FR2736165A1 - Orbital reflective telescope - Google Patents

Abstract

The orbital telescope includes a membrane-type mirror (45) and an associated membrane (46) which protection of the mirror membrane. These are mounted within a sleeve (2) with a protective outer sheath (3). The structure is foldable, and includes integrated electronics for controlling the shape of the mirror. The image observation system is placed at the focus of the mirror, and a further stage is placed at the centre of curvature of the mirror in order to determine and recognise its shape. A light can be provided to illuminate an object viewed by the telescope. The shape of the membrane-type mirror can be controlled by a stack of membranes of different diameters, held together at their common centres.

Description

PERFECT1ON TELESCOPE
FIELD OF THE INVENTION.

 The field of the invention is that of satellite telescopes.

PRIOR STATE OF THE ART.

There is a request for observation of the earth having characteristics which have hitherto been incompatible
a) a strong separating power on the ground, less than a meter,
b) a large field of observation whose diameter should be of the order of a thousand kilometers.

 c) an almost permanent observation.

 In French application 94/11458, a tripod telescope with a membranous mirror without lateral protection is described mainly, although the other structures described can be closed.

 The advantages of such a tripod telescope are its simplicity.

its low weight and the small apparent surface of its chassis minimizing the probability of an encounter with a destructive meteorite.

 The disadvantages are, on the one hand. a set of orientation constraints, since it is necessary to avoid direct solar illumination of the mirror and the impact of micrometeorites on the mirror which has only a dorsal and weakly lateral protection, and.

 on the other hand, the stray light coming from the lighting of the tripod chassis.

 SUMMARY OF THE INVENTION.

 To remedy the parasitic illumination and improve the thermal control of the telescope 1, the invention integrates into the telescope a first sheath 2, and one or more almost independent protective opaque sheaths 3 (FIG. 1).

 In the event of drilling by a meteorite, the holes produced define a possible precise direction of the parasitic solar rays through the successive sheaths.

 In a particular embodiment, the outer sheath 3 is independent and has independent reactive means allowing its positioning; it is then connected to the rest of the telescope by flexible mechanical and electrical means.

 To increase the observable field in geostationary orbit, without overall movement of the telescope 1, the invention allows the exploration, by the optical axis 4 of the mirror 5. of a solid angle 6 having for axis the main optical axis 7 of the telescope (figure i3).

 The invention also makes it possible to increase the observable field without movement of the optical axis 4 of the mirror 5, by scanning the focal plane 8 through a centered circular zone of least aberration 9 (FIG. 16).

 A telescope of this type, in geostationary orbit, can therefore explore. without the expenditure of non-renewable energy. and at a high frequency, a circular terrestrial area.

 For exemple. a mirror 15 meters in diameter, weighing with its control membrane between 5 and 2 kilos, has an angular separating power of approximately 4x1 * -8 radian, and therefore on the ground, a separating power of approximately 1.2 meters.

 A solid exploration angle of 0.6 radians gives an 18 km diameter exploration circle on the ground.

 At any time, a limited area of this 18 km diameter exploration circle can be observed preferentially.

DETAILED DESCRIPTION
Foldable blind cylinders
The blind cylinders 2 and 3 constituting the casing of the telescope and the, or the protective sheaths, are made of a composite material which can be polymerized under the effect of ultraviolet radiation or any other effect known from the prior art.

 Tubes (FIG. 3), longitudinal 1, circular, axial 11, or helical 12, can be stiffened by gas injection according to the prior art; after the introduction of this gas, they restore the primitive shape of the blind cylinders of the telescope and the sheaths.

 The open end of the blind cylinders. whose plane makes an acute angle with the optical axis 7 of the telescope, has an elliptical shape and is closed, in a particular embodiment, by a temporary elliptical veil.

 When the cylinders have taken their final forms, and are stiffened by polymerization, the elliptical haze is eliminated.

 In a particular embodiment, the space between the sheath and the telescope is closed by a ring 14.

 Tubes 13 stiffen the openings which are held approximately elliptical by centering links 15 and 16, in the absence of a closure ring.

Blind tapered or bitronconic cylinders.

 To facilitate folding. in particular embodiments, the blind cylinders are very slightly frustoconical or bitronconic.

Telescopic vertical folding.

Prefabricated open cylinder.

 In a particular embodiment of the invention, the twin-conical cylinder, with a large central diameter 17, is manufactured before folding, either entirely or only over a length sufficient to perform each elementary folding.

 The bottom 18 is added after the first phase of this folding.

 If it is the casing of the telescope, the three stages 19, 2 and 21 of this telescope are secured to the sheath by their arms before folding. or during folding (Figures 4 and 5).

Folding by telescopic invagination. A cylindrical element 22 of the cylinder arranged vertically is taken as a starting element.

 It can be a middle element or an end element.

 Take for example a middle element.

 This cylindrical element is held by external means, and the part of the cylinder above this element is introduced into the interior of said element by folding along a circumference and turning downwards up to a determined height of said cylindrical element.

 In this situation, the first vertical fold thus obtained is immobilized, and. at the upper level of the starting cylindrical element. or slightly above, the folding operation is repeated.

 In this way, the entire cylinder initially located above the starting cylindrical element is folded in the height of this starting cylindrical element, or in a slightly higher height. and forms with this starting cylindrical element a cylindrical torus whose thickness is close to the sum of the thicknesses of the different plies.

 The same operation is made with the lower part of the bitronconical cylinder constituting the casing of the telescope.

 We then have the superposition of the three stages of the telescope and the folding element 23 of the beveled lens hood.

 The enclosure 19 of the mirror stage is extended downwards by a centered mast 24 allowing the communication of the telescope to the outside, through the bottom 25 of the sheath 3. and which supports the solar panels, the means of movement reagent and telecommunication means, not shown.

Radiant folding of the telescope. (Figures 6, 7 and 8)
Each stage of the telescope consists, according to the prior art, of a central enclosure linked, by three or four arms 26 (FIGS. 2 and 4), to the blind cylinder 2.

 Once the vertical folding has been carried out, the three enclosures are superimposed as well as, three by three, the nine or twelve arms 26.

 Radiant folding. according to the invention, is then made with a number of rays multiple of 3 or 4.

Rayon folding device. (Figures 11 and 12)
The folding device consists of linear vertical means 27 internal to the cylindrical folding, some in contact with the ends of the arms, and retaining the cylindrical folding, and linear vertical means 28 external to the cylindrical folding, going in pairs. and taking between the two elements 28a and 28b of the pair the radiating fold retained by the interior means 27 (FIG. 7).

 In the case where the internal vertical folding means 27 are located under the bottom of the blind cylinder, this bottom is pierced with closable holes suitable for letting these internal vertical folding means pass.

 If the external means 28 are moved radially towards the enclosures, using guide devices 36 and 37 (FIGS. 11 and 12), the external means having a predominant action and the internal means an action of radial elastic retaining, the initial cylindrical vertical folding will take the form (figure 7) of a wheel with spokes 3 in contact with the central speakers.

 Under the combined effect of the vertical external means 28 bringing the cylindrical folding against the enclosures, and the internal means 27 retaining them, the part of the vertical folding situated between the spokes is pressed against the enclosures.

 The arms of the enclosures being longer than the radii of the radiating folding, these arms are zigzagged during the movements of the exterior and interior folding means.

Winding of spokes. (figure 8, 9 and 1)
To wind, according to the invention, the spokes 3 around the speakers, a relative rotational movement is animated, around the central axis of the speakers. the internal means 27 relative to the external means 28 which remain fixed and press the vertical folding against the speakers.

 In this way. the radiant folds wrap around the speakers.

 The vertical folding means are then removed.

Folding of the sheaths.

 The folding of a sheath 3 is simplified because it is empty.

 The roller constituted by the telescope is placed in the center of the folding device and the radiating folding of the sheath and its winding is made in contact and around the roller of the telescope.

 The bottom of the sheath is pierced with a hole allowing the passage of the external mat 24.

"Crumpled" folding of the bottoms. (figure 1)
During radiating folding, the bottom of the blind cylinder always remains within the perimeter determined by the radiating folds.

 Under these conditions, the bottoms 18 or 25 adopt a natural or assisted folding, difficult to draw, and are contained in a limited space, and represented by undulations 31 (FIG. 1).

Telescopic vertical unfolding tubes. (figures 4 and 5)
The vertical unfolding tubes 32 and 33 are closed tubes arranged symmetrically around the blind cylinders 2 and 3, along a generatrix.

 They are joined to the blind cylinders 2 and 3 at intervals corresponding to the height of the cylindrical elements of telescopic folding, by links 15 and 16.

 They are folded vertically by telescopic invagination, in the same way as the blind cylinders, into cylindrical elements of the same height as those of the blind cylinders, and at the same time.

 The introduction, through the orifices 34 and 35, of a pressurized gas into these unfolding tubes causes their expansion which leads to the expansion of the blind cylinders.

 They participate in the final rigidity of the blind cylinders.

Unfolding.

Centrifugation. Once orbited, and released from its container, the cylindrical sheath-telescope assembly is rotated around its axis 7 so as to unwind the rays 3 of the sheath 3, then of the telescope 1.

 In this way, the assembly is made up of concentric cylindrical toroids resulting from the vertical folds of the, or the sheaths, and the telescope.

Extension. The vertical unfolding of the telescope is then carried out under the effect of the unfolding tubes 32.

 Once the polymerization has been carried out under solar action.

in the case where this polymerization is carried out in this way, the sheath is deployed and polymerized in turn.

Inflation. In another embodiment, where the blind cylinders are closed at their other end by temporary covers, the telescope and the sheath are deployed by the introduction of a gas within the enclosures themselves.

 The shaping stiffening tubes 1, 11 and 12 are then stiffened, the sheath polymerized by solar UV, its cover removed, then the top of the polymerized telescope, its cover removed and the polymerization of the telescope completed.

Polymerization with a reactive gas.

 In a particular embodiment, the polymerization is obtained by the action of a reactive gas introduced between the sheath and the telescope. or also inside the telescope.

The means of folding.

 In a particular embodiment (Figures 28 and 29). the internal 27 and external 28 folding means consist of mobile carriages 36 and 37 guided radially by guide elements 38 in a horizontal plane, and provided with linear elements 27 and 28 perpendicular to this plane. and can occupy a lower position or a higher position.

 In a particular embodiment, the vertical elements consist of two or a multiplicity of vertical sub-elements capable of relative movements of approximation retaining their parallelism.

 In this way, the displacement means can grasp between their vertical elements the concentric folds resulting from the vertical folding.

The closure lids.

 The purpose of the eliminable closure lids is to give an elliptical shape as perfect as possible, during the polymerization. with bevels ending the telescope and the sheath. and in a particular embodiment, in addition to allow deployment by inflation of the telescope and of the sheath.

The control solenoid.

 The sheath 2 of the telescope 1 is provided at its base, at the level of the mirror stage, with a solenoid 39 consisting of conductive elements 40 surrounding said sheath 2 (FIG. 1).

 The solenoid thus formed generates, when it is traversed by an electric current, a magnetic field parallel to one axis of the telescope.

It constitutes the magnetic dipole provided for in French application 94/11458
The discrete solenoids 41 of the control membrane will interact with this magnetic field so as to maintain the desired shape of said membrane, and its centering on the optical axis of the telescope.

 In a particular realization. the membrane with discrete solenoids is metallized and constitutes the mirror of the telescope.

 In the particular embodiment of application 94/11458, the membrane 42 provided with the solenoids 41 has only approximately the desired shape, and the final shape is given to a simple mirror membrane 5, the shape of which is determined by electrostatic forces. existing between the metallized surface 43 of this mirror membrane 5 and electrodes 44 existing on the membrane 42 of approximate shape then serving as a control membrane.

Mirror control.

 Surface electronic circuits integrated into the membrane during its manufacture control the potentials of the electrodes of action on the mirror, and the magnetic fields of the solenoids of membrane-magnetic dipole interaction.

 The metallized surface 43 of the mirror 5, or a conductive surface, in the case where the reflecting surface is dielectric. is initially at potential 0.

 The electrodes 44 of the control membrane 42 are brought to positive or negative potentials inducing the distance or the relative local approximation of the mirror and the control membrane.

 The necessary tensions will be all the more weak as the two membranes will have a shape closer to the shape desired for the mirror, and that their distance will be shorter.

 Ideally, the applied voltages oscillate around zero with a zero resultant, for a mirror-membrane distance included in a wide range.

 In this way, significant local deformations of the control membrane 42 will not interfere with obtaining the perfect shape of the mirror.

 This weakness of the necessary voltages makes it possible to control them by the surface integrated circuits seen above.

 Surface integrated circuits receive their instructions from control electronics receiving information from the sagittal segment analysis system of application 94/11458.

Macro and micro controls.

 The system claimed in application 94/11458 dissociates a long-range action acting on the control membrane by magnetic fields reacting with the field of the solenoid, and a short-range action of the inter-membrane electric fields.

Field exploration. (figure 13)
This dual system allows significant movement of the mirror 5 such that the optical axis 4 of the said mirror can explore an area included in a certain solid angle 6, while retaining the quality of the image at the fixed focus 45 of the telescope.

 This solid angle 6 is determined by the limits of the magnetic and electrostatic actions possible, taking into account the mechanical characteristics of the membranes, the energy and the voltages available.

Mobile eddy-up. (figure 13)
The eddy system 46 described in application 94/11458.

or any other device for controlling the mirror 5, located at the sagittal segment, moves, according to the invention. inside a circle centered on the optical axis 7 of the telescope, while remaining directed towards the point of intersection of the extended ideal surface of the mirror 5 and of said initial optical axis 7.

 In a new position away from the initial optical axis, the eddy system 46 gives the electronic mirror control device the information necessary to give the mirror membrane 5 a parabolic shape. or any other form of least aberration having its sagittal segment determined by the position of said eddy system.

 This mirror 5 will give on the photoelectric receiving matrix 4 the image 48 of objects located in a direction deviating from the old optical axis 7 by twice the angle including the optical axis of the mirror 5. materialized by the device sagittal control 46, deviates from it.

 To remedy the decline in the quality of the images 48 formed far from the optical axis, the shape of the mirror 5 is optimized by the eddy system 46 itself, associated or not with a focus control system 8, 45 of the Hartmann-Shalk type, or with contrast detection if the telescope is aimed at a field without stars.

 A considerable advantage of such a system is that it keeps the main mass of the telescope stationary. and that it only uses renewable energy from solar panels.

 Another advantage is that the exploration of the solid angle can be done more quickly than by displacement of the whole of the telescope, because of the very low masses of the mirror and of its control membrane.

Gimbal mounting. (figure 14)
To allow the orientation of the mirror 5, the cylinder 49 centering the mirror 5, optionally by means of a motor ring 55, and its membrane 42, is orientable inside a solid angle.

 In a particular embodiment, this cylinder 49 is mounted "Cardan", according to two diameters 50 and 51 and actuators 52 direct the axis of this cylinder towards the eddy-up device.

 In another embodiment (FIG. 15), the centering cylinder 49 of the mirror and of the membrane is centered on a ball joint 53.

Annular exploration. (figure 16)
In a particular embodiment, the eddy system remains centered on the main optical axis 7 of the telescope.

 The generator of the mirror is gradually modified while keeping the mirror its shape of revolution.

 This deformation is such that the image 48 has a centered minimum aberration ring 9 which is enlarged radially on the photoelectric receiving matrix 47, like a circular wave, according to the modifications of the mirror.

 This reception matrix 47 is explored in synchronism with its scanning by the image ring 9 of least aberration.

 In this way, the field of the least aberration image can be considerably enlarged.

 In a particular embodiment, one or more photoelectric receiving arrays 54 are animated by a circular helical movement and explore the ring 9 of least aberration, which allows one exploration of a large area with photoelectric arrays of small area.

Return mirror.

 In a particular embodiment, a movable mirror intercepts the eddy light beam.

 The operation of this mirror replaces the displacement of the eddy-up device 46.

Folding of the mirror and the membrane. (Figures 18 and 19)
The mirror 5 and the control membrane 42 are made wholly or partly by a shape memory material.

 After their manufacture, the mirror 5 and the membrane 42 are deformed under conditions such that this deformation is preserved until the appearance of new conditions bringing back the initial shape.

 The membranes are concave; if one pushes back (figure 18) the bottom of the concavity, in its center, and perpendicular to its tangent plane, one obtains a deformation of circular symmetry which goes up in the concavity.

 Examination of this old concave surface then shows a peripheral concave ring and a convex central surface.

 This convex central surface is also pushed back under the same conditions as above. and we observe then, a new concave surface element centered.

 By continuing these alternately concave and convex surface creations, we obtain a surface resembling a series of centered circular waves (Figures 19 and 20).

 The thickness of this fold can be as small as desired by increasing the number of corrugations.

 Once this deformation has been fixed by suitable physical conditions, the quasi-plane object thus obtained can be folded, first wound in length and then wound in a circle.

Winding for rotating field.

 To allow, in association with the motor ring 55 the rotation of the mirror, several windings are located on the blind cylinder 2. at the level of the mirror stage.

 A supply of these coils by phase-shifted currents induces a rotating field causing the mirror to rotate.

Claims (15)

PERFECTED TELESCOPE CLAIMS 1- Satellite telescope comprising a mirror stage, a focus stage and a mirror control stage, characterized in that the three stages are secured by a blind cylinder (2) stiffened by tubes (10. 11, 12) under pressure and by polymerization of a resin impregnating the blind cylinder and the tubes. 2- Telescope according to claim 1, characterized in that the blind cylinder (2) joining the three stages of the telescope is placed in a protective sheath (3). 3- Telescope according to claim 1. characterized in that the blind cylinder (2) and the protective sheath (3) are folded first by telescopic invagination, then by radiating folding. 4- Telescope according to claim 1, characterized in that radiating folding means (28) external to the sheath have an active centripetal movement, and that radiating folding means (27) internal to the sheath offer a centrifugal radial resistance. 5- Telescope according to claim 1, characterized in that the internal means (27) of folding are animated by a helical movement winding the rays of the radiating folding (3) around the speakers (19. 2, 21) of the telescope. 6- Telescope according to claim 1, characterized in that closed tubes (32,33) associated by links (15, 16) to the sheath (3) or to the blind cylinder (2) of the telescope (1) are bent by telescopic invagination at the same time as the cylinder (2) or the sheath (3), and have orifices (34,35) through which can be introduced a gas under pressure causing their expansion. 7- Telescope according to claim 1, characterized in that the blind cylinder (2) of the telescope (1) and the protective sheath (3) are slightly frustoconical, or bi-frustoconical. 8- Telescope according to claim 1, characterized in that a conductive solenoid (39) is wound around the blind cylinder of the telescope, at the level of the mirror stage. 9- Telescope according to claim 1, characterized in that solenoids (41) arranged symmetrically around the axis (7) of the telescope (1) are fixed on the blind cylinder (2) at the mirror stage.  l- Telescope according to claim 1, characterized in that the internal (27) and external (28) radiating folding means consist of vertical linear elements associated in pairs. vertically movable from a permanent high position to a permanent low position, and integral with radial displacement means (36, 37), moving continuously, from a position remote from the center to a position close to the center. 11- Telescope according to claim 1, characterized in that the control means (46) of the mirror (5), located on the control stage, defining the optical axis of the mirror, moves inside a circle centered on the telescope axis. and perpendicular to this axis. 12- Telescope according to claim 1, characterized in that the means (49, 55) for centering the mirror (5) and its control membrane (42) are mounted on a gimbal (50, 51) or a ball joint (54 ), and fitted with actuators (52). 13- Telescope according to claim 1, characterized in that the means (46) for controlling the mirror (5) continuously deforms the generator of the mirror. keeping the mirror (5) its shape of revolution, so that there is at all times a circle (9) of minimum aberration centered on the optical axis (7) and moving from the optical axis towards the outside, and vice versa. 14- Telescope according to claim 1, characterized in that the photoelectric matrix (47) for examining the image is explored in synchronism with the movement of the ring of least aberration. 15- Telescope according to claim 1, characterized in that one or more photoelectric matrices (54) explore the circle (9) of least aberration. 16- Telescope according to claim 1, characterized in that the mirror (5) and its control membrane (42) are made wholly or partly by a shape memory material. 17- Telescope according to claim 1, characterized in that the mirror (5) and the membrane (42), concave, are made almost planar by a succession of centered deformations, alternately concave and convex.