Beam-steering device for geostationary space satellite telescope

Abstract

The invention relates to a device, for a geostationary space satellite telescope, for steering a first light beam (1) transmitted to the Earth and a second light beam (2) received from the Earth. The steering device comprises a beam-splitting optical module (5) and a focusing optical component (3) configured to form, in a plane (4), an image of the first light beam and an image of the second light beam. The image of the first light beam is distinct from the image of the second light beam. The beam-splitting optical module is positioned in the plane and has a shape configured to let one among the first light beam and second light beam pass without making contact with the beam, and to deflect the other of the first light beam and second light beam.

Description

[0001] "Beam steering device for geostationary space satellite telescope"

[0002] TECHNICAL FIELD

[0003] The present invention relates to the field of optical beam switching and separation systems. It finds particularly advantageous application in the field of optical space telecommunications terminals, and more specifically, in the field of geostationary space satellite telescopes.

[0004] STATE OF THE ART

[0005] In the field of space optical telecommunications, there is equipment on board space optical telecommunications terminals for sending a data stream from the GEO orbit (from the English geostationary orbit, for geostationary orbit) (or from the LEO orbit (from the English low earth orbit, for low Earth orbit) or from the MEO orbit (from the English medium earth orbit, for medium Earth orbit) to the Earth and for receiving from the GEO orbit (or from the LEO orbit or from the MEO orbit) a data stream coming from the Earth. In the case of a data stream sent from a satellite 31 to the Earth 30, we speak of downlink signals, as illustrated by the arrow F1 in figure 1, as distinguished from the uplink signals coming from the Earth 30 (illustrated by the arrow F2).

[0006] In the case of a data stream circulating between the LEO orbit (or the MEO orbit) and the Earth, the switching and separation of the transmitted beam and the received beam are generally carried out by means of a dichroic filter whose transmission and reflection properties depend on the wavelengths of the beams involved. Thus, in order for the transmitted beam and the received beam to be treated differently from each other by the dichroic filter for their separation, the transmitted beam and the received beam have different wavelength values. Furthermore, the transmitted beam and the received beam cannot be modified without modifying the dichroic filter.

[0007] Due to a typical distance of 36,000 km to be covered, transmitting data from GEO orbit to Earth involves the use of beams carrying significant power (compared to that implemented in the case of a satellite positioned in LEO orbit or MEO orbit). Thus, the beam emitted at the geostationary space satellite has significant power compared to the beam received by the satellite and coming from Earth, which is already at the end of its path.

[0008] The technical solutions implemented for data routing and separation in the case of a satellite positioned in a LEO or MEO orbit, such as dichroic filters, are difficult to transpose to the case of a satellite positioned in the GEO orbit. Indeed, the transmission (or reflection) of the high-power emitted beam by the dichroic filter would interfere with the received beam due to the resulting diffusion due to the low power it carries. In addition, the dichroic filter remains poorly suited to acting on the high-power emitted beam. As previously mentioned, the use of dichroic filters implies that the emitted and transmitted beams cannot have a range of contiguous wavelength values ​​because a transition zone is necessary and cannot be modified to be, for example, partially inverted without changing the nature of the dichroic filter.

[0009] Furthermore, existing technical solutions in GEO orbit consist of the use of communication satellites operating through the emission and reception of radio waves. More precisely, an antenna positioned on Earth sends data to a satellite positioned in GEO orbit which in turn sends the information back to different antennas positioned on Earth, thus allowing access to information to many homes. One of the disadvantages of this technical solution is that the data rates involved cannot be high, compared to what an optical link would allow.

[0010] An object of the present invention is therefore to propose a technical solution for switching and separating optical beams propagating between the GEO orbit and the Earth, making it possible to overcome at least part of the drawbacks of existing solutions.

[0011] Other objects, features, and advantages of the present invention will become apparent from the following description and accompanying drawings. It is understood that other advantages may be incorporated.

[0012] SUMMARY

[0013] To achieve this objective, according to a first aspect, a switching device for a geostationary space satellite telescope is provided, for a first light beam transmitted towards the Earth and a second light beam received from the Earth comprising an optical beam splitter module. Advantageously:

[0014] - the switching device comprises a so-called focusing optical component configured to form, at a plane, an image of the first light beam and an image of the second light beam, the image of the first light beam being distinct from the image of the second light beam, and - the optical beam splitting module is positioned at said plane and has a shape configured so as to allow one of the first light beam and the second light beam to pass without being in contact with said beam, and to deflect the other of the first light beam and second light beam.

[0015] In the case of data transmission from GEO orbit to Earth and from Earth to GEO orbit, the distance between Earth and GEO orbit is significant. Because of this distance, the rotation of the Earth between the emission of a beam and its reception on Earth is not negligible compared to the intrinsic divergence of the beams. The communication area on Earth thus moves with the rotation of the Earth between the emission of the beam on Earth and its reception. When transmitting a beam to Earth, in GEO orbit, the direction of propagation of the downward flow is therefore oriented relative to the direction of propagation of the upward flow so as to form an angle between these two directions, called the "forward pointing angle".Thus, at a time t corresponding to the sending of the first beam and the reception of the second beam, the area where the station is positioned on Earth from which the second beam was emitted and the area towards which the first beam is directed on Earth are distinct due to the presence of this forward pointing angle, to take into account the rotation of the Earth.

[0016] The image of the Earth by the imaging optical function or equivalently focusing (of the imaging optical component or equivalently of the focusing optical component) of the switching device can be observed on a plane (or a set of planes) close to or preferably coincident with the image focal plane of the focusing optical function (of the focusing optical component). At this plane, due to the forward pointing angle, the distinct images of the first beam and the second beam at the Earth can be observed. Thus, at this plane, the switching device makes it possible to view the first beam distinctly from the second beam, so that they can be separated by the optical beam splitter module. The optical path of the first and second beams are therefore distinct at this plane, which allows their separation by the optical beam splitter module.

[0017] It is therefore understood that the switching device uses the forward pointing angle implemented in the GEO orbit to make a geometric separation of the first and second beams, and not a spectral separation as is the case for existing solutions implementing a dichroic filter. Consequently, the wavelengths of the first light beam and the second light beam are not taken into account in the process of separating the first beam from the second beam. The first beam and the second beam can thus spread over close spectral bands, for example contiguous, thus limiting the transition zone. Preferably by remaining separated, the nature of the bands can be modified without modifying the separation module.

[0018] Furthermore, since the optical beam splitting module allows one of the first beam and the second beam to pass through without being in contact with it, interference from the other of the first light beam and the second light beam is limited, and preferably avoided. Furthermore, the beam transmitted without contact with the splitting module does not suffer any power loss.

[0019] This solution is therefore particularly suitable for transmitting data between Earth and GEO orbit. Since this transmission is done via optical beams, the transmitted data rate can be significant compared to those transmitted via communication satellites operating through the emission of radio waves.

[0020] A second aspect relates to a switching assembly comprising the switching device and a satellite telescope, preferably a geostationary space satellite.

[0021] A third aspect relates to a method of steering a geostationary space satellite telescope, a first light beam transmitted towards the Earth and a second light beam received from the Earth, comprising:

[0022] - a supply of a switching device,

[0023] - a formation in a plane of an image of the first light beam and an image of the second light beam by the focusing optical component, the image of the first light beam being distinct from the image of the second light beam,

[0024] - following the formation of said images, a separation at said plane, by the optical beam separation module, of the first light beam and the second light beam, the separation comprising a transmission of one of the first light beam and the second light beam without the optical separation module being in contact with said beam, and a deflection of the other of the first light beam and second light beam.

[0025] Thus, this switching method, like the switching device previously presented, allows an image of the first light beam to be formed on a plane that is distinct from that of the second light beam, in order to be able to geometrically separate the first light beam and the second light beam and to switch them. This switching method limits, and preferably avoids, interference from one of the beams on the other beam. As seen previously, the wavelengths transported by the two beams can be modified at will without modifying the nature of the separation module. The associated flexibility is therefore significant (in comparison with the use of a dichroic filter). A terminal can, for example, invert the transmission and reception wavelength band in order to adapt to a terminal with which it wishes to communicate without modifying its hardware structure.It is therefore understood that the switching method has the effects and advantages described in relation to the device according to the first aspect.

[0026] BRIEF DESCRIPTION OF THE FIGURES

[0027] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0028] Figure 1 shows the positioning of the geostationary space satellite relative to Earth where the beams sent and received can be viewed, according to an exemplary embodiment. Figure 2 shows the beams sent to Earth from GEO orbit and received from Earth from GEO orbit where the forward pointing angle can be observed.

[0029] Figure 3 represents a view of Figure 2, reproduced optically at the level of the switching module according to an exemplary embodiment.

[0030] Figure 4A shows the switching module configured on two stages to adapt the size of the beams according to an exemplary embodiment in which the focusing function of the focusing optical component is performed by the mirrors of the link module and the telescope.

[0031] Figure 4B represents the switching module configured on two stages to adapt the size of the beams according to an exemplary embodiment in which the focusing function of the focusing optical component is carried out in particular by a lens.

[0032] Figure 4C represents the device according to the invention according to an exemplary embodiment, in which the first set and the second set can be observed.

[0033] Figure 5 shows the switching module of Figure 4 according to a different view where the path of the second light beam can be observed from the upper mirror of the connection module to the local pointing mirror according to an exemplary embodiment in which the focusing function of the focusing optical component is performed by the mirrors of the connection module and the telescope.

[0034] Figure 6 shows the switching module of Figure 4 in a different view where the path of the first light beam and the path of the second light beam can be observed from the overall pointing mirror to the upper mirror of the link module.

[0035] Figure 7 represents a schematic perspective view of the optical beam splitting module according to an exemplary embodiment.

[0036] Figure 8 represents a schematic front view of the optical beam splitting module according to the embodiment illustrated in Figure 7.

[0037] Figure 9 represents the separation module according to an exemplary embodiment in which the separation module has a U shape.

[0038] Figure 10 represents the separation module according to an exemplary embodiment in which the separation module is a thin-edged mirror having a rectangular shape.

[0039] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications.

[0040] DETAILED DESCRIPTION

[0041] Before commencing a detailed review of embodiments of the invention, optional features which may possibly be used in combination or alternatively are set out below:

[0042] In one example, the focusing optical component is configured to focus the light beams to form the image. In one example, the focusing optical component may be a lens and / or at least one mirror, for example a concave mirror.

[0043] According to one example, the focusing optical component, also called an imaging optical component, is configured to form, at said plane, an image of the second light beam received from the Earth and to project an image of the first light beam located at said plane towards the Earth, the image of the first light beam being distinct from the image of the second light beam.

[0044] According to one example, the focusing optical component, also called an imaging optical component, is configured to image or focus the first and second light beams such that, the first and second light beams having a forward pointing angle between them, the optical path of the first beam and the optical path of the second beam are separated at said plane.

[0045] According to one example, the switching device further comprises a so-called "internal" pupil having a diameter of between 1 mm and 10 mm. According to one example, this pupil is the image of the exit pupil of the telescope, by the magnification of the telescope.

[0046] According to one example, the switching device further comprises a pupil having a diameter greater than or equal to 300 mm, preferably greater than or equal to 350 mm and preferably greater than 400 mm. According to one example, the pupil is the exit pupil of a satellite telescope, preferably a geostationary space satellite. According to one example, the exit pupil is the exit pupil of the telescope of the assembly according to the second aspect of the invention.

[0047] In order for the first beam and the second beam to be separated, it is preferable that their divergence be less than the forward pointing angle. Since their divergence is directly dependent on the diameter of the pupil, and in particular of the exit pupil of the telescope and therefore of the internal pupil image of the exit pupil, a pupil diameter in these ranges allows the forward pointing angle not to be negligible compared to the divergence of the beams. According to one example, the beam splitting optical module is configured to reflect the other of the first light beam and the second light beam.

[0048] Thus, in this way, the other of the first light beam and the second light beam can be, after having been in contact with the separation module, directed in a simple manner towards a direction different from the direction towards which one of the first light beam and the second light beam will be directed. The manufacture of the beam separation module is thus simplified, in particular compared to the dichroic filter treatments of existing solutions.

[0049] In one example, the beam splitting optical module includes an aperture positioned such that one of the first light beam and the second light beam passes through the aperture to the beam splitting optical module, without contacting said module.

[0050] Thus, the positioning of this opening allows one of the first light beam and the second light beam to pass through the space where the separation module is located without being in contact with the separation module.

[0051] In one example, the aperture of the beam splitting optical module is a hole.

[0052] In the case where the opening describes a hole, that is to say an opening whose circumference is closed, and preferably a hole having a symmetry of revolution, for example a substantially circular or ellipsoidal hole, the separation module makes it possible to overcome the rotation of the satellite. Indeed, if the satellite rotates on itself, the hole can allow the light beam to pass regardless of the rotational position of the satellite, relative to other shapes of the separation module. The separation of the light beams is thus simplified.

[0053] According to one example, the beam splitting optical module comprises a mirror, the mirror comprising the aperture, preferably the hole.

[0054] Thus, the fact that the separation module is a mirror comprising the opening (and therefore the hole) makes it possible to form a reflective surface so that the other of the first light beam and the second light beam can be reflected on the separation module.

[0055] According to one example, the optical beam splitting module is based on a material selected from the group consisting of: glass, crystal, metal and ceramic.

[0056] These materials allow a reflective surface to be formed on the surface of the separation module.

[0057] According to one example, the switching device further comprises:

[0058] - A first steerable mirror, called a “local pointing mirror”, configured to receive and steer one of the first beam transmitted towards the Earth and the second light beam received from the Earth, and preferably only one of the first beam and the second light beam,

[0059] - a second orientable mirror, called a “global pointing mirror”, configured to receive and orient the first light beam transmitted towards the Earth and the second light beam received from the Earth,

[0060] - an optical module called "pupil imaging", in which the local pointing mirror, the global pointing mirror and the pupil imaging optical module are configured so that the local pointing mirror and the global pointing mirror are the image of each other, and the optical beam splitting module is arranged between the local pointing mirror and the global pointing mirror along the path of the second light beam. Thus, the local pointing mirror and the global pointing mirror make it possible to manage the forward pointing angle of the beams. The use of two mirrors makes it possible to act independently on the emission and reception. In particular, the first orientable mirror makes it possible to receive and orient the second beam so that it heads in the desired direction and therefore reaches the splitter module (directly or indirectly).The second steerable mirror makes it possible to receive and steer the first beam so that it also heads in the desired direction and therefore with the desired angle towards the Earth. The second steerable mirror also makes it possible to receive and steer the second beam so that it also heads towards the separation module (directly or indirectly) with the desired direction). According to one example, the local pointing mirror is configured to receive and steer the second light beam received from the Earth. The pupil imaging optical module makes it possible, in particular at the planes formed by the pupils (i.e. at the level of the steerable mirrors), to maintain the transverse position of the beams and in particular to prevent a movement of the global pointing mirror or the local pointing mirror from generating a displacement of the beam.Thus, at the level of the steerable mirrors, regardless of the positioning of the global pointing mirror and the local pointing mirror, the pupil imaging optical module maintains the transverse position of the first and second light beams, so that, by a pointing adjustment, the pupil is systematically imaged on the steerable mirrors. Thus, at the level of the different images of the pupil, therefore on the steerable mirrors, the light beam is stable, which is preferable because the entrance pupil of the telescope is generally fixed. On the other hand, when moving away from the pupil planes, the light beams necessarily move laterally.

[0061] According to one example, the switching device further comprises an optical module called a "linking module" comprising a third mirror and a fourth mirror configured together to receive and modify the diameter of the first light beam transmitted towards the Earth and the second light beam received from the Earth, the linking module being arranged between the beam splitting optical module and the global pointing mirror along the path of the second light beam, the pupil imaging optical module and the linking module being configured, with the local pointing mirror and the global pointing mirror, such that the local pointing mirror and the global pointing mirror are the image of each other. According to one example, the third mirror, the fourth mirror, preferably with the telescope, form the focusing optical component.According to another example, and as detailed later, the focusing optical component further comprises or is an additional optical component to the connecting module, for example a lens.

[0062] This configuration and therefore the positioning of the link module makes it possible to create two stages, the first stage and the second stage, in order to obtain a displacement of the beams from one stage to another associated with a modification of the diameter of the beams. The positioning of the third mirror and the fourth mirror makes it possible to modify the size of the beams and so that the first and second beams have a larger diameter in the first stage compared to the second stage. In this way, due to the size of the beams in the different stages, the first stage is intended for the PAT function (for "Pointing And Tracking" in English, which can be translated into French as "Pointage et Suivi"), that is to say to give the beams the desired direction while the second stage is intended for the routing of the transmission and reception beams.In fact, the smaller the diameter of a light beam, the greater the value of the uncertainty in the position becomes and the less important the value of the uncertainty in the angle becomes.

[0063] By configuring the link module, the separation module can therefore be positioned on the second floor because the separation module allows the switching function and therefore the pointing function.

[0064] According to an advantageous example, in the method for transmitting and receiving optical beams by a space satellite telescope, the first light beam and the second light beam have distinct wavelength value ranges between the first and second beams. The integration of the device and the use of the method are facilitated in the usual configurations of the system manufacturers for which the wavelength range of the received beam is different from the wavelength range of the transmitted beam. According to one example, in the switching method, the first light beam and the second light beam have a range of wavelength values ​​separated by a preferably non-zero transition zone.

[0065] According to one example, the method comprises selecting a first range of wavelength values ​​for the first beam, and a second range of wavelength values ​​for the second beam, the first and second ranges of values ​​being distinct, the selection of the first and second ranges of values ​​being made independently of a configuration of the beam splitting optical module.

[0066] Thus, the first light beam and the second light beam can be configured with different wavelength ranges and can be adjusted without modifying the separation module. This therefore allows a significant gain in flexibility. It is notably possible to reverse the two wavelength ranges between the first and second beams. Thus, if for a configuration the first beam carries a first wavelength range and the second beam a second distinct wavelength range, it is possible to reverse the configuration so that the first beam carries the second wavelength range and the second beam the first wavelength range.

[0067] According to one example, in the switching method, the beam splitting optical module comprises a mirror, the mirror comprising an aperture, preferably a hole, upon splitting the first light beam and the second light beam, the beam splitting optical module transmits one of the first light beam and the second light beam through the aperture, and reflects the other of the first light beam and the second light beam through the mirror.

[0068] According to one example, in the switching method, when separating said beams, the first light beam is transmitted without contact with the beam splitting module, and the second light beam is deflected.

[0069] Since the first light beam has a greater power compared to the second light beam, it is transmitted by the separation module while the second light beam is deflected by the separation module. In this way, the light beam having the higher power does not come into contact or only slightly with the separation module, which limits and preferably avoids the diffusion of the high-power beam on the separation module and increases the resistance of the reflective treatment of the separation module. The interference of the lower-power beam by the higher-power beam is therefore limited, and preferably avoided. Although this configuration is the most frequently implemented, another possible configuration is to allow the low-power beam to pass through the hole and to reflect the high-power beam.

[0070] According to one example, in the switching method, the power of the first light beam is between 1 W and 1000 W, preferably between 5 W and 1000 W.

[0071] Thus, the first light beam is configured to travel a significant distance and in particular to go from GEO orbit to Earth. According to one example, the switching method comprises, before the step of providing a switching device, the following step:

[0072] - a handling by the switching device of the second light beam and sending by the switching device of the first light beam, the first light beam being transmitted towards the Earth and the second light beam being received from the Earth, the first light beam and the second light beam have between them a non-zero angular offset, and preferably greater than 15 prad.

[0073] The non-zero angular offset between the first light beam and the second light beam corresponds to the forward pointing angle between the first and second light beams which is fixed so as to take into account the non-negligible distance traveled by the Earth (due to its rotation) during the propagation of the first light beam from GEO orbit to Earth.

[0074] According to another preferred example, in the switching method, the first light beam and the second light beam have a range of wavelength values ​​separated by a non-zero transition zone. According to one example, the separation module can be configured so that the two wavelength ranges can be reversed between the first and second beams, without modification of the device and in particular of the separation module. Thus, if for a configuration the first beam carries a first range of wavelengths and the second beam carries a second range of distinct wavelengths, it is possible to modify the wavelength ranges so that the first beam carries the second range of wavelengths and the second beam the first range of wavelengths.

[0075] Thus, the switching method allows the first light beam and the second light beam to have distinct wavelength ranges that can be reconfigured as needed without changing the separation module, which allows for a significant gain in flexibility. It is specified that in the context of the present invention, the term "distinct" in the expression "one image is distinct from another image" means that these two images are not in contact and that they are positioned at a distance from each other.

[0076] In the following detailed description, terms such as "horizontal", "vertical", "longitudinal", "transverse", "upper", "lower", "top", "bottom", "upstream", "downstream" may be used. These terms must be interpreted relatively in relation to the normal position of the switch module and the propagation of the light beams in this module. For example, an "upstream" element is an element of the module placed before another so-called "downstream" element following the direction of propagation of the light beams in the module. The direction of propagation of the light beams in the switch module is considered to start from the side of the switch module and goes towards the Earth (for the first light beam) and starts from the Earth and goes towards the switch module (for the second light beam).We will also use a reference whose longitudinal or back / front direction corresponds to the x axis, the transverse or right / left direction corresponds to the y axis and the vertical or down / up direction corresponds to the z axis.

[0077] In the present invention, the term "geostationary space satellite" means a satellite positioned in the GEO orbit (i.e. 35,786 km from the surface of the Earth) but also in orbits close to the GEO orbit, i.e. in orbits located at an altitude ranging from 30,000 km to 38,000 km above the surface of the Earth.

[0078] According to one embodiment, the beam steering and splitting device according to the invention is associated with a geostationary space satellite telescope. The beam steering and splitting device according to the invention is configured to separate a first light beam 1 transmitted to Earth from the GEO orbit and a second light beam 2 received from Earth from the GEO orbit for their steering. For this, the beam steering and splitting device comprises an optical beam splitting module 5. The beam steering and splitting device comprises a focusing optical component 3 configured to form, at a plane 4, an image of the Earth along the optical paths of the first 1 and second beams 2. This makes it possible to form an image of the first light beam 1 and an image of the second light beam 2 (the object being the Earth).By "image" is meant here that the beams can be observed at this plane 4, and the sections of these beams in this plane 4 being distinct from each other. Equivalently, at the level of said plane 4, the paths of the first 1 and second 2 light beams are distinct and do not intersect with each other.

[0079] Generally speaking, the optical components involved in a telescope are typically mirrors. However, it is also possible to find telescopes made from lenses. In the context of the present invention, the telescope may preferably be formed from concave and convex mirrors which may be accompanied or replaced by lenses.

[0080] Generally speaking, the role of a telescope is to generate significant magnification. More precisely, its role is to reproduce the exit pupil of the telescope (the one with a diameter of typically around 500 mm and which is positioned on the "space" side (as opposed to the "terminal" side), into a smaller one on the "terminal" side. This second pupil, also called the "internal" pupil, an image of the exit pupil, can typically have a diameter of 1 mm to 10 mm.

[0081] The optical component 3 may be called a “focusing optical component” or even an “imaging optical component”. In general, a person skilled in the art is able to identify the optical component capable of performing the desired focusing function, and in particular imaging the remote terminal with which communication is to be established (the Earth or another satellite). The focusing optical component 3 may, for example, be a lens. The focusing optical component 3 may, as an alternative or in addition, be a concave mirror. The focusing optical component 3 may also be an assembly of several optical parts, such as concave mirrors and / or lenses. More specifically, the focusing optical component 3 may be an assembly comprising two concave mirrors and a lens. In the case of FIG. 4A, the focusing optical component 3 comprises the telescope 7 and the mirrors 11 a and 11 b of the “link” module.In this case, the optics of the link module allow the generation of the focal plane on which it is possible to position the beam splitting optical module 5. The focal length of the focusing optical component 3 (considering the satellite telescope) can be from 10 to 40 m. The diameter of the pupil 7a can be 500 mm. The focal length of the focusing optical component 3 considering only the terminal is between 50 mm and 1000 mm.

[0082] According to one example, it is also possible for the focusing optical component 3 to comprise only the optics 11 a and 11 b of the “linking” module. In this case, a smaller image of the entrance pupil of the telescope (which is the entrance pupil of the terminal) is generated on the side where the second beam arrives at the telescope. The dimension of this image may be a function of the magnification of the telescope. Generally, the dimension of this image may be between 5 mm and 10 mm. In this case, the dimensions of the entrance pupil of the terminal may no longer be between 350 mm and 450 mm, in order to satisfy the function of the switching device. In the case of FIG. 4B, the focusing optical component 3 may be a lens or a mirror, such as the mirror 11 c, having optical power. The linking module may then be a mirror system without optical power, and in particular without focusing power.

[0083] Due to the forward pointing angle a, the image of the first light beam 1 is distinct from the image of the second light beam 2 (Figure 3). The optical beam splitter module 5 is positioned at said plane 4 in order to be able to separate and direct the two beams 1, 2 which can be observed as being distinct at the plane 4. The optical beam splitter module 5 occupies a position configured in such a way that 1) one of the first light beam 1 and the second light beam 2 passes through the space where the splitter module 5 is positioned without coming into contact, i.e. without touching the splitter module 5, and 2) the other of the first light beam 1 and second light beam 2 has its direction changed after its contact with the splitter module 5 (Figures 7 and 8).

[0084] The deflection of a beam on the separation module 5 can cause light scattering. This is the case in particular when the deflected beam is a high-power beam. In order to limit, and preferably to avoid, interference in brightness on the transmitted beam, the deflected beam can be the beam having the lowest power, i.e. the second beam 2. This is particularly advantageous due to the significant difference in power between the beam transmitted to Earth 1 and the beam 2 received from Earth. Even a low interference of the second beam 2 by the first beam 1 can disrupt the telecommunication. Note, however, that it is possible to provide that the deflected beam is alternatively the first beam 1. In the following, it is considered, without limitation, that the undeflected beam is the first beam 1 and that the beam deflected by the module 5 is the second beam 2.

[0085] The invention provides for the possibility that there are several first light beams 1 and several second light beams 2. Thus, there may be 2, 3, 4, 5 or 8 first light beams 1 and 2, 3, 4, 5 or 8 second light beams 2. The first light beam 1 may have a diameter between 0.5 mm and 20 mm. The second light beam 2 may have a diameter between 0.5 mm and 20 mm.

[0086] Since the first light beam 1 is emitted towards the Earth from the separation module 5 and the second light beam 2 is emitted from the Earth towards the separation module 5, at the separation module 5 (and more particularly after the first beam 1 has passed close to the separation module 5 and before the second beam 2 has been deflected by the separation module 5), it can be considered that the first light beam 1 and the second light beam 2 have quasi-parallel propagation directions, being offset due to the taking into account of the forward pointing angle a. After the first beam 1 has passed close to the separation module 5 and before the second beam 2 has been deflected by the separation module 5, the first light beam 1 and the second light beam 2 can thus be adjacent.Downstream of the lens 3, considering the direction of propagation of the first beam 1 emitted towards the Earth, and upstream of the lens 3, considering the direction of propagation of the second beam coming from the Earth, the first light beam 1 and the second light beam 2 may be in contact in part or in full.

[0087] Given the difference in pointing, it is understood that the separation module 5 can be arranged in an angular interval relative to a plane perpendicular to the direction of propagation of each beam 1, 2. More precisely, the first light beam 1 and the second light beam 2 can form with the plane 4 an angle of 90° plus or minus 20°. The first light beam 1 and the second light beam 2 can also form with the plane 4 an angle of 90° plus or minus 10°. The first light beam 1 and the second light beam 2 can also form with the plane 4 an angle of 90° plus or minus 5°. The plane 4 can be substantially perpendicular to the direction of propagation of the first light beam 1, taking into account the forward pointing angle a. Alternatively, the plane 4 can be substantially perpendicular to the direction of propagation of the second light beam 2, taking into account the forward pointing angle a.

[0088] When separating the first light beam 1 and the second light beam 2, the deflected beam is deflected by a first face 12a of the separation module 5 and the beam which passes through the space without being in contact with the separation module 5 propagates from a second face 12b towards the first face 12a. The first face 12a of the separation module 5 is preferably opposite the second face 12b of the separation module 5. Due to the deflection of the second light beam 2 by the separation module 5, the direction of propagation of the second light beam 2 before its deflection by the separation module 5 is different from its direction of propagation after its deflection by the separation module 5.

[0089] According to a possible example, the separation module 5 has at least one surface forming a diopter 5a. The separation module 5 is then configured to allow one of the first light beam 1 and the second light beam 2 to pass without the beam in question being in contact with the diopter 5a, that is to say without the beam in question passing through the diopter 5a. The plane 4 may coincide with the image plane 3a of the focusing optical component 3. The plane 4 may therefore be positioned at a distance DistF from the focusing optical component 3, as illustrated in FIG. 3. The distance DistF is the focal length of the focusing optical component 3. The plane 4 may be at a distance from the image plane 3a of the focusing optical component 3, and preferably parallel to this image plane 3a. The plane 4 may be positioned on one side or the other of the image plane of the focusing optical component 3 at a distance of up to 5 mm.Preferably, the distance between plane 4 and the image plane of the focusing optical component 3 may be between 0 mm and 1 mm. Preferably, plane 4 coincides with the image plane 3a of the focusing optical component 3. Indeed, when plane 4 moves away from the image plane of the focusing optical component 3, the first light beam 1 and the second light beam 2 begin to move closer together. However, for an offset of a few millimeters (up to 5 mm) between plane 4 and the image plane of the focusing optical component 3, the first light beam 1 and the second light beam 2 are sufficiently separated.

[0090] According to one example, the invention provides an assembly comprising a switching device and a space satellite telescope 7. Preferably, the telescope 7 is a geostationary space satellite. Preferably, the assembly comprises a switching device according to the invention and a space satellite telescope 7 comprising a pupil 7a having a diameter greater than or equal to 300 mm. Advantageously, the assembly comprises a switching device according to the invention and a space satellite telescope 7 comprising a pupil 7a having a diameter greater than or equal to 350 mm. Advantageously, the assembly comprises a switching device according to the invention and a space satellite telescope 7 comprising a pupil 7a having a diameter greater than 400 mm.

[0091] In Figure 3, the Airy diffraction task t of the light spots formed by the emission beams 1 and reception beams 2 can be observed at the image focal plane 3a of the lens 3. The distance between the light spots formed by the emission beams 1 and reception beams 2 is directly related to the forward pointing angle a. The size of these light spots (necessary for their separation) is directly related to the divergence of the beams in the telescope 7. Since the divergence of the beams is directly related to the diameter of the exit pupil of the telescope 7, a pupil diameter 7a in precisely selected ranges allows the forward pointing angle a not to be negligible compared to the divergence of the beams.

[0092] More precisely, in GEO orbit (i.e. 36,000 km from Earth), the value of the forward pointing angle a can typically be 18.5 prad (or 15 prad in the case where the GEO satellites do not have a stable altitude and have therefore lost altitude), which represents a ground displacement of 660 m. A formula (based on the dimension of the Airy spot, corresponding to a pupil uniform in irradiance) relating the diameter D of the exit pupil of telescope 7 with the half-angle of divergence 0 of the beams of wavelength A considered could be: e = 1.22.In order to take into consideration different configurations (i.e. central obscuration of the pupil 7a or irradiance as a function of the considered position defined by a Gaussian distribution) and not only a configuration having a pupil 7a uniform in irradiance, preferably the half-angle of divergence 0 of the beams is strictly less than 4.6 prad (or 20<18.5 / 2 prad), (and preferably strictly less than 6 prad), which corresponds to a value of diameter of the exit pupil, preferably strictly greater than 410 nm (and preferably strictly greater than 300 nm) (taking into consideration a wavelength of 1550 nm) (figure 3). The wavelength λ was taken equal to 1550 nm.

[0093] Preferably, the optical beam splitting module 5 is configured so that the second beam 2 is deflected by the module 5 by reflection.

[0094] For this, the optical beam separation module 5 may comprise an opening 8 allowing the first beam 1 to pass through this opening 8. The opening 8 then delimits a passage through which the first light beam 1 propagates. In this way, the first beam 1 passes through the space where the separation module 5 is positioned without coming into contact with said module 5.

[0095] The separation module 5 may further comprise a body 5b configured to deflect the second beam 2. The body 5b may for example be configured to transmit the second beam 2 and deflect it. This deflection of the beam may for example be done according to the optical properties of the beam to be deflected. For example, the second beam 2 may be deflected according to its wavelength. The body 5b of the separation module 5 may for example comprise or be a dichroic filter. Preferably, the deflection of the second beam 2 is done by reflection. The body 5b may for example comprise or be a mirror. The deflection and therefore the separation of the beams is thus simplified. The opening 8 may be at least partly surrounded, and preferably delimited, by the body 5b of the separation module 5.

[0096] The opening 8 can be configured so that the first beam 1 passes through the space defined by the opening 8. It is therefore understood that the first beam 1 passes through the separation module 5 without being in contact with this separation module 5. According to one example, the separation module 5 is positioned in the switching device so that the opening 8 forms a passage aligned with the direction of propagation of the light beam that the opening lets pass. Equivalently, the passage formed by the opening 8 is arranged on the optical path of the light beam that the opening 8 lets pass.

[0097] According to an advantageous example, the opening 8 of the optical beam splitting module 5 is a hole, that is to say an opening 8 whose periphery is closed. As illustrated in FIG. 8, the hole 8 can advantageously be centered on the direction of propagation of the light beam passing through the hole 8, and in particular the first beam 1. The hole 8 can be entirely surrounded, and preferably delimited, by the body 5b of the splitting module 5. Thus, it is understood that if the satellite rotates, the switching device can rotate around the direction of propagation of the beam passing through the opening 8. When the opening 8 is a hole surrounded by the body 5b of the splitting module 5, it is possible to avoid this rotation.The separation module 5 rotating around an axis substantially coincident with the direction of propagation of the first beam 1 passing through the hole 8, a deviation of the second beam 2 can be made whatever the rotational position of the separation module 5.

[0098] Preferably, the hole has a symmetry of revolution around an axis 8a, this axis 8a being substantially coincident with the direction of propagation of the light beam passing through the hole 8, and in particular the first beam 1. The hole 8 can form a passage of circular, square, rectangular or oval section configured so that the beams are not in contact with the separation module 5 when it passes through the space where the separation module 5 is positioned.

[0099] The aperture 8 can be produced by mechanical machining, chemical machining or laser machining. The beam splitter module 5 is thus simple to manufacture, which reduces the cost of the device and the switching process.

[0100] Advantageously, the body 5b of the optical beam splitting module 5 is a mirror. The mirror in question comprises the opening 8. Preferably, the opening 8 is a hole.

[0101] According to an example illustrated by Figure 9, the opening 8 may not have a closed perimeter. The opening 8 may be a recess in the body 5b of the separation module 5, the recess opening onto at least one of the edges of the body 5b of the separation module 5. The beam separation module 5 may for example be U-shaped. In this way, when the beam separation module 5 lets the first light beam 1 pass, the first light beam 1 passes through the area partially surrounded by the U. The separation module 5 can then be oriented so that the second beam 2 is deflected by the body 5b of the separation module 5.

[0102] Due to the dimensions of the light beams in GEO orbit, which are typically between 0.5 mm and 20 mm, the optical components of the separation and switching device are configured, and in particular dimensioned, to act on beams with a diameter of the order of a millimeter, and more particularly beams with a diameter of between 0.5 mm and 20 mm. For example, the opening 8 may be dimensioned so as to have a section substantially perpendicular to the direction of propagation of the beam, with an area greater than at least one, preferably at least two, and preferably at least three times the size of the beam passing through the opening 8. In this section, the opening 8 may have a smaller dimension, for example a diameter, of between 0.5 mm and 50 mm. The opening 8 may also be configured so that it has the minimum size allowing it to pass without being in contact with the first light beam 1.For example, the opening 8 may have a substantially circular outline. Furthermore, the opening 8 may have a size defined so as to take into account the problems of manufacturing tolerance, alignment and variation during use. Thus, the size of the opening 8 may correspond to the minimum size allowing it to allow the beams to pass without being in contact with, to which is added 30% to 40% of this minimum size.

[0103] According to another example illustrated by Figure 10, the body 5b of the separation module 5 may have a shape without an opening, for example a half-spherical or rectangular shape. The separation module 5 may then be arranged on the optical path of the first 1 and second 2 beams so that the first beam 1 passes next to the body 5b without being in contact with this body 5b. The second beam 2 may be incident on the body 5b and therefore be deflected. According to a preferred example, the separation module 5 may comprise a pierced mirror. Thus, the first beam 1 passes through the hole, and the second beam 2 is deflected by reflection on the mirror. The separation and the routing of the first 1 and second 2 beams is thus made reliable and simplified.

[0104] According to a possible example, the body 5b of the separation module 5 is based on, and preferably made of, one of the following materials: glass, crystal, metal and ceramic. The body 5b of the separation module 5 may be at least partially covered by a coating configured to deflect the second beam 2 by reflection.

[0105] The separation module 5 may comprise a drilled dichroic filter. Thus, the hole 8 in the dichroic filter allows the passage of the first beam 1, and the second beam 2 is deflected by the dichroic filter according to its wavelength.

[0106] The switching and separation device may further comprise optical modules for directing the first 1 and second 2 beams. For example, the switching device further comprises:

[0107] - A first orientable mirror, called a “local pointing mirror” 11d. The mirror 11d is configured to receive and give a desired direction to one of the beams, and preferably to the second light beam 2 coming from the Earth,

[0108] - a second orientable mirror, called a “global pointing mirror” 11 e. The mirror 11 e is configured to receive and give a desired direction to the first light beam 1 to be directed towards the Earth and to the second light beam 2 coming from the Earth and

[0109] - a pupil imaging optical module 10.

[0110] The local pointing mirror 11 d is therefore arranged on the optical path of the second light beam 2, and the global pointing mirror 11 e on the optical path of the first 1 and second 2 light beams.

[0111] The local pointing mirror 11d, the global pointing mirror 11e and the pupil imaging optical module 10 are configured, and preferably are positioned so that the local pointing mirror 11d and the global pointing mirror 11e are the image of each other. A person skilled in the art is able to identify possible architectures for obtaining this conjugation relationship.

[0112] The two mirrors, global 11 e and local 11 d, are configured to independently manage the first 1 and second 2 beams. Pupil imaging maintains, at the level of the orientable mirrors, merged with the pupil planes of the device, the transverse position of beams 1, 2 whatever the angular combinations of the two mirrors. This significantly reduces the coupling losses that can be caused by such a displacement, as detailed later.

[0113] In order to separate the first 1 and second 2 beams between the local 11d and global 11e mirrors, the optical beam splitter module 5 can be positioned between the local pointing mirror 11d and the global pointing mirror 11e (as seen in figures 4 and 5 for example). Thus, the global pointing mirror 11e manages the two beams 1, 2, while the local pointing mirror 11d only directs the second beam 2.

[0114] The pupil imaging optical module 10 may comprise two lenses, a second lens 10a and a third lens 10b (Figure 4). The lens 10a is positioned on the path of the first light beam 1. The lens 10b is positioned on the path of the second light beam 2. The lens 10b makes it possible in particular to fix the desired transverse position of the second light beam 2. The lens 10a makes it possible in particular to fix the desired transverse position of the first light beam 1.

[0115] The pupil imaging optical module 10 makes it possible to maintain the transverse position of the beams 1, 2 and in particular to prevent a movement of the global pointing mirror 11 e or of the local pointing mirror 11 d from generating a displacement of the beam. More precisely, a movement of the global mirror 11 e necessarily generates a lateral movement on the local mirror 11 d. Indeed, given that the local mirror 11 d cannot rectify a transverse position defect (whereas it can rectify an orientation defect), a movement of the global mirror 11 e necessarily causes a transverse displacement of the received beam (the second beam 2) which cannot be corrected by the positioning of the local mirror 11 d. The pupil imaging optical module 10 makes it possible to remedy this problem.For this, the third mirror 11 a and the fourth mirror 11 b coupled to the lenses 10 a, 10 b of the pupil imaging optical module connect the local pointing mirror 1 1 d and the global pointing mirror 11 e so that they are the image of each other. Thus, at the level of the orientable mirrors, merged with the pupil planes of the device, during a displacement (in transverse position and angle) of the global mirror 1 1 e, an angular correction carried out by the local mirror 11 d puts the beam back in the right direction without it being displaced transversely. It is therefore understood that the coupling losses can be reduced.

[0116] According to an advantageous example, the switching device further comprises a link module 11 ab (figures 4 and 5). The link module 11 ab is configured to separate the path of the first 1 and second 2 beams into two stages 11 ab1, 11 ab2, the first 1 and second 2 beams having distinct diameters between these two stages 11 ab1, 11 ab2. The two stages 11 ab1, 11 ab2 allow the separation of the PAT (Pointing And Tracking) part on the upper stage 11 ab1, traditionally handled by the satellite designer, and the beam switching and connection with the fibers part on the lower stage 11 ab2, traditionally handled by the terminal manufacturer. The link module 11 ab allows the size of the beams to be modified and thus to maintain a usual size for the PAT and to reduce the diameter for the switching part.Thus, according to this example, the fiber collimators are located before the lens 10a according to the direction of propagation of the first light beam 1 and after the local mirror 11d according to the direction of propagation of the second light beam 2. The telescope is located before the global mirror 11e according to the direction of propagation of the second light beam 2.

[0117] For this, the optical module 11 ab comprises a third mirror 11 a and a fourth mirror 11 b. The third mirror 11 a can be configured to receive and reduce the diameter (by converging it) of the second light beam 2 received from the Earth. The fourth mirror 11 b can be configured to receive and increase the diameter of the first light beam 1 sent towards the Earth (by diverging it). Preferably, the third mirror 11 a, the fourth mirror 11 b and the telescope 7 form the focusing optical component 3 (as illustrated in FIG. 4A).

[0118] In Figure 4C are shown the first assembly 13 and the second assembly 14. The first assembly 13 and the second assembly 14 are arranged respectively in the first 17 and second 18 zones. The first assembly 13 is configured to provide the interface between the link module 11 ab and the telescope 7. The first assembly is typically dedicated to metrology functions, such as beam tracking. The first assembly 13 can be called a “telescope interface assembly”. Typically, in the first assembly 13, the beams can have a diameter having a value between 10 mm and 20 mm.

[0119] The second assembly 14 is configured to direct the beams between the link module 11 ab and the optical fibers. The second assembly 14 may be referred to as a "direction assembly". Typically, in the second assembly 14, the beams may have a diameter having a value less than 1 mm.

[0120] The switching assembly 14 and the interface assembly 13 may be at least partly superimposed, to form a first stage and a second stage at least partly superimposed. The connection module 11 ab may then be considered as an elevator module. The advantage of this configuration is to allow a gain in compactness. Indeed, the available space is often limited in optical terminals.

[0121] Alternatively, the switch assembly and the interface assembly may be on the same floor, for example in continuity with each other.

[0122] In the context of the present application, these sets are designated in a non-limiting manner by the term stage, the first set 13 corresponding to the first stage, the second set 14 corresponding to the second stage.

[0123] The first set 13 may include the global pointing mirror 1 1 e.

[0124] The second assembly 14 may comprise the local pointing mirror 11 d, the fifth mirror 11 c, the second lens 10 a, the third lens 10 b and the beam splitting optical module 5.

[0125] The second assembly may comprise the local pointing mirror 11d, the fifth mirror 11c, the second lens 10a, the third lens 10b, the optical beam splitting module 5, the collimator 15 and the connection area with the optical fibers 16.

[0126] The third mirror can be converging and the fourth mirror can be diverging.

[0127] Note that it is possible to use two converging mirrors for the link module 11 ab. However, this generates a focal point between the two mirrors which should be avoided due to the optical power levels of the beams, and in particular the first beam 1. However, given that the system is designed to operate in a vacuum and there is no risk of plasma formation in the air by focusing, this drawback is limited. Thus, a link module 11 ab formed by two converging mirrors can be used to generate a focal point between the two mirrors which can be used as a separation point for beams 1 and 2 by the beam splitter module. In this case, the link module is a true afocal system and a re-collimation lens to complete the optical train so that the link module is afocal is then no longer useful.At the focal point between the two mirrors, the beam points are then 3 to 4 times smaller than in the classic configuration (i.e. in the configuration where the link module is composed of a converging mirror and a diverging mirror), which can also make the manufacture of the beam splitting module, and in particular the drilled mirror, more complex.

[0128] According to one example, the pupil imaging module comprises at least one lens.

[0129] According to one example, the pupil imaging module and the connecting module are realized by the same optical components. More particularly, according to one example, the pupil imaging module and the connecting module comprise the third mirror and the fourth mirror, and possibly at least one lens.

[0130] Additionally, according to one example, the pupil imaging module is distinct from the linking module and the pupil imaging module comprises at least one lens.

[0131] When the link module is formed by two converging mirrors (instead of one converging mirror and one diverging mirror), the pupil imaging function can be performed by the assembly formed by the telescope and the link module. The focal point is located between the two mirrors, at the point where the drilled mirror can be located to separate the two beams 1 and 2. It is then desirable to position a power optic on each side of the focal point where the beam splitter module is located. A fifth mirror 11 c can therefore serve as pupil imaging optics. The configuration where the link module is formed by two converging mirrors is not the preferred configuration because it places a significant number of functions and therefore constraints on the mirrors of the link module.

[0132] In the case where the link module is formed by a converging mirror and a diverging mirror, the assembly formed by the telescope and the link module are in fact not capable of performing the pupil imaging function on their own. In this case, the focal point is outside the link module and it is desirable to have a lens or power optics at this focal point.

[0133] The third mirror 11a and the fourth mirror 11b can describe an off-axis parabola.

[0134] Preferably, the linking module 11 ab is positioned between the beam splitting optical module 5 and the global pointing mirror 11 e. The pupil imaging optical module 10 and the linking module 11 ab are configured, and preferably positioned, so that the local pointing mirror 11 d and the global pointing mirror 11 e are the image of each other.

[0135] Typically, the first stage 11 ab1 can handle beam diameters of the order of 10 mm while the second stage 11 ab2 can handle beam diameters of the order of 1 mm. The system formed by the mirrors 11 a and 11 b of the link module (which has a residual focal length) can be selected so that it allows the beam size to be increased or decreased in order to obtain the desired beam diameter, typically an increase or decrease of between 5 and 10.

[0136] Advantageously, the switching device may comprise a fifth mirror 11 c. The fifth mirror 11 c has the function of receiving the second light beam 2 (after it has been reflected by the fourth mirror 11 b) to reflect it by directing it towards the separation module 5. The fifth mirror 11 c also has the function of receiving the first light beam 1 (after it has passed close to the switching module 5) to reflect it by directing it towards the fourth mirror 11 b. The fifth mirror 11 c can therefore be used for alignment and adjustment problems.

[0137] According to an example illustrated by Figure 6, the mirror 11 a and the global pointing mirror 11 e are on the upper stage 11 ab1. The fourth mirror 11 b, the local pointing mirror 11 d, the fifth mirror 11 c, the pupil imaging module 10 and the separation module 5 are on the lower stage 11 ab2.

[0138] Regarding the pupil imaging module 10, the second lens 10a can be positioned so that the first light beam 1 passes through the second lens 10a before reaching the separation module 5, depending on the direction of propagation of the first beam 1 in the device. The third lens 10b can be positioned so that the second light beam 2 passes through the third lens 10b after reaching the switching module 5, depending on the direction of propagation of the second beam 2 in the device.

[0139] The fourth mirror of 11 b (located on the lower stage 11 ab2) can be positioned so that it reflects the first light beam 1 towards the third mirror (of the link module) 11 a (located on the upper stage 11 ab1) after it has been reflected by a fifth mirror 11 c and so that it reflects the second light beam 2 after it has been reflected by the third mirror (of the link module) 11 a (located on the upper stage 11 ab1).

[0140] The fifth mirror 11 c can be positioned so that it reflects the first light beam 1 before it has been reflected by the fourth mirror (of the connecting module) 1 1 b (located on the lower stage 11 ab2) and so that it reflects the second light beam 2 after it has been reflected by the fourth mirror (of the connecting module) 11 b (located on the lower stage 11 ab2).

[0141] The optical module 5 can be positioned so that the second light beam 2 reaches the optical module 5 after reaching the fifth mirror 11 c and so that the first light beam 1 reaches the optical module 5 before reaching the fifth mirror 11 c.

[0142] The mirror 1 1d can be positioned so that it reflects the second light beam 2 after it reaches the third lens 10b pupil imaging module 10.

[0143] Advantageously, the invention describes a switching assembly comprising the switching device and a satellite telescope 7. Preferably, the telescope 7 is a geostationary space satellite telescope. The pupil 7a may be the exit pupil of the telescope 7. The magnification of the telescope may typically be 50.

[0144] In the case where the focusing optical component 3 is a lens, this lens can be positioned between the optical module 5 and the mirror 11 c.

[0145] On reading the above, it is understood that the invention describes a method for switching a geostationary space satellite telescope, a first light beam 1 sent towards the Earth from the GEO orbit and a second light beam 2 received from the Earth and coming from the GEO orbit. The switching method comprises in particular: - A provision of the switching device previously described,

[0146] - A positioning of the separation module 5, in a plane 4 close to or merged with the image plane 3a of the focusing optical component 3, so that the image of the first light beam 1 and the image of the second light beam 2 by the focusing optical component 3 (the object being the Earth which is positioned at infinity), are distinct in this plane 4. Due to the forward pointing angle a, the image of the first light beam 1 is distinct from the image of the second light beam 2,

[0147] - Following the formation of said images, a separation at said plane 4, by the separation module 5, of the first light beam 1 and the second light beam 2 is carried out.

[0148] The method may comprise any step enabling the implementation or resulting from the characteristics of the switching device. For example, the beam separation is preferably carried out by reflection on a mirror of one of the light beams, and preferably the second beam 2.

[0149] According to a preferred example, in the switching method, the first light beam 1 and the second light beam 2 each have a range of distinct but close, and preferably contiguous, wavelength values. The device, in particular thanks to the reflection of one of the light beams, allows the wavelength ranges to be configured at will according to the need for communication compatibility between different terminals. Thus, the configuration of the terminal can be modified without modifying the switching device and in particular the separation module, to adapt to the terminals with which the communication must take place. This therefore allows a significant gain in flexibility. The integration of the device and the use of the method by system engineers are therefore facilitated.

[0150] The switching method may comprise a step for adjusting the orientation of the global pointing mirror 11e and the local pointing mirror 11d, in the case where the light beams 1, 2 have been offset from the direction they should have to go towards the separation module 5. The global pointing mirror and the local pointing mirror therefore have the role of finely adjusting the direction of the beams according to the conditions of alignment of the satellite with the ground station.

[0151] According to a preferred example, in the switching method, the power of the first light beam 1 is between 1 W and 1000 W. Preferably, the power of the first light beam 1 is between 5 W and 1000 W.

[0152] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention. The present invention is not limited to the examples previously described. Many other variant embodiments are possible, for example by combining previously described features, without departing from the scope of the invention. Furthermore, the features described in relation to one aspect of the invention may be combined with another aspect of the invention. List of references:

[0153] 1. first light beam

[0154] 2. second light beam

[0155] 3. optical component called imaging or focusing

[0156] 3a. image plan

[0157] 4. plan

[0158] 5. optical beam splitting module

[0159] 5a. diopter

[0160] 7. telescope

[0161] 7a. pupil

[0162] 8. opening

[0163] 8a. axis

[0164] 10. pupil imaging optical module

[0165] 10a. second lens

[0166] 10b. third lens

[0167] 11d. local pointing mirror

[0168] 11th. global pointing mirror

[0169] 11ab. link module l la. third mirror ll b. fourth mirror

[0170] 11 ab1 . upper floor

[0171] 11ab2. lower floor l lc. fifth mirror

[0172] 12a. first side

[0173] 12b. second side

[0174] 13. first set

[0175] 14. second set

[0176] 15. collimator

[0177] 16. connection area with optical fibers

[0178] 17. first zone

[0179] 18. second zone

[0180] 30. Earth

[0181] 31 . satellite

[0182] 20. divergence angle a. forward pointing angle

[0183] DistF. focal length

[0184] D. diameter of the telescope exit pupil t. diffraction spot

[0185] F1 . arrow of descending signals

[0186] F2. Upward signal arrow

Claims

Claims 1. A switching device for a geostationary space satellite telescope, for a first light beam (1) transmitted towards the Earth and a second light beam (2) received from the Earth, the device comprising an optical beam splitter module (5) positioned at a plane (4) and having a shape configured so as to allow one of the first light beam (1) and the second light beam (2) to pass without being in contact with said beam, and to deflect the other of the first light beam (1) and second light beam (2), the switching device being characterized in that it further comprises: • a so-called focusing optical component (3), configured to form, at said plane (4), an image of the first light beam (1) and an image of the second light beam (2), the image of the first light beam (1) being distinct from the image of the second light beam (2), • a first orientable mirror, called a “local pointing mirror” (11d), configured to receive and orient one of the first light beam (1) transmitted towards the Earth and the second light beam (2) received from the Earth, • a second orientable mirror, called a “global pointing mirror” (11 e), configured to receive and orient the first light beam (1) transmitted towards the Earth and the second light beam (2) received from the Earth, • an optical module called “pupil imaging” (10), and in which the local pointing mirror (11 d), the global pointing mirror (11 e) and the pupil imaging optical module (10) are configured so that the local pointing mirror (11 d) and the global pointing mirror (1 1 e) are the image of each other, and the optical beam splitting module (5) being arranged between the local pointing mirror (11 d) and the global pointing mirror (11 e) along the path of the second light beam (2).

2. Switching device according to the preceding claim further comprising a pupil (7a) having a diameter greater than or equal to 300 mm, preferably greater than or equal to 350 mm, the pupil (7a) being the exit pupil of a telescope (7), preferably of a geostationary space satellite.

3. A switching device according to any one of the preceding claims wherein the optical beam splitting module (5) is configured to reflect the other of the first light beam (1) and the second light beam (2).

4. Switching device according to any one of the preceding claims wherein the optical beam splitting module (5) comprises an opening (8) positioned so that one of the first light beam (1) and the second light beam (2) passes through the opening (8) the optical beam splitting module (5), without being in contact with said module (5).

5. Switching device according to the preceding claim in which the opening (8) of the optical beam splitting module (5) is a hole.

6. A switching device according to any one of the two preceding claims, wherein the optical beam splitting module (5) comprises a mirror, the mirror comprising the opening (8), and preferably the hole.

7. Switching device according to any one of the preceding claims in which the optical beam splitting module (5) is based on a material chosen from the group consisting of: glass, crystal, metal and ceramic.

8. Switching device according to any one of the preceding claims, further comprising an optical module called "linking module" (11 ab) comprising a third mirror (11 a) and a fourth mirror (11 b) configured together to receive and modify the diameter of the first light beam (1) transmitted towards the Earth and of the second light beam (2) received from the Earth, the linking module (11 ab) being arranged between the beam splitting optical module (5) and the global pointing mirror (11 e) along the path of the second light beam (2), the pupil imaging optical module (10) and the linking module (11 ab) being configured, with the local pointing mirror (11 d) and the global pointing mirror (11 e) so that the local pointing mirror (11 d) and the global pointing mirror (11 e) are the image of each other.

9. Switching assembly comprising the switching device according to any one of the preceding claims and a satellite telescope (7), preferably a geostationary space satellite.

10. Method for steering a geostationary space satellite telescope, a first light beam (1) transmitted towards the Earth and a second light beam (2) received from the Earth, comprising: • A supply of a switching device according to any one of claims 1 to 8, • A formation in a plane (4) of an image of the first light beam (1) and an image of the second light beam (2) by the focusing optical component (3), the image of the first light beam being distinct from the image of the second light beam (2), • Following the formation of said images, a separation at said plane, by the optical beam separation module (5), of the first light beam (1) and the second light beam (2), the separation comprising a transmission of one of the first light beam (1) and the second light beam (2) without the optical separation module being in contact with said beam, and a deflection of the other of the first light beam (1) and second light beam (2).

11. A switching method according to the preceding claim comprising a selection of a first range of wavelength values ​​for the first beam, and a second range of wavelength values ​​for the second beam, the first and second ranges being distinct, the selection of the first and second ranges being made independently of a configuration of the optical beam separation module. beams.

12. A switching method according to any one of the two preceding claims wherein the optical beam splitting module (5) comprises a mirror, the mirror comprising an opening (8), preferably a hole, when splitting the first light beam (1) and the second light beam (2), the optical beam splitting module (5) transmits one of the first light beam (1) and the second light beam (2) through the opening (8), and reflects through the mirror the other of the first light beam (1) and the second light beam (2).

13. A switching method according to any one of the three preceding claims, wherein, when separating said beams, the first light beam (1) is transmitted without contact with the beam separation module (5), and the second light beam (2) is deflected.

14. Switching method according to any one of the four preceding claims in which the power of the first light beam (1) is between 1 W and 1000 W, preferably between 5 W and 1000 W.

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