FR2489247A1

FR2489247A1 - Controller for satellite orientation during earth's shadow transition - uses selected revolution rate delay of on-board gyroscope

Info

Publication number: FR2489247A1
Application number: FR8115611A
Authority: FR
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1980-08-29
Filing date: 1981-08-12
Publication date: 1982-03-05
Also published as: DE3032571A1; JPS5774300A

Abstract

The method of operating a satellite fitted with a gyro wheel whilst it is passing through the earth's shadow without using batteries, enables the satellite to maintain orientation. Stable alignment of the satellite is maintained during the shadow transition by selecting the decay in the gyro wheel rate of revolution so that the rate does not decrease by more than a half. This results in the angular momentum stored in the gyro wheel being larger than that imparted to the body of the satellite. Alternatively, the rate of revolution can be allowed to diminish by more than one half the original rate if the permissible residual revolution rate for maintainance of a required alignment accuracy has been determined from detailed calculations or tests.

Description

"Procedé d'exploitation d'un satellite sans batterie."
La présente invention concerne un procede d'exploitation d'un satellite sans batterie, equipd d'un volant de type gyros copique ou à moment cinétique, ci-après appelé volant, pour la phase dans laquelle le satellite, dans sa révolution autour de la Terre, traverse la zone d'ombre de celle-ci."Procedure for operating a satellite without battery."
The present invention relates to a method of operating a satellite without a battery, equipped with a flywheel of the gyros-copic or kinetic moment type, hereinafter called flywheel, for the phase in which the satellite, in its revolution around the Earth, crosses its shadow zone.

Dans le cas de la plupart des satellites de telecomntuni- cation connus, il se produit, après plusieurs annees d'exploitation, une defaillance ou une perte totale de la Capacité de la batterie. In the case of most known telecommunication satellites, after several years of operation, a failure or a total loss of the battery capacity occurs.

Le satellite connu Symphonie entait conçu de telle manière qu'en cas de defaillance de l'alimentation en energie dans l'ombre de la Terre, il maintenait sa position. La vitesse de rotation du volant prevu dans ce satellite diminuait jus qu'à atteindre l'arrêt, et de ce fait le satellite commençait a tourner autour de l'axe du plus grand moment principal d'inertie, cette rotation entant stable. Lorsque le satellite entrait a nouveau dans la partie de sa trajectoire éclairée par le soleil, le volant recuperait sa vitesse de rotation et le satellite, par une acquisition de donnees terrestres, avait a nouveau ses antennes orientes vers la Terre. The known Symphony satellite was designed in such a way that in the event of a power supply failure in the shadow of the Earth, it maintained its position. The speed of rotation of the flywheel provided in this satellite decreased until reaching the stop, and therefore the satellite began to rotate around the axis of the greatest main moment of inertia, this rotation being stable. When the satellite re-entered the part of its path lit by the sun, the steering wheel would recover its speed of rotation and the satellite, by an acquisition of terrestrial data, had again its antennas directed towards the Earth.

Ce procède n'est plus applicable dans le cas des satellites de telecommunication de plus grande puissance e-lectri- que tels que, par exemple, INTELSAT, ou-TV-SAT, parce que, dans ce cas, le volant doit necessairement pointer, par un axe de rotation, dans le sens de l'axe de rotation des genera- rateurs solaires, dont le rajustage se fait sur le soleil. I1 se produit de ce fait, en cas d'arrêtt du volant, une rotation autour de l'axe du plus petit moment principal d'inertie, laquelle est instable, le satellite perdant alors complètement sa position, du fait de la constante de temps d'amortissement, dans un ordre de grandeur d'une demi-heure, lorsqu'il sort de l'ombre de la Terre. This process is no longer applicable in the case of telecommunication satellites of higher electrical power such as, for example, INTELSAT, or-TV-SAT, because, in this case, the steering wheel must necessarily point, by an axis of rotation, in the direction of the axis of rotation of the solar generators, whose adjustment is made on the sun. I1 therefore occurs, in the event of the steering wheel stopping, a rotation around the axis of the smallest main moment of inertia, which is unstable, the satellite then completely losing its position, due to the time constant. of amortization, in an order of magnitude of half an hour, when it emerges from the shadow of the Earth.

Les volants d'inertie montes sur roulements à)billes que l'on utilisait jusqu'ici, comme par exemple, dans le cas du satellite Symphonie, mettent à peu près 50 minutes à s'arrêter, de sorte que le satellite, comme dejà explique, n'a pas de stabilisation de la giration pendant la durée maximale de 72 minutes dans l'ombre. Le temps de ralentissement jusqu'à l'ar ru complet peut cependant être prolonge avec les constructions
modernes, ainsi qu'il est connu de le faire, par exemple, par la demande de brevet allemand 2 500 211.The flywheels mounted on ball bearings that were used until now, as for example in the case of the Symphony satellite, take about 50 minutes to stop, so that the satellite, as already explains, does not stabilize gyration for the maximum duration of 72 minutes in the shade. The deceleration time to the full ar ru can however be extended with the constructions
modern, as is known to do, for example, by German patent application 2,500,211.

C'est ici qu'intervient la pressente invention, qui met à profit ce progrès technèlogique et se fixe pour objet d'indiquer, a l'aide des volants de type gyroscopique ou à moment cinétique modernes, un procede par lequel l'orientation du satellite soit maintenue dans l'ombre de la Terre, en déprit de l'absence de batterie. It is here that the present invention comes into play, which takes advantage of this technological progress and sets itself the object of indicating, using gyroscopic type flywheels or with modern kinetic moment, a process by which the orientation of the satellite is kept in the shadow of the Earth, despite the lack of battery.

Ce problème est résolu, selon la présente invention, par le fait que, pour assurer la stabilite de l'orientation du satellite pendant la durée du passage dans l'ombre, la diminution de la vitesse de rotation du volant est choisie de telle maniere que ladite vitesse ne se réduise pas de plus de la moitie, de sorte que le moment cinetique encore accumule dans le volant soit superieur à celui qui a déjà ete imprime au corps du satellite. This problem is solved, according to the present invention, by the fact that, in order to ensure the stability of the orientation of the satellite during the duration of the passage in the shade, the reduction in the speed of rotation of the steering wheel is chosen in such a way that said speed is not reduced by more than half, so that the kinetic moment still accumulated in the steering wheel is greater than that which has already been printed on the body of the satellite.

Il, est, il est vrai, déjà connu qu'en faisant varier la vitesse de rotation du volant, on peut exercer une influence sur la stabilisation du satellite, ainsi qu'il est décrit dans les brevets américains 3 511 452 et 3 767 139, mais il n'etait encore jusqu'ici venu à l'idee de personne, dans les milieux specialises, de remédier, par la mesure simple proposez par la pressente invention, au problème de l'orientation du satellite, en ce qui concerne sa position, pendant la durée de son passage dans l'ombre de la Terre.Avec le procede selon la pressente invention, l'exploitation d'un satellite de television, qui ne peut en règle generale reprendre qu'une demi-heure après qu'il soit ressorti de la zone d'ombre, peut entre re-a- lisée avec le plus grand menagement ou tout à fait sans batterie. On peut ainsi egalement réduire considerablement les exigences relatives aux moyens à mettre en oeuvre sur le plan technique.Avec le procede selon la pressente invention, l'axe satellite reste oriente, de façon stable, parallèlement à l'axe de rotation du volant, de sorte que, lorsque le passage dans l'ombre de la Terre a pris fin, une réorientation vers la terre peut se faire aisément, et que l'exploitation du sa tellite peut reprendre. Par des calculs qui sont familiers au specialiste, on peut fixer une orientation qui ne soit plus tout à fait precise, mais à partir de laquelle une orientation vers la terre soit encore possible, la vitesse de rotation du volant pouvant encore de-croitre davantage dans ce cas. It is, it is true, already known that by varying the speed of rotation of the steering wheel, one can exert an influence on the stabilization of the satellite, as described in the US patents 3,511,452 and 3,767,139 , but it had hitherto never occurred to anyone, in specialized circles, to remedy, by the simple measure proposed by the present invention, the problem of the orientation of the satellite, with regard to its position, for the duration of its passage in the shadow of the Earth. With the method according to the present invention, the operation of a television satellite, which can generally resume only half an hour after it came out of the shadow area, can be re-done with the greatest care or completely without battery. It is thus also possible to considerably reduce the requirements relating to the means to be implemented on the technical level. With the method according to the present invention, the satellite axis remains oriented, in a stable manner, parallel to the axis of rotation of the steering wheel, so that, when the passage in the shadow of the Earth has ended, a reorientation towards the earth can be done easily, and that the exploitation of its satellite can resume. By calculations which are familiar to the specialist, it is possible to fix an orientation which is no longer entirely precise, but from which an orientation towards the earth is still possible, the speed of rotation of the steering wheel being able to further increase in this case.

C'est ainsi qu'une caracteristique additionnelle de la pressente invention prévoit que la vitesse de rotation soit redite de plus de la moitie de sa valeur initiale, la vitesse de rotation encore admissible pour le maintien d'une orientation qui n'est plus tout à fait précise entant determinee par des calculs ou des essais détailles. Thus, an additional characteristic of the present invention provides that the rotational speed is reduced by more than half of its initial value, the rotational speed still admissible for maintaining an orientation which is no longer all very precise as determined by detailed calculations or tests.

Claims

1. Method of operating a satellite without a battery, equipped with a gyroscopic or kinetic momentum type flywheel, for the phase in which the satellite, in its revolution around the Earth, crosses the shadow zone of that -characterized in that, to ensure the stability of the orientation of the satellite for the duration of the passage in the shade, the reduction in the speed of rotation of the steering wheel is chosen in such a way that said speed is not further reduced by half, so that the angular momentum still accumulated in the steering wheel is greater than that which has already been printed on the body of the satellite.

2, Method for operating a battery-free satellite, equipped with a gyroscopic or kinetic momentum flywheel, for the phase in which the satellite, in its revolution around the Earth, crosses the shadow zone of that -characterized in that, in order to ensure an orientation which is no longer entirely precise but from which an orientation towards the Earth is still possible, the speed of rotation is reduced by more than half of its initial value, the rotational speed still admissible for maintaining an orientation which is no longer entirely precise and being determined by detailed calculations or tests.