WO2010018291A1

WO2010018291A1 - Multifrequency automatic rotational shutter for determining the velocity of moving luminous celestial sources such as meteors, fireballs, airships or space machines

Info

Publication number: WO2010018291A1
Application number: PCT/ES2009/070329
Authority: WO
Inventors: Josep M. Trigo Rodriguez
Original assignee: Consejo Superior De Investigaciones Cientificas (Csic)
Priority date: 2008-08-04
Filing date: 2009-07-31
Publication date: 2010-02-18
Also published as: ES2345524B1; ES2345524A1

Abstract

The present invention consists of an internal device which makes it possible to determine, at any time, the angular velocity of any object visible in the sky from a particular terrestrial location. If images of that very object are taken from two geographical locations which are at a sufficient distance, it will also be possible to determine the trajectory, actual velocity and place at which said object falls to the terrestrial surface. Knowing this last parameter with precision is of great help in finding the remains of meteorites. The main features of this patent are: easy assembly and adaptation to different types of cameras, operating capacity, transportability and reduced production price.

Description

AUTOMATIC MULTI-FREQUENCY SPRAY SHUTTER TO DETERMINE THE SPEED OF MOVING LIGHT SOURCES, AS METERS, FIRE BALLS, AIRCRAFT OR SPACES.

SECTOR OF THE TECHNIQUE

The present invention belongs to the sector of apparatus, methods, systems or technical devices capable of measuring, or estimating, physical variables (Metrology). More particularly, this patent describes an apparatus that serves to determine in real time, the speed and direction of an air body or object that is observable from any point of the celestial hemisphere of a particular geographical location, whether terrestrial or maritime.

STATE OF THE PREVIOUS TECHNIQUE

The first instrument invented with the sole purpose of obtaining a panoramic image consisted of an objective optical lens that obtained non-extensive images of a landscape and then, by means of a computer treatment, assemble them and finally turn them into the graphic representation of a large sector of the visible field (Poelstra, TJ, "Method and device for producing panoramic image and a method and device for consulting panoramic devices, US Patent 5563650, 1996). It may well be said that this device was equivalent to a short-angle lens that took pictures successive during a complete rotation of 360. A few years later, another patent was registered for a method capable of correcting the understandable and insurmountable distortion introduced in any image or panoramic view of a landscape when it is projected on a flat surface (Mojaver M. et al., Panoramic imaging and display system with canonical magnifier "US Patent 6833843, 2004). The most novel of this work is the particular computer processing of the image.

Historically, the first system used in the recording and monitoring of the night sky is the camera called CONCAM (RJ. Nemiroff and JB Raffert, "Towards a continous record of the sky", PASP 111, page 886, 1999) that the scientists of An American university. Other devices or assemblies that follow the previous models have also appeared on the market, and are preferably designed to detect cloud masses (see for example, MJ Kosch, "The Skibotn a CCD All-Sky Imager and real time networking onto the WWW, MPAE-T-010-99-12, Max Plank Institute for Aeronomie, Lindau, Germany, 1999.) In this model, a complicated arrangement of mirrors produces an image, almost hemispherical, projected onto a small size detector. Recently, the patent registered under number 200501127 (Castro Tirado AJ, "Night digital camera and its applications for automatic observation of the whole sky") to which they have been submitted to the Spanish Patent and Trademark Office (SPTO). Patent rights were granted dated November 27, 2007. This invention, which is already used in some university and professional astronomical observatories, serves to automatically detect the appearance of and meteors and cars because it allows the technician to obtain the panoramic view of the sky from a specific geographical location, in a single digital image and in a short time. To this end it has a CCD detector (acronym in English for Charge Couple Device, or docking device) cooled, in the optical range of the visible spectrum, a relatively high exposure surface (4096 x 4096 pixels or image elements) and quantum efficiency above 50%. A fisheye lens, or wide angle, high brightness completes the prototype which is capable of presenting an image of the light stroke left by the meteorite. The assembly of this patent does not allow estimates of the physical parameters of the fall flight, it is only an instrument for sighting and automatic observation of moving objects in the night sky. At the same time and on a subject very different from that of optical image capture instruments, an academic paper was presented on the analysis of the chemical elements that constitute meteorites that, from outer space, produce bright fireballs before falling to the ground (JM Trigo Rodríguez "Spectroscopic analysis of cometary and asteroid fragments at the entrance to the Earth's atmosphere". Doctoral thesis. Publications of the University of Valencia, 2002). In this publication, the author recommends to specialists in the field, determine, if possible immediately, the place of fall of these bodies, first-hand witnesses of the physical-chemical processes occurred during the formation of the planets, in order to avoid its contamination or, what would be worse, its loss.

Microelectronics, optics and computing are the three technical specialties that allow us to face and solve the scientific problem outlined in the previous paragraph. Being able to know with sufficient precision and speed the place of fall of these remains requires determining the speed with which they cross the atmosphere, especially in the final section of their trajectory, in which they stop emitting visible light when they are decelerated. In this final phase that specialists call "dark flight", the meteorite or the different pieces into which it may have been divided during its flight, advance until it falls to the ground. It is not possible to estimate the point or area of fall without knowing the exact terminal velocity of the first luminous phase recorded by the observation device. To date, there are not numerous patents or scientific publications based on the determination of the speed of the registered objects. In this Report of the invention a device is presented that installed in any sighting or tracking system, in general, of flying, visible objects allows to determine the speed of fall and that in tandem with an equal system, located at a certain distance, serves to determine the trajectory. The prototype used in the preparation of the examples given here, was mounted, in a first essay, in the "Night digital camera" patented by Dr. D. Alberto J. Castro-Tirado.

DESCRIPTION OF THE INVENTION

BRIEF DESCRIPTION OF THE INVENTION

The present invention consists of a mechanism basically composed of a rotating flat propeller that interrupts, with a certain periodicity, the light beam that comes from an optical objective. The controlled movement of this shutter is achieved thanks to a motor of constant angular speed and adjustable at will, which is connected by a rotor shaft coupled to both internal faces of the protective case or cover. The adjustment of the periodicity of the extinction of the image of the object to be observed, and with the help of a calculation immediately after the data collection, allows to know the trajectory and the place of fall of the object, if it finally falls to the ground.

DETAILED DESCRIPTION OF THE INVENTION

The methodology followed in this patent of invention is based on a generalized conception of the strobe effect that allows to visualize, and analyze, any object that moves, by fractioning the physical (real) fact of the movement in a series of short events in which the movement is absent. Indeed, seen by the naked eye by an occasional observer, if the passage of a meteor is perceived by him as a bright, very bright spot, which quickly crosses the sky of the place, what this technique makes us see on a screen, finally , is an image, static, in which the stroke left by the body appears and disappears periodically.

A computer calculation on the digital image allows to know the instantaneous velocity of the meteor, from that sequence of "trajectory segments displayed during non-extinctions" and depending on the design parameters, and rotation, of the shutter chosen by your operator

Figures 1a (side section) and 1 b (straight section seen from above) generally show the invented multi-frequency shutter. Figure 2 also describes in detail the flat rotating propeller (3) that periodically extinguishes the image projected by the lens, or the lenses, wide-angle lens (1). A metal box (6), figures 1a and 1 b, quadrangular, hollow and flat, saves the most essential piece of the device that is a metal, flat and rotating propeller (3) (Figure 2) that in its movement effects the extinctions of The image projected by the objective (1) in the CCD detector (7). The shape and dimensions of the box (6), or protective cover, may vary according to the type of optical objective (1) and detector (7) to which the shutter is desired. The flat propeller (3) is a metal sheet cut according to the shape specified in Figure 2. It is important to state that in the propeller (3), the number of blades, and the angular speed of rotation, or what is coming to be the same, the number of extinctions of the image per unit of time, may vary, this time, depending on the degree of precision of the calculation to be carried out to determine the trajectory of the moving object. The thickness of the metal sheet is 2 millimeters, to ensure the absence of deformations. Construction and subsequent calibration of the propeller (3) recommends that the number of blades be 6 or 12. Also, a precise angular adjustment of the blades is necessary. The carving of the edges of the propeller (3) must be perfectly radial and symmetrical with respect to the axis of rotation (center of the figure) and, in the end, all of them are perfectly polished with the help, for example, of a spectroscopic method of surface checking. As such blades are responsible for fractionating the image, its arrangement at equidistant angles from each other, must be very precise. This must be so, because defects, both in the finishing of the edges, and irregularities in the arrangement of the blades of the propeller (3) are the source of unwanted calculation errors.

The aforementioned rectangular metal box (6) has in its upper and lower parts two circular hollows where the corresponding threaded connection rings of the wide-angle objective lens (1) and CCD detector (7) have been electrically welded (Figure 1a). In turn, the propeller (3) is moved by an electric stepper motor (2) through a bearing shaft inserted in the upper and lower inner walls of the housing (6). The stepper motor (2), integrated in the housing (6, Figures 1a and 1b), drives the flat propeller (3) by means of a cogwheel which, for simplicity, does not appear in the figures.

Finally, the shutter must be mounted perfectly aligned with the optical axis of the objective lens or optical system (1) (or system, or optical observation apparatus, whatever this may be), and with the CCD detector (7) as and as shown in figure 1a. Precisely, Figure 3 shows the appearance of the device invented before performing this assembly. The angular rotation speed of the shutter can be controlled through an external electronic circuit. Depending on the objective of the study, we will select a greater or lesser angular rotation speed of the rotor system to obtain the desired number of seals / second. In the built-in prototype a "step-by-step" engine has been used (2) that It works with a voltage of 12 Volts DC. The angular motor speed (2) is in the range of 1 to 10 rpm. Said number of revolutions is controlled with a rectifying diode provided with a piezoelectric crystal whose piezoelectricity keeps the speed of rotation constant. The multifrequency shutter thus designed is able to provide the user with a wide range of turning speeds that can be applied to systematically and automatically observe aircraft, meteors and cars, or moving light sources that pass through the celestial field covered by Ia objective lens (1). Note, also, that the angular velocity of the "step by step" motor (2) and the number of blades in the propeller (3) allow to analyze the movement of objects that move at speeds of very different numerical values.

The multifrequency shutter presented allows to systematically observe the movement of aircraft or other moving light sources that pass through the field covered by the CCD camera (7) both in full daylight, and at night. The interposition of a neutral attenuator filter between shutter (1) and CCD detector (7) is not excluded. For the field tests that consisted of monitoring for a long time, the movement of aircraft, artificial satellites or meteors from at least two ground stations, the camera was used to see the whole sky of a place, patented by Dr. AJ Castro Tirado (cited in the State of the Prior Technique section). The digital images obtained by application of this shutter were perfectly sharp and devoid of vignetting (see, for example, Figures 4 and 5).

The main applications of this invention are:

1) In laboratory experiments, to monitor the rapid movement of objects in the field covered by the CCD camera to which the multifrequency turn shutter is applied. 2) In the scientific field to determine the speed of meteors or fireballs.

3) In the military field, this device can be useful in the context of continuously monitoring the movement and speed of aircraft or satellites.

EXAMPLES OF APPLICATION OF THE INVENTION

Although the shutter described above was mounted in the hemispherical chamber patented by Alberto Javier Castro Tirado, in order to demonstrate its practical applicability in two real cases, the present invention is applicable to any type of camera, optical instrument or detector.

EXAMPLE 1. DETERMINATION OF THE POSITION AND SPEED OF AN ARTIFICIAL SATELLITE

This example shows the application of the prototype of this patent to the particular case of the determination of the speed of an artificial satellite.

These bodies are seen with the naked eye, at dusk and dawn, when your body is illuminated by the Sun. In particular, this example has been chosen as a sample of the operation of the multifrequency shutter even in the extreme cases in which the object is It is hundreds of kilometers from the registration stations. Here we study the case corresponding to an artificial satellite located at an altitude of 1,000 kilometers and observed by two different stations both equipped with cameras

CCD (7) that registered it on July 15, 2007 at 3h12m22s TUC

(Coordinated Universal Time) (see Figure 4). Station # 1 was in the province of Girona (specifically, at the coordinates, λ: 357.48 ° φ: + 41.72 ° AIt .: 300 m) and the # 2 station in Barcelona (λ: 357.68 ° φ: + 41.94 ° AIt .: 567 m).

The reduction and calculation procedure is described here very succinctly. First, the position of the stars of the field and the path of the satellite is measured in Cartesian coordinates. Subsequently, once the equatorial coordinates of the stars are known, the coordinates of the object's trajectory in the celestial vault are determined from the two stations (Trigo-Rodríguez, cited work, 2002). From there, the planes containing each station and the satellite path are determined. The intersection of both planes will allow to determine the trajectory and height on the terrestrial surface of the space ingenuity. Thus, the geographical coordinates and the satellite height were determined. When orbiting at a height of about 900 kilometers we can identify that it is a low-orbit satellite, generally known by the English acronym LEOs. In addition, the segments in which the satellite path is divided (Fig. 4b) allow an average speed of 8.0 ± 0.5 km / sec to be estimated. The data obtained are recorded in Table 1.

Table 1. Satellite path of example # 1 measured from both stations. Note that the reason why the initial coordinates of the beginning and end of the satellite from both stations do not coincide since station # 2 registered a weaker section as it was the most sensitive system.

Geographic coordinates Equatorial coordinates

Station λ (°) φ (°) Height α (°) δ (°)

# 1 (km)

Start 351.10 + 0.04 39.81 ± 0.03 872 21.912 +21. 824

N

End 351.46 + 0.04 39.58 ± 0.03 861 20.558 +19. 934

N

Station λ (°) φ (°) Height α (°) δ (°)

# 2 (km)

Start 350.55 ± 0.04 40.15 ± 0.03 905 23.954 +23. 076

N

End 351.70 ± 0.04 39.43 ± 0.03 850 19.863 +17. 178

N

The described example shows a case in which the artificial satellite appears in a very remote and relatively unfavorable geometry. Even so, the system can determine the speed of the object although with a relatively high imprecision given the distance at which the object is contemplated. On other occasions the aircraft may pass much closer distances from the registration station so that the estimated trajectory accuracy and speed increases significantly. An image of a satellite flying over the station in which the shutter is much sharper appears in Fig. 5. EXAMPLE 2. DETERMINATION OF THE POSITION AND SPEED OF A FIRE BALL

From the same stations as in the previous example and with the same instrumental assembly, the passage through the sky of a ball of fire as bright as the planet Venus was recorded on July 14, 2007 at 2h29m11s TUC (Figure 6). The estimated height of the light phenomenon (Table 2) indicates that the detection corresponds to the entry of a meteor into the Earth's atmosphere. The reason is that meteors occur at much lower heights (typically between 120 and 70 km) than those of artificial satellites. To corroborate this suspicion, the average velocity of the particle was 50 km / s, which clearly indicates that it is an interplanetary body, since it is a much greater speed than the escape from the earth's gravitational field.

The astrometric reduction procedure is exactly the same as the previous case. First, the position of the object is obtained based on the position in equatorial coordinates of the stars (Fig. 6c). Once the position and the distance between the stations are known, two planes containing the racing car seen from both stations are determined. The intersection of both planes will allow to define the real trajectory of the car in the atmosphere (Fig. 6d) and its orbit in the Solar System if the speed is determined (Fig. 6e). The calculation method and the equations to be solved are detailed in (Trigo Rodríguez, 2002). The speed of the particle along the trajectory will be determined from the number of segments generated by the shutter (Fig. 6a). Once the particle velocity is known upon entering the atmosphere, the radiant point of origin in the celestial vault (Fig. 6c) and the path followed (Fig. 6d), the heliocentric orbit that followed in the Solar System can be determined (Fig. 6e). Table 2. Trajectory of the fireball described in example # 2 measured from both stations. Note that the reason why the initial start and end coordinates do not match is due to the fact that station # 2 registered a weaker section as it had greater sensitivity.

Geographic coordinates Equatorial coordinates

Station # 1 λ (°) φ (°) Height (km) α (°) δ (°)

Start 356.492 + 0.003 42.028 + 0.002 107.6 + 0.1 27.338 +44.075

N

End 356.682 + 0.003 42.036 + 0.002 86.0 + 0.1 30.604 +46.962

N

Station # 2 λ (°) φ (°) Height (km) α (°) δ (°)

Start 356.539 + 0.003 42.030 + 0.002 102.1 + 0.1 23.954 +23.076

N

End 356,729 + 0.002 42,038 + 0.002 80.6 + 0.1 19,863 + 17,178

N

DETAILED DESCRIPTION OF THE FIGURES AND PHOTOGRAPHS

Figures 1a and 1 b. General scheme of the internal shutter. The dimensions may vary depending on the instrument and the optical system to which it is desired to attach. 1a) Side view of the shutter assembly. 1 b) Aerial view. The following parts are distinguished: 1) Objective, 2) Stepper motor, 3) Blade, 4) Rotor shaft, 5) Lens thread, 6) External housing, 7) CCD detector

Figure 2. General scheme of the internal helix (3) that generates the seals. Note that in the model with 6 blades the angular amplitude (β) between blades is 30 °. The dimensions of the blades and the diameter of the propeller (3) are variable depending on the instrument. In the prototype shown in Fig. 3 the diameter d of the propeller (3) was 15 cm. and the length a of each blade of 6.5 cm.

Figure 3. Aerial view of the shutter prototype built for this invention. Components detail:

1. Objective

2. Stepper motor. 3. Six-blade propeller located internally. The faces of the blades have been polished and measured with a strobe system to achieve an exact adjustment in the cutting interval between each blade. (in DD, above) 4. Motor shaft 5. Thread of adaptation to the objective.

6. Metal housing container.

7. CCD detector

8. Stepper motor power cable.

9. Wiring control of the speed of rotation.

Figure 4. Satellite described in example # 1. a) Part of the image of the entire sky taken from station 1. b) Enlargement of the window shown in the box of a) where the light trail left by the satellite appears, c) Image taken from station # 2. d) Reconstruction of the trajectory seen from both stations where the parallax of the satellite seen from both stations is appreciated. Taking into account the particular geometry, the distance and height of the satellite on the earth's surface can be determined (Table 1).

Figure 5. Part of an image of the entire sky in which the stroke of the International Space Station (ISS) can be seen flying over station # 1. To the observed next to the station its line is brighter and the shutter of the system is very visible. The ISS flew over station # 1 on November 7, 2007 shortly before sunrise. The bright spot in the lower left is the planet Venus.

Figure 6. Images of the fireball described in the second example. A small window indicates the position of the racing car in the CCD images. a) Image of the racing car seen from station # 1. b) Image from station # 2. c) Trajectory of the racing car from both stations where the main constellations appear. Once the astrometry of the images has been carried out, the backward extension allows the determination of the radiant point, d) Determination of the atmospheric trajectory and its projection on the ground, e) Heliocentric orbit of the particle. The orbits of the inner planets and the position of the Earth at the moment of intercepting this interplanetary particle are indicated.

Claims

1. An automatic multifrequency turn shutter to determine the speed of celestial light sources in motion, such as meteors, fireballs, aircraft or spacecraft, and which allows their identification, characterized in that it comprises:

- a lens (1) that projects images on a CCD detector (7);

- a rotating metal propeller (3) comprising a plurality of blades, which is arranged between the target (1) and the CCD detector (7) so that the blades periodically block the images projected by the target (1) onto the detector CCD (7); Y

- a metal box (6) that houses the metal propeller (3), which comprises an upper surface with a first hole to which the objective (1) is fixed and a lower surface with a second hole, facing the first, to which it is Fixed the CCD detector (7).

2. The automatic shutter of claim 1, wherein the metal propeller (3) comprises 6 or 12 blades.

3. The automatic shutter of any of the preceding claims, wherein the thickness of the metal propeller (3) is 2 millimeters.

4. The automatic shutter of any of the preceding claims, wherein the metal box (6) has a flat quadrangular shape.

5. The automatic shutter of any of the preceding claims, wherein the metal propeller (3) is moved by an electric motor "step by step" (2).

6. The automatic shutter of any of claim 5, wherein the speed of the electric motor "step by step" (2) is between 1 and 10 rpm.