Patent Publication Number: US-2021171224-A1

Title: Enhanced radiator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     An Application Data Sheet is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed Application Data Sheet is incorporated by reference herein in its entirety and for all purposes. 
     TECHNICAL FIELD 
     This invention relates generally to a radiator of a spacecraft, and more particularly to techniques for minimizing diurnal temperature variation of a radiator of a spacecraft. 
     BACKGROUND OF THE INVENTION 
     The assignee of the present invention designs and manufactures spacecraft for, inter alia, communications and broadcast services from geosynchronous orbit. The payload capacity of such a spacecraft may be limited by the capability of the spacecraft to reject excess heat. In the vacuum of space, heat rejection is achievable by thermal radiation. Therefore, such a spacecraft typically includes an arrangement of externally facing radiator panels that radiate excess heat from the spacecraft into space. Referring to  FIG. 1 , the spacecraft may be regarded as including a main body enclosed by sidewalls facing, respectively in a north, south, east, west, earth (nadir) and anti-earth (zenith) direction. When the 3-axis controlled spacecraft is operating on-orbit, the radiator panels are preferably selected to be disposed in a north or south facing direction, because the north or south panels experience a solar radiation exposure that is relatively benign and stable compared to that experienced by panels facing in an east/west or nadir/zenith direction. However, the quantity of heat dissipation needed for a desired pay load may exceed the total heat rejection capacity of north and south facing radiators alone, with the result that radiator surfaces, in addition to the north/south facing sidewalls, must be provided. 
     In conventional spacecraft, planar radiating surfaces may also be provided on the east, west, nadir, or zenith facing walls of a spacecraft, notwithstanding that these surfaces may be exposed to a varying degree of solar radiation throughout a given day, as described above. As a result, the efficiency of such non north/south radiators is impaired and thermal variations create significantly large diurnal temperature gradient cycles. 
     SUMMARY OF INVENTION 
     The systems, apparatuses, and spacecraft disclosed herein have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. 
     One innovative aspect of the subject matter described in this disclosure can be implemented in a spacecraft comprising a body, a radiator panel, and a heat dissipating unit thermally coupled with the radiator panel. The spacecraft may be configured to operate in an orbital plane, such that the spacecraft has a yaw axis within the orbital plane and directed from a spacecraft coordinate system origin toward nadir, a pitch axis orthogonal to the orbital plane and passing through the spacecraft coordinate system origin, and a roll axis orthogonal to the pitch axis and the yaw axis and passing through the spacecraft coordinate system origin. The radiator panel may include a surface area external to the body. A first portion of the surface area may face a first direction that is substantially parallel to the roll axis, and a second portion of the surface area may face a second direction that has a substantial component parallel to the yaw axis. 
     In some implementations, the spacecraft may further include a mounting panel internal to the body. The mounting panel may be thermally coupled with the heat dissipating unit. The spacecraft may further include a coupling heatpipe thermally coupling the mounting panel with the radiator panel, the coupling heatpipe having a first section proximate to the mounting panel and a second section proximate to the radiator panel. The mounting panel may include spreading heatpipes, and the radiator panel may include an internal heat transfer mechanism including one or both of: embedded heatpipes or spreader heatsinks. 
     In some implementations, the radiator panel may include a plurality of facets. The facets may be arranged such that each facet forms a side of a segment of a polygon. 
     In some implementations, the radiator panel may have a curved cross-section. 
     In some implementations, the mounting panel may be a planar radiator panel having a heat-rejecting surface. 
     In some implementations, the orbital plane may be an orbital plane of a geosynchronous orbit of Earth. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus comprising a radiator panel configured to be included in a spacecraft and to be thermally coupled with a heat dissipating unit of the spacecraft. The spacecraft may be configured to operate in an orbital plane, such that the spacecraft has a yaw axis within the orbital plane and directed from a spacecraft coordinate system origin toward nadir, a pitch axis orthogonal to the orbital plane and passing through the spacecraft coordinate system origin, and a roll axis orthogonal to the pitch axis and the yaw axis and passing through the spacecraft coordinate system origin. The radiator panel may include a surface area external to a body of the spacecraft, a first portion of the surface may face a first direction that is substantially parallel to the roll axis, and a second portion of the surface area may face a second direction that has a substantial component parallel to the yaw axis. 
     In some implementations, the radiator panel may be configured to be thermally coupled with a mounting panel by way of a coupling heatpipe. The coupling heatpipe may have a first section proximate to the mounting panel and a second section proximate to the radiator panel when the radiator panel is thermally coupled with the mounting panel. The mounting panel may be configured to thermally couple with the heat dissipating unit. The radiator panel may include an internal heat transfer mechanism including one or both of: embedded heatpipes or spreader heatsinks. 
     In some implementations, the radiator panel may include a plurality of facets. The facets may be arranged such that each facet forms a side of a segment of a polygon. 
     In some implementations, the radiator panel may have a curved cross-section. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a spacecraft comprising a body. The spacecraft may also include a mounting panel internal to the body. The mounting panel may include heat dissipating units mounted to a first surface of the mounting panel. The spacecraft may also include a radiator panel including a surface area external to the body. The spacecraft may also include a coupling heatpipe thermally coupling the mounting panel with the radiator panel, the coupling heatpipe having a first section proximate to the mounting panel and a second section proximate to the radiator panel. The spacecraft may be configured to operate in an orbital plane, such that the spacecraft has a yaw axis within the orbital plane and directed from a spacecraft coordinate system origin toward nadir, a pitch axis orthogonal to the orbital plane and passing through the spacecraft coordinate system origin, and a roll axis orthogonal to the pitch axis and the yaw axis and passing through the spacecraft coordinate system origin. A first portion of the surface area may face a first direction that is substantially parallel to the roll axis, and a second portion of the surface area may face a second direction that has a substantial component parallel to the yaw axis. 
     In some implementations, the mounting panel may include spreading heatpipes, and the radiator panel may include an internal heat transfer mechanism including one or both of: embedded heatpipes or spreader heatsinks. 
     In some implementations, the radiator panel may include a plurality of facets. The facets may be arranged such that each facet forms a side of a segment of a polygon. 
     In some implementations, the radiator panel may have a curved cross-section. 
     In some implementations, the mounting panel may be a planar radiator panel having a heat-rejecting surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features of the invention are more fully disclosed in the following detailed description of the preferred embodiments, reference being had to the accompanying drawings, in which: 
         FIG. 1  illustrates a simplified diagram of an example of a spacecraft orbiting Earth, in accordance with some implementations. 
         FIG. 2  illustrates an example of a schematic diagram of a cross-section of a spacecraft, in accordance with some implementations. 
         FIG. 3  illustrates an example of a schematic diagram of a cross-section of a spacecraft, in accordance with some implementations. 
         FIG. 4A  illustrates an isometric view of an example of a radiator panel, in accordance with some implementations. 
         FIG. 4B  illustrates an isometric view of an example of a radiator panel, in accordance with some implementations. 
         FIG. 5  illustrates an example of a schematic diagram of a cross-section of a spacecraft, in accordance with some implementations. 
         FIG. 6  illustrates an example of a schematic diagram of a cross-section of a spacecraft, in accordance with some implementations. 
     
    
    
     Throughout the drawings, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the subject invention will now be described in detail with reference to the drawings, the description is done in connection with the illustrative embodiments. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the subject invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Specific exemplary embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. It will be understood that although the terms “first” and “second” are used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another element. Thus, for example, a first user terminal could be termed a second user terminal, and similarly, a second user terminal may be termed a first user terminal without departing from the teachings of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. The symbol “/” is also used as a shorthand notation for “and/or”. 
     The terms “spacecraft”, “satellite” and “vehicle” may be used interchangeably herein, and generally refer to any orbiting satellite or spacecraft system. 
     The phrase “substantially parallel” as used herein, unless otherwise expressly indicated, refers to a relationship in which a plane or generally flat part or surface is either parallel to, or at a minimum angle close to 0° with respect to, a reference axis. A plane which is substantially parallel to an axis may be, for example, at as much as approximately an 10° maximum angle with respect to the axis and still be considered to be substantially parallel. The terms “parallel” and “substantially parallel” may be used interchangeably herein. 
     The phrase “substantial component” of a vector as used herein, unless otherwise expressly indicated, refers to an amount greater than 10 percent of the magnitude of the vector. By way of illustration, a vector is referred to herein as having a “substantial component” in the x-direction if a projection of the vector onto the x-axis is at least 10% of the total magnitude of the vector. 
     Embodiments disclosed hereinbelow include significant improvements to a spacecraft radiator. As described above, in the absence of the presently disclosed techniques, radiators disposed on non-North or South-facing surfaces of conventional spacecraft may be exposed to a varying degree of solar radiation throughout a given day, resulting in decreases in the efficiency of such non north/south radiators. 
     The presently disclosed techniques, on the other hand, allow for mitigation of diurnal temperature gradient faced by such non north/south radiators, resulting in a more benign temperature environment. 
     The heat radiation systems disclosed herein may be implemented in spacecraft operating in various orbits such as a geosynchronous orbit. For example,  FIG. 1  shows a spacecraft  100  operating in an orbital plane  104  of a geosynchronous orbit of Earth. The spacecraft  100  has a yaw axis  112  within the orbital plane  104 . The yaw axis  112  is directed from the origin of the coordinate system of the spacecraft  100  toward the Earth, i.e. nadir. The spacecraft  100  has a pitch axis  116  orthogonal to the orbital plane  104 , which passes through the origin of the coordinate system of the spacecraft  100 . The spacecraft  100  has a roll axis  120  orthogonal to the pitch axis and the yaw axis  112 , which passes through the spacecraft coordinate system origin. As used herein, and in the claims, the term geosynchronous orbit includes, for example, a geosynchronous equatorial orbit (GEO), a circular, equatorial orbit having a radius of 42,164 kilometers and an orbital period of one sidereal day of (23 hr 56 min. 4 seconds), sometimes referred to a geostationary orbit. A satellite in GEO appears stationary to a ground station on the earth. Other geosynchronous orbits contemplated by the present disclosure may be inclined with respect to the equator, and/or may be elliptical, but still have an orbital period of approximately one sidereal day. 
     The approach disclosed herein allows for the placement of radiators on non-north/south facing directions, while mitigating the daily temperature gradient that would normally be faced by such non-north/south radiators. 
     Several shapes and arrangements of radiators are disclosed herein. These radiators may have a shape and/or placement that mitigates the diurnal temperature gradient problems faced by a conventional planar non-north-south facing radiator, as described above. The radiators disclosed herein may have a variety of geometries that have different uses depending on a desired manufacturing cost and/or tolerable diurnal temperature gradient. 
       FIG. 2  shows an example of a schematic diagram of a cross-section of a spacecraft  200 , in accordance with some implementations. The spacecraft  200  has two radiator panels  220  and  220 , which can radiate heat from the system of the spacecraft  200  into space. The spacecraft  200  also includes a body  202  and heat dissipating units  204  thermally coupled with the radiator panels  220  and  220 . As discussed above, solar impingement of radiator panels  220  varies diurnally. 
     Like the spacecraft  100  of  FIG. 1 , the spacecraft  200  of  FIG. 2  may be configured to operate in the orbital plane  104  of  FIG. 1  in a geosynchronous orbit of the Earth. For example, when the spacecraft  200  of  FIG. 2  operates in the orbital plane  104  of  FIG. 1 , the spacecraft has a yaw axis  112  within the orbital plane  104  and directed from the origin of the coordinate system of the spacecraft  200  toward the Earth, i.e. nadir. The spacecraft  200  has a pitch axis  116  orthogonal to the orbital plane  104  and passing through the origin of the coordinate system of the spacecraft  200 . The spacecraft  200  has a roll axis  120  orthogonal to the pitch axis and the yaw axis  112  and passing through the spacecraft coordinate system origin. 
     In contrast to planar radiator panels, the radiator panels  220  and  220  of  FIG. 2  are curved such that the sun-facing surface of each radiator is exposed to a relatively even amount of sunlight throughout a given diurnal cycle, mitigating the diurnal temperature gradient problem described above. By way of example, the radiator panel  220  includes a surface area external to the body  202 . A first portion  226  of the surface area faces a direction substantially parallel to the roll axis  120 , and a second portion  224  of the surface area faces a second direction that has a substantial component in the yaw direction, e.g. parallel to the yaw axis  112 . 
     Heat transfer between units  204  and the radiator panels  220  and  220  may occur in a variety of manners. For example, in  FIG. 2 , the heat dissipating units  204  are mounted on a mounting panel  208  internal to the body  202  of the spacecraft  200 . The mounting panel  208  may be thermally coupled with the heat dissipating units  204 . In some implementations, the mounting panel  208  may include heat spreading heatpipes  210  to spread heat from the heat dissipating units  204  across the mounting panel  208 . As such, coupling heatpipes  212  and  212  may thermally couple the mounting panel  208  with the radiator panels  220  and  220  such that heat may be transmitted from the mounting panel  208  to each of the radiator panels  220  and  220  by way of the coupling heatpipes  212  and  212 . By way of example, the coupling heatpipe  212  has a first section  213  proximate to, and in conductive contact with, the mounting panel  208  and a second section  214  proximate to, and in conductive contact with, the radiator panel  220  such that heat may be transferred by way of coupling heatpipe  212  from the mounting panel  208  to the radiator panel  220  by conduction. 
     In some implementations, radiator panels  220  may also include an internal heat transfer mechanism  222 . By way of example, such an internal heat transfer mechanism  222  may include embedded heat spreading heatpipes or spreader heatsinks. 
     While a curved radiator panel, such as radiator panels  220  and  220  of  FIG. 2  may be helpful in mitigating problems associated with diurnal temperature variations; such benefits may be achieved with radiators having other shapes that may be cheaper to manufacture than arc-shaped radiators. By way of example,  FIG. 3  shows an example of a schematic diagram of a cross-section of a spacecraft  300 , in accordance with some implementations. The spacecraft  300  has two radiator panels  320 , which can radiate heat from the system of the spacecraft  300  into space. The spacecraft  300  also includes a body  302  and heat dissipating units  304  thermally coupled with the radiator panels  320 . As discussed above, solar impingement of radiator panels  320  varies diurnally. 
     Like the spacecraft  100  of  FIG. 1 , the spacecraft  300  of  FIG. 3  may be configured to operate in the orbital plane  104  of  FIG. 1  in a geosynchronous orbit of the Earth. For example, when the spacecraft  300  of  FIG. 3  operates in the orbital plane  104  of  FIG. 1 , the spacecraft has a yaw axis  112  within the orbital plane  104  and directed from the origin of the coordinate system of the spacecraft  300  toward the Earth, i.e. nadir. The spacecraft  300  has a pitch axis  116  orthogonal to the orbital plane  104  and passing through the origin of the coordinate system of the spacecraft  300 . The spacecraft  300  has a roll axis  120  orthogonal to the pitch axis and the yaw axis  112  and passing through the spacecraft coordinate system origin. 
     In contrast to planar radiator panels, the radiator panels  320  of  FIG. 3  are multi-faceted such that the sun-facing surface of each radiator is exposed to a relatively even amount of sunlight throughout a given diurnal cycle, mitigating the diurnal temperature gradient problem described above. By way of example, the radiator panel  320  includes a surface area external to the body  302 . A first facet  326  of the surface area faces a direction substantially parallel to the roll axis  120 , and a second facet  324  of the surface area faces a second direction that has a substantial component in the yaw direction, e.g. parallel to the yaw axis  112 . 
     In some implementations, the facets of such a multi-faceted radiator may be arranged such that each facet forms a side of a segment of a polygon, e.g. each facet of the radiator panels  320  of  FIG. 3  forms a side of a segment of an octagon. Each facet of the radiator panels  320  is angled to face the sun at different times of the day in order to mitigate the diurnal temperature gradient described above. The radiator panels  320  may be easier to manufacture than the arc-shaped radiator of  FIG. 2  because each facet of the radiator panels  320  is a planar radiator panel. 
     Heat transfer between units  304  and the radiator panels  320  may occur in a variety of manners. For example, in  FIG. 3 , the heat dissipating units  304  are mounted on a mounting panel  308  internal to the body  302  of the spacecraft  300 . The mounting panel  308  may be thermally coupled with the heat dissipating units  304 . In some implementations, the mounting panel  308  may include heat spreading heatpipes  310  to spread heat from the heat dissipating units  304  across the mounting panel  308 . As such, coupling heatpipes  312  and  312  may thermally couple the mounting panel  308  with the radiator panels  320  such that heat may be transmitted from the mounting panel  308  to each of the radiator panels  320  by way of the coupling heatpipes  312  and  312 . By way of example, the coupling heatpipe  312  has a first section  313  proximate to, and in conductive contact with, the mounting panel  308  and a second section  314  proximate to, and in conductive contact with, the radiator panel  320  such that heat may be transferred by way of coupling heatpipe  312  from the mounting panel  308  to the radiator panel  320  by conduction. 
     In some implementations, radiator panels  320  may also include an internal heat transfer mechanism  322 . By way of example, such an internal heat transfer mechanism  322  may include embedded heat spreading heatpipes or spreader heatsinks. 
     The radiator panels described herein may have a variety of 3-dimensional shapes. For example,  FIG. 4A  illustrates an isometric view of radiator panel  220  of  FIG. 2 , in accordance with some implementations. In  FIG. 4A , radiator panel  220  is shown to have a semi-cylindrical shape. Alternatively,  FIG. 4B  illustrates an isometric view of an example of radiator panel  320  of  FIG. 3 , in accordance with some implementations. In  FIG. 4B , radiator panel  320  is shown to have a shape or a portion of an octahedron. It will be understood that such radiator panels may have any 3 dimensional shape configured to minimize diurnal temperature variation such as a 3-dimensional shape having any of the cross-sections described above. 
     In some implementations, the spacecraft described above may be modified to further increase heat rejection capabilities. For instance, a mounting panel to which heat dissipating units are mounted may also function as a radiator with a heat-rejecting surface. By way of example, much like  FIG. 3 ,  FIG. 5  shows an example of a schematic diagram of a cross-section of a spacecraft  500 , in accordance with some implementations. However, unlike in  FIG. 3 , a mounting panel  508  of the spacecraft  500  of  FIG. 5  itself functions as a radiator. 
     In  FIG. 5 , the spacecraft  500  has two radiator panels  520 , which can radiate heat from the system of the spacecraft  500  into space. The spacecraft  500  also includes a body  502  and heat dissipating units  504  thermally coupled with the radiator panels  520 . As discussed above, solar impingement of radiator panels  520  varies diurnally. 
     Like the spacecraft  100  of  FIG. 1 , the spacecraft  500  of  FIG. 5  may be configured to operate in the orbital plane  104  of  FIG. 1  in a geosynchronous orbit of the Earth. For example, when the spacecraft  500  of  FIG. 5  operates in the orbital plane  104  of  FIG. 1 , the spacecraft has a yaw axis  112  within the orbital plane  104  and directed from the origin of the coordinate system of the spacecraft  500  toward the Earth, i.e. nadir. The spacecraft  500  has a pitch axis  116  orthogonal to the orbital plane  104  and passing through the origin of the coordinate system of the spacecraft  500 . The spacecraft  500  has a roll axis  120  orthogonal to the pitch axis and the yaw axis  112  and passing through the spacecraft coordinate system origin. 
     Like radiator panels  320  of  FIG. 3 , the radiator panels  520  of  FIG. 5  are multi-faceted such that the sun-facing surface of each radiator is exposed to a relatively even amount of sunlight throughout a given diurnal cycle, mitigating the diurnal temperature gradient problem described above. By way of example, the radiator panel  520  includes a surface area external to the body  502 . A first facet  526  of the surface area faces a direction substantially parallel to the roll axis  120 , and a second facet  524  of the surface area faces a second direction that has a substantial component in the yaw direction, e.g. parallel to the yaw axis  112 . 
     It will be appreciated that, in some implementations, the radiator panels  520  of  FIG. 5  may instead be curved radiator panels like radiator panels  220  and  220  of  FIG. 2 . 
     Heat transfer between units  504  and the radiator panels  520  may occur in a variety of manners. For example, in  FIG. 5 , the heat dissipating units  504  are mounted on a mounting panel  508  internal to the body  502  of the spacecraft  500 . The mounting panel  508  may be thermally coupled with the heat dissipating units  504 . In some implementations, the mounting panel  508  may include heat spreading heatpipes  510  to spread heat from the heat dissipating units  504  across the mounting panel  508 . As such, coupling heatpipes  512  and  512  may thermally couple the mounting panel  508  with the radiator panels  520  such that heat may be transmitted from the mounting panel  508  to each of the radiator panels  520  by way of the coupling heatpipes  512  and  512 . By way of example, the coupling heatpipe  512  has a first section  513  proximate to, and in conductive contact with, the mounting panel  508  and a second section  514  proximate to, and in conductive contact with, the radiator panel  520  such that heat may be transferred by way of coupling heatpipe  512  from the mounting panel  508  to the radiator panel  520  by conduction. 
     As discussed above, the mounting panel  508  may itself function as a radiator panel, which can radiate heat from the system of the spacecraft  500  into space. 
     In some implementations, radiator panels  520  may also include an internal heat transfer mechanism  522 . By way of example, such an internal heat transfer mechanism  522  may include embedded heat spreading heatpipes or spreader heatsinks. 
     Also or alternatively, heat dissipating units may be mounted directly on multi-faceted radiators such as those described above in the context of  FIGS. 3 and 5 . By way of example,  FIG. 6  shows an example of a schematic diagram of a cross-section of a spacecraft  600 , in accordance with some implementations. The spacecraft  600  has two radiator panels  620 , which can radiate heat from the system of the spacecraft  600  into space. The spacecraft  600  also includes a body  602 , and heat dissipating units  604  thermally coupled with the radiator panels  620 . As discussed above, solar impingement of radiator panels  620  varies diurnally. 
     Like the spacecraft  100  of  FIG. 1 , the spacecraft  600  of  FIG. 6  may be configured to operate in the orbital plane  104  of  FIG. 1  in a geosynchronous orbit of the Earth. For example, when the spacecraft  600  of  FIG. 6  operates in the orbital plane  104  of  FIG. 1 , the spacecraft has a yaw axis  112  within the orbital plane  104  and directed from the origin of the coordinate system of the spacecraft  600  toward the Earth, i.e. nadir. The spacecraft  600  has a pitch axis  116  orthogonal to the orbital plane  104  and passing through the origin of the coordinate system of the spacecraft  600 . The spacecraft  600  has a roll axis  120  orthogonal to the pitch axis and the yaw axis  112  and passing through the spacecraft coordinate system origin. 
     Like radiator panels  320  of  FIG. 3 , the radiator panels  620  of  FIG. 6  are multi-faceted such that the sun-facing surface of each radiator is exposed to a relatively even amount of sunlight throughout a given diurnal cycle, mitigating the diurnal temperature gradient problem described above. By way of example, the radiator panel  620  includes a surface area external to the body  602 . A first facet  626  of the surface area faces a direction substantially parallel to the roll axis  120 , and a second facet  624  of the surface area faces a second direction that has a substantial component in the yaw direction, e.g. parallel to the yaw axis  112 . 
     In some implementations, heat transfer between units  604  and the radiator panels  620  may occur by conduction. By way of example, the units  604  may be in conductive contact with the radiator panels  620 . 
     In some implementations, radiator panels  620  may also include an internal heat transfer mechanism  622 . By way of example, such an internal heat transfer mechanism  622  may include embedded heat spreading heatpipes or spreader heatsinks. Also or alternatively, the radiator panels  620  may be thermally coupled, e.g. connected with each other by way of contacting heatpipes. 
     Referring again to  FIGS. 1-6 , it will be appreciated that the radiators disclosed herein, advantageously, allow for mitigation of diurnal temperature gradient problems faced by a conventional planar non-north-south facing radiator. As a result, spacecraft  200 - 600 ) of  FIGS. 2, 3, 5, and 6  have been shown to suffer less inefficiency resulting from diurnal temperature variation than similar spacecraft having conventional non-north-south facing planar radiators. 
     Although the example implementations described include features suitable for use on a spacecraft disposed in geosynchronous orbit, the techniques disclosed herein are applicable for spacecraft intended for use in other orbits. For example, a spacecraft in a low or medium earth orbit, whether the orbit is equatorial or has an orbit plane substantially inclined to the equator, may benefit from the disclosed techniques. In some implementations, the spacecraft may be configured to perform yaw steering as described, for example, in U.S. Pat. No. 6,311,932, assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference in its entirety. 
     Thus, an improved radiator has been disclosed. The foregoing merely illustrates principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody said principles of the invention and are thus within the spirit and scope of the invention as defined by the following claims.