RU2586890C1 - Method of determining range and height of short-pulse altitude x-ray source using ground-based photodetector - Google Patents

Abstract

FIELD: identification devices.

SUBSTANCE: invention relates to difference ranging methods for determining coordinates of pulse sources of ionising and electromagnetic radiation. Said result is achieved as follows: using ground-based photodetector device, optical pulses of fluorescent radiation is recorded, which occurs as result of X-ray radiation impact upon atmosphere from any source. Photodetector enables to record time and direction of arrival of optical pulse from direction of source. Here zenith angle of source is measured. Besides, using photodetector device, time of arrival of fluorescent radiation optical pulse coming from zenith is recorded. Measuring arrival time difference of optical pulses from zenith and towards source, and measuring inclination angle of source, range to X-ray source and its altitude is determined.

EFFECT: technical result is simplification of method implementation.

1 cl, 1 dwg

Description

The invention relates to differential-ranging methods for determining the coordinates of pulsed sources of ionizing and electromagnetic radiation.

A known method [1] of determining the coordinates of a source of radio emission (IRI) in space. The essence of the method: as the position surfaces of the IRI, planes are used that contain the line of position of the IRI, which is the intersection of two hyperbolic position surfaces corresponding to time-difference measurements. The method is based on the reception of an IRI signal by four antennas, measuring the three differences in signal reception times by the antennas that form the measuring bases, subsequent processing of the measurement results in order to calculate the values of the IRI position parameters and calculate the IRI coordinates as the intersection of three position planes. As a result, an unambiguous determination of linear coordinates occurs. The disadvantage of this method is the need for multiple antennas, as well as the need for binding to a single time system.

There is also known a method [2] for determining the location of an energy radiation source at two observation points, the distance between which is unknown. The signal from an unknown source is recorded at two points of communication and the signal from a known source is recorded at the same points, then the difference in the time of arrival of the signals is measured. Further, according to the time difference for a known source, the distance between the communication points is determined and the coordinates of the energy radiation source are determined. The disadvantage of this method is the need for measurements in at least two registration points, as well as the need for a known radiation source.

The prototype can be a method [3] for detecting nuclear explosions by fluorescence radiation, implemented in the USA. The viewing angle of the photodetector is 120 angular degrees, a nuclear explosion is detected by the optical fluorescent radiation of the luminous layer of the atmosphere. The main disadvantage of this method is the need for the location of several photodetectors to determine the direction of a nuclear explosion.

The technical result of the invention lies in the fact that the measurements are carried out using a single photodetector and does not require binding to a single time system.

The technical result in the proposed method is achieved by measuring the zenith angle of the x-ray source and the difference in the arrival times of pulses of optical fluorescence radiation coming from the direction to the x-ray source and from zenith, and the distance from the photodetector to the x-ray source and its height are determined by certain correlation.

The implementation scheme of the method is presented in figure 1, where 1 is the earth's surface; 2 - height z of the luminous layer of the atmosphere; 3 - source of pulsed x-ray radiation; 4 - the height of the source H; 5 - range D to source 3; 6 - direction to the zenith; 7 - photodetector, 8 - the point of intersection of the x-ray and direction to the zenith 6; 9 - an x-ray going in the direction of zenith from the source to point 8 located at a height of z; ϑ - zenith angle of the source.

The essence of the proposed method is as follows. Suppose that at an altitude of H of the order of 100 km or more, and which must be determined, a pulsed source of x-ray radiation has arisen. The pulse duration is short and amounts to 20-50 ns. X-rays are intensely absorbed by air at a height z of approximately 80 km.

Absorption in the atmosphere occurs mainly due to the photoelectric effect, in which an electron flux occurs. These electrons, interacting with atoms and molecules of air, lead them to metastable states of excitation. The removal of excitation at such a height occurs predominantly by radiation. As a result, a fluorescent glow of air similar to the northern lights arises at a height of z. The emission spectrum is linear, with characteristic lines at different wavelengths in the range from 0.35 to 1.5 microns. Thus, the conversion of x-rays into optical fluorescence occurs. This optical radiation is detected by a photodetector (FPU) installed in clause 7. Due to the short duration of the X-ray pulse, clause 7 observes a bright flash first in direction 5 to source 3, and then a narrow luminous ellipsoidal figure propagates rapidly in the sky. When this figure reaches the zenith direction at point 8, a short pulse of optical radiation occurs, which is recorded using the FPU 7. The photodetector 7 has two fields of view: one wide at about 120 angular degrees, covering the entire sky; the second is a narrow field of view with an angle of about 2-4 angular degrees directed to the zenith at point 8. In a wide field of view, the moment and direction 5 of arrival of direct optical radiation are recorded and the angle ϑ is measured between direction 5 to source 3 and direction 6 to zenith. In a narrow field of view, the time of arrival of an optical fluorescence pulse is recorded and the difference Δt of the time of arrival of pulses from the direction to the source 3 and the zenith direction 6 is measured. The distance D to the source is determined by the established ratio:

where c is the speed of light; z is the height of the luminous layer of the atmosphere; Δt is the measured difference in the times of arrival of optical fluorescence pulses to the photodetector in the direction of the source and zenith; ϑ is the measured zenith angle of the source. The height H of the source is determined by the formula

Thus, by measuring the parameters Δt and ϑ, they determine the distance to the source and its height using a single photodetector, which is an advantage of this method over existing ones.

Information sources

1. Saibel A.G., Grishin P.S. The differential-range measuring method for determining the coordinates of a radio emission source and its device / Patent No. 2309420 - Russia, 2007

2. Anderson N.S. A system for determining the location of energy radiation sources at two observation points / Patent No. 3137854 USA, 1964

3. Westervelt DR, Term X. Los Alamos atmospheric fluorescence detection system. // TIIER, 1965, v. 53, No. 12, p. 2287-2292.

Claims (1)

A method for determining the range and height of a short-pulse high-altitude x-ray source using a ground-based photodetector, including detecting pulses of optical fluorescence radiation from the atmosphere resulting from the exposure of the x-ray from the source to the atmosphere, characterized in that the zenith angle of the x-ray source and the pulse arrival time difference are measured optical fluorescence radiation coming from the direction to the x-ray source and radiation from zenith, and the distance D from the photodetector to the source of x-ray radiation and its height H is determined by the formulas:

and

where c is the speed of light; z is the height of the luminous layer of the atmosphere; Δt is the measured difference in the times of arrival of optical fluorescence pulses to the photodetector in the direction of the source and zenith; ϑ is the measured zenith angle of the source.

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