimum altitude of its orbit; and deducing a trajectory (TJ_SAT) of the moving object (M₁).

Description

METHOD FOR OPTICALLY DETECTING SPACE MOBILES, TELESCOPE SYSTEMS FOR MOBILE DETECTION

SPACE.

FIELD

The field of the invention relates to the detection of mobiles present in space at low and high altitudes by optical methods implementing a set of telescopes. More particularly, the field of the invention relates to the detection of satellites and space debris as well as aircraft or any mobile and the calculation of their orbit and their trajectory with a view to preventing their fall on earth, a collision in space or entering a danger zone.

STATE OF THE ART

At present, the surveillance of near space and in particular objects presenting a potential danger whether natural or artificial has become a major problem to ensure the safety and integrity of any target possibly targeted by a collision.

This surveillance concerns both end-of-life and uncontrolled satellites as well as debris from previous collisions, or asteroids or comets potentially dangerous for the Earth.

Space agencies and private operators have started various surveillance programs grouped together under the name of "Space Situational Awareness".

Even in the case where a meteorite is relatively small, the risks induced by a fall remain significant. It therefore poses a danger for people and infrastructure on the surface of the Earth for any falling mobile whose fragmentation in the atmosphere can cause significant damage. One of the problems encountered is the identification of the small bodies of the solar system whose orbit intersects that of the Earth and their monitoring in order to evaluate their dangerousness.

There are more and more artificial objects in low or high orbits. Space congestion seems to be increasing each year due to the presence of more and more satellites, and to the multiplication of catastrophic collisions leading to an increase in the number of debris. The bad or the non-tracking of their trajectory after their end of life remains a growing problem.

Projections suggest a situation in which the increase in the debris population larger than 1 cm will result in control and monitoring of these more and more difficult to maintain.

These objects will be called "debris" in the remainder of the text knowing that this notion of debris includes debris properly so called, operational or non-operational satellites, or even meteorites.

A first problem concerns the fall of debris on the surface of the earth and a second problem concerns the collision of debris between them or with active satellites. The monitoring of debris in space, and more particularly in low orbits, helps to prevent these two consequences.

Finally, the problem of monitoring the various mobile space also concerns those, by extension, discrete mobiles moving at very low altitude such that aircraft, for example ultralights or drones, which can define a danger for example when their overflight is carried out near a sensitive site, for example a nuclear power plant.

A difficulty is to find a large-field optical system to cover different altitudes, distant and close, and to follow objects at low altitudes with high speeds and therefore difficult to detect.

Indeed, a problem of the detection and monitoring of space debris, whose orbit and / or trajectory is not known a priori, is the consideration of the light intensity of third sources which disturbs the detections. These sources may come from the sky, the sun, the moon, and local weather conditions that affect the stability of the shooting conditions. The monitoring system must be able to take into account a multitude of light conditions making it possible to maximize detections in all circumstances. Detection taking place by considering a point or an area of the surface of the globe, the condition of the field of view of the observer is an extremely important in the calculation of the probability of detection of a mobile and the calculation of its trajectory.

The problem of debris monitoring concerns different orbits to be taken into account in space mobile detection methods. For natural objects such as meteorites, their orbits are usually gravity-centered, which means that meteorites can potentially approach the Earth at any altitude and in any direction. With regard to artificial objects, their Earth orbit can be included in different families of orbits.

The first family of orbits is known by the acronym LEO, denoting "Low Earth Orbit" in the English terminology. It is a family of low orbits up to 2000 km. This family of orbits is very busy with communications satellites, military, detection, weather, etc.

A second family of orbits is known by the acronym GEO, meaning "Geostationary Orbit" which includes a geostationary orbit defined at 35784 km above the equator. A revolution of a mobile at this altitude is 24h. The mobile in a geostationary orbit is fixed with respect to a terrestrial position. However, debris can leave their orbit and have scrolling orbits. This orbit is very busy with communication satellites (military or civilian), remote sensing, meteorology, etc.

A third family of orbits is better known by the acronym MEO, referring to "Medium Earth Orbit" which is a medium orbital family, generally elliptical. This is the case of GPS satellites.

A fourth family of orbits is referred to as the HEO, whose highly elliptical orbits, such as the Molniya or Tundra orbits, make it possible to communicate or monitor regions of high latitudes.

A fifth family of orbits is designated by the acronym GTO, meaning "Geostationary Transfer Orbit". This family includes elliptical orbits. Their apogee is of the order of 42000 km and their perigee is of the order of 650km. This family of orbits is very convenient for injecting satellites into a geostationary orbit, so it is used during satellite launches as a transitional orbit for geostationary orbit placement.

Today, different methods of detecting space debris and their trajectory exist.

In particular, there is a family of methods known as "active methods", especially for the detection of debris in LEO orbits. The active methods are based on a "radar" type of operation in which a mobile is illuminated by a source emitting a signal. The signal is then reflected and it is the reflection of the signal that informs a receiver of mobile position data.

A first disadvantage of this method is that the received power varies as d ^"4 , where" d "is the distance from the mobile to the transmitter / receiver, therefore the received stream will remain weak during the detection, even if a strong transmission power is envisaged.

A second disadvantage is the relatively large installation of radar type system that this method imposes. These facilities are expensive and require significant maintenance and are easily detectable. In addition, these systems consume a lot of energy and must therefore be installed near an electrical network.

Among the active methods, there are also the LIDARs which rely on an illumination of a mobile by a Laser. This method achieves better results than the radar in terms of power detected because the laser light is better focused. On the other hand, the detection cones are much weaker and are not very suitable for "blind" detections of mobiles located in low and elliptical orbits. Another family of methods exists, these are the passive methods in which the targets are not lit by a terrestrial source. As far as passive methods are concerned, the luminous flux captured by a detector varies with the distance "d" to the mobile as a function of d ^"2 which offers better results than the active methods on the light flux captured from the mobile. In contrast, the disadvantage major is the strong dependence on illuminations from external sources such as the sun, the stars or the moon. The advantage of these solutions lies in their low costs and the relative simplicity of their implementation from detectors based on optical instruments capable of viewing objects of small sizes at all altitudes.

Regarding the mobile geostationary orbit, a telescope or a radar or other electromagnetic means can detect a stationary point on a background of moving stars during the time of installation. With a large-field telescope, it is then possible to detect space mobiles on a geostationary belt and their trajectory.

In the case of other orbits, so-called "scrolling" so non-geostationary, that is to say non-fixed vis-à-vis a point of observation of the earth, it is difficult to detect space mobiles, their height, their inclination, the different nodes of their orbit, whose nodes ascending and descending.

A difficulty comes from the speed of scrolling space mobiles which can exceed 1 ° / s at the zenith for a low orbit. The detection is done by the capture of a trace vis-à-vis specific traces or streaks depending on the sidereal movement and therefore the observation window in the sky.

The method then consists of discriminating the traces, to detect the presence of a space debris. If the inclination can be optionally detected according to the analysis of the trace left by the mobile, however, it remains very difficult to obtain a real speed of movement of the mobile because of the unknown altitude. As a result, it is difficult to deduce elements from its trajectory by extrapolating the trace analyzes. In the general case, it is necessary to have three measurements of the angular position of the mobile to derive its orbit. Two measurements are sufficient if the mobile is in a circular orbit.

The problem can be solved by increasing the field of a telescope to increase the traces and their number, but the detected images, as explained above, can become difficult to analyze due to the complexity of the telescopes to be used, light pollution. surrounding, the strong confusion caused by all the objects of the field, and the very large size of the necessary sensors.

In fact, a large-field optics makes it possible to deduce information as to the trajectory of the mobile; on the other hand, a large field is more likely to be affected by parasitic light sources. In addition, it remains very difficult to design large field telescopes without encountering design problems, specific optical scheme complexity. The presence of a large focal plane also causes many aberrations. When an electronic detector is coupled to a large-field optics, it must be very large; the sizes and number of pixels can be very large and the design costs are significant and the operation is difficult.

There are telescope systems making it possible to obtain very large fields by coupling a matrix of single-field large field telescopes as proposed by ASTRIUM, in particular with the solution described in patent document WO2012 / 007361. A disadvantage of this solution is the cost of such a system that requires many telescopes of very large field. One solution is to reduce the number of telescopes and to associate a motorized tracking system with larger field telescopes having at least a 5 ° field, and in practice 14 ° in the example cited in the patent document ( 10 ° x 10 ° on the square detector).

Nevertheless this solution remains complex to implement and expensive.

SUMMARY OF THE INVENTION

The invention solves the aforementioned drawbacks. In particular, the invention relates to a method for detecting a mobile in space as well as to a method for multiplexing a telescope field distribution for detecting a mobile in space.

In addition, the invention also relates to an optical system comprising a first set of telescopes for implementing either the detection method of the invention. An object of the invention relates to a method for detecting a mobile in the space comprising:

A generation of a plurality of fields of view (Z _kp ) by means of a first set of telescopes (T), each telescope defining a detection telescope, the set of fields (FOVy) of each telescope (Ty) having a spatial distribution in at least one plane of space in an open geometric form (CC), said open geometric form (CC) defining a wide detection field;

Detection of at least one trace of a mobile (Mi) in the field (FOVy) of at least one telescope (Ty) by an electronic detector coupled to each telescope (Ty), the integration time of the detector electronics being defined to obtain a multi-pixel trace spread of the electronic detector for a given maximum running speed (V _M ) of a moving body and a minimum altitude of its orbit;

• a deduction of a trajectory (TJ _S AT) of the mobile (Mi) in the image plane of said telescope (Ty).

When the open geometric shape is the intersection of a plane and a conical crown, an object of the invention relates to a method for detecting a mobile in the space comprising:

A generation of a plurality of fields of view by means of a first set of telescopes, the set of fields of each telescope having a spatial distribution forming part of a conical crown of a plane of space, said conical crown defining a wide field of detection;

Detection of at least one trace of a mobile in the field of at least one telescope by an electronic detector coupled to each telescope, each telescope defining a detection telescope, the integration time of the electronic detector being defined to obtain a multi-pixel trace spread of the electronic detector for a given maximum scroll speed of the mobile and a minimum altitude of its orbit; • a deduction of a trajectory of the mobile in the image plane of said telescope.

One advantage is to provide a wide field from a particular arrangement of a number of telescopes. The method of the invention makes it possible to increase the probabilities of detection while covering a large area of the sky. Telescopes having limited fields, for example less than 3 °, can be combined to form a field of more than 30 ° with which a probability of detection is associated. This solution is simple to implement and inexpensive.

The method of the invention can be implemented by an optical system also object of the invention also called meta-telescope.

Advantageously, the conical ring is defined with respect to a theoretical median optical axis, the theoretical median axis being determined so that at a minimum determined altitude, each field of each detection telescope of the first set is included in the conical ring.

All embodiments are compatible with an open geometric shape resulting from the intersection of a plane of space with all the telescope fields of the system of the invention. The principle of an open geometric form of the invention is to be able to benefit from a wider detection zone in the sky and an effective detection method on this zone.

A particular case of an intersection between a plane of space and the fields of the telescopes, forming a conical crown and defining then in the plane of section a circular or elliptical ring, is more particularly detailed in the description but does not limit the invention to this precise geometric form.

Advantageously, the spatial distribution of the fields of each detection telescope is determined with respect to a desired probability of detecting a trajectory a mobile intercepting the conical crown. Advantageously, the field of a telescope of the first set is in a range of 0.5 ° to 5 ° and the diameter of the conical ring defines a field greater than 30 °. Advantageously, the integration time of at least one electronic detector is defined in order to obtain two traces successively captured on a plurality of pixels of at least one electronic detector for a maximum running speed V _M given to the mobile and a minimum altitude of its orbit, the integration time of one of at least one electronic detector being configured for a passage in the optical plane of at least one telescope.

An advantage of obtaining two successive traces of the mobile in the detector is that it allows to deduce the first elements of the trajectory of the mobile.

Advantageously, the direction of movement of the mobile, the inclination of its orbit and its speed of movement is deduced from an analysis of the timestamped traces of the mobile captured by the electronic detector.

Advantageously, the detection telescopes of the first set are distributed in different ground stations distributed at different geographical positions on the surface of the earth.

Advantageously, the different groups of telescopes are spaced a maximum distance, the maximum separation distance allowing simultaneous observation of each telescope in the same weather conditions of the same portion of the sky.

When the shooting conditions are different, it is also possible to implement a telescope associated with the meta-telescope to correct the brightness or deviation of each telescope of the meta-telescope, or to supplement the information acquired with a meta-telescope. better accuracy, or by an active means, a LIDAR for example.

Advantageously, the fields of the telescopes of the first set continuously cover the periphery of the conical crown. This configuration makes it possible to obtain a detection probability of 100% when the trajectory of the mobile intercepts the conical crown for a maximum running speed V _M and a minimum altitude.

Advantageously, computation means make it possible to correlate time-stamped data of the traces captured by at least two electronic detectors so as to deduce a direction of movement of the mobile, an inclination of its orbit and a speed of displacement, and more generally its parameters. orbit.

The timestamping of the traces captured on the electronic detector associated with each detection telescope makes it possible to correlate the data of the different meta-telescope detection telescopes of the invention.

Advantageously, means for controlling the displacement of the optical axis of each detection telescope make it possible to:

^■ modify the telescope distribution in the conical crown;

^■ to modify the shape of the monitored field in the space;

^■ either to change the orientation of the conical ring into the space while maintaining the same field distribution in said conical crown;

^■ to compensate for a sidereal movement so as to make the stars fixed on the images captured by the detectors.

The control means may be preferably synchronized so as to obtain coherence of the measurements and to minimize the transition times during a change of configurations.

Advantageously, control means of at least one tracking telescope make it possible to guide the optical axis of said tracking telescope so as to continue the movements of a mobile of the space after a first trace detection of one of the telescopes. detecting the first set of said mobile.

One advantage is to enslave the direction of the optical axis of the tracking telescope on a supposed direction of the mobile previously calculated by dynamically correcting this enslavement on the measurements made.

Advantageously, at least one tracking telescope allows:

Recovering the positions of at least one trace captured by the electronic detector of one of the telescopes of the first set;

• Extrapolate from at least one captured trace of at least one telescope a trajectory to follow;

• control the optical axis of the tracking telescope so as to follow the presumed path of the mobile;

• to capture new timestamped positions of the mobile.

Another subject of the invention concerns a method of multiplexing a telescope field distribution for the detection of a mobile in space, said method comprising:

A generation of a plurality of fields of view by means of a first set of telescopes, the set of fields of each telescope having a first spatial distribution during a first determined duration, the spatial distribution being in a geometric form a defined plane of space, called the theoretical optical plane, said theoretical optical plane being non-parallel to at least one of the optical axes of a telescope, said geometric shape having a larger dimension defining a wide detection field ;

A calculation of a completeness factor of the geometrical shape corresponding to the proportion of the surface of the geometrical shape covered by all the fields of the telescopes of the first set;

A calculation of a minimum number of changes in positions of the optical axis of at least one telescope of the first set, called "distribution number", each new position of at least one telescope defining a new distribution, so to obtain a desired completeness factor; • a calculation of a maximum duration of change of distributions corresponding to the exposure time of each distribution and the time of passage from one distribution to another, the distributions succeeding one another in a determined duration, called "duration of multiplexing", the multiplexing duration allowing the passage to all the determined distributions, the maximum duration of change of distributions being calculated according to a desired probability of detection of a mobile moving at a maximum speed of movement and at a minimum altitude and whose trajectory intercepts the geometric form.

An advantage of the invention is to generate a geometric shape appropriate to the coverage of an area of the space while providing a detection rate of a mobile space for a given period of time, while using a reduced number of telescopes through multiplexing.

Advantageously, the geometric shape is open and it results from the intersection of a plane of the space and all the fields of the telescopes of the system of the invention.

Advantageously, the geometric shape is a form selected from the following list:

^■ a conical crown;

^■ a circular crown;

^■ a plurality of parallel circular arcs therebetween; A plurality of curves parallel to each other;

^■ a plurality of parallel lines.

Another object of the invention relates to an optical system comprising a first set of telescopes which makes it possible to implement either the detection method of the invention, or the method of multiplexing a telescope field distribution for the detection of a mobile in space. According to the invention, the fields of each telescope have a spatial distribution in a theoretical plane of space in an open geometric form, said theoretical optical plane being non-parallel to at least one of the optical axes of a telescope, said open geometric shape having a diameter defining a wide detection field. In this case, calculation means recover the data captured by each optical detector of the telescopes of the first set, said calculation means making it possible to process the different data captured by the electronic detectors of the first set to deduce at least one trajectory of a mobile whose orbit crosses the open geometric form.

The "diameter" of the open geometrical shape is then called, depending on the case, for example, one of the following distances:

· The largest distance separating two edges of the geometric form;

• the average distance between two edges of the geometric shape;

• or the minimum distance separating two edges of the geometrical form.

In these cases the distance can be calculated by measuring the distance between two points of the edges and passing through the center of gravity of the open geometric form.

This is an exemplary embodiment, but other ways of calculating the diameter can be envisaged in the invention.

When the open geometric shape is the intersection of a plane is of a conical crown, an object of the invention relates to an optical system comprising a first set of telescopes which allows to implement either the detection method of the invention, the method of multiplexing a telescope field distribution for the detection of a mobile in space. According to the invention, the fields of each telescope have a spatial distribution inscribed in a conical ring of a defined plane of space, called the theoretical optical plane, said theoretical optical plane being non-parallel to at least one of optical axes of a telescope, said conical ring having a diameter defining a wide detection field and computing means recovering the data captured by each optical detector of the telescopes of the first set, said calculation means making it possible to process the various captured data by the electronic detectors of the first set to deduce at least one trajectory of a mobile whose orbit passes through the conical crown.

All the embodiments of the optical system of the invention are compatible with an open geometrical shape which results from the intersection of a plane of space with all the fields of the telescopes of the system of the invention.

Advantageously, the optical system comprises at least one telescope whose field is defined inside the ring.

Advantageously, the electronic detector is a CCD camera, EMCCD, a CMOS or sCMOS detector or an infrared detector or any type of detector allowing the acquisition of images of the sky.

According to one embodiment, the optical system comprises at least 10 telescopes having fields substantially close to 3 ° in a conical ring whose diameter covers a field of 30 °.

According to another embodiment, the optical system comprises at least 15 telescopes having fields substantially close to 2 ° in a conical ring whose diameter covers a field of 30 °.

According to another embodiment, the optical system comprises at least 15 telescopes having fields substantially close to 10 ° in a conical ring whose diameter covers a field of 60 °.

According to one embodiment, the optical system comprises at least 10 stations arranged on the surface of the Earth each comprising at least one detection telescope, the optical system comprising:

• At least 3 to 4 stations substantially close to an equatorial latitude distributed in longitude; • at least 3 stations substantially between latitudes 30 ° and 55 ° North and South, divided into longitude and latitude;

• at least 2 stations beyond latitudes of 60 °.

One advantage of this configuration is that it allows the entire sky to be covered from a given number of telescopes. This configuration can benefit from multiplexing so as to cover the entire sky with a high probability of detection.

One or more telescopes may be associated with this configuration, in particular to correct the measurements or to track a target.

This configuration can be associated with a table of brightness corrections and shooting differences between the various telescopes.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will emerge on reading the detailed description which follows, with reference to the appended figures, which illustrate:

^■ Figure 1: a telescope system of the invention for defining a coverage area for the detection of space mobiles;

^■ Figures 2A, 2B: a conical crown and different cutting planes defining circular or elliptical rings in which a distribution of fields of view is defined by the method of the invention;

FIG. 3: a first configuration of distribution of different scanning zones for the detection of space mobiles forming part of a geometric shape in an average image plane;

^■ Figure 4: a second configuration different areas covered for the detection of space mobiles forming a geometric shape in a medium image plane;

^■ Figure 5: a graph showing different portions of orbits views by a given field of the telescope; ^■ Figure 6A, 6B, 6C: different distributions telescopes fields generated from the multiplexing method of the invention. DESCRIPTION

The invention relates to a method for detecting at least one mobile space and a system for its implementation.

Figure 1 shows an embodiment of the invention. A telescope system T is formed. The telescopes are distributed over three geographical sites called "stations" and denoted ST, ST ₂ , ST ₃ . As will be detailed later, a distribution of telescopes in stations distant from each other by a certain distance makes it possible to detect the positions of the mobile in height and to deduce a 3D trajectory.

In the example of FIG. 1, the first station ST-ι comprises 4 telescopes denoted Tu, T ₂ , T ₃ , T ₄ , the second station ST ₂ comprises 4 telescopes denoted T ₂ , T ₂₂ , T ₂₃ and T _24. . The third station ST ₃ comprises two telescopes T ₃ and T ₃₂ and a third telescope called "tracking telescope TS".

Telescopes whose fields form a geometric shape, such as a conical crown, are referred to as "detection telescopes" in the present description.

The three stations ST, ST ₂ , ST ₃ are located in a region making it possible to obtain substantially the same atmospheric conditions and meteorological observations. A distance between two stations can be of the order of a few hundred meters to a few kilometers. An inter-station distance of 10km makes it possible to obtain a configuration making it possible to implement the method of the invention with good results in order to deduce 3D trajectories for all the orbits monitored by the meta-telescope. In addition, in some embodiments, the stations may be co-located so as to be located within a few meters of each other. Different configurations can be envisaged so, for example, to have stations close to each other and others more distant according to the design choices and the performance of the system to be achieved.

According to one embodiment, all the telescopes are in the same station. The system and method of the invention are not restricted to a limited number of stations. In one embodiment, each telescope is identical to the others, however this is not a necessity to implement the method of the invention. The system may include different telescopes of different natures. By way of example, the optical system, its spectral sensitivity (wavelengths), the frame, the lenses or the fields may possibly vary from one telescope to another. For a better understanding of the invention, the following description is detailed taking into consideration a plurality of identical telescopes whose individual fields are substantially the same.

Each telescope of the invention therefore comprises a given field, for example in one embodiment, each telescope Ty comprises a field substantially of 3 ° taken in its diameter.

The system formed by all the telescopes of the various stations is called a "meta-telescope". The invention makes it possible to configure a part of the set of telescopes Ty so as to define a distribution of fields forming part of a predefined geometric shape. Figure 1 shows a geometric shape defining a conical ring called CC. The geometric shape can be defined in 3-dimensional 3D or two-dimensional 2D. FIGS. 2A, 2B show in a first approximation the conical crown CC as well as sectional planes Pce substantially perpendicular to a median optical axis Acc. The stations being close to each other, they can be likened to a point on the surface of the earth as a first approximation for the representation of the conical ring CC comprising all the cones CC _kp corresponding to the fields of view of each telescope T _kp . The conical ring CC can therefore be understood as a surface forming an ellipse or a circle around the median optical axis Acc. The conical crown CC can also be understood as the volume formed by the set of optical fields Z _kp contained in the cones CC _kp of each telescope T _kp . The volume thus formed substantially corresponds to a 3D conical crown, as shown in FIGS. 2A and 2B, at the deviations near geographical positions of the telescopes in the stations vis-à-vis the median optical axis Acc.

Figure 2A shows the conical crown CC when the meta-telescope is oriented at Zenith. Figure 2B shows the conical crown CC when the meta-telescope is oriented at a given elevation, approximately 35 °.

FIG. 2A illustrates two telescopes T ₄ and T ₃₂ spaced apart by a distance d (T ₄ , T ₃₂ ) each having a field Z ₄ and Z ₃₂ forming part of the conical crown CC from a certain altitude. It is considered that from a certain altitude, a cone CCi ₄ corresponding to the field of view of a telescope T ₄ is inscribed in the conical ring CC in 3 dimensions. As a first approximation, the cone CCi ₄ can be considered as part of the theoretical conical ring whose axis of revolution is the axis Acc.

The Z ₄ and Z ₃₂ fields of each telescope T ₄ and T ₃₂ are respectively in CCi ₄ and CC ₃₂ cones. In the remainder of the description, the method of the invention describes in one embodiment how the distance d (T ₄ , T ₃₂ ) inter-telescope is used to calculate the altitude of the mobile and the height inclination of the trajectory of the latter.

Figure 2B illustrates that the meta-telescope field, when tilted with a given elevation, can cover a larger area of the sky than the area covered when pointed at the zenith.

The traces detected in each telescope field make it possible to deduce an inclination of the trajectory of the mobile.

Each field of each telescope is therefore part of this conical 3D ring whose apex is for example an average position of each telescope on the surface of the earth. In FIG. 1, the fields of each telescope represented are denoted Zn, Z ₂ , Z ₃ , Z ₄ , Z ₂ , Z ₂₂ , Z ₂₃ , Z ₂₄ , Z ₃ , Z ₃₂ . The fields are distributed so as to be uniformly distributed in a section of the conical 3D crown or in the 3D crown itself. However, the invention is not limited to a given distribution in the conical ring CC and it can implement different distributions for example whose fields are not uniformly distributed.

We consider the trajectory TJ _S AT of a satellite SATV In this case the mobile Mi is a satellite SAT- | . Four positions on the trajectory TJ _S AT are illustrated in Figure 1: POS _1; POS ₂ , POS ₃ , POS _t .

In this example, it is considered that the trajectory TJ _S AT of the satellite SAT-ι, for example flying over a low orbit, intercepts the CC conical crown intercepting two Z ₃ and Z ₃₂ fields from two telescopes T ₃ and T ₃₂ . There are two positions in FIG. 1: POS i and POS ₂ which illustrate these interceptions.

A position of the satellite denoted POS ₂ is located inside the conical ring CC and is thus not detected at this position by a telescope of the meta-telescope in the configuration of FIG. We shall see in particular in the light of FIGS. 3 and 4 that complementary telescopes Tc at the telescope detection telescopes T _kp can enable detections inside or outside the conical ring CC, but these are not present in Figure 1. Finally, a fourth position denoted POS _t is SAT-i satellite which is followed by a tracking telescope noted TS ^. Note that the detection of the mobile in two points allows to know its existence and to have a trajectory vector. When the orbit is circular, two points are enough to know all the parameters of the orbit.

In this example, the tracking telescope TS ^ is arranged in the third station TS ₃ . The tracking telescope TS 1 is a telescope which may optionally be integrated with the meta-telescope of the invention in one embodiment. It can also be one of the detection telescopes not actively participating in the current detection. Finally it can be a telescope implementing another measurement method, for example active, as a LIDAR. Nevertheless, the invention is not restricted to the use of such a tracking telescope which allows an improvement of certain measurements in certain configurations of mobile orbits passing through the conical ring CC. The tracking telescope makes it possible to continue the assumed trajectory of the satellite detected SAT-ι outside the conical crown CC. In FIG. 1, the tracking telescope TS 1 makes it possible to track the satellite SAT-1 after its trajectory has intercepted the conical ring CC.

The tracking telescope may be coupled to a telescope for detecting the meta-telescope, for example, by offering the possibility of tracking the mobile previously detected by the detection telescope outside the conical ring CC. A tracking telescope can therefore obtain a more precise orbit or trajectory retrieval by obtaining other traces detection or intermediate points of passage of the mobile inside or outside the conical ring CC.

In one embodiment, a plurality of tracking telescopes can complete a configuration of the meta-telescope.

The method of the invention makes it possible to define a filling factor of the conical ring CC. This filling factor makes it possible to deduce a probability of intersection of a trajectory of a mobile with fields of telescopes distributed in the conical crown CC, we also speak of completeness factor.

In one embodiment, the method of the invention may optionally take into account a factor intended to define a minimum mean travel angle of the path of the mobile to rule out all the trajectories comprising acute angles and / or corresponding to no trajectory possible to a space mobile, except consider for example the turns made by an ultralight which represents a particular embodiment of the invention. Note that a single detection at the entrance of the crown allows to deduce the first elements of the trajectory of the mobile.

Taking into account a minimum angle corresponding to a minimum curvature of the trajectory can be used to finely calculate the probability of a detection of a meteorite passing through the conical crown CC.

In the example of FIGS. 1 and 3, the field distribution makes it possible to obtain a filling ratio of 50% to 60% of the conical ring CC. However, the detection rate of a trajectory can be greater than 80% since each trajectory intercepting at least once the conical crown intercepts it a second time. Therefore, for a path is not detected, it must avoid two fields distributed in the conical crown CC. It is here an advantage of the invention that makes it possible to define a geometrical shape adapted to optimize the ratio between a given field filling rate and a maximum mobile detection rate corresponding to this field distribution and to the family of orbits or the type of mobiles studied.

In the example in which the fields are substantially equal to 3 ° with 10 telescopes, the angular area actually perceived is 472 deg ² . The meta-telescope thus makes it possible to monitor the equivalent field of a single telescope of the same pupil but with a field of 24 °.

It is an impact factor calculation calculated with the sum of the projections of the circles in any direction. In the example of Figures 1 and 3, the geometric shape is a circle. The projection of each circle corresponding to the field of each detection telescope projected in one direction, eliminating the overlaps, makes it possible to obtain the proportion of the covered area formed by the diameter of the field obtained by considering the diameter of the meta-telescope. We consider this diameter D obtained with the following opening angle: 30 ° + 3 ° / 2 + 3 ° / 2 = 33 °. In this case, we find that the impact factor is 6x3 ° / 32 ° = 55%.

In spherical geometry the angular surface on the sky is given by A (ster): 2-pi- (1 -cos (Theta / 2)) where theta is the opening angle of the cone. In square degrees: A (deg ² ) = 20626.5- (1 - cos (theta / 2)).

So for 33 °, A = 850 deg ² . Either 55% of A corresponds to 467 deg ² .

This surface corresponds to the surface covered on the sky by a cone of 24 ° diameter. It would take a telescope equivalent to 24 ° field: such a field is typical of a camera lens, but is very difficult to achieve for a telescope larger diameter.

The method of the invention makes it possible to define a configuration of the meta-telescope determining a given field distribution in a conical ring CC so as to obtain a probability of detection of a spacecraft intercepting the conical ring CC. The method of the invention makes it possible to define a fraction of the sky observed to define a detection zone with which a probability of detection is associated. This probability of detection can be adjusted according to the number of telescopes of the meta-telescope defining fields in the crown, their distribution as well as the size of their field.

An advantage of the detection method is to have telescopes with reduced fields typically less than 5 °, or even limiting them to fields of the order of 1 ° to 3 ° while having good detection rates. mobile devices associated with these telescope choices and a oversized field wider than would have been possible with a monolithic large-field telescope.

The conical crown CC makes it possible to cover a portion of the sky that can cover a wide field, for example slightly greater than 30 ° according to the configuration of the meta-telescope of FIGS. 1, 3 and 4.

Figure 3 shows a section of a conical crown CC forming in a plane a circular crown. Depending on the configuration envisaged and the area of the sky pointed, the conical crown 3D can form different conical shapes such as ellipses most often, but it can also form as shown in Figure 3 a circular crown.

In this example, the distribution of the Z _kp fields of the telescopes T _kp substantially respects the distribution illustrated in FIG. 1, in which 10 telescopes have a field substantially of 2.75 ° -3 ° which fits in the conical ring CC. The diameter formed by the conical crown CC is substantially close to 30 ° -32 ° field, which covers a significant fraction of the local sky.

In another configuration, 15 telescopes of 2 ° of field can register their field in a crown of 30 °. According to yet another configuration, 15 telescopes of 10 ° field can enroll in a conical crown CC whose diameter is in a 60 ° angle. According to yet another example, 15 telescopes of 1 ° of field can enroll in a conical crown CC whose diameter fits in an angle of 15 °.

The number of telescopes T _kp , the choice of their field of view for each telescope, the geometric shape chosen to cover a fraction of the sky and the distribution of the fields of view in said geometric shape make it possible to define a probability of detection of a mobile intercepting the geometric form. This probability can be adjusted by one of the following parameters: dimensions of the geometric shape, field of each telescope, number of telescopes and distribution of telescopes in the geometrical form, considered orbit family (equatorial, polar, elliptic, etc.). ). In this example, three complementary Tcy telescopes covering three z fields inside the conical crown CC have been associated with the peripheral fields Z _kp of the detection telescopes T _kp . Tcy complementary telescopes can be used in different ways that can be complementary:

or, they make it possible to increase the probability of detecting trajectories not covered by the distribution of the fields in the conical ring CC by increasing the coverage of the theoretical field contained in the diameter of the conical ring CC;

- Or, they can track the target detected by a first telescope by performing a tracking operation, or tracking in the English terminology; in the latter case, it is a tracking telescope as previously introduced;

- Or they allow to obtain complementary measurements, for example to better characterize the mobile, as the measurement of the polarization of light, its spectrum, its infrared signature, its reflectivity to a laser, etc.

The fields of the Tcy complementary telescopes and / or of the Tsy monitoring may be different from the fields of the detection telescopes T _kp . In particular, they may be lower for example in the case of a tracking telescope and may be higher when it comes to complementary telescopes internal to the crown to increase the total detection field.

Complementary telescopes or tracking telescopes may have identical or different pupil diameters from those of detection telescopes. These can be configured on other frequency detection bands and thus detect other wavelengths emitted by the mobile. Finally, a tracking LIDAR device can be used in conjunction with the system of the invention to enable the orbit derived by the "meta-telescope" and possibly its tracking telescopes to be refined with great accuracy. FIG. 3 illustrates a trajectory TJ _S AT intercepting a first peripheral field Z _KP , a central field zy and a second peripheral field Z _KP . A trajectory of a satellite TJ _S AT offering the best detection configuration has therefore been represented in FIG.

In this case, the method of the invention makes it possible to obtain at least

3 traces as we will detail later, including at least one trace in each field Z _KP , zy.

FIG. 3 makes it possible to represent the angles of opening of the field covered by the diameter of the "theoretical" optics formed by the meta-telescope on a first axis DEGi: North-South and a second axis DEG ₂ : East-West. Other repositories for defining the observed fraction of the sky can be used. FIG. 3 shows that the diameter of the conical crown CC makes it possible to reach a little more than 30 ° on the first axis DEGi and a little more than 30 ° on the second axis DEG ₂ .

FIG. 4 shows a case in which the conical ring CC is entirely covered by a plurality of fields of different detection telescopes T _kp , approximating the position of the stations around the theoretical median optical axis Acc. Depending on the opening angle of the conical ring CC, that is the angular width of the band forming the ring, and its diameter a minimum number of telescopes T _kp is defined as being able to cover the entire crown conical CC.

In the example of FIG. 4, a telescope has approximately 2.75 ° of field along one of the angular axes DEGi or DEG ₂ . The conical ring CC has a diameter of about 32 °. 34 telescopes generate as many fields as possible to fully cover the conical crown CC. In this case the meta-telescope can monitor substantially 808 deg ² of angular area.

Similarly, a 30 ° diameter conical crown with 3 ° field telescopes would require about 30 telescopes to substantially cover all of the positions of a CC conical crown plane above a certain altitude, cf. Figures 2A, 2B, 850 Deg ² of angular area. The geometrical shape obtained by the meta-telescope can be adapted according to the cases and the orientations of selected observations. For example, an ellipsoidal crown allows the surveillance of a greater part of the equatorial belt than a circular crown more adapted to observe a zone at the zenith. An advantage of the flexibility of the configuration of the geometrical shape obtained by the meta-telescope is to make it possible to form other fields than circular fields. Indeed, an individual telescope can not generate an ellipsoidal field because circular optics and rectangular detectors are generally used. The meta-telescope of the invention thus makes it possible to generate fields forming a geometry adapted to a detection of mobiles which is optimized according to the line of sight with respect to its elevation, and according to the family of orbits studied. For example, for an elevation of 30 °, the meta-telescope provides a covered area that can be optimized by a suitable geometric shape such as an ellipsoid whose dimensions will be configured to maximize the detection rate of mobiles in the space.

According to one embodiment, the geometric shape may comprise a plurality of lines or two curves substantially parallel to each other. The thickness of the lines or curves corresponds to the field of a detection telescope. The distribution of the fields can form for example a checkerboard between the different lines. Any other distribution is possible.

In another configuration, the geometric shape may comprise a series of arcs of circles or ellipses whose width corresponds to a field of a detection telescope. The meta-telescope is then configured to distribute, according to a given distribution, fields of view of detection telescopes in these arcs. According to one embodiment of the invention, the intersection of a plane of the space and of all the fields of the telescopes of the system of the invention defines an open geometric shape. An open geometric shape is then called a shape in which certain zones are not covered by the telescope field of the system of the invention. An annular shape falls into the category of open geometric shapes. A global field whose intersection with a plane of space gives an ellipsoidal band is also an open geometric form. Other cases may be made according to the method of the invention as a geometric shape of diamond or square type in which the fields of the telescopes are distributed according to the device of the geometric shape.

FIG. 5 represents different portions of different mobile orbits perceived by the meta-telescope of the invention, or by any other given field instrument, when the observation takes place at the zenith as a function of the meta-telescope field or a large field telescope.

Consider the orbit noted Alt (0 ₃ ) which is an orbit at 2000km, the graph allows us to see that for a field of 5 ° of the meta-telescope or a large-field telescope, a portion of 1 ° of the orbit of the mobile is perceived. On the same curve, it is understood that for a field of 35 ° typical of the meta-telescope, a portion of about 10 ° of the orbit of the mobile is perceived. The field of the meta-telescope is noted FOV on the abscissa axis of the graph.

Identically, considering the orbit of a mobile Alt (0 ₄ ) located at 5000 km, a portion of 25 ° of the orbit of the mobile can be seen on a field covered by 35 ° by the meta-telescope.

For low orbits, the local horizon of the site will cause a small portion of the orbit or trajectory to be perceived. For example, the mobile orbit rated Alt (O-i) at 500 km provides only a 2.5 ° portion of the trajectory for a 35 ° meta-telescope field. However, for a telescope with a very large field of 10 ° will only see 0.7 ° of this same orbit.

The optics of each telescope of the meta-telescope can be adapted and selected to meet a specific need. Thus, it is possible to use specific filters and to accentuate detections at different wavelengths such as the bands in the visible, the infrared, the ultraviolet or more particular frequency bands from spectroscopy of the received luminous flux.

A telescope of detection of 600mm of focal length makes it possible to obtain a field of about 3 ° on a detector of the type CCD of 3cm of side. Such a telescope of detection has the advantage of being simple and inexpensive. Each telescope of detection can be coupled to an electronic detector such as a camera of 3cm of side.

The field of a telescope is entirely governed by its focal length F and the size of the detector X. The field can be given by the following equation FOV = Arctan (X / F).

A field calculation for a focal length of 600mm and 3cm for the detector gives 2.86 ° field. Depending on the optical configuration, it may be necessary to integrate an optical corrector so as not to limit the field.

For example, in the case of a 600mm focal length telescope with 6 ° field, it is necessary to have a 6cm detector. Such a detector is expensive. In addition, the optical scheme that supports 6 ° field is complex to implement.

A parameter representative of the feasibility of a telescope is the ratio of the focal length to the diameter: F / D.

A ratio of F / D = 0.5 represents a theoretical limit because it corresponds to the center of a sphere. In practice, to go below a ratio F / D = 3 it is necessary to define specific optics. This can be achieved relatively easily up to a ratio of F / D = 2.5 or 2 for instruments not too bulky, beyond the difficulty and residual aberrations are a brake to the design of such optics .

Each telescope T _kp of the meta-telescope is coupled to an electronic detector. Such a telescope is then called a "telescope of detection". We will talk about a telescope detection most often evoking its coupling to an electronic detector that collects trace data by analyzing a pixel area changing state over a given period of time. In addition, complementary telescopes and tracking telescopes can also be coupled to electronic detectors.

The electronic detector can be a CCD camera, EMCCD, CMOS detector, sCMOS, infrared detector, or any other suitable detector. In one embodiment of the invention, the electronic detectors have a reading time between 1 s and 5 s. The detectors allow to generate images with fixed or variable rates. The reading rate can be adjusted to first detection indices so as to adapt a better detection according to the type of mobile moving in space.

The meta-telescope of the invention makes it possible to configure the exposure time and the rate of shots of each electronic detector so as to respond to a given configuration.

By way of example, according to the embodiment of FIGS. 1 and 3 with 10 telescopes and a field of each telescope of about 3 °, a rate of 3s can be configured and a reading time of 1s. The following table is presented for a mobile with a low orbit of 500km:

- A: Scroll speed of the mobile;

- B: crossing time of the meta-telescope whose diameter of the geometric shape covers a field of 30 °;

- C: crossing time of the telescope of detection of the meta-telescope whose diameter of the geometrical shape covers a field of 3 °;

- D: crossing time of one pixel of 15 micron, or 5.3 ";

- E: crossing time of a pixel of 5 micron, or 1, 5 ";

- F: crossing time of a telescope with a very large field of 10 °.

It is understood that the worst case is obtained for a running speed of 3000arcsec / s: the crossing time of the field of a detection telescope will be 3.6s. This duration will offer the possibility of recording only one trace on the electronic detector. But in the majority of other cases, the electronic detector can measure at least two traces. Two traces make it possible to deduce trajectory data more quickly. However, a second trace will be acquired after 36s by the second telescope at the exit of the monitored zone, which is a much more favorable case both for the measurement accuracy (and thus the restitution of the orbit) than for the management of the system. as the system with a very large field telescope, as seen by comparing columns B and F.

The meta-telescope includes a computer and data storage means for processing all the data collected by each detection telescope, each complementary telescope or tracking each station. One advantage is to enable the activation of, for example, a tracking telescope following detection of a trace of a detection telescope.

When a trace is detected, the computer makes it possible to perform correlation measurements with a possible second trace detected in order to derive parameters from it on the trajectory of the mobile.

Another advantage is to correlate the data from different detection telescopes so as to reconstruct orbits having intercepted the meta-telescope field at different locations of the geometric shape, that is to say the conical ring CC.

Another advantage is to be able to deduce from the direction and velocity information given by the first trace analysis the best position for detection by a second telescope of the system, thus enhancing the probability and accuracy of the measurements, thanks to dynamic management of the system.

The comparison of "test" traces detected by different telescopes taken individually also makes it possible to reinforce the calibration of these and the adjustment of the detection threshold configurations of each and of the entire meta-telescope.

In addition, mobile trace data captured by an electronic detector can be stored to initiate new observations in the same configuration of the meta-telescope to derive an orbit from different passes of a mobile. In one embodiment, a feedback loop is used to refine the observations and the calculation of the trajectory of the mobile and to foresee possible future passages.

Finally, in one embodiment, the meta-telescope comprises means for connecting its various elements to a network so as to drive and exploit the data collected remotely. The network connection can be made wired or wireless. In a particular embodiment, a connection to a satellite can be envisaged for the implementation of the invention. When at least one trace is detected by a first detection telescope and at least one trace is detected by a second detection telescope, it is then possible to deduce the trajectory and direction parameters of the mobile by correlating the data of these two traces.

When at least two traces are detected by a first telescope, it is then possible to deduce the trajectory and direction parameters of the mobile by correlating the data of these two traces.

When a single trace is detected by a first telescope without a second telescope of detection or telescope internal to the conical crown CC detects a second trace, a tracking telescope can be activated to obtain a second trace on a supposed trajectory of the mobile. The case of a detection generating only a single trace can occur according to:

- the distribution of the fields of the telescopes in the conical crown CC;

- the trajectory, the speed of movement and the altitude of the mobile.

The speed of travel of a satellite and the speed of movement of this satellite are related so that one can be deduced from the other in knowledge of the altitude or the orbit of the satellite.

The data collected by the tracking telescope can be correlated with the data of a telescope of detection to deduce trajectory and direction parameters of the mobile in space. In any case, a tracking telescope can be triggered since it is not known a priori if the orbit of the mobile will intercept another field of a detection telescope included in the conical crown CC. According to one embodiment, the meta-telescope enables the telescopes to be made removable:

or to reconfigure a new geometric shape according to a given point of aim;

- to target another fraction of the sky with the same geometric shape;

or to track a mobile detected by a tracking telescope previously detected by at least one detection telescope.

- To modify the distribution of detection telescopes in the geometric form from a multiplexing function; - or to adapt a telescope of detection to a tracking telescope by allowing the movement of its line of sight to pursue a mobile

or to compensate for a sidereal movement so as to render the stars fixed on the images captured by the detectors.

These different possibilities can be combined.

In these embodiments, the meta-telescope includes movable mounts for each of its telescopes or a part thereof.

In one embodiment, the mobility of the meta-telescope enables sidereal tracking. This configuration makes it possible to obtain that the stars are seen in point form and the mobiles in the form of traces. This solution has the advantage of directly observing the traces of mobiles moving through the meta-telescope field in the images captured by each detector.

When the meta-telescope is fixed, it is necessary to discriminate traces of mobile captured traces of stars from the sidereal movement of the earth. This discrimination can be achieved by digital processing. The digital processing can be automatic when the traces of the mobiles can be deduced for example by comparing their length on the sensors of the detectors or by an analysis of the brightness captured by studying their radiometry. The detection thresholds can be configured according to the illumination of a set of pixels. A calibration of the brightness of the stars can be performed beforehand to make mobile trace detection more efficient.

Finally, the meta-telescope can be made removable to map large areas of the sky by juxtaposing broad fields of 30 ° to 40 ° on a given region of the sky.

The meta-telescope of the invention makes it possible for the detection of traces by the electronic detectors of the timestamps. The measurements are thus dated with a precision, for example of the order of a millisecond or a microsecond, depending on the type of detector. A GPS map can be used for this purpose.

The time stamp also makes it possible to deduce parameters of the trajectory and the speed of movement of the mobile, in particular by comparing two successive traces left by the same mobile.

One embodiment for the detection of traces is the implementation of the Hough transform. This transform makes it possible in particular to deduce parametric coordinate vectors from the plane lines generated by the traces of a mobile on the electronic detector.

In order to speed up calculations, different hardware resources can be used, such as multi-core processors or GPU (Graphical Processing Unit) cards.

According to a particular embodiment of the invention, the meta-telescope comprises a configuration called "multiplexing configuration". In this multiplexing configuration, certain telescopes are controlled so that their field evolves in the conical crown. The control of the displacement of the fields in the conical crown CC can be programmed automatically so that a field travels a portion of the conical crown CC in a given time or makes "leaps" at different points of the conical crown CC. An advantage of this solution is to allow to observe portions of the crown conical CC not covered by a field of a telescope at regular intervals.

In such a configuration, the switching time of a field of a detection telescope covering a first zone to a second zone and then returning to the first zone can be calculated so as not to miss a trace of a mobile for a second time. maximum scrolling speed given and a given altitude.

A particular configuration allows with a given number N _T telescopes, not allowing to cover alone in a fixed position the entire conical crown CC, to ensure by a multiplexing configuration the completeness of the conical crown CC. The completeness of the conical crown CC can be likened to the notion of "filling ratio" previously used considering a given period of time during which different positions of the fields in the conical crown CC will allow to cover all positions not initially covered.

If N _c denotes the number of telescopes necessary to obtain the completeness of the ring, we obtain the completeness factor of the conical ring: Y = N _T / N _c .

We deduce a multiplexing factor k = nint (1 / Y) natural integer.

In this case, the method and the system of the invention make it possible to define a position of the optical axis AO (T) of a detection telescope Ty or a plurality of meta-telescope detection telescopes so as to what they cover k positions in a certain period of time, noted t _k .

In the example of Figure 3, only 10 telescopes partially cover the conical crown CC by their field. In the example of Figure 4, it is necessary to have 34 telescopes to cover the entirety of the same conical crown CC.

In this case, the completeness factor is about 0.3, the multiplexing factor is nint (3.4) = 4. The multiplexing factor gives the number of minimum position changes of each telescope to cover all the potential field of the conical crown CC.

The simplest multiplexing configuration is that each telescope of the case of Figure 3 switches to 4 different axial positions. According to the configuration modes, each telescope can perform a circular permutation so as to traverse a corner portion of the conical crown CC before returning to its initial position. Another possibility is that each telescope points a portion of the circular ring among 34 possible positions in the example of FIG. 4 and this within a determined period of time t _k .

The method of the invention allows to configure an optimized duration t _k so that any mobile intercepting the conical crown is detected from a minimum threshold altitude and a maximum scrolling speed defining a threshold.

Taking again, the example of the table previously evoked time of crossing of a mobile for a configuration of a meta-telescope of 30 ° of diameter equivalent to a corresponding field and telescopes of 3 ° of field, for a zenith observation with an orbit of 500km, the meta-telescope traversal time is 36s and a 3.6s telescope field. By performing a change of position every 1 s, assuming that it takes 1 s to make this change, the method of the invention allows to fill 2/3 the condition of completeness. However the result obtained is equivalent to a meta-telescope of 20 telescopes. This equivalence shows an advantage of the present meta-telescope with respect to current solutions that require many optical means to cover a wide field.

In the case of an observation at 30 ° with the scrolling speeds given in the table above, and changes of positions every 2s with an additional time of 1 s of change time, the meta-telescope in a multiplexed configuration allows to obtain a completeness of the conical crown CC.

FIGS. 6A, 6B and 6C represent three distributions applied to the circular geometrical shape represented in FIGS. 3 and 4. A first distribution R-ι is represented in FIG. 6A, a second distribution R ₂ is represented in FIG. 6B and a third distribution R ₃ is shown in Figure 6C. To pass from the first distribution R-ι to the second distribution R ₂ , each detection telescope drives a movement of its optical axis Ao (T) so that its field remains integrated in the conical ring CC. This movement is noted Rot (0) and represents a center rotation the conical crown CC in a clockwise direction by a predetermined angle Θ. The movement of the optical axis Ao (Ty) of each detection telescope Ty makes it possible to generate a movement of the optical field of each detection telescope Ty forming part of the ring of the conical crown CC. Similarly, to move from the second distribution R ₂ to the third distribution R ₃ , each detection telescope drives a movement of its optical axis Ao (Ty) so that its field remains integrated in the conical ring CC while continuing the rotation rot (0).

In this example, a fourth distribution corresponds to the first distribution R- | . Indeed, a movement of the optical axis Ao (Ty) of each detection telescope Ty to change from the third distribution R ₃ to a new distribution in the continuity of the movement of the fields inscribed in the conical crown CC of the rotation Rot ( 0) would lead to the first distribution.

The rotational movement Rot (0) in the conical ring CC is configured so that two successive distributions do not overlap. Consequently, the circles formed by the fields of the telescopes on two successive distributions can be, for example, substantially juxtaposed so as to obtain a maximum degree of completeness of the conical ring CC.

Thus in this example, the three distributions may result in substantially covering the area formed by the conical crown in a given time window. The given time window can be sized to intercept any mobile whose trajectory intercepts the conical crown CC from a minimum altitude and below a maximum scrolling speed.

The control of the optical axis Ao (Ty) of a telescope Ty can be performed by the detection telescope Ty itself or by a motor means coupled to said telescope or a motor means whose control is performed by a centralized means to all telescopes. These embodiments are also possible with other telescopes than detection telescopes. An advantage of the multiplexing configuration is to increase the probabilities of intercepting a trajectory of a mobile with the conical crown CC. This advantage is even more convincing for low orbit covers at a 30 ° elevation.

When the meta-telescope covers a geometric area such as a conical crown CC a multiplexing configuration can be combined with a sky scan which is performed by juxtaposing the geometric shapes with each other by a displacement of said geometric shape in the sky .

According to a configuration of ST stations, ST ₂ , ST ₃ on the ground and distances separating them to each other, the angles corresponding to the fields of the different detection telescopes will be slightly different. This is illustrated in Figure 2A which shows two telescopes T ₄ and T ₃₂ spaced apart by a distance d (T ₄ , T ₃₂ ).

A pseudo-parallax will be induced by the angle difference of the different optical axes A ₀ (T ₄ ) and A ₀ (T ₃₂ ) in the measurements of the traces of a mobile traversing different fields.

For a mobile orbit of 500km, a distance of 100m between two stations corresponds to a parallax of 40. Taking the previous example of the table showing the different running times of a mobile in a low orbit with a size of 5.3 "pixel, the parallax is detectable.

The measurement of the parallax makes it possible to deduce a position in height of the mobile and makes it possible to measure a displacement of the mobile in a reference frame in 3 dimensions.

As a result, the meta-telescope of the invention makes it possible, according to a particular configuration, to dimension the spacings between stations so as to produce a parallax in the detections of traces in order to extract a datum relative to the altitude of the mobile.

For a geostationary orbit, a distance of 1 km between two stations with at least one telescope each, the parallax is about 5 "on the sky, so a distance greater than 1 km seems to offer a better configuration to deduce a parallax if necessary at these altitudes. The size of the pixel for 3 ° telescopes makes it possible to detect this order of parallax when they are greater than 5. To correlate the parallax measurements between the fields of two detection telescopes having detected a mobile, the correction can be introduced. to correct the error related to the distance traveled by the mobile between the two fields intercepted.The correction can introduce a simple linear method to deduce a position in the absence of parallax.An analysis of the differences of a theoretical position in the absence of parallax and a real position measured on a field, the parallax of the mobile can be deduced by a calculation of this difference.The parallax makes it possible to deduce a height, that is to say the altitude of the mobile.

The position of the mobile in the second field will be a combination of its predicted position from the calculation of its movement speed and the distance traveled and the parallax of the mobile. The difference between the predicted position and the real position in the field of the second telescope will make it possible to deduce an angular parallax of the mobile and thus its height by calculating the tangent.

According to one embodiment, the meta-telescope comprises a configuration allowing a complete monitoring of the space, in particular mobiles flying over the orbits of low altitudes (LEO).

For this, a dozen stations can be distributed at different longitudes / latitudes.

An example of distribution to cover low orbits includes:

• 3 to 4 stations near the equator;

· 3 stations at temperate latitudes (eg latitude of

France) and;

• 2 stations near each pole.

To cover the geostationary orbits, 3 to 4 stations substantially located near the equator are sufficient. The complete monitoring of the space can thus be carried out from a set of stations distributed at different latitudes and longitudes on the Earth defining a complete meta-telescope.

One of the advantages of this embodiment is the modularity and the possibility of reproducing its components of each station which allow an easy installation in a large number of sites. Another advantage is to be able to offer a complete coverage of the space at a lower cost because each element of the meta-telescope is identical. A management system, management and processing both distributed and centralized can be implemented in this embodiment.

Telescopes of the meta-telescope can be powered by a power line or a diesel generator. Consumption being reduced the invention can be combined with local sources of renewable energies such as wind, the sun, or a micro-hydroelectric source, etc. Advantageously, they can be compact and have a volume of less than one meter. When the telescopes are identical, the system includes the possibility of reproducing a configuration in a station identical to another station and provides a very economical meta-telescope.

The meta-telescope of the invention can be used according to different possibilities of detecting mobiles depending on the nature of the mobile. Thus the meta-telescope can be adapted and / or configured for detecting ULM, aircraft, missiles or mobiles in suborbital flight.

In particular, for an aircraft flying at 10 km altitude at a travel speed of 800km / h, the crossing time is:

^■ 23s for the field of a meta-telescope of 30 °;

^■ 2s for the field of a telescope of 3 ° detection of the meta-telescope.

In addition, according to some embodiments, special optical filters may be associated with the telescopes and the electronic sensors according to the day and night configurations and the type of aircraft. The methods of the invention and the meta-telescope of the invention allow a simple configuration of a set of telescopes to construct a geometric shape covering a wide field.

The method of the invention makes it possible to reduce the number of telescopes generally used to cover a wide field. A probability of detection can be adjusted in different ways by the individual control of each telescope constituting it and by controlling the assembly:

- Adaptation of the meta-telescope field;

- Adaptation of the shape of the meta-telescope field;

- Adaptation of the number of telescopes and the rate of completeness;

- Adaptation of the number of complementary telescopes and tracking;

- Adaptation of the multiplexing of the field distribution of each telescope of the meta-telescope.

Accordingly, the meta-telescope of the invention provides configuration adaptive flexibility to detect moving space moving in a wide range of orbits and in a wide range of travel speeds.

Claims

Method for detecting a mobile in space, characterized in that it comprises:

A generation of a plurality of fields of view (Z _kp ) by means of a first set of telescopes (T), each telescope defining a detection telescope, the set of fields (FOV) of each telescope (Ty) having a spatial distribution in at least one plane of space in an open geometric form (CC), said open geometric form (CC) defining a wide detection field;

• a deduction of a trajectory (TJSAT) of the mobile (M-i) in the image plane of said telescope (Ty).

Method for detecting a mobile in space according to the claim

1, characterized in that the open geometric shape is a section of a conical crown (CC).

Method for detecting a mobile in space according to the claim

2, characterized in that the conical ring (CC) is defined with respect to a theoretical median optical axis (A _cc ), the theoretical median axis (Acc) being determined so that at a given minimum altitude, each field of each detection telescope (Ty) of the first set is included in the conical crown (CC).

A method of detecting a mobile in space according to any one of claims 2 to 3, characterized in that the The spatial distribution of the fields (FOVy) of each detection telescope (Ty) is determined with respect to a desired probability of detecting a trajectory (TJ _S AT) of a mobile (Mi) intercepting the conical ring (CC).

A method of detecting a mobile in space according to any one of claims 2 to 3, characterized in that the field of a telescope (Ty) of the first set is in a range of 1 ° to 5 ° and in that the diameter of the conical ring (CC) defines a field greater than 30 °.

A method of detecting a mobile in space according to any one of claims 2 to 4, characterized in that the integration time of at least one electronic detector is defined to obtain two traces captured successively on a plurality of pixels of at least one electronic detector for the maximum traveling speed (V _M ) of a mobile and a minimum altitude of its orbit, the integration time of at least one electronic detector being configured for a passage in the plane optical of at least one telescope (Ty).

A method of detecting a mobile in space according to claim 6, characterized in that the direction of movement of the mobile (Mi), the inclination of its orbit and its speed of movement is deduced from an analysis of the traces stamped mobile (Mi) captured by said at least one electronic detector.

A method of detecting a mobile in space according to any one of claims 2 to 6, characterized in that the detection telescopes (Ty) of the first set are distributed in different ground stations (ST-i, ST ₂ , ST ₃ ) themselves distributed at different geographical positions on the surface of the earth.

A method of detecting a mobile in space according to claim 8, characterized in that the different earth stations (ST-i, ST ₂ , ST ₃ ) telescopes are spaced a maximum distance, the maximum separation distance allowing simultaneous observation of each telescope (T) under the same meteorological conditions of the same portion of the sky.

10. A method of detecting a mobile in space according to any one of claims 2 to 9, characterized in that the fields of the telescopes (Ty) of the first set continuously cover the periphery of the conical ring (CC).

1 1. Method for detecting a mobile in space according to any one of Claims 2 to 10, characterized in that calculation means make it possible to correlate time-stamped data of the traces captured by at least two electronic detectors so as to deduce a direction of movement of the mobile (Mi), an inclination of its orbit and its speed of displacement.

12. A method of detecting a mobile in space according to any one of claims 2 to 1 1, characterized in that means for controlling the displacement of the optical axis (Ao (Ty)) of each telescope of detection allow:

^■ modify the telescope distribution in the cone ring (CC);

^■ modify the shape of the monitored field in the space; Or changing the orientation of the theoretical median optical axis (A _cc ) of the conical ring (CC) in space while maintaining the same distribution of fields in said conical ring (CC);

13. A method of detecting a mobile in space according to any one of claims 2 to 12, characterized in that control means of at least one tracking telescope (Tsi) to guide the optical axis said tracking telescope so as to continue moving a space mobile after a first detection of a trace of the detection telescopes of the first set of said mobile.

14. A method of detecting a mobile in space according to claim 1 3, characterized in that at least one tracking telescope, allows:

Recovering the positions of at least one trace captured by the electronic detector of one of the telescopes (T) of the first set;

• control the optical axis of the tracking telescope (TS-i) so as to follow the presumed path of the mobile (M-i);

• to capture new timestamped positions of the mobile (M-i).

15. A method of multiplexing a telescope field distribution for the detection of a mobile in space, characterized in that it comprises:

A generation of a plurality of fields of view (Z _kp ) by means of a first set of telescopes (Ty), the set of fields (FOVy) of each telescope (Ty) having a first spatial distribution during a first determined duration, the spatial distribution being in a geometric form of a defined plane (P ₀ ) of the space, called the theoretical optical plane, said theoretical optical plane being non-parallel to at least one of the optical axes (A ₀ (Ty)) of a telescope (Ty), said geometrical shape having a larger dimension defining a wide detection field;

A calculation of a minimum number of changes in positions of the optical axis of at least one telescope of the first set, called the "distribution number", each new position at least one telescope defining a new distribution, so as to obtain a desired completeness factor; • a calculation of a maximum duration of change of distributions corresponding to the exposure time of each distribution and the time of passage from one distribution to another, the distributions succeeding one another in a determined duration, called "duration of multiplexing", the multiplexing time allowing the passage to all the determined distributions, the maximum duration of change of distributions being calculated according to a desired probability of detection of a mobile moving at a maximum scrolling speed (V _M ) and at an altitude minimal and whose trajectory intercepts the geometric form.

The method of multiplexing a telescope field distribution for the detection of a mobile in space according to claim 15, characterized in that the geometric shape is a form selected from the following list:

^■ An open resulting geometric shape of an intersection between a plane of the space and for example a conical ring;

^■ a circular crown;

^■ a plurality of parallel circular arcs therebetween;

^■ a plurality of parallel curves therebetween;

^■ a plurality of parallel lines.

An optical system comprising a first set of telescopes (Ty) for implementing either the detection method of any one of claims 1 to 14 or the method of multiplexing a telescope field distribution for the detection of a mobile in space according to any one of claims 15 to 16, characterized in that the fields (FOVy) of each telescope (Ty) have a spatial distribution in a theoretical plane of the space in a form open geometric plane, said theoretical optical plane being non-parallel to at least one of the optical axes (Ao (T)) of a telescope (Ty), said open geometric shape (CC) having a diameter defining a wide detection field and in that calculation means recover the data captured by each optical detector of the telescopes of the first together, said calculation means for processing the different data captured by the electronic sensors of the first set to derive at least one path of a mobile (Mi) whose orbit passes through the open geometric form (CC). 18. Optical system according to claim 17, characterized in that the open geometric shape is a section of a conical ring (CC).

19. Optical system according to claim 18, characterized in that it comprises at least one telescope whose field is defined inside the ring.

20. Optical system according to any one of claims 17 to 19, characterized in that the electronic detector is a CCD camera, EMCCD, a CMOS detector, sCMOS or an infrared detector.

21. Optical system according to any one of claims 17 to 20, characterized in that it comprises at least 10 stations arranged on the surface of the Earth each comprising at least one detection telescope, the optical system comprising:

• At least 3 to 4 stations substantially close to an equatorial latitude distributed in longitude;

• at least 3 stations substantially between latitudes 30 ° and 55 ° North and South, divided into longitude and latitude;

· At least 2 stations beyond latitudes of 60 °.