Title of Invention

"DEVICE FOR THE MICROMETIC POSITIONING OF A SUPPORT OF AN OPTICAL ELEMENT IN SPACE, WITH SIX DEGREES OF FREEDOM"

Abstract

The invention concerns a device for the micrometric positioning, in relation to a frame (1), of a support (2) of an optical element (3) incorporated into a space system, which contains three mountings (4, 5, 6) integral with the frame (1) and, for each mounting, first adjusting means (9 to 12) in a first direction, second adjusting means (20 to 22) in a second direction, third micrometric adjusting means (30 to 35) in a third direction, and means comprising at least one locking screw and one packing shim for locking the support (2) into the set position in relation to the frame (1) .

Full Text

The invention concerns a device for the micrometric positioning of a support of an optical element incorporated in a space system, that is to say a system designed to be launched into space, for example an artificial satellite, an orbital station, a planetary probe... Space systems often incorporate optical systems, for example for the reception of images (planetary or astronomical observations), or even sometimes for the emission of rays or light signals. The efficiency and the accuracy of these optical systems are closely linked to the correct positioning of the optical elements of which they are composed, in relation to an integral frame of the space system. Certain on-board optical systems contain optical systems, termed active, able to be adjusted in space from the ground. These systems are sophisticated, heavy and unwieldy, are therefore extremely expensive, and are reserved for special applications (for example astronomical observations) for which mobility and operational adjustments are imperative. On the other hand, numerous optical systems incorporated in space systems contain optical elements, termed passive, that is to say those that are adjusted and set in relation to the frame on the ground, and whose position cannot be adjusted in flight. The problem which arises with such optical systems is thus the accuracy of the initial adjustment on the ground and the maintenance of this setting during the liftoff stages (during which the system has to withstand severe accelerations, typically 30 g or more), then in space in the absence of gravity. Now, if these adjustments can be easily implemented with one, two or three degrees of freedom (for example for the centring of a spherical mirror), or with low accuracies (above 10 µm) , the problem is to position such an optical element on the ground with an accuracy of the order of a micron and with six degrees of freedom. This problem occurs in particular in the positioning of the aspherical mirrors of a planetary observation telescope, whose positioning errors cannot be compensated by decentring as for telescopes with spherical mirrors, and which must enable very fine resolutions to be obtained. The invention therefore aims to overcome these drawbacks by proposing a micrometric positioning device with six degrees of freedom of an optical element in relation to a frame of a space system, permitting adjustment on the ground with high accuracy, locking in position and maintenance in position during liftoff and in space, the accuracy being retained. The invention also aims to obtain this positioning in a simple, less costly manner, and with low weight and more compact arrangement of the components integrated into the space system. The invention aims more particularly to propose a micrometric positioning device for the mirrors of a telescope with aspherical mirrors incorporated into an Earth observation satellite. _ Accordingly, the present invention relates to device for the micrometric positioning, in relation to a frame, of a support of an optical element designed to be incorporated into a space system, characterised in that it contains three mountings integral with the frame and, for each mounting: first of translatory adjustment in a first direction of a first section of the support in relation to the mounting, second of translatory adjustment in a second direction, at least orthogonally to the first direction, of a second section of the support in relation to the mounting, third of micrometric translatory adjustment in a third direction, at least orthogonally to the first and to the second direction, of a third section of the support in relation to the mounting, these third of micrometric adjustment containing means for micrometric measurement of the distance separating the third section of the support and a section facing the mounting, the different first, second and third adjusting mechanism of the different mountings being designed to be capable of supporting and maintaining the support and the optical element in place in relation to the frame, and to allow adjustment of the position of the support in relation to the ' frame, with six degrees of freedom, for locking the support into a set position in relation to the frame, and comprising: at least one locking screw connected to the support and to the mounting via connecting mechanism designed to be compatible with different relative positions and orientations able to be adopted by the support in relation to the mountings, taking into account ranges allowed for the adjustment values for the different adjusting means of the different mountings, the locking screw and the connecting mechanism-, after screwing up, being designed to lock the mounting and the support into position in relation to each other, at least one shim, the thickness of which is determined according to the distance measured between the third section of the support and the section facing the mounting, this shim being placed, along with said connecting means, so as to completely fill the space separating the mounting of the support around the locking screw so that the position of the support in relation to the frame can be set on the ground with great precision and six degrees of freedom, then locked with locking screws enabling this set position to be maintained during the launching of the space system, and in space. In order to achieve this, the invention concerns a device for the micrometric positioning, in relation to a frame, of an optical element designed to be incorporated into a space system, characterized in that it contains three mounting integral with the frame and, for each mounting: first means of translatory adjustment in a first direction of a first section of the support in relation to the mounting, • second means of translatory adjustment in a second direction, at least more or less orthogonally to the first direction, of a second section of the support in relation to the mounting, • third means of micrometric translatory adjustment in a third direction, at least more or less orthogonally to the first and to the second direction, of a third section of the support in relation to the mounting, these third means of micrometric adjustment containing means for micrometric measurement of the distance separating the third section of the support and a section facing the mounting, the different first, second and third adjusting means of the different mountings being designed to be capable of supporting and maintaining the support and the optical element in place in relation to the frame, and to allow adjustment of the position of the support in relation to the frame, with six degrees of freedom, • means for locking the support into a set position in relation to the frame, and comprising: at least one locking screw connected to the support and to mounting via connecting means designed to be compatible with different relative positions and orientations able to be adopted by the support in relation to the mountings, taking into account ranges allowed for the adjustment values for the different adjusting means of different mountings, the locking screw and the connecting means, after screwing up, being designed to lock the mounting and the support into position in relation to each other, at least one shim, the thickness of which is determined according to the distance measured between the third section of the support and the section facing the mounting, this shim being placed, along with said connecting means, so as to completely fill the space separating the mounting of the support around the locking screw, so that the position of the support in relation to the frame can be set on the ground with great precision and six degrees of freedom, then locked with locking screws enabling this set position to be maintained during the launching of the space system, and in space. The possibilities for adjustment in three orthogonal directions at three separate mountings allow adjustment with six degrees of freedom for the support and the optical element. Furthermore, the locking with the aid of locking screws, and with shims, whose thickness is determined by means of a micrometric thickness measurement, enables the optical element to withstand the liftoff and flight stages without misalignment. Throughout the present application, the expression "at least more or less in one direction" encompasses this direction and the directions making with this direction an angle that is less than or equal to permitted angular variations for the support in relation to this direction in the ranges permitted for the adjustment values for the different adjusting means. It should be noted in this connection that while the device allows micrometric positioning, the values of the adjustments are small, so that the three directions of space can be defined in an equivalent manner for the general kinematics of the device, either with reference to the support or with reference to the frame. The support is, furthermore, designed to define reference and support planes of adjusting means which, in the nominal position (corresponding to the position of the support in relation to the frame as theoretically defined if all the components and assemblies are perfect), are parallel to the reference and support planes of the adjusting means of the frame. This measure enables said first, second and third directions to be defined and fixed in relation to the frame or in relation to the support. These three directions are preferably defined and fixed in relation to the frame. Moreover, the first, second and third directions designate geometrical directions common to the three mountings. The first, second and third directions are three directions which are more or less orthogonal in pairs, that is to say they are normally orthogonal in pairs in the nominal position of the optical element in relation to the frame, but in certain positions, one or more of them may not meet this strict orthogonality condition in variants where at least one direction is defined and fixed in relation to the support while at least one other direction is defined and fixed in relation to the frame. Thus, the main condition which these three directions and different adjusting means should satisfy is to allow relative displacements in at least one specific range of values, enabling micrometric positioning of the optical element in the optimum operating position, with six degrees of freedom. Advantageously, and according to the invention, the third micrometric adjusting means are designed to permit adjustment with at least three separate degrees of precision, that is a coarse degree of precision, a medium degree of precision and a fine degree of precision. Advantageously, and according to the invention, the fine degree of precision is less than or equal to 1µm and said coarse and medium degrees of precision are of the order of 100 µm and 10µm, respectively. Advantageously, and according to the invention, the third micrometric adjusting means comprise a coarse adjustment device designed to allow adjustment to the coarse degree of precision, and a separate fine adjustment device designed to allow adjustment to medium and fine degrees of precision. Advantageously, and according to the invention, the coarse adjustment device has no means for measuring the distance between the third section of the support and the section facing the mounting. These measuring means can be formed at or incorporated in the adjustment device or, in a variant, be separate from the coarse and fine adjustment devices, and specifically provided for this purpose. Advantageously, and according to the invention, the coarse adjustment device comprises: two elastic return elements designed to exert opposing restoring forces on a first part which is integral with either the mounting or the support, a screw/nut system for adjusting the distance between a second part which is integral either with the support (if the first piece is integral with the mounting) , or the mounting (if the first part is integral with the support), respectively, and a supplementary part, one of the elastic return elements resting on said supplementary part while the other elastic return device rests on this second part. "Integral with" means that the part is carried by or is formed by the mounting or the support. Advantageously, and according to the invention, the return devices operate by compression. Advantageously, and according to the invention, the two elastic return elements are cylinders made of synthetic elastic material under compression, and the screw/nut system is designed so that the two cylinders are in the compressed state in every position of adjustment. Advantageously, and according to the invention, the stiffness of each of the elastic return elements is designed to enable the position of the support to be maintained in relation to the frame under the effect of gravity, but to allow adjustments by action on the first and second adjusting means and on the fine adjustment device of the third micrometric adjusting means. Advantageously, and according to the invention, the screw/nut system comprises a rod passing through a bore machined through said first part, and this bore has an internal diameter that is greater than the external diameter of the rod, so as to permit relative displacements and adjustments in said first and second directions. Advantageously, and according to the invention, washers made from a material having a low static coefficient of friction are interposed on each side of the bore between each end of the elastic return elements and one support face facing the first part, so as to facilitate relative displacements in the first and second directions under the effect of the first and second adjusting means. Advantageously, and according to the invention, the fine adjustment device is designed to push said first and second parts against the elastic return elements of the coarse adjustment device. Advantageously, and according to the invention, the fine adjustment device includes micrometric means for measuring the distance separating the third section of the support and the section facing the mounting, with two separate sensitivities, that is a medium sensitivity and a fine sensitivity. Advantageously, and according to the invention, the medium and fine sensitivities correspond to said medium and fine degrees of precision, and are in particular of the order of 10 µm and less than or equal to 1 µm, respectively. Advantageously, and according to the invention, the fine adjustment device comprises a body supported by the mounting and a rod moveable in the third direction, whose free end comes into contact and rests on a bearing surface of the third section of the support. Advantageously, and according to the invention, the fine adjustment device is formed by a differential micrometric thrust block. Advantageously, and according to the invention, this differential micrometric thrust block comprises a moveable rod, whose free end comes to rest against a bearing surface, and this bearing surface, at least in the nominal position, is perpendicular to the axial direction of displacement of the moveable rod of this thrust block. Advantageously, and according to the invention, each locking screw extends at least more or less in said third direction. Furthermore, advantageously, and according to the invention, the connecting means comprise, for each locking screw, two pairs of washers with spherical bearing surfaces in contact, these pairs of washers coming to rest against bearing surfaces orientated in the opposite direction so as to allow the locking screw to be tightened with different orientations relative to the support and to the mounting. As a variant and according to the invention, the connecting means include a ball-and-socket linkage for each locking screw. Advantageously, and according to the invention, the device is characterised in that, for each locking screw, the support contains a tapping for receiving one end of the locking screw, and the mounting contains a bearing surface for a head of the locking screw, and a bore through which the locking screw passes, and in that the internal diameter of the bore exceeds the external diameter of the locking screw by a value that is sufficient to allow the locking screw to be screwed into the thread in any position of the support in relation to the frame adjusted in the first and second directions, as far as the adjustment travel allows. Advantageously, and according to the invention, the connecting means comprise a pair of washers with spherical bearing surfaces in contact interposed between the head of the locking screw and the bearing surface of the mounting, and a pair of washers with spherical bearing surfaces in contact placed around the locking screw between the mounting and the support. More particularly, advantageously, and according to the invention, a pair of washers with spherical bearing surfaces in contact comes to rest on a bearing surface of the mounting orientated towards the support. Advantageously, and according to the invention, the shim is a washer interposed between this pair of washers with spherical bearing surfaces in contact, which comes into contact with a bearing surface of the mounting, and a bearing surface of the third section of the support. Furthermore, advantageously, and according to the invention, the first adjusting means and/or the second adjusting means contain a micrometric thrust block carried by the mounting or by the support, this micrometric thrust block having a rod whose free end comes into contact with a bearing surface facing the support or the mounting, respectively. Advantageously, each bearing surface, at least in the nominal position, is perpendicular to the axial direction of the displacement of the rod of the thrust block. Preferably, and according to the invention, the micrometric thrust blocks of the first, second and third adjusting means are carried by the mountings and their moveable rod comes to rest against the bearing surfaces facing the support. Advantageously, and according to the invention, the three mountings extend as a whole in the same plane, at least more or less perpendicularly to said third direction, the adjusting means in the first and second direction being means for centring the optical element in relation to the mountings. For preference, the three mountings are arranged in a relative angular distribution (allowing for the other limitations of the device and the optical system, in particular the shape of the optical element) which is as close as possible to 120 degrees between them, around an axis at least more or less parallel to the third direction. Advantageously, and according to the invention, the different adjusting means have parts designed to be detachable and to be removed from the frame and/or the support after locking into the set position. In particular, advantageously, and according to the invention, the elastic return elements and the screw/nut system of the coarse adjustment device of the third micrometric adjusting means, and the different micrometric thrust blocks are mounted so as to be detachable after locking into the set position. Advantageously, and according to the invention, the locking means are designed so as to be capable of withstanding a maximum acceleration of between 15 g and 60 g in any direction, without change of adjustment. The invention also extends to a device characterised in that it contains in combination all or some of the features mentioned heretofore or hereafter. The invention also concerns more particularly the application of a device according to the invention for the micrometric positioning of an aspherical mirror of a telescope for terrestrial observation from space. Nevertheless, the invention also permits micrometric positioning of any other optical element of a similar nature (detector, light source, lens, ...) for other optical systems (interferometer...) or other space systems (planetary probes, astronomical observation satellites, orbital stations...). Other features, objects and advantages of the invention will be revealed on reading the following description which refers to the attached figures, of which: Figure 1 is a perspective view illustrating an embodiment of a device according to the invention for the micrometric positioning of an aspherical mirror shown in the adjustment configuration, Figure 2 is a similar view to Figure 1, the device being shown in the flight configuration, Figure 3 is a perspective and sectional view in the plane of the locking screws of one of the mountings of the device of Figure 1 in the adjustment configuration, Figure 4 is a similar view to Figure 3 and with a detailed partial sectional view of a locking screw, the device being shown in the flight configuration, Figure 5 is a perspective and sectional view in a plane in the second direction passing through the third adjustment means of one of the mountings of the device of Figure 1 in the adjustment configuration, - Figure 6 is a similar view to Figure 5, the device being shown in the flight configuration. Figure 1 shows a micrometric positioning device in relation to a frame 1 of a support 2 of an aspherical 3 mirror forming part of a telescope with aspherical mirrors incorporated into an Earth observation satellite. The frame 1 is integral with the structure of the satellite. Each of the mirrors of the telescope is mounted on a support connected to the frame 1 by means of a micrometric positioning device according to the invention. The mirrors are positioned in relation to each other with a very high degree of precision. In Figure 1, the micrometric positioning device is shown in the adjustment configuration on the ground, the principal optical axis of the mirror 3 being at least more or less horizontal. The device according to the invention contains three mountings 4, 5, 6, which are integral with the frame 1 and are arranged around an opening 7 made through the frame 1 to receive the support 2. The mountings 4, 5, 6 are arranged in a relative angular distribution which is as close as possible to 120° between them, around the opening 7. The mountings 4, 5, 6 are generally in the form of a bracket, so as to have sections which extend radially and are offset towards the centre of the opening 7 to face the support 2 inserted into the opening 7. The support 2 has a generally rigid form (Figures 3 and 4), and the mirror 3 is connected in the known manner to this support 2 via suitable mounting lugs 8 producing an isostatic mounting. Each mounting 4, 5, 6 contains at least one micro-metric thrust block 9, 10, 11, 12 for translatory adjustment in a first direction, which in the embodiment shown is the vertical direction of a first section 13, 14, 15, 16 facing the support 2. Each micrometric thrust block 9, 10, 11, 12 contains a body 17 of the thrust block carried by the mounting 4, 5, 6 and an actuating rod 18 coming to rest against a bearing surface 19 which is at least more or less perpendicular to the axial direction of the rod 18 (that is to say to the vertical direction) and which is integral with said first section 13, 14, 15, 16 of the support 2. The bearing surfaces 19 are preferably formed from detachable parts of special alloy of extreme hardness (for example marval steel) . In the embodiment shown, for preference and according to the invention, the device contains an upper right-hand mounting 4, a lower right-hand mounting 5 and a left-hand mounting 6 placed at a median height. The upper right-hand mounting 4 contains a vertical micrometric thrust block 9 designed to push the first section 13 facing the support 2 downwards. The lower right-hand mounting 5 contains a vertical micrometric thrust block 10 designed to push the first section 14 facing the support 2 upwards. The median left-hand mounting 6 contains an upper vertical micrometric thrust block 11 pushing a section 15 facing the support 2 downwards, and a lower vertical micrometric thrust block 12 pushing a section 16 facing the support 2 upwards. The different thrust blocks 9 to 12 are designed to act in the vertical direction in opposing directions, and thus allow isostatic adjustments. In the vertical direction the support 2 is carried by the two micrometric thrust blocks 10, 12, the actuating rods of which are directed vertically upwards. Each mounting 4, 5, 6 likewise contains at least one micrometric thrust block 20, 21, 22 for translatory adjustment in a second direction, which is the transverse horizontal direction in the plane of the opening 7 of a second section 24, 25 facing the support 2. This second direction is orthogonal to the first direction. These micrometric thrust blocks 20, 21, 22 are made up in the same way as the vertical micrometric thrust blocks 9, 10, 11, 12, and therefore contain a body 17 carried by the mounting 4, 5, 6 and a moveable rod 18 whose free end comes to rest against a bearing surface 26 integral with the support 2. The bearing surface 26 extends at least more or less perpendicularly to the axis of the moveable rod of the thrust block 20, 21, 22, and is advantageously formed from a detachable part on the support 2, and made from an alloy of extreme hardness. The upper right-hand mounting 4 contains a horizontal micrometric thrust block 20 pushing the section facing the support 2 (not visible in the figures) horizontally to the left. The lower right-hand mounting 5 contains a micro-metric thrust block 21 pushing the second section 24 facing the support 2, horizontally to the left. The median left-hand mounting 6 contains a horizontal micrometric thrust block 22 pushing a second section 25 facing the support 2, horizontally to the right. The different thrust blocks 20 to 22 are also designed to act in the transverse horizontal direction in opposite directions, and thus allow isostatic adjustments. In this manner, the various vertical micrometric thrust blocks 9, 10, 11, 12 and horizontal micrometric thrust blocks 20, 21, 22 form first means 9 to 12 of translatory adjustment in the vertical direction and second means 20 to 22 of horizontal translatory adjustment, respectively, enabling the support 2 to be centred in relation to the three mountings 4, 5, 6 and in relation to the opening 7 of the frame 1. The support 2 contains three extensions 27, 28, 29, extending perpendicularly to its plane, so as to face each of the mountings 4, 5, 6, to define the different sections of the support 2, which cooperate with the various vertical and horizontal micrometric thrust blocks 9 to 12 and 20 to 22 for centring the support 2 in the opening 7. The three extensions 27, 28, 29 are therefore arranged with the same angular distribution as the mountings 4, 5, 6, that is to say at least more or less 120° to each other on the frame forming the support 2. The vertical micrometric thrust blocks 9, 10, 11, 12 thus form first means 9 to 12 of translatory adjustment in the first vertical direction of a first section 13 to 16 of the support 2 in relation to the mounting 4, 5, 6. The transverse horizontal micrometric thrust blocks 20, 21, 22 extending parallel to the plane of the opening 7, form second means 20 to 22 of translatory adjustment in a second direction, orthogonal to the first direction, of a second section 24, 25 of the support 2 in relation to the mounting 4, 5, 6. In the configuration shown, this second direction therefore corresponds to the transverse horizontal direction, that is to say in the horizontal direction parallel to the plane of the opening 7. The micrometric positioning device according to the invention further contains third means 30 to 35 of translatory micrometric adjustment in a third direction which is orthogonal to the first and second direction, of a third section 36, 37, 38 of the support 2, in relation to the mounting 4, 5, 6. This third direction is preferably the horizontal axial direction of the opening 7, that is to say the horizontal direction that is orthogonal to the first vertical direction and to the second transverse horizontal direction. This third direction likewise generally corresponds to the axis of the optical sight of the telescope, and/or to the principal axis of the mirror 3, and the support 2 is less inclined or not inclined in relation to this third direction, according to the configuration of the optical system (centred or off axis). More particularly, it should be noted that when the support 2, in the form of a plane frame, is in its perfect position of adjustment, the extensions 27, 28, 29, define a vertical plane which is less inclined or not inclined in relation to the vertical plane of the opening 7, and thus in relation to the vertical plane defined by the mountings 4, 5, 6. In particular, this inclination is sufficiently small so that the relative angles between the first, second and third directions referred to the frame 1, and the corresponding vertical, transverse horizontal and horizontal axial directions, respectively, referred to the support 2, have values of the order of several tens of milliradians corresponding to the maximum travels of the permitted adjustments of the support 2 in the third direction. The three mountings 4, 5, 6, extend as a whole in the same perpendicular plane in the third direction, and the first adjusting means 9 to 12 and the second adjusting means 20 to 22 in the first and second direction, respectively, are centring means of the support 2 and of the mirror 3 in relation to the mountings 4, 5, 6, and in relation to the opening 7. The three mountings 4, 5, 6, are preferably arranged at least more or less at 120° to each other around an axis that is at least more or less parallel to the third direction. During adjustment, the third direction is preferably at least more or less horizontal and the first direction is at least more or less vertical. Nevertheless, the orientation of the device during adjustment is actually not important, and other orientations are possible. In particular, in a variant, the third direction corresponding to the optical axis of the mirror can be collinear in the vertical direction during integration on the ground. The orientation of the device according to the invention in relation to the direction of thrust of the rocket during launching is also unimportant, the device being set to a clamped/locked configuration to withstand the acceleration of liftoff (30 g or more) in any direction. The third micrometric adjusting means 30 to 35 comprise, for each mounting 4, 5, 6, a coarse adjustment device 30, 31, 32 designed to allow adjustment to a coarse degree of precision, and a fine adjustment device 33, 34, 35, designed to allow adjustments to medium and fine degrees of precision. Figures 3 and 5 show a sectional view of the third adjusting means 32, 35 of the left-hand median mounting 6. These third means 32, 35 are described in detail below, given that the same elements and devices are provided for the other two mountings - the upper right-hand mounting 4 and lower right-hand mounting 5. The coarse adjustment device 32 contains a threaded rod 40, one end of which is screwed into a blind tapping 41 of the support 2. The rod 40 and the tapping 41 extend parallel to the axial horizontal direction of the support 2, that is to say more or less in the third direction, the inclination between these two directions being zero in the nominal position, and small after adjustment. The rod 40 extends in the direction of the mounting 6, which it passes through via a bore 42 whose internal diameter is greater than the external diameter of the rod 40. The third section 38 of the support 2 facing the mounting 6 contains a housing 43 for receiving a cylinder 44 made of elastic synthetic material through which the rod 40 passes axially. This cylinder 44 is therefore interposed between the support 2 and the mounting 6 and extends around the rod 40. At least one washer 45 made of material having a low static coefficient of friction, for example TEFLON, or coated in NUFLON (registered trademarks), is interposed between the bottom of the housing 43 of the support 2 and a corresponding end of the cylinder 44. Similarly, at least one washer 46 made of material having a low static coefficient of friction is interposed between the other end of the cylinder 44 and a bearing surface 52 of the mounting 6. The cylinder 44 and the washers 45, 46 have an internal diameter that corresponds to the external diameter of the rod 40. For preference, two washers 45, 46 are provided at each end of the cylinder 44. The rod 40 is extended beyond the bore 42 in order to receive from the other side of this bore 42 and the mounting 6, a cylinder 47 of elastic synthetic material similar to the cylinder 44. The rod 40 passes axially right through the cylinder 47 and the end of this rod 40 receives a nut 48. At least one washer 50 made of material having a low static coefficient of friction is interposed between the nut 48 and the corresponding end of the cylinder 47. Similarly, at least one washer 51 made of material having a low static coefficient of friction is interposed between the other end of the cylinder 47 and a corresponding bearing surface defined around the bore 42 of the mounting 6. For preference, two washers 50, 51 are provided at each end of the cylinder 47. In this way the various washers 45, 46, 50, 51 facilitate and permit relative displacements, in the first and second direction, of the support 2 in relation to the mounting 6, under the influence of the first and second adjusting means. The free end of the rod 40 is designed to allow it to be used in conjunction with a tool for screwing up and unscrewing this rod 40 in relation to the tapping 41 of the support 2. This free end 49 is square, for example. The nut 48 is screwed onto the rod 40 to axially compress the two cylinders 44, 47. Each of these two cylinders 44, 47 has a length such that both are in a compressed state in every position of adjustment of the support 2 in relation to the frame 1. The two elastic cylinders 44, 47 therefore constitute elastic return elements which exert opposing restoring forces on the mounting,6, that is to say, on each side of the bore 42 The rod 40 and the nut 48 form a screw/nut system for adjusting the distance between the third section 38 of the support 2 and the nut 48, the cylinder 47 resting on the nut 48 via the washer or washers 50, while the cylinder 44 rests on this third section of the support 2 via the washer or washers 51. The stiffness of each of the cylinders 44, 47 in the axial direction (third direction) is designed to allow the position of the support 2 to be maintained in relation to the frame 1 under the effect of gravity, but to allow adjustments by action on the first adjusting means 9 to 12 and second adjusting means 20 to 22, and on the fine adjustment device 33 to 35 of the third micrometric adjusting means 30 to 35 described below. The difference between the internal diameter of the bore 42 and the external diameter of the rod 40 is designed to allow relative displacements and adjustments in the first and second directions. As can be seen, this coarse adjustment device 32 has no means for measuring the distance separating the third section 38 of the support 2 from the section facing the mounting 6 (which is formed from the bearing surface 52 , around the bore 42 on which the cylinder 44 rests via the washer 46). The measurement during the coarse adjustment is actually effected by micrometric measuring means formed by the fine adjustment device 35. The two cylinders 44, 47, are compressed by screwing up the nut 48 on the threaded rod 40, and the mounting 6 is made to approach the support 2 in the third axial direction. If p is the pitch of the threaded rod 40, Kl is the coefficient of axial stiffness of the cylinder 47 interposed between the nut 48 and the mounting 6, and K2 is the coefficient of axial stiffness of the cylinder 44 interposed between the support 2 and the mounting 6, the coarse degree of precision of this adjustment device 32 is equal to p x K2/(K1 + K2) per turn of the nut 48, that is p/2 if Kl = K2. This coarse degree of precision can thus be adapted to the desired value within the limit of possible values for Kl and K2, by suitable choice of the ratio K1/K2 and of the pitch p of the threaded rod 40 and of the nut 48. For example, if p equals 0.5 mm/turn and if Kl = K2, a coarse degree of precision of the order of 62,5 µm. is obtained for a quarter of a turn. The cylinders 44, 47 are advantageously formed from elastomer material such as rubber, the stiffness of which is of the order of 50 N/mm, for example. As a variant, compression springs can be used instead of the cylinders 44, 47. It should be noted that other variants for realizing this coarse adjustment device 30 to 32 are possible. For example, the rod 40 and the nut 48 can be replaced by a screw, the head of which replaces the nut 48, and whose free end is inserted into a tapping in the support 2, which is sufficiently long to allow screwing up and unscrewing of this screw for the purpose of adjustment. In another variant, the rod 40 can pass through the support 2, which is then fitted with a bore of greater diameter in place of the tapping 41, the threaded rod then being screwed into a tapping of the mounting 6 and the lock nut being arranged on the other side of the support 2, that is to say on the mirror 3 side. In this case the elastic return cylinders are placed on either side of the support 2 and exert opposing restoring forces, not on the mounting, but on the support 2. From the kinematic standpoint, this latter assembly is equivalent to the former inasmuch as the effect of tightening the nut will again compress the two cylinders and bring the mounting 6 closer to the support 2. The fine adjustment device 35 is designed to push the support 2 and the mounting 6 against the elastic return cylinders 44, 47 of the coarse adjustment device 32. This fine adjustment device 35 is composed of a differential micrometric thrust block, that is to say a micrometric thrust block containing two knurled adjusting nuts with two different degrees of precision, that is one knurled adjusting nut with a medium degree of precision and a knurled adjusting nut with a fine degree of precision. The fine degree of precision is less than or equal to 1 µm. in order to allow adjustment in the third direction close to one micron. The medium degree of precision is of the order of 10 µm., for example. The differential micrometric thrust block 35 contains a body 53 carried by the mounting 6, and a rod 54 moveable in the third direction, the free end of which comes to rest on a bearing surface 55 facing the third section 38 of the support 2 (Figure 5). By turning the knurled adjusting nuts of the thrust block 35, the rod 54 is extended and pushes on this bearing surface 55, the effect of which is to move the support 2 away from the mounting 6, that is to decompress the cylinder 44 while compressing the cylinder 47. It should be noted that the three differential micrometric thrust blocks 33 to 35 push the support 2 in the axial horizontal direction - all three pushing in the same direction - the return in the other direction being provided by the elastic cylinders 44, 47 of the coarse adjustment device 30 to 32. From now on, an isostatic adjustment is also allowed in this third direction of the support 2 in relation to the frame 1. This differential micrometric thrust block 35 is likewise composed of means allowing micrometric measurement of the distance separating the third section 38 of the support 2 and the section facing the mounting 6, and this with two separate sensitivities, that is a medium sensitivity of the order of 10 µm. and a fine sensitivity of less than or equal to 1 µm.. The differential micrometric thrust block 35 is employed both for the micrometric adjustment of the position of the support 2 in relation to the mounting 6 in the third direction, and for the micrometric measurement of the distance separating the support 2 from the mounting 6, the medium and fine sensitivities corresponding to the medium and fine degrees of precision. It should be noted, however, that in a variant it should be possible to provide separate micrometric measuring means for the fine adjustment device. To measure this distance, starting from the set position, it suffices to insert a shim of standard thickness around the rod 54 of the thrust block 35 and to release this thrust block 35 (that is to say retract the rod 54 by operating the knurled nuts) until the bearing surface 55 of the support 2 and the bearing surface 51 facing the mounting 6 come into contact with the shim. Knowing the thickness of this shim, the initial distance between the bearing 55 of the support and the bearing surface 52 of the mounting 6 can be determined. Furthermore, as the differential micrometric thrust block 35 is fitted with verniers, it is easy to return to this position of adjustment, and to the desired precision of l µm. The micrometric positioning device according to the inventxon therefore contains the three coarse adjustment dvices 30, 31, 32. which are all similar to the devicT32 described above, and three differential micrometric thrust blocks 33, 34, 35, similar to the thrust block 35 described above. Thus, the third micrometric adjusting means 30 to 35 in the third direction are two-stage adjusting means, that is a coarse stage with a screw/nut system, and a fine stage with a differential micrometric thrust block. The different adjusting means 9 to 12, 20 to 22 and 30 to 35 of the device according to the invention, in the three orthogonal directions, form an isostatic connecting assembly between the support 2 and the frame 1, so that the displacements relative to the support 2 that are made in one direction do not influence the adjustments of the position of the support 2 in the other two orthogonal directions, and the adjustments are made much easier. It should be noted that the extensions 26, 27, 28 of the support 2 define plane bearing surfaces 19, 26, 55 extending perpendicularly in the directions of thrust of the opposing micrometric thrust blocks 9 to 12, 20 to 22, 33 to 35. The same applies to each of the thrust blocks of each mounting 4, 5, 6, on which the cylinders 44, 47 rest, which are perpendicular to the axis of the threaded rods 40 and tappings 41 of the coarse adjustment device 30 to 32. Once the adjustment to the optimum operating position has been made by the adjustment means described above, in the three directions in space and for the three mountings 4, 5, 6, that is to say with six degrees of freedom, the support 2 is locked in position in relation to the frame 1, by the locking means 56 to 76, 79 to 82 of the device, which are illustrated in Figures 2, 4 and 6. The means for locking into the set position are also described below with reference only to the median left-hand mounting 6, given that they are similar for the other two mountings 4, 5. The locking means contain two parallel screws 56, 57, the threaded free end of which is engaged in a blind tapping 58, 59 made in the third axial direction in the third section 38 of the support 2. For each of the locking screws 56, 57, the mounting 6 contains a receiver housing 60, 61, and an bore 63, 64, of which the internal diameter is greater than the external diameter of the screw 56, 57, so that this screw 56, 57 can be engaged in the tapping 58, 59, whatever the set position of the support 2 in relation to the mounting 6. The housings 60, 61 receive the heads 65, 66 of the screws 56, 57. For each locking screw, a pair of washers 67, 68, with spherical bearing surfaces in contact, is interposed between the head 65, 66 of the screw and the bottom of the housing 60, 61 of the mounting 6, so that the locking screw 56, 57 rests on this bottom of the housing and thus on the mounting 6, whatever the inclination of the axis of the locking screw in relation to this bottom of the housing, and in relation to the axis of the bore 63, 64. On the other side of the bore 63, 64, another pair 69, 70 of washers with spherical bearing surfaces in contact is also placed around the screw 56, 57 and in contact with a bearing surface 71, 72 of the mounting 6. Moreover, a washer 73, 74 is interposed between this pair of washers 69, 70 with spherical bearing surfaces in contact, and a bearing surface 75, 76 facing the third section 38 of the support 2. The two locking screws 56, 57 are therefore linked to the mounting 6 by connecting means comprising two pairs 67, 68 and 69, 70 of washers with spherical bearing surfaces in contact, respectively, which rest against bearing surfaces of the mounting 6, and are orientated in opposite directions. Thus, one washer of a first pair 67, 68 rests against the bottom of the housing 60, 61 orientated towards the head of the screw 56, 57, and one washer of a second pair 69, 70 rests against the bearing surface 71, 72 orientated towards the support 2. These bearing surfaces (bottoms of the housings 60, 61, and bearing surfaces 71, 72) are defined by plane faces that are perpendicular to the third axial direction around the open ends of the bore 63, 64 of the mounting 6. The bearing surface 71, 72 of the mounting 6 is a bearing surface that supports the head 65, 66 of the locking screw 56, 57 by way of the pair of washers 67, 68. The washer 73, 74 interposed between the pair of washers 69, 70 with spherical bearing surfaces in contact, and said bearing surface 75, 76 of the third section 38 of the support 2, acts as a shim whose thickness is adapted during adjustment (for example by straightening) according to the distance measured between the third section 38 of the support 2 and the section facing the mounting 6, due to the differential micrometric thrust block 35. Thus, this washer 73, 74, along with the pair of washers 69, 70 with spherical bearing surfaces, completely fills the space separating the mounting 6 and the support 2 around the locking screw 56, 57. This space is therefore maintained when the locking screw 56, 57 is tightened. Moreover, the faces of the pairs of washers with spherical bearing surfaces 67, 68 and 69, 70, in contact with the corresponding bearing surfaces of the mounting 6 are such that they have the highest possible static coefficient of friction, so that the tightening of the locking screws 56, 57 also locks the support 2 in relation to the mounting 6, by preventing relative displacements in the first and second directions. In the embodiment shown, for each mounting 4, 5, 6, the device contains at least advantageously two parallel locking screws 56, 57; 79, 80; 81, 82, placed on either side of the coarse adjustment device 30 to 32, and as close as possible to this coarse adjustment device 30 to 32. The number of locking screws provided is adapted according to the mechanical loads that these screws have to withstand in the operating condition (in particular during liftoff). The coarse adjustment device 30 to 32, the fine adjustment device 33 to 35 and the two locking screws 56, 57; 79, 80; 81, 82 are arranged so as to act in conjunction with the axial extensions 27, 28, 29 in the third direction of the support 2, and to be as close as possible to each other. Due to the washers with spherical bearing surfaces in contact, and the difference in diameter between the bores 63, 64 and the locking screws, these locking screws 56, 57; 79, 80; 81, 82 can be screwed into the tappings 58, 59 of the support 2 with different relative positions and orientations being able to be adopted by the support 2 in relation to the mountings 4, 5, 6, taking into account the ranges permitted for the values of adjustment for the different adjusting means of the different mountings. The locking screws and their means 58, 59, 67 to 70 for connection to the support 2 and to the mounting 6 are designed to lock the mounting 6 and the support 2 into position after tightening, the locking screws extending at least more or less in the third axial direction. All the locking screws are preferably orientated axially and tightened in the same direction. In a variant, not shown, for each locking screw the two pairs of washers with spherical bearing surfaces in contact can be replaced by a ball-and-socket linkage. Furthermore, the different adjusting means have parts designed to be detachable and removed from the frame 1 and/or the support 2 after locking into the set position. In particular, the elastic cylinders 44, 47, the threaded rods 40 with their nuts 48 and their washers 45, 46, 50, 51, that is to say the assembly of the coarse adjustment device 32 of the third micrometric adjusting means, and the different vertical, transverse horizontal, and axial horizontal micrometric thrust bearings 9 to 12, 20 to 22, 33 to 35, are detachable after locking into the set position and can be removed from the mounting 6 and the support 2. The bearing surface 55 of the third section 38 of the support 2, on which the rod 54 of the differential micrometric thrust bearing 35 rests, is formed by a part 77 which, by means of screws, is mounted in a detachable fashion in relation to the corresponding extension 27, 28, 29 of the support 2. This detachable part 77 is arranged so as to re-close the housing 43, which is in the form of a groove made in the third section 38 of the support 2 to receive the elastic cylinder 44. Thus, when this part 77 defining the bearing surface 55 is removed, the housing is open towards the centre of the support 2 and the cylinder 44 can be removed transversely. From now on, to dismantle the coarse adjustment device 32, it is sufficient to unscrew the screw 40 by acting on its square end 49, to remove the part 77 forming the bearing surface 55, and to extract the cylinder 44 from the housing 43 via the opening thus made free. The micrometric thrust bearings 9 to 12 and 20 to 22 for adjustment in the first and second direction are advantageously carried by individual supports 78 attached to each mounting by screws. By dismantling the individual supports 78, the corresponding micrometric thrust blocks are dismantled at the same time. In a variant, for certain of the micrometric thrust blocks, for example for the transverse horizontal micrometric thrust block 22 of the mounting 6, and for the axial differential micrometric thrust blocks 33, 34, 35, the bodies of these micrometric thrust blocks are directly attached by screwing into the tapping of the mounting. When all the locking screws 56, 57; 79, 80; 81, 82 are tightened and the various parts of the adjusting means are dismantled, the positioning device is in the flight configuration as illustrated in Figures 2, 4, 6. The contact bearing surfaces 19 for the vertical micrometric thrust blocks 9 to 12 are shown in Figure 4, but obviously these bearing surfaces could also be dismantled prior to liftoff. For the sake of clarity the frame 1 is not shown in Figures 3 and 4, only the mountings 4, 5, 6. It should also be noted that the cylinders of elastomer material 44, 47, which could not be integrated into a space system (on account of the degassing of the rubber in the vacuum) are dismantled after the support 2 is locked into the set position. The various micrometric thrust blocks and the bearing surfaces 19, 26 and 55 on which they rest, are made of a material designed to allow adjustment and support of the support 2 and of the mirror 3 during adjustment on the ground, taking into account the total mass suspended in this manner. Moreover, the bearing surface 55 for the moveable rod of the differential micrometric thrust blocks 33, 34, 35, and these thrust blocks themselves, are chosen so as to be able to move the support 2 away from the mounting against the elastic cylinder 47. All these thrust blocks and corresponding bearing surfaces are made of an extremely hard material and are designed to withstand large axial loads, in particular of the order of 50 N to 150 N, for a support 2 and a mirror 3 having a total mass which can be as much as 15 kg. The various micrometric thrust blocks 9 to 12, 20 to 22 and 33 to 35 are, for example, thrust blocks as marketed by the MICRO-CONTROLS Co., (EVRY, FRANCE). Similarly, the various mountings 4, 5, 6 are formed from an extremely strong and rigid material in order to prevent any variation in the adjustment of the position of the mirror 3 when the locking screws 56, 57 are tightened, and then during liftoff. The device according to the invention operates in the following manner. Firstly, the support 2 is placed in the opening 7 by fitting the threaded rods 40, previously attached to the support 2, through the bores 42 of the mountings 4, 5, 6, and after having inserted the washers 45, 46 and the cylinders 44. The mountings 4, 5, 6 are fitted with the adjusting micrometric thrust blocks 9 to 12, 20 to 22, 33 to 35. On the other hand, the locking screws are not installed during adjustment. To facilitate this initial centring, at least two centring pins can be mounted in advance in the tappings 58, 59, respectively, which are eventually intended for the locking screws. These pins thus come to rest radially in the corresponding bores 63, 64 of the mountings 4, 5, 6. The nuts 48 of the various coarse adjustment devices 30, 31, 32 are then tightened up. The centring of the support 2 and the mirror 3 is then carried out by placing the seven vertical and transverse horizontal thrust blocks 9 to 12 and 20 to 22, respectively, in contact with their respective bearing surface. The tilt and focus positions of the support 2, that is to say the inclination and axial position in relation to the axis of the opening 7, are then adjusted - first by means of the nuts 48 of the coarse adjustment devices 30 to 32, then to the closest micron - by means of the differential micrometric thrust blocks 33 to 35, to a medium degree of precision then to the fine position. These adjustments are made in successive steps and by optical measurements by checking the quality of the image obtained. When the adjustment to the optimum position is obtained, the axial distance separating the bearing surfaces 55 of the support 2 from the bearing surfaces 52 of the mountings 4, 5, 6 is measured in the third axial direction by means of the various differential micrometric thrust blocks 33 to 35 as described above. Each of the washers 73, 74 (shims) is then chosen, the thickness being determined according to this distance measurement, then the various locking screws 56, 57; 79, 80; 81, 82 are fitted and tightened to the nominal tightening torque. An optical check of the quality of the image obtained is carried out again. If this is not satisfactory, a new micrometric measurement is made to evaluate the modifications to be made to the washers 73, 74 (shims). Next, the locking screws and the shim washers are unscrewed and removed, the thickness of the shim washers is modified according to the previous measurement, the locking screws are refitted, then a new optical check is carried out. Successive steps are then carried out until the image obtained is considered satisfactory after the locking screws have been tightened to the nominal torque. All the detachable parts used for the adjustments as indicated above are then removed. The device according to the invention allows an isostatic adjustment followed by isostatic locking of the support 2 in relation to the frame 1. An extremely fine micrometric adjustment of the positioning of the mirror 3 in relation to the frame 1, and locking of the position of the mirror 3 adjusted in this way, is thus obtained, which is compatible with the accelerations to which the device is subjected at liftoff (typically 30 g or more). The device shown in the figures can be applied to the micrometric positioning of an aspherical mirror of a telescope for observing the Earth from space. Nevertheless, the invention is also applicable to the micrometric positioning of any other optical element with six degrees of freedom, in an optical system intended to be incorporated in a space system. Moreover, the embodiments described and shown in the figures can be the subject of numerous variants. In particular, from a kinematic and mechanical point of view, other equivalent embodiments of different adjusting and locking means can be provided. For example, the micrometric thrust blocks 9 to 12, 20 to 22 and 33 to 35, can be carried by the support 2 and not by the mountings 4, 5, 6. Similarly, the coarse adjustment devices 30 to 32, can be permanently attached to the mountings 4, 5, 6 and not to the support 2. Equally, the locking screws 56, 57; 79, 80; 81, 82 can rest directly on the mounting and/or be screwed into a tapping of the mounting, the washers with spherical bearing surfaces or the ball-and-socket linkage being provided to act in conjunction with the support 2, fitted with a bore through which the locking screw passes. Furthermore, in accordance with the geometry of the optical element under consideration, the relative positions of the three mountings 4, 5, 6 can differ from those illustrated and described. WE CLAIM: 1. Device for the micrometric positioning, in relation to a frame (1), of a support (2) of an optical element (3) designed to be incorporated into a space system, characterised in that it contains three mountings (4, 5, 6) integral with the frame (1) and, for each mounting (4, 5, 6): first means (9 to 12) of translatory adjustment in a first direction of a first section (13 to 15) of the support (2) in relation to the mounting (4, 5, 6), second means (20 to 22) of translatory adjustment in a second direction, at least orthogonally to the first direction, of a second section (24, 25) of the support (2) in relation to the mounting (4, 5, 6), third means (30 to 35) of micrometric translatory adjustment in a third direction, at least orthogonally to the first and to the second direction, of a third section (36 to 38) of the support (2) in relation to the mounting (4, 5, 6), these third means (30 to 35) of micrometric adjustment containing means (33 to 35) for micrcmetric measurement of the distance separating the third section (36 to 38) of the support (2) and a section facing the mounting (4, 5, 6), the different first, second and third adjusting means (9 to 12, 20 to 22, 30 to 35) of the different mountings (4, 5, 6) being designed to be capable of supporting and maintaining the support (2) and the optical element (3) in place in relation to the frame (1), and to allow adjustment of the position of the support (2) in relation to the frame (1), with six degrees of freedom, means (56 to 76, 79 to 82) for locking the support into a set position in relation to the frame (1), and comprising: at least one locking screw (56, 57, 79 to 82) connected to the support (2) and to the mounting (4, 5, 6) via connecting means (58, 59, 67 to 70) designed to be compatible with different relative positions and orientations able to be adopted by the support (2) in relation to the mountings (4, 5, 6), taking into account ranges allowed for the adjustment values for the different adjusting means of the different mountings (4, 5, 6), the locking screw (56, 57, 79 to 82) and the connecting means, after screwing up, being designed to lock the mounting (4, 5, 6) and the support (2) into position in relation to each other, at least one shim (73, 74), the thickness of which is determined according to the distance measured between the third section (36 to 38) of the support (2) and the section facing the mounting, this shim (73, 74) being placed, along with said connecting means, so as to completely fill the space separating the mounting (4, 5, 6) of the support (2) around the locking screw (56, 57, 79 to 82) so that the position of the support (2) in relation to the frame (1) can be set on the ground with great precision and six degrees of freedom, then locked with locking screws (56, 57, 79 to 82) enabling this set position to be maintained during the launching of the space system, and in space. 2. Device as claimed in claim 1, wherein the third micrometric adjusting means (30 to 35) are designed to allow adjustment with at least three separate degrees of precision, that is a coarse degree of precision, a medium degree of precision and a fine degree of precision. 3. Device as claimed in claim 2, wherein the fine degree of precision is 1 jim. 4. Device as claimed in any one of claims 2 and 3, wherein said coarse and medium degrees of precision are of the order of 100 jim and 10 5. Device as claimed in any one of claims 2 to 4, wherein the third micrometric adjusting means (30 to 35) comprise a coarse adjustment unit (30 to 32) designed to allow adjustment to the coarse degree of precision, and a separate fine adjustment unit (33 to 35) designed to allow adjustment to medium and fine degrees of precision. 6. Device as claimed in claim 5, wherein the coarse adjustment unit (30 to 32) comprises: two elastic return cylinders (44, 47) designed to exert opposing restoring forces on a first part which is integral with either the mounting (4, 5, 6) or the support (2), a screw/ nut system (40, 48) for adjusting the distance between a second part which is integral either with the support (2) or the mounting (4, 5, 6) respectively, and a supplementary part (48), one of the elastic return cylinders resting on said supplementary part (48) while the other elastic return cylinder (44) rests on this second part. 7. Device as claimed in claim 6, wherein the two elastic return elements (44, 47) are cylinders made of synthetic as herein described under compression, and that the screw/nut system (40, 48) is designed so that the two cylinders (44, 47) are in the compressed state in every position of adjustment. 8. Device as claimed in any one of claims 6 and 7, wherein the stiffness of each of the elastic return elements (44, 47) is designed to enable the position of the support (2) to be maintained in relation to the frame (1) under the effect of gravity, but to allow adjustments by action on the first and second adjusting means and on the fine adjustment unit (33 to 35) of the third micrometric adjusting means. 9. Device as claimed in any one of claims 6 to 8, wherein the screw/nut system (40, 48) comprises a rod (40) passing through a bore (42) made through said first part, and that this bore (42) has an internal diameter that is greater than the external diameter of the rod (40), so as to permit relative displacements and adjustments in said first and second directions. 10. Device as claimed in claim 6, wherein washers (45, 46, 50, 51) made from a material as herein described having a low static coefficient of friction are interposed on each side of the bore (42) between each end of the elastic return cylinders (44, 47) and one support face facing the first part, so as to facilitate relative displacements in the first and second directions under the effect of the first and second adjusting means. 11. Device as claimed in any one of claims 6 to 10, wherein the fine adjustment unit (30 to 32) is designed to push said first and second parts against the elastic return elements (44, 47) of the coarse adjustment unit (30 to 32) 12. Device as claimed in any one of claims 5 to 11, wherein the fine adjustment unit (33 to 35) has micrometric means for measuring the distance separating the third section of the support and the section facing the mounting, with two separate sensitivities, that is a medium sensitivity and a fine sensitivity. 13. Device as claimed in claims 5 and 12, wherein the medium and fine sensitivities correspond to said medium and fine degrees of precision. 14. Device as claimed in claim 5, wherein the fine adjustment unit (33 to 35) comprises a body (53) supported by the mounting (4, 5, 6) and a rod (54) moveable in the third direction, whose free end comes into contact and rests on a bearing surface (55) of the third section (36 to 38) of the support (2). 15. Device as claimed in claim 5, wherein the fine adjustment unit (33 to 35) is formed by a differential micrometric thrust block. 16. Device as claimed in claim 1, wherein each locking screw (56, 57, 79 to 82) extends at least in said third direction. 17. Device as claimed in any one of claims 1 to 16, wherein the connecting means comprise, for each locking screw (56, 57, 79 to 82), a ball and socket linkage, two pairs of washers (67 to 70) with spherical bearing surfaces in contact, these pairs of washers coming to rest against bearing surfaces (60, 61, 71, 72) orientated in the opposite direction so as to allow the locking screw (56, 57, 79 to 82) to be tightened with different relative orientations of the support (2) and of the mounting (4, 5, 6). 18. Device as claimed in claim 1, wherein for each locking screw (56, 57, 79 to 82), the support (2) contains a tapping (58, 59) for receiving one end of the locking screw, and the mounting (4, 5, 6) contains a bearing surface (60, 61) for a head (65, 66) of the locking screw, and a bore (63, 64) through which the locking screw passes, and that the internal diameter of the bore (63, 64) exceeds the external diameter of the locking screw by a value such as herein described that is sufficient to allow the locking screw to be screwed into the tapping (58, 59) in any position of the support (2) in relation to the frame (1) adjusted in the first and second directions. 19. Device as claimed in claim 17, wherein the connecting mechanism comprise a pair of washers (67, 68) with spherical bearing surfaces in contact interposed between the head (65, 66) of the locking screw (56, 57, 79 to 82) and the bearing surface (60, 61) of the mounting (4, 5, 6), and a pair of washers (69, 70) with spherical bearing surfaces in contact placed around the locking screw between the mounting (4, 5, 6) and the support (2). 20. Device as claimed in claim 19, wherein a pair of washers (69, 70) with spherical bearing surfaces in contact comes to rest on a bearing surface (71, 72) of the mounting (4, 5, 6) orientated towards the support (2). 21. Device as claimed in claim 20, wherein the shim (73, 74) is a washer interposed between this pair of washers (69, 70) with spherical bearing surfaces in contact, which comes into contact with a bearing surface (71, 72) of the mounting, and a bearing surface (75, 76) of the third section (36 to 38) of the support (2). 22. Device as claimed in claim 1, wherein the first adjusting means (9 to 12) and/or the second adjusting means (20 to 22) contain a micrometric thrust block carried by the mounting (4, 5, 6) or by the support (2), this micrometric thrust block having a rod (18) whose free end comes into contact with a bearing surface (19, 26) facing the support (2) or the mounting (4, 5, 6), respectively. 23. Device as claimed in claim 1, wherein the three mountings (4, 5, 6) extend as a whole in the same plane, at least perpendicularly to said third direction, the adjusting means in the first and second direction being means for centring the optical element (3) in relation to the mountings (4, 5, 6). 24. Device as claimed in claim 1, wherein the different adjusting means (9 to 12, 20 to 22, 30 to 35) have parts designed to be detachable and to be removed from the frame (1) and/or the support (2) after locking into the set position. 25. Device as claimed in claims 6, 22 and 24, wherein the elastic return elements (44, 47) and the screw/nut system (40, 48) of the coarse adjustment unit (30 to 32) of the third micrometric adjusting means 30 to 35), and the different micrometric thrust blocks (9 to 12, 20 to 22, 33 to 35) are mounted so as to be detachable after locking into the set position. 26. Device as claimed in claim 1, wherein the locking means (56 to 76, 79 to 82) are designed so as to be capable of withstanding a maximum acceleration of between 15 g and 60 g in any direction, without change of adjustment. 27. A device as claimed in any one of claims 1 to 28, used for the micrometric positioning of an aspherical mirror (3) of a telescope with three mirrors for terrestrial observation from space. 28. Device for the micrometric positioning, in relation to a frame of a support of an optical element substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

796-del-1998-abstract.pdf

796-del-1998-claims.pdf

796-del-1998-correspondence-others.pdf

796-del-1998-correspondence-po.pdf

796-del-1998-description (complete).pdf

796-del-1998-drawings.pdf

796-del-1998-form-1.pdf

796-del-1998-form-13.pdf

796-del-1998-form-19.pdf

796-del-1998-form-2.pdf

796-del-1998-form-3.pdf

796-del-1998-form-4.pdf

796-del-1998-form-6.pdf

796-del-1998-gpa.pdf

796-del-1998-petition-137.pdf