RU2616439C1 - Retroreflective spherical system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention can be used in the optical range as a passive autonomous retroreflective spherical system (RSS) for the calibration of the distance measurements by the laser range finders. The RSS comprises non-through holes uniformly located in the spherical casing, inside of which the corner prismatic light reflectors (LR) and the hoods are mounted with the lateral faces in the form of a triangle and the corner cuts at the front face. The LRs are rounded, have three fields parallel to the input face, and are mounted on the step of the non-through hole side walls, and fixed by the hoods in the form of cylinders with the outer annular and radial grooves at the ends of the prismatic LR fixation. The radius of the LR light aperture, the hood height, the LR view angle with the hood, the LR prism height and the LR number are interconnected. In the second embodiment the non-through holes contain a cylindrical casing, which is the frame for the LR and the hood.

EFFECT: increasing the effective scattering surface, reducing dead zones, excluding of slowing and stopping the proper rotation of the retroreflective spherical system, providing sub-millimeter root mean square error of the range determination.

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Description

The invention relates to passive autonomous retroreflective spherical systems (RCC) operating in the optical range and used to solve the problems of calibrating range measurements with laser rangefinders.

Such RCCs are autonomous satellites with a significant ratio of the mass to the cross-sectional area M / S (at least 500 kg / m ^{2. The} passive nature of the target implies the reflection of the range finder signal through retroreflectors (NE) - corner reflectors (triple prisms).

RCCs with metal spherical bodies, on which SVs are located, are widely known, for example, the satellites ETALON-1, ETALON-2/1 /, LARETS (Russia) / 2 /, LARES (ESA) / 3 / .

In the previously created RCC analogs, the CB group is involved in the formation of the reflected signal: from 70 CB units, as in the ETALON-1 and ETALON-2 RCCs, to 2-3 CBs, as in the LARETS RCC. Reflection from spatially separated NEs leads to uncertainty in the real value of the measured range. A standard error (RMS) of range determination occurs. The size of the standard deviation for the RCC ETALON-1, 2 is 47 mm and 2 mm for the RCC LARETS. These RCCs give a response signal regardless of the RCC angle, since the fields of view of the CBs participating in the reflection overlap each other, and there are no “dead zones” for the formation of the response signal.

The development of modern laser range-finding establishes the requirement to reduce the standard deviation of range measurement to submillimeter values (standard deviation <1 mm).

The submillimeter value of the standard deviation is realized in the RSS “WESTPAC” / 4 / developed at JSC “NPK SPP”. The WESTPAC satellite operates on the principle of “one CB - one direction of location”. Only one SW is involved in reflection due to the introduction of the light hood of the SW, which limits the field of view of the SW, into the design. However, this leads to the appearance of angular “dead zones” between neighboring NEs. In order to ensure the rapid passage of these zones from one NE to another, a WESTPAC swirl was made around the center of mass of the satellite. RCC "WESTPAC" successfully worked as a flickering target, in which the response pulses were separated by time intervals due to the "dead zones" between the NE.

Over time, the axial rotation of the WESTPAC satellite began to slow down, and at the end of its mission, the WESTPAC stopped and stopped reflecting the transmitting signal of the ground-based range finder, apparently turning in the direction of one of the “dead zones” to the Earth. The reason for the deceleration of rotation and the stopping of axial rotation was the occurrence of eddy currents in the metal casing of the structure, induced by the electromagnetic field of the Earth and counteracting the initial rotation of the WESTPAC satellite around its own center of mass.

Patented PCC / 5 / is known, containing retroreflective elements dispersed over a spherical body — lenses with mirrors located in the foci of each lens.

The disadvantages of these RCC are the ability to slow down the rotation and the increased error in determining the range due to the work of the SV group, and not one SV, as in the proposed device.

RCC "WESTPAC" is the closest analogue (prototype) / 4 / of the proposed technical solution. "WESTPAC" contains uniformly located NEs in a uniform metal spherical body, three pieces on each of the twenty faces of the icosahedron inscribed into the sphere, through holes. Inside the holes there are mounted in a frame corner prismatic CBs made of optical quartz glass with side faces in the shape of a triangle and sections of the corners at the input face. A light hood is screwed onto the CB mount.

In the RCC "WESTPAC" used the design of the mounting corner prism CB in a metal frame / 1 /. All details of the WESTPAC design, except for CB, are metal.

The main disadvantages of the prototype are:

- a significant angular space of the "dead zones" of at least 30% of the sphere in 4 π steradians, the time of inefficient location of which increased during the mission of the satellite due to the deceleration of axial rotation;

- the final stop of the satellite’s own rotation at the end of the mission in the direction of one of the “dead zones” to the Earth due to the inhibitory effect of the eddy currents induced by the electromagnetic field of the Earth, and as a result, the absence of a reflected signal;

- a reflective aluminum coating was applied to the side faces of CB WESTPAC. The reflection coefficient of SW due to losses on 3 aluminized faces did not exceed 0.57.

The first minimum radiation pattern (BF) of the SW (Airy distribution) of the WESTPAC RCC for the working wavelength λ = 0.532 μm and the light aperture diameter D = 20.5 mm is 1.22 λ / D = 6.5 angles. sec When analyzing the BF of any BSS, one should take into account the phenomenon of high-speed light aberration, which consists in the fact that the reflected beam deviates forward in the direction of the satellite's velocity vector by a certain angle, depending on the satellite’s orbit height, zenith distance, and the satellite’s angle of elevation above the horizon. For low-orbit satellites, which include the WESTPAC RCC, the angular magnitude of the speedy light aberration is in the range from 5 to 10 angles. sec

As a result, the working angular annular zone of aberration of the speed of light with a width of 5 to 10 angles. sec, with normal incidence of light on the input face of the SW, it fell to the minimum levels of the beam, where the intensity of the reflected radiation tends to zero. As a result, WESTPAC STs actively worked only with oblique incidence of light, when the beam expanded. The effective scattering surface (EPR) of the WESTPAC RCC reached approximately 10 ⁴ -10 ⁵ m ² .

The objective of the proposed technical solution is to eliminate these disadvantages.

The technical result consists in increasing the EPR of the proposed RRS to approximately 10 ⁶ m ² ; in reducing the space of "dead zones"RCC; in the exclusion of deceleration and stopping the own rotation of the RCC; in providing a submillimeter (<1 mm) standard deviation of range determination; providing a sufficiently high ballistic coefficient M / S ~ 640 kg / m ² .

This is achieved by the fact that in a PCC containing uniformly arranged in a uniform spherical body, for example, three pieces on each of the twenty faces of an icosahedron inscribed in a sphere, through holes are installed inside which corner prism reflectors (CB) are made of optical quartz glass with side with the faces in the shape of a triangle and sections of the corners at the entrance face and the hood, the spherical body and hood are made of a dielectric, for example, a heavy flint TF5, through holes have side walls of a stepped silt with an annular bore from the entry side of the hood, and the prismatic SVs made rounded have three platforms parallel to the entrance face and are mounted on damping sealant at the step of the side walls of non-through holes, and are fixed by hoods, which are made in the form of separate cylinders with an outer ring and radial bores at the ends by fixing prism NE, and adhered to the sidewalls of non-through holes flush with the surface of the sphere, in addition, the light aperture radius R _CB CB prism height bleu h rows _bl, field angle ± θ with the lens hood unit CB and the number N CB in a spherical housing interconnected by the relations

θ = arccos (1-2 / N),

where n is the refractive index of the material of the retroreflector.

According to the second version of the RCC technical solution, this is achieved by the fact that in the RCC containing uniformly arranged in a uniform spherical body, for example, three pieces on each of the twenty faces of the icosahedron inscribed in the sphere, through holes are installed inside of which are angled prism reflectors made of quartz glass optical with side faces in the shape of a triangle and cuts of corners at the entrance face and hood, each through hole additionally contains a cylindrical body in the form of a sleeve, which is a reference oh for a retroreflector and a hood, while the spherical body, cylindrical body and hood are made of a dielectric, for example, TF5 heavy flint, the inner walls of the cylindrical body have a stepped profile with an annular bore on the entrance side of the hood, and prismatic reflectors made rounded have three platforms parallel to the entrance face, and mounted on a damping sealant at the step of the inner walls of the cylindrical bodies, and are fixed by hoods, which are made as separate cylinder with an outer circumferential and radial bores at the ends by the reflectors fixed and adhered to the inner wall of the casing is flush with the surface of the sphere, moreover radius light aperture R _CB prism CB height blend h _plaque, field angle ± θ of unit CB with a blend of , the prism height h _CB CB and the number N CB in a spherical body are interconnected by the relations

θ = arccos (1-2 / N),

where n is the refractive index of the material of the retroreflector.

The technical solution is illustrated by drawings, which depict on

FIG. 1 - general view of the RCC;

FIG. 2 - placement of NE in a through hole of a spherical body (first option);

FIG. 3 - placement of NE in a through hole of a spherical body (second option).

PCC in FIG. 1 contains uniformly arranged in a uniform spherical body 1, for example, three pieces on each of the twenty faces of the icosahedron inscribed in a sphere, through holes 2, inside of which are mounted corner prismatic CB 3 of optical quartz glass with side faces in the shape of a triangle and sections of corners at the entrance face. The prismatic CB 3 are rounded, have three platforms 4, which are made in the upper part of the corner cuts, and are parallel to the input face 5. Through holes 2 have side walls of a stepped profile with an annular bore on the side of the rays input. CB 3 are installed on damping sealant 6 at the step 7 of the side walls of non-through holes 2 and are fixed by hoods 8. Hoods 8 are made in the form of separate cylinders with an external annular groove 9 and 10 radial grooves at the ends from the fixation side of the prismatic CB 3 and glued to the side walls through holes 2 flush with the surface of the sphere of a spherical body 1.

According to the second embodiment of the PCC technical solution, each non-through hole 2 further comprises a cylindrical body 11 in the form of a sleeve, which is the frame for the retroreflector 3 and hood 8. The inner walls of the cylindrical body 11 have a stepped profile with an annular bore on the entrance side of the hood. Prismatic retroreflectors are also rounded, have three platforms 4, parallel to the input face 5, and are mounted on damping sealant at the steps of the inner walls of the cylindrical bodies 11, and are fixed by hoods 8. Hoods 8 are made in the form of separate cylinders with an external annular and radial 10 grooves on the ends from the side of fixing the retroreflectors 3 and are glued to the inner walls of the cylindrical bodies flush with the surface of the sphere (spherical body 1).

The spherical body 1, the cylindrical body 11 and the hood 8 are made of a dielectric, for example, a heavy flint TF5.

In the second embodiment of the proposed device, a pre-glued assembly is installed in the through holes of the spherical body, consisting of a cylindrical body 11 (frame), in which a prismatic CB 3 and a hood 8 are installed in series. This assembly is then glued into the through hole of the spherical body. Such a design option may be more convenient for assembly, alignment, interchangeability of individual device assemblies. It is also more technologically advanced in the manufacture of PCC, since drilling a complex step hole in the housing for installing a prismatic CB is more complicated than drilling a cylindrical hole for a frame.

SV can be structurally performed both without a reflective coating of the side faces operating in this case on the basis of total internal reflection, and with an interference dielectric or other reflective coating.

The technical result is achieved by the fact that in the proposed device the “dead zone” of the RCC location is reduced as a result of the selection of the light radius CB R _CB and the height of the hood h _bl .

The radius of the light aperture R _{CB of the} prismatic CB, the height of the hood h _bl , the angle of view ± θ of a single CB with a hood, the height of the prism CB h _CB and the number N of CB in a spherical housing are interconnected by the relations

θ = arccos (1-2 / N).

The solid angle of view of a single NE is

Ω = 2π⋅ (1-cosθ).

The total spatial field of view of N CB relative to a sphere of 4π steradians is

The condition for the absence of "dead zones" RCC:

Ω _rel = 1, whence

θ = arccos (1-2 / N).

At N = 60, the field of view of a single SW with a hood should be approximately θ = ± 15 angles. hail.

For the values selected in the device, R _CB = 12 mm, h _CB = 19.1 mm and h _bl = 25 mm, the viewing angle of a single CB will be θ = 17.5 ang. hail., and the relative solid angle of view (reflection) -

Ω _rel ~ 1.3.

The real relative solid angle of reflection of the BSS in this case will be close to 1, since near the boundaries of the field of view of the SW with the hood, the reflected signal tends to 0.

Ω _{rel real} <1.3 → 1.

For the angle of the field of view θ = 15 ang. deg., when, as shown above, Ω _rel = 1, the real relative solid angle will be less than 1, which will lead to the formation of "dead zones" near the boundaries of the field of view of the SW.

With a decrease in the hood height h _bl <25 mm, the value of the relative solid viewing angle Ω _{rel will} increase, more than 1 CB will participate in the reflection, and the standard error of the range determination will exceed the submillimeter values.

Information sources:

1. V. B. Burmistrov, N.M. Soyuzova, T.P. Startsev, T.I. Khorosheva, V.D. Shargorodsky. / “Development of laser retroreflector antennas based on corner retroreflectors for high-precision range measurements to spacecraft” // Electromagnetic Waves & Electronic Systems, No. 2, vol. 2, 1997, p. 50-57 /.

2. V.B. Burmistrov, N.N. Parkhomenko, V.D. Shargorodsky, V.P. Vasiliev. "REFLECTOR, LARETS and METEOR-3M." 14th International Workshop on Laser Ranging, San Fernando, Spain 7-11 June, 2004.

Internet access:

[ http: //cddis.gsfc . nasa . gov / lw 1 4 / docs / papers / tar 3 a _vbm.pdf].

3. Ciufolini, A. Paolozzi, C. Paris. Overview of the LARES Mission: orbit, error analysis and technological aspects. JOURNAL OF PHYSICS. CONFERENCE SERIES, vol. 354, p. 1-9, 2012.

Internet access:

[ http: // iopscience .iop.org / 1742-6596 / 354/1/012002 / pdf / 1742-6596_354_1_012002.pdf].

4. Scientific-technical note for user - NASA

Internet access:

[ http://ilrs.gsfc.nasa.gov/docs/Westpac_final.pdf ]. - The prototype.

5. US patent No. 5357371, class. G02B 5/126, 1994 and RU, patent No. 2101737, class. G02B 5/10, 1998.

Claims (6)

1. Retroreflex spherical system containing evenly spaced in a uniform spherical body, for example, three pieces on each of the twenty faces of the icosahedron inscribed in a sphere, through holes, inside which are mounted angular prism reflectors made of quartz optical glass with side faces in the shape of a triangle and sections of corners at the entrance face and a hood, characterized in that the spherical body and hood are made of a dielectric, for example, a heavy flint TF5, through holes have side the walls of the stepped profile with an annular bore from the entry side of the hood, and prismatic reflectors made rounded, have three platforms parallel to the input face and are mounted on damping sealant at the step of the side walls of non-through holes, and are fixed by hoods, which are made in the form of separate cylinders with external annular and radial grooves at the ends from the side of fixation of prism reflectors, and glued to the side walls of non-through holes flush with the surface of the sphere, chrome moreover, the radius R _{CB of the} light aperture of the prism reflector, the height of the hood h _bl , the field of view ± θ of a single reflector with a hood, the height of the prism h _{CB of the} reflector and the number N of retroreflectors in a spherical housing are interconnected by the relations

where n is the refractive index of the material of the retroreflector. 2. A retroreflective spherical system containing evenly spaced in a uniform spherical body, for example, three pieces on each of the twenty faces of the icosahedron inscribed in a sphere, through holes, inside which angular prism reflectors are made of optical quartz glass with side faces in the shape of a triangle and sections of corners at the entrance face, and a hood, characterized in that each through hole additionally contains a cylindrical body in the form of a sleeve, which is a frame for lights the refractor and the hood, the spherical body, the cylindrical body and the hood are made of dielectric, for example, TF5 heavy flint, the inner walls of the cylindrical body have a stepped profile with an annular bore on the entrance side of the hood, and prismatic retroreflectors made rounded have three platforms parallel to the inlet face, and mounted on a damping sealant at the stage of the inner walls of the cylindrical bodies, and are fixed by hoods, which are made in the form of separate cylinders with External Expansion annular and radial bores at the ends by the reflectors fixed and adhered to the inner wall of the casing is flush with the surface of the sphere, in addition, the radius R _CB light aperture prism reflector, the height of the hood h _plaque, field angle ± θ single reflector with a hood, the prism height h _{CB of the} retroreflector and the number N of retroreflectors in a spherical body are interconnected by the relations

where n is the refractive index of the material of the retroreflector.

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