Radar system and method for de-icing its cylindrical parabolic reflector

Abstract

Disclosed is a ground-based radar system (1) for observing space objects (A) in orbit, the radar system (1) comprising at least one transmit antenna (2) for transmitting incident electromagnetic waves (S) and at least one cylindrical parabolic reflector (6), the cylindrical parabolic reflector (6) being fixedly mounted and comprising a reflective outer surface (7) suitable for concentrating the incident electromagnetic waves (S) into a beam of determined pointing direction (D), the reflective outer surface (7) being exposed to bad weather, the radar system (1) comprising at least one de-icing fluidic network (10) extending under the reflective outer surface (7) of the cylindrical parabolic reflector (6), the de-icing fluidic network (10) being controllable between an inactive mode (OFF), and an active mode (ON) in which a de-icing fluid (F10) flows through the de-icing fluidic network (10) in order to de-ice the reflective outer surface (7) so as to preserve the determined pointing direction (D).

Description

Radar system and method for de-icing its parabolic-cylindrical reflector

[0001] The present invention relates to the field of radar systems and aims at the de-icing of a parabolic cylindrical reflector.

[0002] It is known to use ground-based radar systems to monitor orbiting space objects, typically low-Earth orbit satellites located between 200 km and 2000 km above the ground. Such radar systems conventionally include one or more antennas designed to transmit incident electromagnetic waves and a reflector designed to focus these waves into a beam pointed at the space object being observed. The incident electromagnetic waves are typically generated, modulated, and amplified by a transmission chain connected to the antennas via a waveguide. The reflector and one or more receiving antennas, often identical to the transmitting antennas, guide the electromagnetic waves reflected by the space object to a receiving chain, allowing the data to be extracted.

[0003] It is particularly well known in the form of parabolic-cylindrical reflectors, which have an external reflective surface in the shape of a parabolic cylinder mounted fixed to the ground with its concave side facing the sky. Such parabolic-cylindrical reflectors allow for the combination of a large number of antennas, in practice more than a hundred, to obtain a high-power beam with a narrow beamwidth, typically with a gain greater than 45 dB and a beamwidth of less than 1°, enabling precise observation of distant space objects.

[0004] Such parabolic trough radar systems provide both surveillance, namely the detection of space objects, and tracking through electronic antenna scanning, allowing for rapid adjustment of the beam's pointing direction. This distinguishes them from mechanically scanned parabolic reflectors, whose beam is slow to reposition and cannot track space objects. Furthermore, mechanical scanning is more prone to failure and requires regular maintenance, which is difficult to perform at remote sites.

[0005] In practice, however, such parabolic reflectors have the disadvantage of being exposed to the elements, particularly frost and snow, which can form and accumulate on the external reflective surface. Such a deposit of frost and / or snow can alter the pointing direction of the emitted beam and reduce its range by absorbing some of the beam's energy, thus undesirably disrupting the detection of space objects.

[0006] In the case of parabolic reflectors, several devices are known to combat frost formation. One such device, described in patent application WO9711505A1, involves mounting a radome around the parabolic reflector and circulating hot air between the reflector and the radome. However, such a radome is expensive and not feasible for large reflectors, particularly parabolic-cylindrical reflectors, which typically extend up to 25 meters in length.

[0007] It is also known, through patent application WO2023022332A1, to integrate a heating resistive layer beneath the reflective surface of a parabolic reflector. However, such a solution is too energy-intensive to be considered for a parabolic cylindrical reflector, which is considerably larger.

[0008] Patent application US2020 / 381798A1 describes a fluidic chamber between the reflector wall and the outer wall of a satellite antenna reflector, heated by geothermal energy or a radiator. Patent application JPH02308603A1 describes hot air generators attached to a thermally insulating material on the support structure of a reflector. Patent application RU2192074C2 describes a reflector with air cavities into which hot air is diffused.

[0009] The invention aims to prevent the accumulation of frost and / or snow on a parabolic cylindrical reflector of a radar system in a simple and energy-efficient manner. PRESENTATION OF THE INVENTION

[0010] The invention relates to a ground-based radar system for observing orbiting space objects, the radar system comprising at least one antenna for emitting incident electromagnetic waves and at least one parabolic-cylindrical reflector, the parabolic-cylindrical reflector being fixedly mounted and comprising an external reflective surface adapted to concentrate the incident electromagnetic waves into a beam with a determined pointing direction, the external reflective surface being exposed to the weather.

[0011] The invention is remarkable in that the radar system includes at least one de-icing fluid network extending under the external reflective surface of the parabolic-cylindrical reflector, the de-icing fluid network being controllable between an inactive mode and an active mode, in which a de-icing fluid circulates in the de-icing fluid network to de-ice the external reflective surface so as to maintain the determined pointing direction.

[0012] The invention advantageously provides a simple and effective way to de-ice the parabolic trough(s) of a radar system. In active mode, the circulation of the de-icing fluid within the de-icing fluid network heats the external reflective surface of the parabolic trough. This prevents the deposition or accumulation of frost and / or snow that could deflect the direction of the wave beam and absorb some of its energy, thus reducing its range. Thanks to the invention, the pointing of the incident electromagnetic wave beam is achieved with a precise and reliable direction and range, enabling optimal detection and monitoring of space objects. The de-icing fluid network has the advantage of being inexpensive compared to a radome and less energy-intensive than heating elements.

[0013] According to one aspect of the invention, the radar system comprises: at least one transmitting module adapted to generate the incident electromagnetic waves connected to the transmitting antenna and at least one cooling device for the transmitting module adapted to circulate a cooling fluid in the transmitting module, the de-icing fluid network comprising at least one heat exchanger configured to transfer heat from the cooling fluid at the outlet of the transmitting module to the de-icing fluid.

[0014] Thanks to this invention, the defrosting of the parabolic trough reflector is achieved in an energy-efficient manner by utilizing the heat rejected by the emission module's cooling system. The heat from the cooling fluid, resulting from its circulation within the emission module, is advantageously used to warm the reflector's external reflective surface. This eliminates the need for a dedicated heat source for the defrosting fluid system. Furthermore, the heat exchanger is passive and, advantageously, requires no control.

[0015] According to one aspect of the invention, the transmitting module is located less than 10 meters, preferably less than 5 meters, from the parabolic trough reflector. This positioning is constrained to ensure good transmission of the incident electromagnetic waves. The invention thus makes it possible to exploit the heat accumulated by the cooling fluid near the reflector, without the need for long pipes and without heat loss.

[0016] According to one aspect of the invention, the radar system includes at least one pump configured, in active mode, to circulate the de-icing fluid within the de-icing fluid network. Preferably, in inactive mode, the de-icing fluid remains stationary within the de-icing fluid network. This allows for simple and convenient control of the reflector de-icing.

[0017] Preferably, the radar system includes a control device for the de-icing fluid network, preferably the pump, configured to activate the active mode when an external or reflector measured parameter falls below a predetermined threshold. The measured parameter is preferably the temperature of the reflector's external reflective surface. This simple and practical control requires no human intervention.

[0018] According to one aspect of the invention, the defrosting fluid network is in the form of a closed circuit. The operation of the defrosting fluid network and the cooling circuit are optimized, with the reflector forming the cold source and the emission module the hot source.

[0019] According to one aspect of the invention, the external reflective surface of the parabolic cylindrical reflector comprises a lower and an upper portion relative to a gravity axis, with the de-icing fluidic network extending only below the lower portion. This reduces de-icing costs by limiting it to the lower portion, which is more prone to frost and / or snow accumulation.

[0020] According to one aspect of the invention, the lower part of the external reflective surface has a tangent at each point that forms an angle greater than 35° with respect to the axis of gravity. The lower portion extending substantially horizontally is more prone to the deposition of frost and / or snow.

[0021] According to one aspect of the invention, the external reflective surface of the parabolic cylindrical reflector has a length greater than 15m, preferably greater than 20m. The invention advantageously allows for the simple and inexpensive de-icing of a large reflector.

[0022] According to one aspect of the invention, the defrosting fluid network is attached in a separate manner beneath the external reflective surface of the parabolic trough. This simplifies its installation and maintenance.

[0023] The invention also relates to a method of defrosting the parabolic-cylindrical reflector of a radar system as described above, in which the defrosting fluid network is initially in the inactive mode, the method of use consisting of piloting the active mode to circulate the defrosting fluid in the defrosting fluid network to defrost the external reflective surface so as to maintain the determined pointing direction. PRESENTATION OF THE FIGURES

[0024] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0025] This is a schematic representation in profile view of a radar system comprising a de-icing fluidic network according to one embodiment of the invention.

[0026] This is a schematic top-view representation of the radar system when the de-icing fluid network is in active mode.

[0027] This is a schematic top-view representation of the radar system when the de-icing fluid network is in inactive mode.

[0028] It should be noted that the figures explain the invention in detail for implementing the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0029] With reference to the, the invention relates to a ground-based radar system 1 B for the observation of orbiting space objects A, typically low-Earth orbit satellites located between 200 km and 2000 km above ground B. The radar system 1 classically comprises an incident electromagnetic wave transmission module 3 S, one or more incident electromagnetic wave transmission antennas 2 S, one or more reflectors 6, one or more receiving antennas 2' (see figures 2 and 3) for electromagnetic waves reflected by the space object A and a receiving module 4 for reflected electromagnetic waves.

[0030] Referring to Figures 1 and 2, the reflector 6 of the radar system 1 is of the parabolic-cylindrical type, meaning that it comprises an external reflective surface 7 in the shape of a parabolic cylinder with its longitudinal axis X extending horizontally relative to the axis of gravity G and its concavity facing upwards. The external reflective surface 7 concentrates the incident electromagnetic waves S into a beam with a specific pointing direction D for observing a spatial object A. The external reflective surface 7 also concentrates the electromagnetic waves reflected by the spatial object A towards the receiving antennas 2'.

[0031] In the example shown in Figures 1 and 2, the external reflective surface 7 is supported by a structure fixed to the ground B. The external reflective surface 7 is exposed to the elements, i.e., it is free of a radome or protective cover. The external reflective surface 7 typically extends over a length L along the longitudinal axis X greater than 15 m, preferably greater than 20 m. A single reflector 6 is shown in the example, but it is understood that the invention also applies to a radar system 1 equipped with several reflectors 6.

[0032] Referring to Figures 1 and 2, the incident electromagnetic waves S are emitted by an array of transmitting antennas 2, typically comprising more than one hundred antennas 2. The transmitting antennas 2 are positioned next to the reflector 6, typically within 10 m, preferably within 5 m. The transmitting antennas 2 are aligned in a direction parallel to the longitudinal axis X of the reflector 6. The transmitting antenna array 2 produces a high-power beam with a narrow beamwidth, typically with a gain greater than 45 dB and a beamwidth of less than 1°, enabling precise observation of space objects A over a long range. The transmitting antennas 2 are of the electronically scanned type, allowing for simple and rapid adjustment of the beam's pointing direction D for tracking space objects S.The receiving antennas 2' of the electromagnetic waves reflected by the spatial object A are preferably aligned with the transmitting antennas 2 and of similar structure.

[0033] With reference to figures 1 and 2, the transmission module 3, known to those skilled in the art as the "transmission chain", produces, modulates and amplifies the incident electromagnetic waves S. The transmission module 3 is connected to the transmission antennas 2 by microwave cables (not shown), which require minimizing the distance between the transmission antennas 2 and the transmission module 3 to limit the attenuation of the incident electromagnetic waves S. The transmission module 3 is therefore typically positioned next to the reflector 6, preferably less than 10 m away, preferably less than 5 m away.

[0034] With reference to figures 1 and 2, the receiving module 4, known to those skilled in the art as the "receiving chain", allows the data to be extracted from the electromagnetic waves reflected by the space object A. The receiving module 4 is connected to the receiving antennas 2' by microwave cables (not shown) which require minimizing the distance between the receiving antennas 2' and the receiving module 4 to limit the attenuation of the incident electromagnetic waves S. The receiving module 4 is therefore typically positioned next to the reflector 6, typically less than 10 m away, preferably less than 5 m away.

[0035] With reference to Figures 1 and 2, the radar system 1 includes one or more cooling devices 5 adapted to circulate a cooling fluid F5 through the transmitting module 3, and preferably the receiving module 4, in order to remove heat. The cooling fluid F5 is typically in the form of a liquid, preferably water or a glycol-based solution.

[0036] According to the invention and as illustrated in Figures 1 to 3, the radar system 1 further comprises a de-icing fluid network 10 extending under the external reflective surface 7 of the parabolic-cylindrical reflector 6 (shown in dashed lines in Figures 2 and 3 by transparency). Also according to the invention, the de-icing fluid network 10 is controllable between an inactive OFF mode (see) and an active ON mode in which a de-icing fluid F10 circulates in the de-icing fluid network 10 to de-ice the external reflective surface 7 (see Figures 1 and 2).

[0037] The de-icing fluid network 10 advantageously allows, through the circulation of the de-icing fluid F10 in active mode (ON), the heating of the external reflective surface 7 of the parabolic trough 6. This prevents the deposition or even accumulation of frost and / or snow that could deflect the direction of the wave beam. Thanks to the invention, the pointing of the incident electromagnetic wave beam S is precise and reliable, enabling optimal detection and monitoring of space objects A. The de-icing fluid network 10 has the advantage of being inexpensive compared to a radome and less energy-intensive than heating elements.

[0038] According to a preferred aspect illustrated in Figures 1 and 2, the defrosting fluid network 10 comprises one or more tubes 15 mounted on the lower face 8 of the external reflective surface 7. The defrosting fluid F10 is typically in the form of a liquid, preferably water or a glycol-based solution.

[0039] According to a preferred design illustrated in Figures 1 and 2, the defrosting fluid network 10 includes a heat exchanger 12 configured to transfer heat from the cooling fluid F5 at the outlet of the emission module 3 to the defrosting fluid F10. The heat exchanger 12 is typically mounted, on the one hand, upstream of the tubes 15 of the defrosting fluid network 10, and on the other hand, on a return line 11 of the defrosting fluid F10 downstream of the emission module 3. The heat from the cooling fluid F5 is advantageously used to warm the external reflective surface 7 of the reflector 6 in the active ON mode. This eliminates the need for a dedicated hot air source for the defrosting fluid network 10 and helps to reduce the energy cost of the cooling device 5.The defrosting of reflector 6 is thus advantageously implemented in an energy-efficient manner by utilizing the heat rejected by the nearby cooling device 5. Furthermore, the heat exchanger 12 has the advantage of being a passive component requiring no control.

[0040] Preferably, as illustrated in Figures 1 to 3, the defrosting fluid network 10 includes a pump 13 configured, in the active ON mode, to drive the defrosting fluid F10 in the defrosting fluid network 10. The circulation of the defrosting fluid F10 increases heat exchange in the heat exchanger 12 and guides the heated defrosting fluid 10 in the tubes 15 to defrost the external reflective surface 7. In the inactive OFF mode, the pump 13 is stopped so that the defrosting fluid F10 stagnates in the defrosting fluid network F10, which greatly reduces heat exchange.

[0041] Preferably, the defrosting fluid network 10 forms a closed circuit in which the heat exchanger 12 forms the hot source and the reflector 6 the cold source. Preferably, the defrosting fluid network 10 includes an expansion tank 14.

[0042] According to a preferred configuration, the pump 13 is in the inactive OFF mode by default. A control device 17, such as a controller, is configured to activate the valve 13 in the active ON mode when a measured parameter P, typically the temperature of the external reflective surface 7, is below a predetermined threshold Ps. The predetermined threshold Ps is, for example, between 20°C and 25°C. The parameter P is typically measured by a temperature sensor.

[0043] According to a preferred design illustrated in Figures 1 to 3, the de-icing fluid network 10, more specifically the tubes 15, extends only to a lower portion 9 of the external reflective surface 7 of the reflector 6 relative to the axis of gravity G. The upper portion 16 of the external reflective surface 16 is free of the de-icing fluid network 10. Preferably, the tangent T at each point of the lower portion 9 forms an angle α greater than 35° with respect to the axis of gravity G. The lower portion 9 corresponds to the substantially horizontal portion of the external reflective surface 7 where frost and snow are more likely to form and / or accumulate. The lower portion 9 typically represents less than 50% of the external reflective surface 7, which reduces the installation and operating costs of the de-icing fluid network 10.

[0044] In the example shown in Figures 1 to 3, the de-icing fluid network 10 is mounted separately on the reflector 6, in this example fixed to the underside 8 of the external reflective surface 7. This facilitates its installation and maintenance on an existing radar system 1. Alternatively, the de-icing fluid network 10 could be integrated into the reflector 6, for example, as a channel formed beneath the external reflective surface 7.

[0045] Preferably, the de-icing fluid network 10 extends over at least 80% of the length of the external reflective surface 7 for complete and effective de-icing. In this example, the de-icing fluid network 10 comprises a single coiled tube 15 covering the entire lower portion 9 of the external reflective surface 7. Alternatively, the de-icing fluid network 10 comprises several tubes 15, in particular parallel tubes, supplied by an inlet manifold and terminating in an outlet manifold. Alternatively, the radar system 1 could comprise several de-icing fluid networks 10 extending in a complementary manner beneath the external reflective surface 7.

[0046] With reference to Figures 2 and 3, the invention also relates to a method for de-icing one or more parabolic reflectors 6 of the radar system 1. As illustrated in Figure 3, the de-icing fluid network 10 is initially in the inactive OFF mode. In this example, the pump 13 is stopped, preventing the circulation of the de-icing fluid F10 in the de-icing fluid network 10. The inactive OFF mode is typically the default mode of the radar system 1.

[0047] As illustrated in the figure, in the presence of icing conditions, for example when the temperature of the external reflective surface 7 falls below the predetermined threshold Ps, the active ON mode of the pump 13 is activated to circulate the de-icing fluid F10. This allows the external reflective surface 7 to be warmed by heat exchange with the de-icing fluid F10, thus preventing the deposition or even accumulation of frost and / or snow.

[0048] The invention advantageously provides a simple and efficient way to de-ice a parabolic cylindrical reflector 6 of a radar system 1. This ensures normal operation of the radar system 1 in icing conditions without human intervention to clear the snow from the reflector 6. This is particularly advantageous for radar systems 1 installed in remote locations. Furthermore, the invention has the advantage of reducing the energy cost of the radar system 1 by utilizing the heat captured by the cooling device 5 of the adjacent transmitting module 3, thus eliminating the need for a dedicated heat source for de-icing.

Claims

A ground-based radar system (1) for observing orbiting space objects (A), the radar system (1) comprising: at least one transmitting antenna (2) for incident electromagnetic waves (S) and at least one parabolic-cylindrical reflector (6), the parabolic-cylindrical reflector (6) being fixedly mounted and comprising an external reflective surface (7) adapted to concentrate the incident electromagnetic waves (S) into a beam with a predetermined pointing direction (D), the external reflective surface (7) being exposed to the weather, at least one de-icing fluid network (10) extending below the external reflective surface (7) of the parabolic-cylindrical reflector (6), the de-icing fluid network (10) being controllable between an inactive mode (OFF) and an active mode (ON), in which a de-icing fluid (F10) circulates in the de-icing fluid network (10) to defrost the external reflective surface (7) so as to maintain the determined pointing direction (D),at least one transmission module (3) adapted to generate the incident electromagnetic waves (S) connected to the transmission antenna (2) and at least one cooling device (5) for the transmission module (3) adapted to circulate a cooling fluid (F5) in the transmission module (3), the defrosting fluid network (10) comprising at least one heat exchanger (12) configured to transfer heat from the cooling fluid (F5) at the outlet of the transmission module (3) to the defrosting fluid (F10). Radar system (1) according to claim 1, wherein the transmitting module (3) is located less than 10m, preferably less than 5m, away from the parabolic cylindrical reflector (6). Radar system (1) according to any one of claims 1 and 2, comprising at least one pump (13) configured, in active mode (ON), to drive the de-icing fluid (F10) into motion in the de-icing fluid network (10). Radar system (1) according to any one of claims 1 to 3, wherein the de-icing fluidic network (10) is in the form of a closed circuit. Radar system (1) according to any one of claims 1 to 4, wherein the external reflective surface (7) of the parabolic cylindrical reflector (6) has a lower part (9) and an upper part (16) with respect to an axis of gravity (G), the de-icing fluidic network (10) extending only under the lower portion (9). Radar system (1) according to claim 5, wherein the lower part (9) of the external reflective surface (7) has a tangent (T) at each point which forms an angle (α) greater than 35° with respect to the axis of gravity (G). Radar system (1) according to any one of claims 1 to 6, wherein the external reflective surface (7) of the parabolic cylindrical reflector (6) has a length greater than 15m, preferably greater than 20m. Radar system (1) according to any one of claims 1 to 7, wherein the de-icing fluidic network (10) is fixed in a related manner under the external reflective surface (7) of the parabolic cylindrical reflector (6). Method of defrosting the parabolic cylindrical reflector (6) of a radar system (1) according to any one of claims 1 to 8, wherein the defrosting fluid network (10) is initially in the inactive mode (OFF), the method of use consisting of piloting the active mode (ON) to circulate the defrosting fluid (F10) in the defrosting fluid network (10) to defrost the external reflective surface (7) so as to maintain the determined pointing direction (D).

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