Passive ranging to source of known spectral emission to cue active radar system

A method for passive determination of the range of a source of known spectral emission by use of optical apparatus for viewing the source to cue an active radar system, comprising the steps of:

• receiving radiation propagating from the source via an atmospheric path to the optical apparatus, the atmosphere providing for selective attenuation of frequency components of the radiation as a function of frequency of the frequency components;
• storing a known spectrum of the radiation as emitted by the source, at least a portion of said known spectrum being continuous with substantially constant amplitude and having act least a first frequency component and a second frequency component;
• analyzing a received spectrum of the radiation as received by the optical apparatus, the received spectrum having at least a first frequency component and a second frequency component;
• wherein said first and said second frequency components of said received spectrum are alterable from said first and said second frequency components of said known spectrum by Doppler frequency shift due to motion of said source;
• said method further comprising steps of obtaining spectrally dependent attenuation characteristics of the atmosphere;
• computing plural amplitude ratios of the frequency components wherein one of said amplitude ratios is the ratio of amplitudes of the first and the second frequency components of said known spectrum and a second of said amplitude ratios is the ratio of amplitudes of the first and the second frequency components of said received spectrum;
• determining the range of the source based on said amplitude ratios and on said attenuation characteristics of the atmosphere;
• wherein said continuous substantially constant spectral portion enables said ratios to be independent of Doppler frequency shift;
• and
• transmitting the range, as a function of optical frequencies, of the source from said computer means to an active radar system, said active radar system being cued by the receiving of the range of the source to switch from a passive mode to an active mode.

A system for passive determination of the range of a source of known spectral emission to cue an active radar system, comprising:

• optical apparatus for receiving radiation propagating from the source via an atmospheric propagation path to the optical apparatus, the atmosphere providing for selective attenuation of spectral lines of the radiation as a function of frequency of the spectral lines;
• at least one computer, and a data storage medium operatively coupled to said at least one computer that stores known atmospheric attenuation data for at least a first frequency component and a second frequency component, said first frequency component being attenuated by propagating through a known distance in the atmosphere, said second frequency component being attenuated in a lesser amount by propagating through the same distance in the atmosphere;
• a spectrum analyzer operatively coupled to said at least one computer that analyzes a received spectrum of the radiation as received by said optical apparatus, said received spectrum having at least a first frequency component and a second frequency component;
• wherein said first and said second frequency components of said received spectrum are alterable from said first and said second frequency components of said known spectral emission by Doppler frequency shift due to motion of said source;
• said system further comprises an atmosphere information unit that provides said at least one computer with spectrally dependent attenuation characteristics of the atmosphere;
• said at least one computer computes plural amplitude ratios of said frequency components wherein one of said amplitude ratios is the ratio of amplitudes of the first and the second frequency components of said known spectrum and a second of said amplitude ratios is the ratio of amplitudes of the first and second frequency components of said received spectrum;
• said continuous substantially constant spectral portion enables said ratios to be independent of Doppler frequency shift;
• said at least one computer is operative further to determine the range of the source based on said amplitude ratios and on said attenuation characteristics of the atmosphere;
• and
• an active radar system receiving the range of the source as a function of optical frequencies from said at least one computer, said active radar system being cued by the receiving of the range of the source to switch from a passive mode to an active mode.

A system for passive determination of the range of a source of known spectral emission to cue an active radar system, comprising:

• optical apparatus to receive radiation propagating from the source via an atmospheric propagation path to the optical apparatus, the atmosphere providing for selective attenuation of spectral lines of the radiation as a function of frequency of the spectral lines, said optical apparatus further comprising:
• a wide-band optical detector to convert, from optical energy to a spectral portion electrical signal, a portion of the received spectrum of the radiation as received by the optical apparatus, said portion of the received spectrum having at least a first frequency component and a second frequency component;
• first and second narrow-band optical detectors, to convert from optical energy to respective first and second narrow-band electrical signals, the radiation propagating from the source via the atmospheric propagation path to the optical apparatus, said first narrow-band optical detector receiving through a respective spectral line filter said first frequency component, but not said second frequency component, and said second narrow-band optical detector receiving through a respective line filter said second frequency component, but not said first frequency component;
• a spectrum analyzer unit coupled to said wide-band optical detector to analyze the spectral portion electrical signal, said spectrum analyzer further coupled to said first and second narrow-band optical detectors and being activated only upon an indication based on the first and second narrow-band electrical signals of the presence of said first and second frequency components;
• a computer, and computer readable storage media operatively coupled to said computer,
• said computer readable media storing a known spectrum of the radiation as emitted by the source, at least a portion of said known spectrum being continuous with substantially constant amplitude and including at least said first frequency component and said second frequency component;
• said computer computing plural amplitude ratios of frequency components wherein one of said amplitude ratios is the ratio of amplitudes of the first and second frequency components of said known spectrum and a second of said amplitude ratios is the ratio of the first and second frequency components of said spectral portion;
• and
• said computer is operative further to determine the range of the source based on said amplitude ratios and on said attenuation characteristics of the atmosphere;
• and
• an active radar system receiving the range of the source as a function of optical frequencies from said at least one computer, said active radar system being cued by the receiving of the range of the source to switch from a passive mode to an active mode.

A method for passive determination of the range of a source of known spectral emission to cue an active radar system, comprising:

• receiving radiation propagating from the source via an atmospheric propagation path to the optical apparatus, the atmosphere providing for selective attenuation of spectral lines of the radiation as a function of frequency of the spectral lines;
• storing a known spectrum of the radiation as emitted by the source, at least a portion of said known spectrum being continuous with substantially constant amplitude and having at least a first frequency component and a second frequency component;
• converting, from optical energy to a spectral portion electrical signal, a portion of the received spectrum of the radiation propagating from the source via the atmospheric propagation path to the optical apparatus by a wide-band optical detector in said optical apparatus, said portion of the received spectrum corresponding to said spectral portion being continuous with substantially constant amplitude and having at least said first frequency component and said second frequency component;
• converting, from optical energy to first and second narrow-band electrical signals, the radiation propagating from the source via the atmospheric propagation path to the optical apparatus by first and second narrow-band optical detectors in said optical apparatus, said first narrow-band optical detector receiving through a respective spectral line filter said first frequency component, but not said second frequency component, and said second narrow-band optical detector receiving through a respective spectral line filter said second frequency component, but not said first frequency component;
• analyzing the spectral portion electrical signal corresponding to the portion of the received spectrum converted by the wide-band optical detector in response to determining that said first and second frequency components are present in the received spectral portion of the source radiation;
• computing plural amplitude ratios of frequency components wherein one of said amplitude ratios is the ratio of amplitudes of the first and second frequency components of said known spectrum and a second of said amplitude ratios is the ratio of the first and second frequency components of said spectral portion;
• determining the range of the source based on said amplitude ratios and on said attenuation characteristics of the atmosphere;
• and
• cuing an active radar system with the range of the source as a function of optical frequencies, said active radar system switching from a passive mode to an active mode in response to receiving the range of the source.