Compact deployable opto-mechanical system

Abstract

The invention relates to an opto-mechanical system for a spacecraft, comprising a chassis, a primary mirror comprising a plurality of petals (2A, 2B, 2C), a secondary mirror (5) and a photosensitive sensor for collecting the rays reflected by the mirrors. The secondary mirror is mounted on a secondary platform, and each of the petals is mounted on an individual primary platform deployable between a furled storage configuration and a deployed operation configuration. The chassis comprises an openwork hollow pillar, delimiting a free central volume, and to which each primary platform or each primary mirror is secured. The openwork hollow pillar comprises at least three longitudinal bars (13A, 13B, 13C) distributed around the central volume, the top ends of which bars bear elements (16B,16C) connecting with the secondary platform. The secondary mirror is positioned beyond these top ends in a volume delimited by straight lines extending the bars, at least in the deployed configuration.

Description

[0001] DESCRIPTION

[0002] Title: COMPACT DEPLOYABLE OPTO-MECHANICAL SYSTEM

[0003] Technical field

[0004] This application relates to an opto-mechanical system, such as a telescope, intended to be carried on board a spacecraft. Such a system is used in particular in the context of Earth observation space missions.

[0005] Prior art

[0006] We know of telescopes comprising a large primary mirror configured to reflect and concentrate the rays received towards a smaller secondary mirror, which itself reflects the rays received towards a photosensitive sensor.

[0007] We generally seek to offer opto-mechanical systems that are constrained in terms of mass and volume, in particular to reduce their launch cost.

[0008] Patent US2015 / 0146288 in the name of Utah State University Research Foundation entitled “Multiple petal deployable telescope” discloses a deployable telescope comprising a primary mirror in the form of several petals that can be moved between a folded-down storage position and a deployed operating position. However, such a telescope is complex and, moreover, its accuracy is limited.

[0009] There is therefore a need to improve the precision of this type of telescope deployed in orbit, while meeting requirements in terms of mass and volume reduction.

[0010] Statement of the invention

[0011] The invention aims to overcome at least one of the aforementioned drawbacks, by proposing an opto-mechanical system that is both less complex and more efficient.

[0012] The invention provides an optomechanical system for a spacecraft, comprising a frame, a primary mirror comprising a plurality of petals, a secondary mirror and a photosensitive sensor configured to collect rays reflected by the primary and secondary mirrors, each of the petals having a mirror face and a rear face, the secondary mirror having a mirror face and a rear face, the secondary mirror being mounted on a secondary platform, each of the petals being mounted on an individual primary platform deployable relative to the frame between a stowed storage configuration and a deployed operating configuration, the mirror faces of the petals being configured to focus the reflected rays towards the secondary mirror in the deployed operating configuration.

[0013] The opto-mechanical system according to the invention is characterized in that:

[0014] - the frame includes a hollow openwork pillar delimiting a free central volume,

[0015] - each primary platform or each primary mirror, in the folded storage configuration, is secured to said hollow openwork pillar by at least one first stacking mechanism,

[0016] - the hollow openwork pillar comprises at least three longitudinal bars distributed around the free central volume, each of said bars having a base and a top,

[0017] - the tops of the bars carry connecting elements with the secondary platform,

[0018] - the secondary mirror is positioned beyond the tops of the bars in a volume delimited by straight lines extending from the bars, at least in the deployed operating configuration,

[0019] - the secondary platform is deployable relative to the chassis between its folded storage configuration and its deployed operating configuration, and the connecting elements between the chassis and the secondary platform (6) comprise three arms (16), including two rigid arms (16A, 16B) and a foldable arm (16C), which form, in the deployed position, a tripod supporting the secondary platform (6), each of the three arms having a lower end connected to the chassis by a lower hinge (161) defining a lower pivot connection and an upper end connected to the secondary platform (6) by an upper hinge (162) defining an upper pivot connection, the foldable arm further having an intermediate articulation (163) between its lower and upper ends defining an intermediate pivot connection, the secondary mirror (5) or its secondary platform (6), in the folded storage configuration,being folded down facing the hollow openwork pillar and secured to the hollow openwork pillar by at least one second stacking mechanism,

[0020] - the chassis comprises a base (11) on which the hollow openwork pillar is fixed, which base has an opening (110) at the location of said zone of concentration of the light rays, the opto-mechanical system comprising, on said base opposite the secondary mirror (5), a tertiary mirror (18) having a tertiary focal axis and a deflection mirror (17) configured to receive the rays leaving the secondary mirror and to deflect these rays towards the tertiary mirror, the photosensitive sensor (19) being arranged on the tertiary focal axis to capture the rays returned by the tertiary mirror.

[0021] According to a feature of the invention, the petals, in the deployed operating configuration, are each arranged opposite a gap between two consecutive bars of the openwork hollow pillar which is configured so that the rays reflected by each of the petals towards the secondary mirror do not encounter the openwork hollow pillar, the light rays reflected by the secondary mirror being directed towards a zone of concentration of the light rays arranged between the bases of the bars.

[0022] According to another feature of the invention, there are at least three petals, three pivot axes of said petals being arranged in an equilateral triangle, so that said three petals are arranged around a central axis of the opto-mechanical system at 120°C from each other.

[0023] According to another feature of the invention, each of the petals has a rectangular or square projection in a plane orthogonal to its primary focal axis, the bases of the bars being arranged so that straight lines tangent to the lateral edges of the petals, in the deployed configuration, pass between the bars.

[0024] According to another feature, the optomechanical system according to the invention further comprises nanometric positioning actuators arranged in the primary platforms and in the secondary platform for adjusting the orientation and position of each of the petals and the secondary mirror.

[0025] According to another feature of the invention, the nanometric positioning actuators of each of the petals are constituted by at least three linear nanometric actuators bearing on the rear face of said petal and the nanometric positioning actuators of the secondary mirror are constituted by at least three linear nanometric actuators bearing on the rear face of the secondary mirror.

[0026] According to another particularity, the opto-mechanical system according to the invention further comprises:

[0027] - deployment devices for deploying the petals and / or the secondary mirror between their folded storage configuration and their deployed operating configuration, and

[0028] - locking devices in the deployed operating configuration.

[0029] Another subject of the invention relates to an observation satellite comprising an opto-mechanical system according to the invention.

[0030] Brief description of the drawings

[0031] The invention, according to exemplary embodiments, will be well understood and its advantages will appear better on reading the detailed description which follows, given for information purposes only and in no way limiting, with reference to the appended drawings given as examples in which:

[0032] [Fig. 1] Figure 1 is a perspective view of an exemplary embodiment of an opto-mechanical system according to the invention, in folded configuration;

[0033] [Fig. 2] Figure 2 is a perspective view of the optomechanical system of Figure 1, in the deployed configuration; [Fig. 3] Figure 3 is a schematic representation, seen from the side and in the folded configuration, of different elements of an optomechanical system according to the invention which may correspond to Figure 1;

[0034] [Fig. 4] Figure 4 is a schematic representation, seen from the side and in the deployed configuration, of the opto-mechanical system of Figure 3, with only one petal shown;

[0035] [Fig. 5] Figure 5 is a schematic representation, in profile, of a part of an example of an opto-mechanical system according to the invention illustrating the kinematics of deployment of said opto-mechanical system which may correspond to Figure 1;

[0036] [Fig. 6] Figure 6 represents an example of a petal mounted on the chassis of an opto-mechanical system according to the invention, seen in profile in the folded position, which may correspond to Figure 1;

[0037] [Fig. 7] Figure 7 represents the petal of Figure 6 in the deployed position;

[0038] [Fig. 8] Figure 8 shows an example of an observation satellite according to the invention;

[0039] [Fig. 9] Figure 9 illustrates an example of a method for controlling the opto-mechanical system according to the invention.

[0040] Detailed description

[0041] Identical or similar elements shown in the above figures are identified by identical reference numerals.

[0042] The opto-mechanical system according to the invention may be part, in a non-limiting manner, of a telescope 400 and in particular of an Earth observation satellite 401, as shown in Figure 8.

[0043] As shown in Figure 1, the illustrated optomechanical system comprises a primary mirror, arranged around a central A and segmented into three petals 2A, 2B, 2c (reference 2 generically designating any one of said petals) here in a folded storage configuration. Each of the petals is mounted on a primary platform 3A, 3B, 3C (reference 3 generically designating any one of the primary platforms), which integrates three nanometric linear actuators 4a, 4b, 4c (reference 4 generically designating any one of said actuators).

[0044] Each petal comprises a primary mirror face 20 and a rear face 21 opposite the mirror face 20 and on which the nanometric linear actuators 4 rest directly or indirectly. The rear faces 21 are arranged outwards while the mirror faces 20 are arranged opposite a hollow openwork central pillar forming part of the chassis.

[0045] Alternatively, each petal in the folded position can, for example, be inserted totally or partially between two bars of the hollow openwork central pillar, then having housings for this purpose.

[0046] As shown in Figure 1, the frame comprises in particular a base 11 secured to a hollow openwork pillar comprising three bars arranged orthogonally relative to the base. The hollow openwork pillar comprises three bars 13A, 13B and 13c parallel to the central axis A of the optomechanical system, said bars being hereinafter generically designated by the reference 13. The hollow openwork pillar comprises for example an openwork reinforcement structure forming for example a lattice (not shown) connecting each of the two consecutive bars 13.

[0047] As shown in Figure 1, the hollow openwork pillar leaves a free central volume, around which the bars 13 are distributed. Each bar 13 has a base fixed to the base 11 and a top. The hollow openwork pillar comprises three bars located at 120° from each other, the bases of the bars corresponding to the three vertices of an equilateral triangle, the free central volume consequently being of equilateral triangular section and extending in the axial direction.

[0048] Alternatively, the hollow openwork pillar could, for example, include double bars. Alternatively, the hollow openwork pillar could, for example, include four bars placed at 90° to each other at the four vertices of a square.

[0049] As shown in Figure 1, in the folded storage configuration, the petals 2A, 2B, 2c of the primary mirror are secured to the central pillar by stacking mechanisms. Each of the petals 2 is for example held in the folded position by one (or possibly several) primary stacking mechanisms during the launch and orbiting phases of the satellite. Each petal 2 is mounted on its primary platform 3 which is articulated relative to the chassis around an axis of rotation parallel to the reference plane of the base, i.e. orthogonal to the central axis A of the optomechanical system. Each primary platform 3 comprises two mounting arms 31, 32 articulated by pivot links on a yoke 33 fixed on the base 11 of the chassis.

[0050] As shown in Figure 1, the optomechanical system also comprises a secondary mirror 5 carried by a secondary platform 6 which integrates three nanometric linear actuators 7. Elements for connecting the secondary platform 6 with respect to the frame 10 comprise two rigid arms 16A, 16B and a foldable arm 16c. Each of the arms 16A, 16B, 16C (whether rigid or foldable) comprises a first end, articulated to the top of one of the bars 13A, 13B, 13C by a lower hinge 161, and a second end articulated on the secondary platform 6 by an upper hinge 162. These connections can also be of the ball joint type.

[0051] As shown in Figure 1, the foldable arm 16c further comprises an intermediate articulation 163 which divides the foldable arm into two portions, namely a lower portion 164 and an upper portion 165, which makes it possible to fold said arm in two. The bars 13A, 13B on which the rigid arms 16A, 16B are articulated are for example longer than the bar 13c on which the foldable arm 16c is articulated so that, when the secondary mirror 5 is in the folded position, the two rigid arms 16A, 16B form an angle less than or equal to 90° with the bar 13A, 13B to which they are respectively attached. Thus the secondary mirror 5 lowers below the top of the central pillar. When the secondary mirror 5 is in the folded configuration, the foldable arm 16c is completely folded in two, that is to say that its two portions 164, 165 are substantially parallel and pressed against each other, the intermediate articulation 163 forming an angle close to 0°.Furthermore, still in the folded configuration, the lower portion of the foldable arm forms an angle close to 0° with the bar 13c to which the foldable arm 16c is attached. Thus, the optomechanical system is particularly compact when the secondary mirror 5 is in the folded configuration.

[0052] Alternatively, the bar 13c may also, for example, comprise extensions, which form a receiving housing and a support for the secondary platform 6 and the secondary mirror 5 in the folded configuration.

[0053] In the folded configuration, the secondary platform 6 or the arms 16 are, for example, held by stacking mechanisms during the launch and orbiting phases of the satellite.

[0054] The stacking mechanisms for the secondary mirror, as well as the stacking mechanisms for the primary mirror, are for example configured to open on command for the purpose of deploying the opto-mechanical system.

[0055] For example, petal stacking mechanisms are attached to the petals or primary platforms. Attaching the petal directly to the chassis via the stacking mechanism will prevent the forces generated during launch from being applied to the actuators.

[0056] The secondary mirror stacking mechanism(s) are, for example, attached to the secondary mirror or to the secondary platform. Attaching the secondary mirror directly to the chassis by the stacking mechanism will prevent the forces generated during launch from being applied to the actuators.

[0057] As shown in Figure 2, the secondary mirror 5 can for example be moved from its folded position to a deployed position in which the secondary mirror 5 is centered on the central axis of the optomechanical system and in which its mirror face is oriented towards the base 11 of the chassis. The secondary mirror 5 is located on the central axis A of the optomechanical system, in the axial extension of the free central volume delimited by the central pillar, at a distance beyond the tops of the bars 13. The secondary mirror 5 is thus positioned beyond the tops of the bars in a volume delimited by straight lines coming in the extension of the bars 13, in the deployed operating configuration. Its mirror face is oriented towards the primary mirror.

[0058] For greater precision and stability, each of the passive pivot links, namely the lower hinges 161 and the upper hinges 162 of the three arms 16A, 16B, 16c, are for example provided with stops and end-of-travel locks (not shown) which advantageously make it possible to lock the link elements in the deployed position. The optomechanical system thus gains in reliability. The height of the secondary mirror 5 in the deployed position relative to the base 11 of the chassis (which height corresponds approximately to the cumulative length of a bar 13 and the arm 16 which extends said bar) may for example be such that the focusing zone of the secondary mirror, towards which the rays reflected by the secondary mirror converge, is located substantially at the level of the base 11 (that is to say between the bases of the bars) or nearby, on one side or the other of the base.

[0059] Alternatively, a secondary mirror could be provided which is fixed relative to the chassis and positioned on its secondary platform in the position corresponding to Figure 2.

[0060] As shown in Figure 2, the three petals 2A, 2B, 2C of the primary mirror can be moved from their folded position to a deployed position in which they form the segmented primary mirror returning the received light rays to the secondary mirror 5. The axis of rotation of the petal can be for example located in the plane defined by the two bars or a parallel plane and outside the pillar. Each of the petals 2 has for example:

[0061] - an internal edge which extends parallel to and in the immediate vicinity of the axis of rotation of the petal defined by the pivot links 34, 35, of its primary platform,

[0062] - two lateral edges 27, 28 which extend from the ends of the internal edge towards the outside of the opto-mechanical system,

[0063] - and an external edge 29, opposite the internal edge. In Figure 2, the petals illustrated have a shape (we are talking here about their projection in a plane orthogonal to their primary focal axis FP) which is square or rectangular.

[0064] Alternatively, the petals could, for example, have a trapezoidal shape with an outer edge longer than the inner edge, or a circular shape, a hexagonal shape, or a non-polynomial shape. The shape of the petals can indeed be adapted to the needs of the mission.

[0065] Alternatively, the petals could themselves be segmented and deployable into multiple parts, each of these multi-part petals facing, for example, a gap between two consecutive bars 13.

[0066] As shown in Figure 2, each petal 2 and its primary platform 3 are for example arranged facing a free interval between two consecutive bars (the petal 2A is thus located between the bars 13A and 13B), said consecutive bars being arranged on either side of the straight lines which are tangent to the lateral edges 27, 28 of the petal. Thus, the light rays reflected by the petal 2 in the direction of the secondary mirror 5 do not encounter the bars 13, nor the arms 16 which carry the secondary platform.

[0067] The positioning of the petals and the secondary mirror, by controlling at least three nanometric positioning actuators, can be controlled in a known manner by a phase recovery method which makes it possible to adjust the positions of the mirrors according to the images received by the photosensitive sensor. A telecommunications module is provided for implementing the phase recovery method. Conventionally, this operation is carried out in collaboration with the ground segment, by phase recovery, on the basis of analyses of images captured by the photosensitive sensor 19 while the optomechanical system is pointed towards a given star.The nanometric positioning actuators 7 of the secondary mirror and the nanometric positioning actuators 4 of the petals are then controlled to place the primary and secondary mirrors in an initial adjustment configuration, which gives the optomechanical system the desired performance, particularly in terms of sharpness, resolution, precision. Alternatively, a method may be provided comprising a step Etp001 of calibrating the mirrors consisting of a phase recovery method, followed by one or more steps Etp002 of monitoring and repositioning.

[0068] Preferably, after the calibration step, several monitoring and repositioning steps are carried out, for example, at regular time intervals, as shown in Figure 9. Thermoelastic variations are, for example, corrected by monitoring and repositioning every 10 seconds. For the measurement itself, a laser instrument can, for example, operate at a few kHz. It is, for example, possible to average several measurements.

[0069] As shown in Figure 3, a monitoring and repositioning module 62 monitors and controls the positioning of the primary and secondary mirrors, based on distance data measured on board generated from the distance measurement sensors placed on each of the petals (2, 2A, 2B, 2C) and on the secondary mirror 5. Advantageously, these monitoring and repositioning operations make it possible to guarantee, over time, a nanometric positioning of the petals and the secondary mirror relative to the chassis. Advantageously, this routine can be executed on board and the performances are guaranteed throughout the mission despite the thermoelastic disturbances suffered by the optomechanical system in the space environment.

[0070] As shown in Figure 4, the repositioning operations use distance measurements provided by a LASER 60 transceiver, in cooperation with targets 25 and 50 attached to the mirrors.

[0071] The initial adjustment by phase recovery is advantageously used to establish distance measurements in an initial configuration. These distance measurements thus serve as a reference for adjusting the positions of the mirrors.

[0072] For this purpose, for example, three targets are used for each petal 2 and three targets for the secondary mirror 5, targets whose positions are measured relative to a LASER transmitter receiver placed on one of the bars of the hollow openwork pillar.

[0073] Advantageously, these operations, requiring few computing resources and energy, are for example carried out autonomously by the opto-mechanical system, without intervention from the ground segment, requiring neither telecommunication with the ground, nor image analysis.

[0074] Advantageously, such repositioning using the monitoring and repositioning module 62 and the distance sensors takes very little time, compared to a phase retrieval operation (also referred to as “phase retrieval” in English), such as the initial calibration operation, which requires specifically modifying the orientation of the optomechanical system towards a given star, exchanging with the ground and carrying out image analyses.

[0075] Advantageously, such repositioning, using the monitoring and repositioning module and distance sensors, also allows a saving in operational time as well as a saving in terms of energy and material resources necessary for the calculation.

[0076] Advantageously, such repositioning, using the monitoring and repositioning module and the distance sensors, does not require an interruption of the mission, but is carried out, for example, regardless of the direction pointed by the optomechanical system, in masked time, or even when the optomechanical system is capturing images for the mission. However, it may be preferable to interrupt the measurements at the time of image capture if the wavelength of the LASER 60 rangefinder is such as to disturb the photosensitive sensor 19.

[0077] As shown in Figure 4, the opto-mechanical system comprises, for example, distance measuring sensors used for detecting the position and orientation of the secondary mirror 5 and each of the petals 2 relative to the frame. The distance measuring sensors comprise, for example:

[0078] - for each of the petals 2, three targets 25 of the cube corner type, not aligned, fixed to the periphery of said petal on the side of its primary mirror face (a single target 25 is shown in figure 4),

[0079] - for the secondary mirror 5, three targets 50 of the cube corner type, not aligned, fixed to the periphery of said secondary mirror 5 on the side of its secondary mirror face (a single target 50 is shown in figure 4).

[0080] As shown in Figure 4, the LASER transceiver emits measurement radiation in the direction of the targets and is capable of detecting radiation reaching it in the same direction as the measurement radiation, the LASER transceiver 60 being fixedly mounted on the chassis in a location visible by all the targets 25 of the three petals and by all the targets 50 of the secondary mirror. Advantageously, for ground tests, it is possible to use a commercially available LASER metrology module, such a module being subsequently spatialized for integration into a spacecraft.

[0081] Preferably, the location chosen to position the LASER transmitter-receiver allows measurements at less than 45°, that is to say that the LASER transmitter-receiver 60 oriented parallel to the central axis can see all of the targets in two upper and lower cones having a solid angle of 45°. For example, it is planned to install the LASER transmitter-receiver sufficiently far from a reference plane of the primary mirror and from a reference plane of the secondary mirror in the axial direction so that, whatever the target 25 or 50 considered, the angle between the central axis A and the measurement direction, which connects the target 25 considered and the LASER transmitter-receiver, is less than or equal to 45°. The reference plane of the primary mirror passes through the virtual center of the primary mirror and is orthogonal to the central axis. The reference plane of the secondary mirror passes through the center of the secondary mirror and is orthogonal to the central axis.

[0082] Thus, the larger the diameter of the primary mirror, the higher the height at which the LASER 60 rangefinder is positioned, for example, which may require also moving the secondary mirror further away in the deployed position and dimensioning the bars 13 and / or the arms 16 accordingly.

[0083] As shown in Figure 4, the LASER transmitter-receiver 60 is for example fixed near the top of the bar 13A. Advantageously, the openwork nature of the hollow central pillar makes it easy to find a location on the chassis to receive the LASER transmitter-receiver and three locations on each petal as well as three locations on the secondary mirror where the targets 25 and 50 are respectively installed and so that all the targets 25, 50 are visible to the LASER transmitter-receiver 60.

[0084] As shown in Figure 4, the base 11 of the chassis has an opening 110 centered on the central axis A of the optomechanical system, opposite the empty central volume delimited by the openwork hollow pillar and opposite the secondary mirror 5 in the deployed configuration. The rays received and reflected by the secondary mirror 5 in the deployed position pass for example through the empty central volume then the opening 110 then are deflected by a deflection mirror 17, fixed under a lower face 111 of the base axially opposite the opening 110, in the direction of a tertiary mirror 18, fixed under the lower face 111 of the base. The tertiary mirror

[0085] 18 returns and concentrates the received rays towards a photosensitive sensor

[0086] 19 also fixed under the lower face 1 11 of the base.

[0087] Alternatively, the aperture could be removed to place a photosensitive sensor in the area where the light rays are concentrated.

[0088] A microprocessor control unit 23, for example, allows the optomechanical system to be operated via data, addressing and control buses.

[0089] For example, at least one radiant element 25 is provided for cooling the various components of the optomechanical system which are likely to heat up.

[0090] The opto-mechanical system also includes, for example:

[0091] - a telecommunications module for calibration 61 and

[0092] - a monitoring and repositioning module 62 comprising a control loop.

[0093] The telecommunications module, like the monitoring and repositioning module, are presented for example in the form of a hardware and software electronic module. Figure 3 shows the opto-mechanical system of Figure 4, in the folded storage configuration. Deployment is for example obtained by a single rotation actuator 301 which acts on the intermediate articulation 163 of the foldable arm 16c; the other pivot connections of the arms 16 being for example passive.

[0094] Alternatively, for reasons of redundancy, an additional rotation actuator can however be provided at the same location.

[0095] The use of a single actuator 301, possibly redundant, for the entire deployment structure allows in particular a significant weight saving.

[0096] As shown in Figure 3 or 6, it is possible, for example, to provide, for each petal, a stacking mechanism 9 arranged at an external angle of said petal or its primary platform or at a lateral edge of the petal or its primary platform, the stacking mechanism being configured to keep the petal 2 or its primary platform 3 attached to one of the two bars 13 of the chassis in the folded position.

[0097] As shown in Figures 6 and 7, each primary platform 3 is for example associated with a single rotary actuator 302 (with, possibly, a redundant backup actuator) acting on the pivot link 34 for the deployment of the petal from the folded position (Figure 6) to the deployed position (Figure 7), the pivot link 35 being passive.

[0098] In the deployed position, each primary platform 3 may, for example, come to bear on the yoke 33. End-of-travel stops (not shown), against which a rear face of the primary platform 3 comes to bear, may be provided on each yoke 33. These stops, for example, define a reference position for the deployed position of the petal. The simplicity of the deployment kinematics of the primary mirror makes it possible, for example, to use a single rotary actuator per petal, which results in a weight saving.

[0099] The position just after deployment has, for example, micrometric precision. Figure 5 shows an example of deployment kinematics of the connecting elements allowing the secondary mirror 5 to move from the folded position to the deployed position. The solid line 200 represents the foldable arm 16c, the secondary platform 6 and the first rigid arm 16A (the second rigid arm 16B being parallel to the first and masked by it in profile view) in the folded position. The dotted line 201 (first type of dotted line) represents the foldable arm 16c, the secondary platform 6 and the first rigid arm 16A in a first intermediate position. The dotted line 202 (second type of dotted line) represents the foldable arm 16c, the secondary platform 6 and the first rigid arm 16A in a second intermediate position.The dotted line 203 (third type of dotted line) represents the foldable arm 16c, the secondary platform 6 and the first rigid arm 16A in the deployed position.

[0100] For each petal 2, three nanometric linear actuators 4a, 4b, 4c are for example provided. These actuators are for example integrated into the primary platform 3 of the petal.

[0101] The mirror is for example supported by bipods connected elsewhere to a rear interface, the nanometric actuators acting on this interface.

[0102] Alternatively, the mirror can be made from a single piece with the interface on which the nanometric actuators act.

[0103] In the deployed configuration, the primary platforms 3 of the petals and the secondary platform 6 of the secondary mirror are made integral with the frame (i.e. fixed relative to it), for example by locking mechanisms. Thus in the deployed configuration, the nanometric actuators exert their action on a petal or on the secondary mirror, while also being supported on the frame.

[0104] The actuators are for example fixed to the panel of a platform and act by moving a support surface on the mirror. The actuators are for example arranged in the platform 3 so that their working axis is parallel to the primary focal axis Fp of the petal.

[0105] The mirrors are for example adjustable in rotation and translation by controlling the nanometric actuators. Thus the three nanometric linear actuators allow for example to very precisely adjust the position of the petal according to the primary focal axis of the petal (or more generally according to the working direction of the actuators) and the orientation of the petal around three axes orthogonal to said focal axis.

[0106] In a similar way to the petals, the secondary platform 6 integrates for example three nanometric linear actuators 7 which make it possible to adjust with nanometric precision the orientation of the secondary mirror, as well as its position along the secondary focal axis FS which corresponds to the central axis A of the optomechanical system in the deployed configuration.

[0107] The optomechanical system aims to capture the light rays which reach it in the direction of its central axis A. The path taken by the rays reflected by the petals of the primary mirror in the direction of the secondary mirror 5 is specific to the invention thanks to the bars 13 of the openwork hollow pillar and the arms 16 connected to the tops of these bars. The light rays are thus not disturbed by the bars or the arms which do not meet them.

[0108] For example, three light fluxes are captured by the petals and entirely reflected towards the secondary mirror, before being entirely concentrated towards an area located between the bases of the bars.

[0109] The architecture proposed according to the invention also makes it possible to obtain a light and compact optomechanical system to be embedded in satellites of smaller size. The launch cost is thus advantageously reduced.

Claims

CLAIMS 1. Optomechanical system for a spacecraft, comprising a chassis, a primary mirror comprising a plurality of petals (2, 2A, 2B, 2C), a secondary mirror and a photosensitive sensor (19) configured to collect the rays reflected by the primary and secondary mirrors, each of the petals having a mirror face (20) and a rear face (21), the secondary mirror (5) having a mirror face and a rear face, the secondary mirror being mounted on a secondary platform (6), each of the petals being mounted on an individual primary platform (3, 3A, 3B, 3C) deployable relative to the chassis between a folded storage configuration and a deployed operating configuration, the mirror faces of the petals being configured to concentrate the reflected rays towards the secondary mirror in the deployed operating configuration, characterized in that: - the frame includes a hollow openwork pillar delimiting a free central volume, - each primary platform or each primary mirror (3), in the folded storage configuration, is secured to said hollow openwork pillar by at least one first stacking mechanism (9), - the hollow openwork pillar comprises at least three longitudinal bars (13, 13A, 13B, 13c) distributed around the free central volume, each of said bars having a base and a top, - the tops of the bars carry elements (16A, 16B, 16c) for connection with the secondary platform (6), - the secondary mirror (5) is positioned beyond the tops of the bars in a volume delimited by straight lines extending from the bars (13), at least in the deployed operating configuration, - the secondary platform is deployable relative to the chassis between its folded storage configuration and its deployed operating configuration, and the connecting elements between the chassis and the secondary platform (6) comprise three arms (16), including two rigid arms (16A, 16B) and one foldable arm (16c), which form, in the deployed position, a tripod supporting the secondary platform (6), each of the three arms having a lower end connected to the chassis by a lower hinge (161) defining a lower pivot connection and an upper end connected to the secondary platform (6) by an upper hinge (162) defining an upper pivot connection, the foldable arm further having an intermediate articulation (163) between its lower and upper ends defining an intermediate pivot connection, the secondary mirror (5) or its secondary platform (6), in the folded storage configuration, being folded down facing the openwork hollow pillar and secured to the openwork hollow pillar by at least one second stacking mechanism, - the chassis comprises a base (11) on which the hollow openwork pillar is fixed, which base has an opening (110) at the location of said zone of concentration of the light rays, the opto-mechanical system comprising, on said base opposite the secondary mirror (5), a tertiary mirror (18) having a tertiary focal axis and a deflection mirror (17) configured to receive the rays leaving the secondary mirror and to deflect these rays towards the tertiary mirror, the photosensitive sensor (19) being arranged on the tertiary focal axis to capture the rays returned by the tertiary mirror.

2. Optomechanical system according to claim 1, in which the petals, in the deployed operating configuration, are each arranged opposite a gap between two consecutive bars (13) of the openwork hollow pillar which is configured so that the rays reflected by each of the petals towards the secondary mirror do not encounter the openwork hollow pillar, the light rays reflected by the secondary mirror being directed towards a zone of concentration of the light rays arranged between the bases of the bars.

3. Opto-mechanical system according to one of claims 1 to 2, in which the petals are at least three in number (2A, 2B, 2C), three pivot axes of said petals being arranged in an equilateral triangle, so that said three petals are arranged around a central axis (A) of the opto-mechanical system at 120°C from each other.

4. Opto-mechanical system according to one of claims 1 to 3, in which each of the petals (2) has a rectangular or square projection in a plane orthogonal to its primary focal axis (FP), the bases of the bars being arranged so that straight lines tangent to the lateral edges (27, 28) of the petals, in the deployed configuration, pass between the bars.

5. Optomechanical system according to one of claims 1 to 4, further comprising nanometric positioning actuators (4, 7) arranged in the primary platforms and in the secondary platform for adjusting the orientation and position of each of the petals (2) and of the secondary mirror (5).

6. Optomechanical system according to claim 5, in which the nanometric positioning actuators of each of the petals (2) are constituted by at least three linear nanometric actuators (4a, 4b, 4c) bearing on the rear face (21) of said petal and the nanometric positioning actuators of the secondary mirror are constituted by at least three linear nanometric actuators (7) bearing on the rear face of the secondary mirror.

7. Opto-mechanical system according to one of claims 1 to 6, characterized in that it comprises: - deployment devices (301, 302) for deploying the petals (2) and / or the secondary mirror (5) between their folded storage configuration and their deployed operating configuration, and - locking devices in the deployed operating configuration.

8. Observation satellite comprising an opto-mechanical system according to one of claims 1 to 7.

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