Aeronautics and astronautics – Spacecraft – Attitude control
Reexamination Certificate
1999-08-18
2001-06-05
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Spacecraft
Attitude control
Reexamination Certificate
active
06241193
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to three-axis stabilized geostationary satellites and, more particularly, to the thermal control of the said satellites.
2. Description of the Related Art
It is known that electronic equipment carried on board satellites dissipates energy in the form of heat. To maintain the said equipment within an optimal operating temperature range, it is therefore necessary to remove, from the satellite, the excess thermal energy. It is moreover known that such removal of thermal energy can only be achieved through radiation into space.
In the case of a three-axis geostationary satellite stabilized in its orbit, especially a telecommunications satellite, comprising a north face and a south face, which are opposite one another and respectively orthogonal to the axis of the poles of the Earth, it is usual for the radiation of the heat from the satellite into space to be effected by the said north and south faces, used as a thermal radiator. Such a process of heat removal is advantageous since the said north and south faces:
undergo, over an annual period, minimum exposure to sunlight relative to the other faces of the satellite; and
have constant illumination over one day, that is to say over one revolution, thereby making it possible to avoid overly large temperature variations.
However, in the case of very large thermal energy dissipation by the said electronic equipment, it may happen that the removal of heat by the north and south faces is insufficient to afford the said equipment an optimal operating temperature.
The object of the present invention is therefore to increase the on-board heat removal capabilities of a satellite, so as to avoid this drawback.
SUMMARY OF THE INVENTION
To this end, according to the invention, the geostationary satellite stabilized in its orbit along three of its axes and comprising at least one first face and at least one second face, which are such that a first face is illuminated by the sun when a second face is in shadow and vice versa, is noteworthy in that it comprises means of thermal coupling between at least one first face and at least one second face.
Thus, according to the invention, at least one first face and at least one second face are together considered as a whole for additional thermal control of the satellite, by transferring the excess thermal power from the sunlit side of the satellite (which has a minimum capacity for sinking heat to the outside) to the side in shadow, which has a high potential for removing heat to the outside. The overall heat sinkage capacity for the satellite is thus increased as is therefore its radio-frequency power.
In an advantageous embodiment, in order to ease the removal, to the outside of the satellite, of the heat generated by radiating devices (electronic equipment) mounted on board the said satellite, these radiating devices are at least in part carried by the said first and second faces and the said means of thermal coupling ensure the transfer of heat between the said devices carried by at least one first face and the said devices carried by at least one second face. Thus, the heat generated by radiating devices carried by a face illuminated by the sun (and hence hardly if at all thermally dissipating) is transmitted from the shadow side of the satellite where it can more easily be dissipated to the outside.
Such first and second faces may consist of an east face and a west face, which are opposite one another and respectively transverse to the said orbit. Likewise, first and second faces may consist of an earth face, permanently directed toward the Earth, and an anti-earth face, permanently directed away from the Earth, the said earth and anti-earth faces being respectively orthogonal to the plane of the equator.
The said means of thermal coupling may consist of any device able to conduct heat. However, preferably, such means of coupling are heat pipes (also generally referred to as fluid loops) containing an evaporatable and condensable fluid alternately undergoing switches from the liquid phase to the vapor phase and then from the vapor phase to the liquid phase.
Especially in the case of a satellite for telecommunications, the said heat-radiating devices may be traveling-wave tubes, generally designated by the initials TWT, especially those said to have a radiating collector allowing large transmission powers. Such traveling-wave tubes have a collector operating at a very high temperature, of the order of 200° C. as compared with the body of the tube which remains at a temperature of the order of 80° C. In this case, it is advantageous for the bodies of the said traveling-wave tubes to be fixed on first and second faces of the satellite and for their collectors to be disposed outside the said satellite, at least on the side of one of the latter's north or south faces.
REFERENCES:
patent: 3749156 (1973-07-01), Fletcher et al.
patent: 4880050 (1989-11-01), Nakamura et al.
patent: 5332030 (1994-07-01), Spencer et al.
patent: 5372183 (1994-12-01), Strickberger
patent: 5494241 (1996-02-01), Poulain
patent: 5839696 (1998-11-01), Caplin et al.
patent: 5957408 (1999-09-01), Hall et al.
patent: 0647559 (1995-04-01), None
patent: 2463058 (1981-02-01), None
Cassagne Jean-Christophe
Courteau Pascal
Lebleu Denis
Moschetti Bernard
Alcatel
Jordan Charles T.
Palo Francis T.
Stevens Davis Miller & Mosher LLP
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