FR2789652A1 - Telecommunications payload low orbit satellite configuration having lengthened trapezoidal body with small upper rigid panel holding satellite controls and larger lower panel holding payload. - Google Patents

Abstract

The satellite construction has a lengthened platform (10) with a trapezoidal section with an upper rigid panel on the small base holding the satellite control unit. The control unit has attitude and propulsion control, positioning digital processing and power distribution. The lower rigid panel (18) holds the useful load, for instance a telecommunications payload.

Description

SATELLITE FOR USE IN LOW ORBIT, IN PARTICULAR

TELECOMMUNICATIONS SATELLITE

  The present invention relates to satellites intended to be placed in low orbit, frequently, not equatorial and to carry a payload, which will be

  general telecommunications payload.

  The invention finds a particularly important, although not exclusive, application in the field of telecommunications satellites belonging to a constellation of satellites distributed in longitude so

  to be in direct sight of each other.

  Often, the satellite is assembled or integrated in a clean room from components coming from various origins. In particular, it is frequent that the telecommunications payload is supplied by an industrialist different from that or those who supply the propulsion, setting and holding devices and the solar power supply generators.

electric.

  The present invention aims in particular to provide a satellite whose constitution is such that the assembly is simpler than in the past, which in particular makes it possible to reduce the duration of the manufacturing cycle and stay in the integration room. To this end, the invention proposes in particular a satellite comprising an elongated platform with approximately trapezoidal section having a rigid panel occupying the small base and carrying practically all of the attitude and propulsion control members of the satellite and another rigid panel occupying the great

base and carrying the payload.

  Such a modular constitution allows two sub-assemblies to be manufactured independently, each having a rigid panel, one dedicated to the control members.

  attitude and propulsion and the other to the payload.

  This modular construction greatly facilitates final integration, in particular in the form of a box comprising four longitudinal members connecting end panels and side walls, as well as the two

  rigid panels occupying the bases, fixed to the side members.

  These beams can be connected by partitions distributed at regular or irregular intervals, constituting

  couples and ensuring the rigidity of the platform.

  The rigid panel occupying the small base will generally carry a solar generator made up of two wings, by means of an articulated arm movable between a stored state o it allows the folded wings to be applied against the lateral faces of the platform (notably during launch) and a deployed state where it spreads the wings of the platform, making it possible to free the radioelectric and optical fields of view required by the transmitters and receivers required by the payload and

the platform.

  The components carried by the rigid panel occupying the small base are advantageously distributed on both sides, - the arm of the solar generator, the components of a propulsion system and most of at least the position and orientation sensors on the external side; - actuators, such as wheels, gyrodynes or magnetocouplers, for attitude control and the factors

electronics on the other side.

  In general, the satellite will be kept stationary in an orientation such that its direction of elongation constitutes an axis of roll, the panel constituting the large base being oriented towards the ground and carrying antennas for transmitting and receiving communications with the ground. as well as antennas or optical transceivers for liaison with the other satellites of the

  constellation to which the satellite belongs.

  To dissipate the heat given off, in particular in the emission circuits and the batteries, two pairs of planar radiators are advantageously mounted on the side faces of the platform by hinges located near the longitudinal ends of the side faces. These hinges can be oriented parallel to the end edges of these lateral faces, so that the planar radiators can be applied against the lateral faces during the launching phases and possible transfer of an orbit.

  intermediate to the final orbit.

  An additional couple of radiators (not shown) can be stored on the nadir side, then deployed by 180 to bring them in line with the

nadir panel.

  Satellites in low orbit are frequently mounted in clusters on the same launcher, which brings them into an intermediate orbit from which they are brought to station in a higher orbit, for example at about 1400 km altitude, by a propellant mounted on the satellite. In an advantageous embodiment, the attachment points of the platform on a mounting plate belonging to a launcher are all located on a terminal face in the direction of elongation. This method of attachment facilitates the installation of an adjustable number of satellites under the cover of the various launchers

likely to be used.

  The above features as well as others

  will appear better on reading the description which follows

  of a particular embodiment of the invention, given

  by way of nonlimiting example. Description refers

  in the accompanying drawings, in which: - Figure 1 is a perspective view of a satellite according to a particular embodiment, in the operational state, showing in particular the face directed towards the earth in normal operation; - Figure 2 is a perspective view showing the satellite platform stripped of its side panels; - Figure 3 is a detail view on a large scale showing in particular the arm of the solar generator, in the folded position; - Figure 4 is a perspective view of the panel occupying the small base of the platform, in the inverted position relative to Figure 2; - Figure 5 is a detail view on a large scale showing the components carried by the end face facing forward; FIG. 6 is a diagram intended to show the successive positions taken by the satellite solar generator at successive positions on the same orbit; - Figures 7A to 7D are diagrams showing how satellites according to Figure 1 can be grouped under the cover of a launcher; - Figure 8 is an exploded view for showing the state of the solar generator and radiators for launch; - Figure 9 is an implementation flow diagram. The satellite, the general constitution of which is shown in FIGS. 1, 2 and 4, comprises a platform 10 carrying the payload and a solar generator 12 connected to the platform by an arm 14. In FIG. 1, the satellite is shown in the disposition that he takes when he is at post, with the arm extended, while the

  Figure 2 shows it with the arm folded.

  The platform appears in Figures 1 and 2.

  It is elongated in a direction which will generally be that of the roll axis X, tangent to the trajectory, and it is of trapezoidal section perpendicular to this direction. It can be viewed as constituting a box having a structure visible in FIG. 2, and rigid panels fixed to the structure. A rigid panel 16 occupying the small base of the trapezium carries the major part of the easements (satellite control and propulsion control members) as well as the foldable arm 14. A rigid panel 18 occupying the large base of the trapezium is intended to be directed towards the earth (towards the nadir), therefore orthogonal to the yaw axis Z, when the satellite is at position. The panel 18 carries practically all the members constituting the payload. The panels 20 corresponding to the sides of the trapezoid (FIG. 1) essentially constitute structural elements and bear on their internal face

  payload elements, possibly electronic.

  They help dissipate the heat dissipated on board. Finally, the panels occupying the end faces close the box and can carry the elements which do not

  can be found on panel 16.

  The rigidity of the body is ensured by four longitudinal members 24, generally made of carbon, on which the panels are fixed by means not shown. These beams are connected from place to place by partitions

  constituting couples 26 (FIG. 2).

  The external face of the panel 16 carries the folding arm 14, the main thrust member with its supply tank and most of the propulsion. The member shown in FIG. 1 is a Hall effect ion propulsion nozzle 28 supplied by a xenon tank 30. This nozzle can be fixed under the internal face for reasons of space.

(Figures 1 and 4).

  Additional thrust members 32 directed along the roll X, pitch Y and yaw Z axes make it possible to provide thrusts in the form of short pulses of low value. They can consist of two sets of four micro-nozzles 32 supplied with xenon and equipped with a heating resistor. These nozzles are carried by the panel 16, by

  through a support bracket 34.

  The external face of the panel 16 also carries telemetry and remote control antennas 36 projecting in the directions X and -X and stellar sensors 38 (not visible in FIG. 3). She also wears

  GPS 40 antennas in the + X and -X directions.

  The internal face of the panel 16 carries in particular the avionics and attitude control members of the satellite. In the embodiment illustrated in FIG. 4, these members include four reaction wheels 42 having different axes and a torque generator 44, operating by interaction with the earth's magnetic field. At each end, the internal face can carry an amplifier 46 associated with a solar collector, not shown. The on-board computer 50 and circuits 52 for managing and distributing electrical power can also be carried by the internal face. The lateral zones are reserved for the passage of harnesses 54

electrical connection.

  The panel 18, which corresponds to the large base of the trapezoidal section, is assigned to the payload. It carries, on the face directed towards the nadir, the antenna 56 of emission towards the ground and the antenna 58 of reception from the ground. The transmitting antenna is placed between two sets of transducers 60 for connection with other satellites, generally by optical means. Several antennas of each type could be provided. Because of their number, these transducers have a wide field of view around the yaw axis Z. The side panels 20 do not carry any sensor or propellant. As will be seen later, this allows a wide latitude in the orientation of the solar generator 12. They can support radiators 62 and 64 which, in the deployed state, are oriented orthogonally to the roll direction X or in a little different position. The satellite represented in FIG. 1 comprises two sets of panels 62 and 64, one placed at the front and the other at the rear. Two additional radiators can be mounted so as to be orientable orthogonally to the yaw axis Z. Each panel is mounted on articulation and displacement members 66 which make it possible to bring it from a state where it is flat against the corresponding panel 20 (Figure 8) in a state where it is deployed. In general, the elements 66 constitute a hinge defining an axis of tilting of the panel parallel to the end edge of the side panel 20 and close to this edge. The elements 66 may in particular comprise an actuating bar made of a shape memory alloy, the

  heating brings the radiator to the deployed position.

  The solar generator 12 shown in FIG. 1 is kept away from the satellite platform by the arm, when this arm 14 is unfolded. The generator consists of two wings. In the figures, they each consist of several solar panels 70 of

  same width, of which only a few are shown.

  A bracket 72, the projection of which corresponds substantially to the width of each solar panel 70, connects each part to the end of the arm 14 by means of actuators. These actuators include first motors 74 making it possible to rotate the wings around an axis parallel to the pitch axis Y so as to keep the generator 12 facing the sun S, as indicated in FIG. 6. These motors make it possible to give a panoramic movement with the solar generator, at the orbital frequency. Two other motors 76 (bias motors), each placed between a motor 74 and the corresponding wing, can be provided to orient the wings in a limited angular range, around an axis orthogonal to the axis of the panoramic movement, and parallel to the plane of the wings, this to take into account the seasonal variations in the orientation of the earth relative to the sun. Because the organs for connection with the ground and between satellites are placed only on the panel which faces the nadir, the solar generator cannot enter the field of view of these organs, unless it is given an excessive bias: in in practice, we can easily tolerate a bias of around twenty degrees around a median position. Since the detection and propulsion units are placed only at the ends of the panel placed facing the zenith, there is also no interference with the nozzles and transducers, except

for high angles of bias.

  When the solar panels are in the folded position, that is to say in the state where they are shown in FIG. 8, and where the bracket 72 is itself folded over the wing in the stored configuration, the two parts of the solar generator 12 can be brought against the side panels of the platform. The solar generator does not interfere in any way with the operation of the various members mounted on the panels 16 and 18 and on the end panels. It is consequently possible to cause, using the nozzle 28, possibly orientable, the passage of the satellite from an orbit of

  transfer at low altitude to a final orbit.

  The trapezoidal cross-section of the platform and the possibility of completely folding the solar panels on the lateral faces make it possible to easily group a variable number of satellites under the cover of a launcher, this number being a function of the diameter of the launcher. Figures 7A to 7D show several possible configurations. In the case of a launcher intended to carry a single satellite in a space defined by the circle 88, the almost triangular shape of the footprint of the satellite allows it to occupy most of the available space. A back-to-back configuration is also possible (FIG. 7B) in the case of a launch of two satellites. In the case of a platform whose two side faces make an angle close to 90, a grouping of four satellites (Figure 7C) or five

  satellites can be easily implemented.

  A simple method of fixing the satellite consists in providing it with anchoring points, intended for example to receive explosive bolts, placed only at the angles 90 of the rear face, directly in the alignment of the longitudinal members. The structure under cover is

thus enormously simplified.

  The altitude and attitude control mode in normal operation, when the satellite is stationary, can be carried out in a relatively conventional manner. FIG. 9 schematically shows the normal station-keeping mode 80, during which the computer receives information from the stellar sensors 38 and the

  information collected by GPS 40 antennas.

  The attitude can be corrected by action on the wheels of

  reaction 42 and the magnetic torque generators 44.

  Speed changes can be made by

  activation of the Hall 28 nozzle and micro-

  32 nozzles which can act as well in the direction of

  acceleration than deceleration.

  In survival mode 82, in the event of a serious failure or after separation from the launcher, operation is made simple and robust. The attitude is determined from information supplied by a magnetometer and possibly by a solar sensor 84 or by GPS information or coming from the ground. The actuators involved are the magnetic torque generators 44 and the reaction wheels 42 as well as, in the case where it is

required, micro-nozzles 32.

  Finally, in mode 86 of ascent to the final orbit and of displacement towards a cemetery orbit, the necessary thrust is produced by the nozzle 28 and the correct attitude is maintained using the generators

  of magnetic torque 44 and reaction wheels 42.

Claims (10)

  1. Satellite comprising an elongated platform (10) of approximately trapezoidal section having a rigid panel (16) occupying the small base and carrying the resources and the equipment for the satellite and another rigid panel (18) occupying the large base and carrying a payload.   2. Satellite according to claim 1, characterized in that said resources and easements include equipment for determining attitude, propulsion, telecommunications, location,   data processing and power distribution.   3. Satellite according to claim 1 or 2, characterized in that the platform constitutes a box comprising four side members connecting end panels and side walls, as well as the two rigid panels (16,18) occupying the bases, attached to the side members. 4. Satellite according to claim 3, the longitudinal members of which are connected by partitions distributed at intervals in the direction of elongation, constituting   couples and participating in the rigidity of the platform   form. 5. Satellite according to any one of   Claims 1 to 4, characterized in that the panel   rigid occupying the small base carries a solar generator, via a folding articulated arm in a stored state where it allows the folded generator to be applied against the side faces of the platform to   a deployed state where it removes the generator from the platform   form. 6. Satellite according to claim 5, characterized in that the solar generator consists of two symmetrical wings and the articulated arm deployed brings the wings in a position releasing the radioelectric and optical fields of view required by the payload and by resources.   7. Satellite according to any one of   previous claims, characterized in that two   couples of planar radiators are mounted on the side faces of the platform by hinges located near the longitudinal ends of the side faces. 8. Satellite according to any one of   claims 1 to 7, characterized in that the said   resources include a Hall effect ion propulsion nozzle (28) supplied by a xenon tank (30)   and oriented in the direction of elongation.   9. Satellite according to claim 8, characterized by two sets of additional thrust micro-nozzles (32) directed along the roll axes X, pitch Y and   yaw Z, supplied by the said reservoir.   10. Satellite according to any one of   Claims 1 to 9, characterized in that the panel   occupying the large base carries antennas (56,58) of emission towards the ground and reception from the ground, as well as two sets of transducers (60) of connection by optical way, the two sets being directed in direction   otherwise in the direction of elongation.