WO2007063537A1

WO2007063537A1 - A method and system for locating an unknown emitter

Info

Publication number: WO2007063537A1
Application number: PCT/IL2006/001370
Authority: WO
Inventors: Moshe Fiereizen
Original assignee: Elta Systems Ltd.
Priority date: 2005-11-30
Filing date: 2006-11-28
Publication date: 2007-06-07
Also published as: IL172267A0; IL191816A; IL191816A0

Abstract

The present invention provides a method and system for locating an unknown emitter. According to an embodiment of the invention, the method for locating an unknown emitter comprises launching from a platform a vehicle equipped with an RF receiver/transmitter; and gathering measurements of electromagnetic signal emitted by the unknown emitter and collected by said platform and said vehicle, thereby enabling Time-of-Arrival processing of said measurements for deriving the location of the unknown emitter.

Description

A Method and System for Locating an Unknown Emitter

FIELD OF THE INVENTION

This invention relates generally to the detection and processing of electromagnetic signals (e.g. RF, microwave) and more specifically, to methods and systems for locating unknown emitters, for military and civilian use.

BACKGROUND OF THE INVENTION

Locating of unknown and perhaps hostile emitters is of crucial importance to military and civilian intelligence, surveillance, and reconnaissance. Such unidentified and unknown emitters may be anti-aircraft radars, communication centers, and other devices. There exist locating methods and systems that employ the known TDOA

(Time-Difference-of-Arrival, also known as TOA - Time-of-Arrival) technique. In this technique, a signal transmitted by the unknown emitter travels along two or more independent paths of unequal length. Therefore, the Time-of-Arrival and Angle-of-Arrival of the signal to different receivers in the independent paths differs. As the locations of the receivers are identified, the time difference of arrival of the signal to the various receivers provides information on the location of the unknown emitter. Also known are FDOA (Frequency Difference of Arrival) techniques.

US Patent No. 6,933,888 discloses a system provided for rapidly ascertaining the position of a pulse train emitter such as radar using multiple collectors without requiring more than one platform to measure the same pulse. Thus time-of-arrival measurements at a number of collecting platforms are performed, with the positions of the platforms being accurately ascertainable using GPS data, and with time synchronization between the spaced-apart collectors performed by utilizing atomic clocks. In the multi-ship case, geolocation can be performed on ten milliseconds of data as opposed to 30 seconds of data for measurements involving a single platform. The subject system is preferable to conventional time-difference-of-arrival geolocation systems because those systems require that each of the collecting platforms measure the same pulse from the emitter, which severely constrains the flight paths of the collectors, limits the amount of usable data, and increases the system's sensitivity requirements. US Patent No. 6,255,992 discloses a passive system for locating a distant source of radio frequency energy, for example a pulsed radar transmitter, from a portable platform such as a moving aircraft. The disclosed system is non- ambiguous in locating ability by way of using time difference of arrival and time difference of arrival-rate processing of signals received from the distant source. This is in contrast to phase-based locating wherein location ambiguities are inherent. The disclosed system is supported by an included recalibration subsystem enabling practical maintenance of time difference of arrival system algorithm accuracy notwithstanding physical component and signal delay changes attributable to thermal or other environment effects. Maintenance of delay measurements accurate into the tens of picosecond range by this recalibration arrangement are employed to obtain usefully precise energy source locations. Mathematical equation-based disclosures of signal delay algorithms and their recalibration are included.

US Patent Application No. 2005/052315 discloses a process and system for the location of emitters in the radar frequency range on the basis of cross position-finding by at least two flying platforms with, in each case, at least one passive HF sensor for ascertaining the geometrical and electronic properties of the emitter beams, whereby the flying platforms mutually exchange data for describing the geometrical and electronic properties of the emitter beams, and whereby from the plurality of the position-finding beams' possible intersection points, which arise from the emitter surveying operation, use is made, in order to determine the emitter position, of those intersection points at which the electronic properties of the intersecting emitter beams are identical.

The following publications also relate to methods and systems for locating unknown emitters: US Patents Nos. 5,008,679, 6,018,312, 6,100,845, 6,614,012, 6,734,824 and 6,759,983.

There is thus a need in the art for an emitter locating method and system for operation over hostile territories without endangering expensive surveillance aircraft. There is further a need in the art for methods and systems for efficient, rapid and cost-effective emitter location. There is also a need in the art for emitter locating methods and systems employing only one aircraft, and for emitter locating methods and systems embodied onboard a tactical aircraft.

SUMMARY OF THE INVENTION According to one embodiment of the invention there is provided a method for locating an unknown emitter, the method comprising:

- launching from a platform a vehicle equipped with an RF receiver/transmitter; and

- gathering measurements of electromagnetic signals emitted by the unknown emitter and collected by said platform and said vehicle thereby enabling Time-of-Arrival processing of said measurements for deriving the location of the unknown emitter.

According to another embodiment of the invention, there is provided a system for locating an unknown emitter, the system comprising a platform carrying a first RF receiver/transmitter, at least one detachable vehicle having a second RF receiver/transmitter in communication with the first RF receiver/transmitter, and a control system configured for operating the platform to launch the vehicle, for receiving and analyzing measurements of electromagnetic signals emitted by the unknown emitter and collected by said - A - first and second RP receiver/transmitter, thereby enabling Time-of-Aπϊval processing of the measurements for deriving the location of the unknown emitter.

According to yet another embodiment of the invention there is provided a system for locating an unknown emitter, the system comprising a platform carrying a first RF receiver/transmitter, at least one detachable vehicle having ^• a second RF receiver/transmitter in communication with the first RF receiver/transmitter; and a control system configured for operating the platform to launch the vehicle, for receiving and analyzing measurements of electromagnetic signals emitted by the unknown emitter and collected by said first and second RF receiver/transmitter, and for tracking the vehicle and generating time and position indications corresponding to said measurements, thereby enabling Time-of-Arrival processing of said measurements for deriving the location of the unknown emitter.

According to yet another embodiment of the invention there is provided a system for locating an unknown emitter, the system comprising a platform carrying a first RF receiver/transmitter, at least one detachable vehicle having a second RF receiver/transmitter in communication with the first RF receiver/transmitter; and a control system configured for operating the platform to launch the vehicle, for receiving and analyzing measurements of electromagnetic signals emitted by the unknown emitter and collected by said first and second RF receiver/transmitter, and for tracking the vehicle and generating time and position indications corresponding to said measurements, thereby enabling Time-of-Arrival processing of said measurements for deriving the location of the unknown emitter, wherein the control system comprises a vehicle control utility and a data analyzer that includes:

- a processing utility;

- memory coupled to the processing utility;

- a signal analysis module; and

- a location calculation module, wherein said vehicle control utility is configured for launching the vehicle; and wherein said data analyzer is configured to run said signal analysis module and location calculation module for:

- receiving measurements of electromagnetic signal emitted by the unknown emitter collected by said platform and said vehicle;

- based on data received from at least one of a radar, a navigator and a communication unit, tracking said vehicle and generating time and position indications corresponding to said measurements of electromagnetic signal collected by said platform and said vehicle; and - based on said measurements and said indications, deriving the location of the unknown emitter by performing Time-of- Arrival processing.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, certain non limiting embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 is an illustration of a general architecture of a locating system according to an embodiment of the invention; Fig. 2 is another illustration of the general architecture shown in Fig. 1;

Fig. 3 is yet another illustration of the general architecture shown in Fig. l;

Fig. 4 is an illustration of another general architecture according to another embodiment of the invention; Fig. 5 is a flow chart illustrating a sequence of operations carried out according to an embodiment of the invention;

Fig. 6 is a block diagram illustrating an aspect of a locating system according to an embodiment of the invention; Figs. 7a-7d are block diagrams illustrating another aspect of a locating system according to several embodiments of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention provides highly accurate, rapid and cost-effective emitter locating, useful for locating of moving or stationary emitters, e.g. radars, radars operating in anti-ARM (Anti Radiation Missile) mode, communication centers, and more. The invention employs TDOA (also known as TOA) techniques for locating the relative location or the geolocation of the unknown emitter, and at least two receiver/transmitters that share the same system of reference, e.g. an aircraft and a missile, anti radar missile decoy or a UAV (Unmanned Airborne Vehicle) launched therefrom.

General architecture of a locating system 10 according to an embodiment of the invention is illustrated in Fig. 1: in the exemplified embodiment, the locating system 10 comprises a first airborne platform - aircraft 100 in this non- limiting example, from which an airborne vehicle - a missile 110 in this non- limiting example, is launched. According to certain embodiments of the invention, aircraft 100 is a search aircraft. According to other embodiments, aircraft 100 is a tactical aircraft. Both aircraft 100 and missile 110 are equipped with an RF receiver/transmitter, and are capable to communicate with one another (uplink/downlink). An emitter 5 of unknown location (hereinafter referred to as the unknown emitter) emits signal 50, which is received by the aircraft 100 and missile 110. According to certain embodiments of the invention, missile 110 relays signal 50 forward to aircraft 100 and also provides aircraft 100 with information about its position at the time-of-arrival of signal 50. According to other embodiments of the invention, the information provided to the aircraft includes information about the position of the missile at the Time-of- Arrival of signal 50 as well as certain parameters that characterized the signal 50 (e.g. the phase). This information is then used by aircraft 100, utilizing known TOA techniques, to calculate the relative or absolute position of emitter 5.

Fig. 2 is another illustration of the general architecture shown in Fig. 1: point P_10O represents the position of aircraft 100, which is known (e.g. aircraft 100 is equipped with INS/GPS systems). t_1Oo represents the time- of- arrival of signal 50 to aircraft 100 while located at P_1Oo- Point P_11O represents the position of missile 110, which is also known or can be calculated (e.g. missile 110 is equipped with INS/GPS systems, missile 110 is equipped with a GPS translator or aircraft 100 is equipped with tracking arrangement e.g. radar for tracking missile 110). t₁₁₀ represents the time-of-arrival of signal 50 to missile 110 while located at P₁₁₀. According to certain embodiments of the invention, missile 110 forwards aircraft 100 with information allowing determination of T¹¹⁰ and P₁₁₀ (e.g. time of arrival) via signal 52 shown in Fig. 1. Therefore D, the distance between P_1Oo and P₁₁₀ could be determined. The inter-lobe angle α, which indicates the location of the unknown emitter - P₅, is easily determined by the relation:

[ 1 ] cosα = C x (T¹⁰¹LT¹¹⁰)/D where C is the speed of light. Typically, TOA calculations involve calibration procedures and error corrections in order to overcome errors accumulated by the various subsystems while determination of e.g. Time-of- Arrival and position of receivers at time of arrival. Missile 110 is launched from aircraft 100, and therefore both aircraft and missile share the same reference system. Therefore, errors are minimized and the overall response time is relatively short.

In order to simplify explanation, only one reading of TOA data is illustrated in Fig. 2. However, in operations, several iterations of measurement collections and cycles of calculations are executed, yielding a highly accurate result, until a predetermined degree of accuracy is met. This is illustrated in Fig. 3 that shows another illustration of the general architecture shown in Figs. 1 and 2: Pioo(ti)? Pioofø) ^an(i Pioofø) represent the positions of the aircraft 100 in three collection times t_1? t₂ and t₃. PnoOiX PiIoCt₂) and Pnote) represent the corresponding positions of missile 110 that was launched from aircraft 100, at times t_l3 t₂ and t₃. D(tχ), D(t₂) and D(t₃) represent the distance between the aircraft 100 and the missile 110 at times t_1? t₂ and t₃. Following equation [1], the location of the unknown emitter — P₅, is determined by the relation: [2] cosα(t) = C x (T¹⁰⁰(t) - T¹¹⁰(t))/D(t) where C is the speed of light.

As shown in Fig. 3, the course of aircraft 100 is constrained by line B, which, in this non-limiting example, represents a borderline. Aircraft 100 is required not to cross borderline B as the territory bordered by line B is hostile. In contrast, missile 110 is free from this limitation and is launched and directed to fly above the hostile territory. The relative displacement of the aircraft 100 and the missile 110 - represented by the angle between the flight directions (between dashed lines DF_10O and FD₁₁₀ shown in Fig. 3) is preplanned, such that for several measurement collection times — e.g. t_1? t₂ and t₃ as exemplified in Fig. 3 - the resultant inter-lobe angle α is increased (α(ti) < α(t₂) < α(t₃), and consequently, D(ti) < D(t₂) < D(t₃).

In other words, the flight directions of the aircraft and the missile are geometrically preplanned such that the inter-lobe angle α is increased for a certain period of time. This could be realized, for example, by launching missile 110 from aircraft 100 substantially perpendicular to line B and upon launch, changing the flight direction of the aircraft 100 to fly substantially in parallel to line B. As is known in the art of interferometry, the inter-lobe angle α affects the accuracy of TOA calculations, and higher α values yield better accuracy. Referring now to the vehicle direction FDi io_> the platform direction FD ₁₀₀ and axis Z, all shown in Fig. 3 : according to one embodiment of the invention, at least for a predetermined period, there is provided a non-zero angle between direction FD₁₁₀ and location plain of the platform, that is the plain defined by the platform direction FD_10O and axis Z.

According to an embodiment of the invention, aircraft 100 is a tactical aircraft and vehicle 110 launched therefrom is a guided missile carrying a weapon (e.g. warhead) and capable of receiving guidance instructions from e.g. the aircraft 100. According to this embodiment, upon locating the unknown emitter 5, target information and guidance instructions are provided such that missile 110 is directed toward the emitter and aimed to hit it. According to another embodiment of the invention, another missile is launched towards the emitter, preferably from the same aircraft or from another aircraft. According to another embodiment of the invention, coarse positioning information regarding the location of the emitter (e.g. direction) is provided, using method known perse, prior to launch. The missile is launched toward the emitter based on the coarse positioning information available at launch time, and at a later stage, upon locating the emitter using the techniques described above, accurate guidance information is transmitted to the missile.

According to another embodiment of the invention, illustrated in Fig. 4, the aircraft carries several missiles and launches more than one missile; the location of the unknown emitter is made using TOA calculations based on information gathered from more than one missile. In the non-limiting example of Fig. 4, the TOA information relating to t_x is gathered from missile 110, and the TOA information relating to t₂ and t₃ is gathered from missile 111. Note that the resultant inter-lobe angle α is increased, although the inter-lobe angle corresponding to t_x relates to missile 110 (noted as α¹¹⁰^)) and inter-lobe angles corresponding to t₂ and t₃ relate to missile 111 (noted as α^πi(t₂) and α^m(t₃)). Put differently, α^llo(tθ < α^m(t₂) < α^m(t₃).

Having presented several general architectures of several embodiments of the present invention, there follows a description of a sequence of operations 500 carried out according to an embodiment of the invention, as illustrated in Fig. 5: In operations 510 and 520: performing radar search and analyzing search result in order to detect unknown emitters. These operations are carried out by hardware onboard an airborne platform, e.g. aircraft 100 shown in Fig. 1. Note that these operations are known per se and do not form part of the present invention. According to certain embodiments of the invention, operations 510 and 520 further include determining a coarse direction and/or location of the unknown emitter, by employing techniques known per se. Theses operations may be carried out autonomously by the platform or by an external system.

In operation 530: in case an unknown emitter is detected, launching a vehicle (e.g. missile 110 shown in Fig. 1). According to certain embodiments of the invention, the vehicle may be launched towards a general location of the unknown emitter or in a general direction towards the unknown emitter. According to another embodiment of the invention, the vehicle is launched in a predefined direction, for example substantially perpendicular to the flight direction of the aircraft. Note that launching of the vehicle in the predetermined direction may require the aircraft to perform launch maneuvers including temporary deviation from its flight direction.

In the embodiment of the invention illustrated in Fig. 5, the vehicle is launched from the platform in response to the detection of an unknown emitter, e.g. by radar on-board the platform. According to another embodiment of the invention, the vehicle is launched based on a coarse location of the emitter, e.g. as defined by an external source. According to yet another embodiment of the invention, a succession of vehicles is launched, and upon detection of an unknown emitter, TOA processing is carried out with respect to the platform and at least one vehicle. According to another embodiment of the invention, TOA processing is carried out with respect to substantially all launched vehicles, thereby covering an area.

According to an embodiment of the invention, the vehicle (e.g. missile 100) is equipped with a transponder (a receiver/transmitter), and is configured for collecting the signal emitted by the unknown emitter and relaying it to the aircraft.

In operation 540: collecting measurements of signals, including measurements of signal portions received at the aircraft and signal portions received by the vehicle and relayed to the aircraft.

In operation 550: tracking the vehicle. Operation 550 is carried out substantially simultaneously with operation 540. According to an embodiment of - l i ¬

the invention, the vehicle is further equipped with GPS (Global Positioning System) and/or INS (Inertial Navigation System) units. Therefore, the vehicle can generate and provide the aircraft with its GPS and/or INS information. According to another embodiment of the invention, vehicle tracking is performed based on information generated at the aircraft, e.g. radar tracking. According to yet another embodiment, the vehicle is equipped with a GPS translator, allowing it to provide the platform with the vehicle's GPS information.

In operation 560: using techniques known per se, Time-of- Arrival indications as well as position indications of both the aircraft and the vehicle are used to time-tag the signal measurement, thereby allowing, in operation 570, the calculation of the location of the unknown emitter. Several calculations are carried out until a predefined degree of certainty is reached (checked in operation 580) and the location of the unknown emitter is determined.

Operations 540-580 and specifically operations 540-560 are presented as separate operations; however it is clear that these operations can be carried out simultaneously. Furthermore, these operations could be integrated into a single algorithm, and be carried out by the same processing module.

Fig. 6 schematically illustrates a system 600 for locating an unknown emitter according to an embodiment of the invention. According to an embodiment of the invention, system 600 is a moving platform, e.g. an airborne, naval or land platform. System 600 includes, inter-alia, a receiver/transmitter 610, a tracking arrangement e.g. radar 620, a navigator 630 e.g. GPS (Global Positioning System) unit and/or INS (Inertial Navigation System) unit, and a software/hardware control system 635. According to an embodiment of the invention, control system 635 comprises a vehicle control utility 640 for controlling a detachable vehicle mounted on board the platform (not shown in Fig. 6), and a software/hardware location utility 650, all interconnected.

The vehicle (not shown in Fig. 6) could be e.g. a missile, a guided missile, a UAV (Unmanned Airborne Vehicle), an anti-radar decoy or the like. The vehicle is controlled by the control system 635 which is responsible e.g. for launching the vehicle, e.g. in response to detection of an unknown emitter. According to one embodiment of the invention, the control system 635 is further responsible for controlling the flight of the vehicle upon launch. According to yet another embodiment of the invention, the control system 635 is further responsible for directing the vehicle, upon location, toward the unknown emitter. According to another embodiment, the vehicle carries a weapon and the control system 635 is further responsible for controlling the weapon, e.g. activating it to kill or damage the emitter.

According to an embodiment of the invention, software/hardware vehicle control utility 640 comprises a target provisioning module 642 and a guidance module 644. According to an embodiment of the invention, the target provisioning module 642 is configured to receive e.g. from the radar 620 an indication of the operation frequency of a respective unknown emitter. Module

642 is further configured to set, in a manner known per se, the transponder mounted onboard the vehicle to operate at the corresponding bandwidth. This allows for equipping the vehicle with a relatively light and cheap transponder, which in turn allows for better vehicle range and performance.

According to an embodiment of the invention, location utility 650 comprises a software and/or hardware processing utility (PU) 652, a memory coupled to PU 652 and a signal analysis module 656 and location calculation module 658. PU 652 is configured to run the signal analysis module for performing the following: receiving from the communication unit 610 measurements of electromagnetic signals emitted by the unknown emitter and collected by the platform and the vehicle (e.g. the vehicle relaying the collected measurements to the platform); and based on data received from at least one of the radar 620, the navigator 630, and the communication unit 610, tracking the vehicle and generating time and position indications corresponding to the measurements of electromagnetic signals collected by said platform and said vehicle.

PU 652 is further configured to run the location calculation module for deriving the location of the unknown emitter by performing Time-of-Arrival processing based on said measurements and said indications.

Vehicle control utility 640 and location utility 650 were illustrated in Fig.

6 in a non-limiting manner as stand-alone utilities. However, it should be understood that these utilities could be integrated together. Furthermore, each of these software and/or hardware utilities can be integrated with onboard hardware and/or software without departing from the scope of the invention.

Figs. 7a-7d illustrate vehicles 701, 702, 703 and 704 according to various embodiments of the present invention. In Figs. 7a-7d, similar elements are represented by similar reference numerals. As can be seen, according to the various embodiments, the vehicle is equipped with an RF transponder (receiver/transmitter) 710, configured to communicate with the receiver/transmitter of the platform (element 610 in Fig. 6). According to an embodiment of the invention illustrated in Fig. 7b, the vehicle further includes a signal analysis unit 720, thereby allowing the vehicle to provide information that characterizes the signal emitted by the emitter (e.g. phase, time of arrival). According to an embodiment of the invention illustrated in Fig. 7c the vehicle is further equipped with a GPS/INS system 730 and is therefore capable of providing the platform with its position information. According to yet another embodiment of the invention, illustrated in Fig. 7d, the vehicle is equipped with a GPS translator 740, allowing it to relay GPS signals to the platform, thereby enabling its tracking. The vehicle is further equipped with a guidance unit 750 and weapon unit 760 (e.g. warhead), and is therefore capable of damaging and hopefully destroying the emitter. It should be noted that the present invention is not limited to the illustrated vehicle configurations and many others are possible, all as required, without departing from the scope of the invention. In the exemplified embodiment of the invention illustrated e.g. in Figs. 5- 7, Time-of-Arrival processing is carried out on-board the platform from which the vehicle was launched. It should be understood that the invention is not limited by the exemplified embodiment and other configurations are possible within the scope of the invention. According to one embodiment of the invention, both the platform and the vehicle relay the received signal to a third receiver/transmitter at a remote unit, thereby allowing the remote unit to perform Time-of-Arrival processing. In such an embodiment, the remote unit may also control the operation of the vehicle e.g. to target it to the location of the emitter. In the exemplified embodiment of the invention illustrated e.g. in Figs. 5-

7, only two bodies - the platform and the vehicle - each having its own receiver/transmitter, are used for locating the un-known emitter. However the invention is not limited by this exemplified embodiment. According to another embodiment, a relay station is used to communicate between the first and second receiver/transmitters (on board the platform and the vehicle, respectively). Such a relay station may be another platform (e.g. an aircraft), another vehicle launched from the platform, or any other type of relay station.

In the exemplified embodiment of the invention illustrated e.g. in Figs. 5- 7, both bodies - the platform and the vehicle - are moving entities. It should be understood that the invention is not limited by this configuration. Therefore the present invention may be implemented, with necessary modifications, using a stationary platform (e.g. artillery platform) and a vehicle moving away from the stationary platform.

It should be understood that the invention may be implemented utilizing already existing platforms and vehicles by equipping such platforms and vehicles with appropriate software and/or hardware.

For simplicity, certain embodiments of the invention have been presented for locating a stationary target. Note that the invention is also applicable to the location of moving targets, including airborne, land and naval targets, with necessary modifications and alterations. Furthermore, the invention is not limited by the type of electromagnetic radiation emitted by the target, and is applicable for locating emitters of pulsed or continuous-wave signal.

Claims

CLAIMS:

1. A method for locating an unknown emitter, the method comprising:

- launching from a platform a vehicle equipped with an RP receiver/transmitter;

- gathering measurements of electromagnetic signal emitted by the unknown emitter and collected by said platform and said vehicle thereby enabling Time- of- Arrival processing of said measurements for deriving the location of the unknown emitter.

2. A method according to Claim 1, comprising tracking the vehicle and generating time and position indications corresponding to said measurements, and utilizing the indications in said Time of Arrival processing.

3. A method according to Claim 1 or 2, wherein said vehicle relays the collected measurements to the platform.

4. A method according to any one of Claims 1 to 3 wherein said Time-of- Arrival processing are carried out on-board said platform.

5. A method according to any one of Claims |l to 3| wherein said Time-of- Arrival processing are carried out by a remote unit.

6. A method according to |any one of preceding Claims] wherein said vehicle is a missile, a guided missile, an Unmanned Airborne Vehicle (UAV), or an antimissile radar decoy.

7. A method according to [any one of preceding Claims] wherein said platform is one of a group consisting of: an airborne platform, a naval platform, a land platform, a moving platform and a stationary platform.

8. A method according to ajny one of preceding Claims wherein upon launch, an inter-lobe angle is defined between the platform, the unknown emitter and the vehicle; and wherein said launching operation includes launching the vehicle at a direction such that the inter-lobe angle is increased for at least a predetermined period of time.

9. A method according to |any one of preceding Claims), wherein said launching operation includes launching the vehicle at a direction defined for at least a predetermined period of time, by a non-zero angle with respect to the platform location plain, thereby improving the accuracy of the Time of Arrival Processing.

10. A method according to jany one of preceding Claims] wherein said launching operation includes provisioning said RF receiver/transmitter of the vehicle to operate at a desired bandwidth corresponding to the electromagnetic radiation emitted by the unknown emitter.

11. A method according to any one of Claims 1 to 10 wherein said launching is triggered by detection of said unknown emitter.

12. A method according to any one of Claims 2 to 11, wherein said vehicle is equipped with GPS (Global Positioning System) and/or INS (Inertial Navigation System) units and said tracking operation is performed based on GPS and/or INS information generated by the vehicle and transmitted to the platform.

13. A method according to any one of Claims 2 to 12 wherein said platform is equipped with a tracking arrangement, said tracking operation being performed based on tracking information generated on-board the platform.

14. A method according to any one of Claims 2 to 13 wherein said vehicle is equipped with a GPS translator, said tracking operation being performed based on GPS information relayed by the vehicle to the platform.

15. A method according to any one of Claims 1 to 14 further comprising: - upon deriving the location of the emitter, providing navigation guidance instructions allowing to direct a weapon toward said emitter.

16. A method according to Claim 15 wherein said vehicle carries said weapon and said operation of providing navigation guidance instructions includes directing said vehicle toward the emitter.

17. A system for locating an unknown emitter, the system comprising a platform carrying a first RP receiver/transmitter, at least one detachable vehicle having a second RP receiver/transmitter in communication with the first RP receiver/transmitter, and a control system configured for operating the platform to launch the vehicle, for receiving and analyzing measurements of electromagnetic signal emitted by the unknown emitter and collected by said first and second RP receiver/transmitter, thereby enabling Time-of-Arrival processing of said measurements for deriving the location of the unknown emitter.

18. A system according to Claim 17 wherein said control system is further configured for tracking the vehicle and generating time and position indications corresponding to said measurements, and utilizing the indications in said Time- of- Arrival processing.

19. A system according to Claim 17 or 18 wherein said vehicle is a missile, a guided missile, an Unmanned Airborne Vehicle (UAV)₅ or an anti-missile radar decoy.

20. A system according to any one of Claims 17 to 19 wherein said platform is one of a group consisting of: an airborne platform, a naval platform, a land platform, a moving platform and a stationary platform.

21. A system according to any one of Claims 17 to 20 wherein said Time-of- Arrival processing is carried out on-board said platform.

22. A system according to any one of Claims 17 to 20 wherein said Time-of- Arrival processing is carried out by a remote unit having a third receiver/transmitter in communication with at least said first receiver/transmitter.

23. A system according to any one of Claims 17 to 22 wherein upon launch, an inter-lobe angle is defined between the platform, the unknown emitter and the vehicle; and wherein said control system is configured^' for launching the vehicle at a direction such that the inter-lobe angle is increased for at least a predetermined period of time.

24. A system according to any one of Claims 17 to 23 wherein said control system is configured for launching the vehicle at a direction defined for at least a predetermined period of time, by a non-zero angle with respect to the platform location plain, thereby improving the accuracy of the Time-of-Anϊval processing.

25. A system according to any one of Claims 17 to 24 wherein said control system is configured for provisioning said second RF receiver/transmitter to operate at a desired bandwidth corresponding to the electromagnetic radiation emitted by the unknown emitter.

26. A system according to any one of Claims 18 to 25 wherein said vehicle is equipped with GPS (Global Positioning System) and/or INS (Inertial

Navigation System) units and is configured for transmitting navigation information generated by said GPS and/or INS to the platform, and said control system is configured for performing said tracking based on GPS and/or INS information generated by the vehicle and transmitted to the platform.

27. A system according to any one of Claims 17 to 25 wherein said platform is equipped with tracking unit and said control system is configured for performing said tracking based on tracking information generated on-board the airborne platform.

28. A system according to any one of Claims 17 to 27 wherein said vehicle is further equipped with a GPS translator for relaying GPS information to said platform.

29. A system according to any one of Claims 17 to 28 wherein said control system is further configured, upon deriving the location of the emitter, to provide said vehicle with navigation guidance instructions allowing directing a weapon toward said emitter.

30. A system according to Claim 29 wherein said vehicle carries said weapon and said vehicle control utility is further configured to direct said vehicle toward the emitter.

31. A system for locating an unknown emitter, the system comprising a platform carrying a first RP receiver/transmitter, at least one detachable vehicle having a second RF receiver/transmitter in communication with the first RF receiver/transmitter; and a control system configured for operating the platform to launch the vehicle, for receiving and analyzing measurements of electromagnetic signal emitted by the unknown emitter and collected by said first and second RF receiver/transmitter, and for tracking the vehicle and generating time and position indications corresponding to said measurements, thereby enabling Time-of- Arrival processing of said measurements for deriving the location of the unknown emitter.

32. A system according to Claim 31, wherein the control system comprises a vehicle control utility and a data analyzer that includes:

- a processing utility;

- memory coupled to the processing utility;

- a signal analysis module; and - a location calculation module, wherein said vehicle control utility is configured for launching the vehicle; and wherein said data analyzer is configured to run said signal analysis module and location calculation module for: - receiving measurements of electromagnetic signal emitted by the unknown emitter collected by said platform and said vehicle;

- based on data received from at least one of a radar, a navigator and a communication unit, tracking said vehicle and generating time and position indications corresponding to said measurements of electromagnetic signal collected by said platform and said vehicle; and

- based on said measurements and said indications, deriving the location of the unknown emitter by performing Time-of- Arrival processing.