Multi-orbital space surveillance device

Description

Technical Field

[0001] The present invention relates to a space surveillance system for monitoring near and far space from the ground in order to detect objects in this space, determine their precise trajectories and monitor these trajectories.

[0002] Such a system makes it possible to track the evolution of the trajectories of objects and to catalogue these objects and their trajectories. Previous technique

[0003] Near-Earth space is defined as the portion of space located up to a few hundred thousand kilometers from Earth. Monitoring near-Earth space therefore primarily, but not exclusively, involves detecting objects orbiting Earth, generally between a hundred and 36,000 km above the Earth's surface.

[0004] The context of the present invention is the observed increase in the number of objects orbiting the Earth. These objects can be, for example, debris, operational satellites, or even meteorites.

[0005] The invention focuses, among other things, on objects in low Earth orbit (LEO) between 200 km and 2000 km, the increasing number of which leads to a growing risk of collisions that could, in the long term, worsen the situation and, more importantly, pose risks to operational space assets, whether military, scientific, or commercial. To manage these risks, it is essential to catalog all potentially hazardous objects and associate them with valid orbital parameters that describe their trajectories.

[0006] Observed from a fixed point on Earth, objects in low Earth orbit are characterized by their rapid movement across the sky. Furthermore, at any given moment, several objects cross the sky at multiple locations. Depending on their orbital parameters, the time interval between two objects successively traversing the local sky can vary from a few tens of minutes to several hours.

[0007] Various effects such as tides, atmospheric braking, radiation pressure, and irregularities in Earth's gravitational field affect orbits. This prevents us from accurately describing these orbits in the long term with an invariant set of orbital parameters.

[0008] Moreover, the size distribution of objects varies from a characteristic radius of a few millimeters, for example propulsion residues, paint or meteorites, to several tens of meters, notably satellites or artificial orbital systems, whether they are operational or not.

[0009] Conducting a survey of objects orbiting the Earth involves: detect objects in low Earth orbit, without prior knowledge of their existence or position, define their trajectory or orbital parameters with a precision adapted to the intended use, update, over time, the orbital parameters of the detected objects and integrate them into a tracking catalogue.

[0010] It is also necessary to reacquire the same objects and refresh the measurement of their orbital parameters each time they pass through the field of view of the observation means so that their accuracy remains suitable for the use which must be made of them, for example to implement the processes of identification and consolidation of collision risks (or "tracking" in English) or of mapping and monitoring of space objects ("survey" in English).

[0011] Finally, the system must be able to refine on demand the accuracy of the knowledge of the orbital parameters of a given object, so as to be able to determine as precisely as possible its position in the near future, typically a few days.

[0012] Performing these monitoring functions requires the following: with a wide field of view, sensitivity to detect objects of interest, and measurement accuracy of the evolution of objects crossing this field of view sufficient to estimate their orbital parameters with the required level of performance.

[0013] Orbital parameters are estimated based on a time series of measurements of the position / velocity vectors of objects acquired during their transit through the field of view.

[0014] US patent 7,319,556 deals with a wide-field telescope adapted to a system performing these functions.

[0015] The main techniques currently being considered and implemented for monitoring low Earth orbit rely on ground-based radars: the so-called "Space Fence" radars of the US Department of Defense; the GRAVES radars implemented by the French Ministry of Defense (phased array radar, bi-static, continuous emission), the missile warning radars (mono-static phased array radar, pulsed emission).

[0016] Although offering many advantages (wide field of view allowing interception of 180° azimuth zones over several tens of degrees in elevation, simplified access to speed information thanks to Doppler measurements, insensitivity to weather and the day / night cycle, etc.), radar-based solutions suffer from numerous drawbacks, mainly residing in their development, operation and maintenance costs, and in their environmental impact: The frequencies used are high (L-band); there is a significant generation of magnetic losses; power levels of several tens of megawatts are required, with low efficiency; the mean time between failures (MTBF) of radars, like all high-power electrical equipment, is low and results in high maintenance costs; the orbital population accessible by each radar is determined by its location on the globe, which leads to their placement in the equatorial zone, which offers severe temperature and humidity conditions for electrical and electronic components, thus increasing the cost of operation and maintenance.

[0017] As an alternative, optical systems have already been considered for space surveillance. Purely passive, their principle lies in detecting sunlight reflected by natural or artificial objects orbiting Earth or beyond, such as asteroids and planetesimals. Such systems provide access to time series measurements of the objects' angular positions, for example, azimuth and elevation.

[0018] Various methods are applied to measure these positions, including a method based on measuring at each instant the position of the detected objects relative to the stars present in the field of view, stars whose position is known with very high precision.

[0019] The major advantage of optical systems over radar systems lies in their low cost in development, production, operation and maintenance, their reliability and their simplicity of implementation.

[0020] And, being purely passive, they require little infrastructure, energy, buildings, or means of transport.

[0021] Optical systems are normally used to monitor the geostationary orbit (or GEO for "Geostationary Earth Orbit"), but also to monitor the intermediate orbit (or MEO for "Middle Earth Orbit"), located between LEO and GEO, because objects on these two orbits have the particularity of passing very little over the celestial vault, which facilitates the long observation times necessary for the detection of small objects and / or objects of very low light intensity.

[0022] The US Air Force's GEODSS system is an operational example of such systems. It consists primarily of metric telescopes with a narrow field of view on the order of a degree. For these GEO and MEO applications, long integration (exposure) times, from one to several seconds, can be used to increase the signal-to-noise ratio, making it possible to detect small objects with a characteristic diameter of a few tens of centimeters.

[0023] An example of a multi-sensor implementation is described in US document 2009 / 0147238.

[0024] Several studies have also been initiated to define solutions capable of monitoring LEO.

[0025] For example, the French experimental system SPOC (Système Probatoire pour l'Observation du Ciel) integrated four small telescopes with an aperture of around 10 cm oriented according to the four cardinal points with an elevation of a few tens of degrees and each offering a field of view of around 10°.

[0026] Other concepts propose sensitive catadioptric systems with metric or, more commonly, wide field apertures of around 5°, dedicated to LEO monitoring, such as the system described in the aforementioned US patent 7,319,556.

[0027] However, the aforementioned solutions currently proposed do not resolve the fundamental difficulties and constraints related to LEO monitoring, namely: the need for rapid detection (within a few days) of any new object, in particular to identify any fragmentation or explosion phenomenon in orbit; the need for frequent re-acquisition (every few days) of each object, and an update of its orbital parameters in order to maintain usable orbital parameter accuracy, particularly with regard to the operational assessment of collision risks; the detectability of objects being interdependent with the geographical location of the optical system and orbits (inclination in particular) of the objects, linked to their illumination conditions; optical observations linked to local meteorological conditions (cloud cover);

[0028] Due to these constraints, LEO monitoring also requires specific optical systems with very high sensitivity, excellent resolution, and a wide field of view. Existing telescopes typically have high sensitivity, large apertures and / or long integration times, and high resolution, which comes at the expense of a wide field of view, since they are designed for conventional astronomical applications or monitoring minor planets or asteroids: they are therefore not suitable for monitoring LEO objects.

[0029] Furthermore, the principle of observation does not include object tracking. Therefore, during LEO observation, long integration times do not improve object detectability, which is assessed based on the signal-to-noise ratio in each illuminated pixel. This is because, in the case of conventional integration (the second), the object passes through several pixels of the sensor (CCD or CMOS) during the integration time, which not only hinders position determination and dating but also introduces noise, thus degrading the signal-to-noise ratio once the pixel has been traversed.

[0030] From another point of view, the known solutions are not adapted to the detection conditions in LEO, and therefore do not allow the observation of the set of observable objects with an appropriate revisit time.

[0031] Finally, wide-field telescopes remain limited, such as the telescopes known from document US 2009 / 009897 or document EP 1 772 761.

[0032] Other examples of telescopes are given in documents US 7 045 774, US 2007 / 0188610 and US 2009 / 0015914.

[0033] It is also known, from documents EP 2 593 366, EP 2 593 367, and EP 2 593 368, from space watch systems for near space surveillance.

[0034] It is also known from US document 2010 / 278521 as a device for monitoring objects in space orbit around the Earth. Description of the invention

[0035] The main purpose of the present invention is therefore to provide a passive optical device for monitoring objects in space orbit around the Earth in near, medium and geostationary orbits, with a wide monitoring field with a capacity of at least 120° azimuthal opening.

[0036] According to one object of the invention, a device for monitoring objects in space orbit around the Earth is proposed, the device comprising a chassis, a platform, at least three optical monitoring modules, and a power and control unit housed at least partially inside the chassis, the platform being mounted on the chassis, and each optical monitoring module being mounted on the platform and comprising a rotating turret, an image sensor mounted on the rotating turret, and a passive optical system mounted on the input of the image sensor, the rotating turret being configured to rotate more than 360° around a first axis perpendicular to the plane in which the platform extends and to rotate 90° around a second axis perpendicular to the first axis and parallel to the plane in which the platform extends.

[0037] The device according to the invention thus forms a passive optical system device for the monitoring of space objects, said at least three optical modules providing a large simultaneous monitoring optical field and making it possible to reduce the time required to detect objects in space orbit around the Earth, and thus to increase the number of objects that can be detected in a given time.

[0038] In a first embodiment of the device, the rotating turrets can be motorized turrets comprising at least one motor enabling the rotation to be driven along the two axes of rotation, and the power and control block includes a control unit for each rotating turret configured to control a rotating turret independently of the other rotating turrets.

[0039] The optical modules can thus be controlled by an automated and / or remote control, and they can be controlled independently of each other, which makes it possible to track an object being detected by one optical module while the other optical modules do not move or move in different directions.

[0040] According to a second embodiment of the device, the chassis can include height-adjustable feet, the feet being adjustable between at least two different lengths to have a platform that can be positioned between a first height of 1000 mm and a second height of 2030 mm.

[0041] The adjustable feet allow the height of the platform to be adjusted according to the environment in which the device is installed, while maintaining reasonable dimensions and weight, and placing optical devices in the best conditions to have the clearest possible field of observation.

[0042] According to a third embodiment of the device, the platform may include a central opening through which the power and data cables coupled between the optical monitoring modules and the power and control unit pass.

[0043] The central opening of the tray allows all the cables coupled to the different optical modules to be concentrated in the center of the device to direct them towards the power and control unit, thus reducing the bulk of the device and reducing the risk of the cables entering the field of view of one of the optical modules.

[0044] According to a fourth embodiment of the device, the rotating turrets are preferably made of aluminum to reduce their weight and thus the overall weight of the device. Alternatively, the rotating turrets can also be made of stainless steel to reduce manufacturing costs.

[0045] According to a fifth embodiment of the device, the rotating turrets are preferably distributed uniformly over a circle with a diameter smaller than the inscribed circle of the platform.

[0046] The uniform distribution of optical modules along the perimeter of a circle optimizes the field of observation and reduces the overlap area of ​​the fields of observation of the different optical modules.

[0047] According to a sixth embodiment of the device, the device may further include a temperature control unit mounted on the power and control unit and configured to regulate the temperature of the power and control unit between +13°C and +23°C. The power and control unit may be in the form of a power supply bay incorporating a control unit. The temperature control unit enables the device to be placed and used in environments where conditions are normally less favorable for the proper functioning of the device. The temperature control unit may be a heating unit, a cooling unit, or an air conditioning unit configured to heat or cool the power and control unit according to the environmental conditions.

[0048] According to a seventh embodiment of the device, the device may further include a humidity control block fixed on the power and control block configured to regulate the humidity inside the power and acquisition block to a humidity level between 30% and 60%.

[0049] The humidity control unit allows the device to be placed and used in environments where conditions are normally less favorable to the proper functioning of the device.

[0050] In one embodiment, the temperature control block can be a heating block and the humidity control block can be an air conditioning block configured to cool the power bay and regulate its humidity.

[0051] According to an eighth embodiment of the device, the device preferably comprises six optical monitoring modules distributed uniformly over a circle whose diameter is less than the diameter of the inscribed circle of said plate.

[0052] The use of six optical modules allows for optimized optical coverage.

[0053] According to a ninth embodiment, the rotating turrets can be limited in minimum rotation around the first axis to 10° of amplitude, being able to reach a maximum rotation of 360° and have a displacement step of 1° and being able to reach a step of up to 0.1°. Brief description of the drawings

[0054] Other features and advantages of the present invention will become apparent from the description given below, with reference to the attached drawings which illustrate an example of an embodiment without any limiting character. [ Fig. 1 ] There figure 1represents a perspective view of a device for monitoring objects in space orbit around the Earth according to an embodiment of the invention. Fig. 2 ] There figure 2 represents a top view of the device figure 1 . [ Fig. 3 ] There figure 3 represents a perspective view of the chassis and platform of the device figure 1 . Description of the implementation methods

[0055] On the figure 1 is schematically represented a perspective view of a device 1 for monitoring objects in space orbit around the Earth according to an embodiment of the invention.

[0056] Device 1 includes a chassis 2, a platform 3, six optical monitoring modules 4, a power supply and control block 5, and a function regulation block 6.

[0057] As illustrated on the figure 3 which represents a perspective view of chassis 2 and platform 3 of device 1 of the figure 1 , chassis 2 includes a U-shaped base 200 comprising three segments 202 and four assemblies 204 each bolted to one end or corner of the base 200 and intended to fix the base 200 to the ground on which the device 1 will be fixed.

[0058] The chassis 2 further includes four feet 206, each screwed at a first end 2060 onto the base 200. The four feet 206 with anti-vibration devices are arranged at the four corners of a square extending in a plane parallel to the plane in which the base 200 extends. The first two feet 206 are joined together by a first cross member 208, and two second feet 206, separate from the first feet, are joined together by a second cross member 210.

[0059] Each foot 206 comprises a lower part 206a and an upper part 206b partially fitting onto the lower part 206a. The first cross member 208 is fixed to the lower parts 206a of the first two feet 206, and the second cross member 210 is fixed to the lower parts 206a of the second two feet 206.

[0060] The upper part 206b of each foot 206 slides along the lower part 206a to which it is associated, the lower part 206a sliding inside the upper part 206b. The height of each foot 206 can thus be adjusted between a low and a high position depending on the environment of the device 1 to ensure that the field of vision of the optical modules is unobstructed.

[0061] Each foot 206 includes a second end 2065 fixed to the plate 3. The first end 2060 of each foot 206 corresponds to an end of the lower part 206a never covered by the upper part 206b, and the second end 2065 of each foot 206 corresponds to an end of the upper part 206b.

[0062] As illustrated on the figure 2 which presents a top view of device 1 of the figure 1 , the tray 3 has a disc shape and includes a lower surface 300 opposite the chassis 2 on which the tray 3 is fixed and an upper surface 302 opposite the lower surface 300, the optical modules 4 being mounted on the upper surface 302 of the tray 3.

[0063] The platter 3 further includes a central hole 304 passing through the center of the disk on which is mounted a cover 306 with a hexagonal base, having a top face 308 parallel to the top surface 302 of the platter 3 and six side faces 310 extending perpendicularly to the platter 3 between the top surface 302 of the platter 3 and the top face 308 of the cover 306. Each side face 310 of the cover 306 is pierced with a hole 312 to allow cables to pass through a hole 312 of the side face and the central hole 304 of the platter 3.

[0064] The optical modules 4 are arranged regularly around the perimeter of a circle whose diameter is less than the outer perimeter of the disk formed by the platter 3. Thus, each optical module 4 is separated from the next optical module 4 by an angle of 30° measured with respect to the center of the platter 3 disk. This separation angle between modules can vary depending on the configurations.

[0065] If the platform had a shape other than that of a disk, a polygonal shape for example, the circle on which the optical modules 4 would be arranged would have a diameter smaller than the diameter of the circle inscribed in the polygonal shape of the platform 3.

[0066] Each optical module 4 includes a motorized rotating aluminum turret 400 to maintain the lightest possible weight at a reduced cost. Each turret 400 includes a support 402 fixed to the platform 3, the support 402 being surmounted by a foot 404 which can pivot about a first axis perpendicular to the plane in which the platform 3 extends, the platform 3 extending parallel to a plane comprising the X and Y directions, and the first axis extending in a direction parallel to a Z direction as illustrated in the figure 1 .

[0067] The turret 400 of each optical module 4 also includes an arm 406 coupled to the foot 404 of the turret 400. The arm 406 is mounted on the foot 404 in a rotatable manner about a second axis which is perpendicular to the first axis and which extends parallel to the plane comprising the X and Y directions.

[0068] On the arm 406 of each turret 400 is mounted an image sensor 408 coupled, on its optical input, to a passive optical system 410 such as a set of lenses.

[0069] Thus each assembly consisting of an image sensor 408 and its associated passive optical system 410 can be oriented in two directions, the first direction and the second direction.

[0070] The 404 base of a 400 turret can pivot about the first axis, i.e., Z, 185° in one direction and 185° in the other direction, thus covering 370° in a plane parallel to the XY plane. The 406 arm of a 400 turret can pivot about the second axis 90° in one direction and 90° in the other direction, thus covering 180° in a plane perpendicular to the XY plane.

[0071] For clarity, the cables connecting the optical modules 4 to the power and control unit 5 are not shown. Each cable passes through an opening 312 on a side face 310 of the cover 306 before passing through the central opening 304 of the platform 3 and then being routed to the power and control unit 5. The power and control unit 5 can thus control the power supply to the motors of the turrets 400 and the image sensors 408 of the optical modules, the orientation of the feet 404 and the arms 406 of each turret, and the acquisition of images by the image sensors 408.

[0072] The power and control unit 5 is designed to be placed within the volume defined by the chassis 2 and the platform 3, specifically between the feet 206 of the chassis 2. The power and control unit 5 further includes a control module for each turret 400, thus allowing each turret 400 to be controlled independently of the other turrets 400.

[0073] The operating control block 6 is thermodynamically coupled to the power supply and control block 5 and is configured to regulate the temperature and humidity inside the power supply and control block 5. The temperature in this latter block 5 can thus be maintained at a temperature between +13°C and +23°C and at a humidity below 60% humidity for optimal operation of the device 1.

Claims

1. A device (1) for monitoring objects in space orbit around the Earth, the device (1) comprising a chassis (2), a plate (3), at least three optical survey modules (4), and a power supply and control block (5) housed at least partially inside the chassis (2), the plate (3) being mounted on the chassis (2), and each optical survey module (4) being mounted on the plate (3) and including a rotating turret (400), an image sensor (408) mounted on the rotating turret (400), and a passive optical system (410) mounted on the inlet of the image sensor (408), the rotating turret (400) being configured to pivot over more than 360° about a first axis perpendicular to the plane in which the plate (3) extends and to pivot over 90° about a second axis perpendicular to the first axis and parallel to the plane in which the plate (3) extends.

2. The device (1) according to claim 1, wherein the rotating turrets (400) are motorized turrets comprising at least one motor for actuating the rotation along the two axes of rotation, and the power supply and control block (5) includes a control unit for each rotating turret (400) configured to control a rotating turret (400) independently of the other rotating turrets (400).

3. The device (1) according to any of claims 1 or 2, wherein the chassis (2) comprises height-adjustable feet (206), the feet (206) being adjustable between at least two different lengths to have a plate (3) that can be positioned between a first height of 1,000 mm and a second height of 2,030 mm.

4. The device (1) according to any of claims 1 to 3, wherein the plate (3) comprises a central orifice (304) through which the power and data cables pass, coupled between the optical survey modules (4) and the power supply and the control block (5).

5. The device (1) according to any of claims 1 to 4, wherein the rotating turrets (400) are made of aluminum.

6. The device (1) according to any of claims 1 to 5, wherein the rotating turrets (400) are uniformly distributed on a circle with a diameter smaller than the inscribed circle of the plate (3).

7. The device (1) according to any of claims 1 to 6, further comprising a temperature regulation block (6) fixed on the power supply and control block (5) and configured to regulate the temperature of the power supply and control block (5) between +13°C and +23°C.

8. The device (1) according to any of claims 1 to 7, further comprising a hygrometric regulation block (6) fixed on the power supply and control block (5) configured to regulate the hygrometry inside the power supply and control block (5) at a humidity level comprised between 30% and 60%.

9. The device (1) according to any of claims 1 to 8, comprising six optical survey modules (4) uniformly distributed on a circle whose diameter is smaller than the diameter of the inscribed circle of said plate (3).

10. The device (1) according to any of claims 1 to 9, wherein the rotating turrets (400) are limited in rotation about the first axis to 10° of amplitude and have a displacement pitch of 1°.