One of the main areas of any fight situation is concentrate on identification or reputation. In aerial fight, the condition is compounded because of large amounts and similar looking fighter aircraft. Unless a menace is ascertained, counter offensive action cannot be initiated. The problem of target identification in the present air combat circumstance has been further complicated due to the large range of the new era Beyond Visual Range (BVR) missiles. Within the yesteryears, procedural control and systems like Identify Good friend or Foe (IFF) were set up, they didn't guarantee positive id, since they are not standalone in aspect. Therefore there was need to develop a standalone system with the capacity of identifying airborne risks.
2. Thereafter Non Cooperative Goal Identification (NCTR) techniques were developed, which did not depend on any direct contribution from the mark for id purposes. Along with the emergence of the technology, a large hope was created that this strategy would be handle all the id issues. The NCTR technology started gaining momentum in the middle eighties which is yet to verify its functionality, almost 25 years on. Despite scientific advances in pcs, NCTR is yet to see the light of your day. Though many modern day Airborne Interception (AI) radars feature NCTR, it continues to be not being used as the principal means of goal identification. NCTR at present is being used in conjunction with IFF and other procedural methods generally because of its reduced reliability.
3. Incorporation of NCTR technology in the elderly AI radars may entail change of the radar itself. Considering this and the fact that NCTR technology has not totally matured, is NCTR really the most economically feasible solution for airborne focus on identification at the moment? Or is there a much better system designed for this goal?
Methodology
4. Assertion of Problem. Modern day air battle environment is dense with both friendly as well as hostile aeroplanes. Identification is a significant problem and this has been further compounded by significantly large amounts of new era air to air missiles. Erstwhile methods of target recognition like IFF have failed in many situations, leading to fratricides. Would occupation Non Cooperative Focus on Recognition techniques together resolve this matter?
5. Hypothesis. NCTR as a technology is very requiring on the computer hardware as well as software. So at the moment NCTR may well not be the best answer for problems related to airplane recognition in a thick air combat environment. You'll be able to get inputs from all available receptors like AI radars, AWACS, aerostats etc and incorporate them to create an intelligent composite picture and identify friends from foes. However NCTR as a concept continues to be very profitable.
6. Justification of Analysis. The requirement and importance of target identification is rather obvious and history will endure testimony to the actual fact that almost all of the fratricides have been scheduled to incorrect id. Previously systems have failed mostly because the onus of recognition was with the target. Inability to prove himself for whatever reason, resulted in a friendly target being announced hostile. While NCTR as a thought appeared to be a good solution, the technological execution of the concept has still not emerged fail confirmation. Also, integration of various other existing receptors in a networked environment to create an intelligent composite picture appears to be a more viable solution.
7. Scope. The scope of this paper is to look at concerning whether NCTR is actually the path forward, so far as target identification moves. The paper will look in to the complexities associated with database necessary for airborne target identification (3 dimensional space, multiple aeroplanes configurations etc. ) as well as the technical limitations associated with implementation of NCTR. The newspaper would also study the feasibility of implementing other techniques of id. The opportunity would be limited by logical analysis predicated on available information about them and wouldn't normally involve any clinical experiment or mathematical computations.
8. Ways of data collection. NCTR as a subject has gained momentum only in the past few years and therefore has very few publications presenting basic insight. A lot of the data has been collected on the internet including tender copies of the catalogs and validated thesis by others. The options are described in the bibliography at the end of the paper.
9. Company of the Dissertation. It is proposed to review the topic in the following manner:-
(a) Section I - Introduction and Strategy. On this chapter the subject is unveiled. This section also defines the assertion of problem, the justification for the study and the technique involved.
(b) Chapter II - Need for Airborne Target Recognition systems. This chapter brings out the requirement and complexities involved in airborne target recognition.
(c) Chapter III - Record of NCTR. This section gives a brief insight in to the background of NCTR
(d) Chapter IV - How exactly NCTR Works. To understand the complexity mixed up in airborne identification process, it's important to understand how exactly NCTR functions. This section brings about the complexities involved in the working of NCTR.
(e) Section V - NUMEROUS KINDS of NCTR Techniques. This chapter brings out the types of NCTR techniques available for use. Although chapter is complex in nature, it's important to assimilate the many techniques to be able to comprehend the complexity and short comings of the machine.
(f) Section VI - Databases Technology. The efficiency of whole process involved with NCTR is determined by a precise and exhaustive data source. This chapter brings about the methods available and the restrictions in generating sufficient repository. Again this section like the prior chapter is somewhat technical in characteristics despite best attempts of keeping it as simple as possible.
(g) Section VII - Complex Limitations of the System. While up to now the paper dealt with the program aspects, this section would draw out the technical limits of the hardware required by the radar for functioning of NCTR.
(h) Chapter VIII - Alternatives to NCTR. This chapter talks about the alternatives to NCTR for concentrate on identification.
(j) Chapter IX - Conclusion. This section concludes this issue.
CHAPTER II
NEED FOR AIRBORNE Concentrate on IDENTIFICATION SYSTEMS
"In the event that you know the opponent and know yourself, you will need not dread the results
of 100 fights. " - SUN TZU
Introduction
1. In any hostile situation it's important to recognize the adversary. Without knowing who the foe is, you can fight? Same is true for aerial combat, only with added degree of difficulty. Within the earlier years, plane identification was largely restricted to visible id, with improvement in technology this was no longer possible. The increasing tool runs post World Warfare II made it difficult to visually identify aeroplanes in air during fight.
2. And in addition, any given airspace may contain friendly, neutral as well as hostile plane. You can flame at an plane without ascertaining its mother nature / intention. Therefore aircraft recognition forms a vital part prior to weapon launch.
Tragic Incidents.
3. Record is full of tragic event of misidentification in air. You'll find so many examples of neutrals having been taken from the sky. There also many circumstances of fratricides even in the recent conflicts. A few of them have been enumerated below :-
(a) On 5 October 2001, a Russian Sibir Tu-154 Airliner flying from Israel to Russia was thought to have been shot down by way of a missile fired by Ukrainian troops in a military exercise.
(b) In Apr 1994, 02 USAF F-15 plane under positive control, accidently taken down their own Military Black colored Hawk Helicopters in North Iraq.
Visual Recognition of Aircraft
4. World War Era. In both the first and second world warfare, aircraft recognition didn't pose any significant problem. In this era, the kill solution was achieved by use of weapons and therefore the weapon ranges were much closer as compared to the distances of which the targets were discernable. The aeroplanes were gradual moving and it was possible to identify and identify the sort of aeroplanes before commencing unpleasant action. The combat was basically within the so called 'Aesthetic Bubble' of the pilot/s. As can be seen from Fig 2. 1, the airplane can be visually recognized by discovering the distinct form, colour and characteristic visual top features of the aircraft. Credited training was imparted because of this. In fact, in United Kingdom, The Royal Observer Corps (ROC) was formed, which acquired civilian staff specially trained for identifying aircraft.
Fig 2. 1 : Aircraft of World Conflict Ihttp://www. military-aircraft. org. uk/ww1-fighter-planes/nieuport-17. jpgRoyal Aeroplanes Manufacturer SE5A - World Warfare One Aircraft
5. Post World War II. However post World Conflict II, there was an instant improvement in the fighters and tool technology. With all the advent of close combat air to air missiles and upsurge in weapon runs, the hostile airplane had to be recognized by at least 2-3 kilometres to initiate evasive action. Also the newer jets were similar looking in conditions of form and size. Within the Fig 2. 2, photos of F-15 and MiG-29 aircraft are placed hand and hand for contrast. While F-15 can be an American fighter, MiG-29 is from erstwhile Russia. One can simply appreciate the similarity of features which may cause one being recognised incorrectly as the other. If this is the case at close runs (20 - 30m), it might be reasonable to suppose that visual id would be almost impossible at ranges of 2 km and beyond.
Fig 2. 2 : Visible Comparability of F-15 and MiG-29 Fightershttp://www. atfx. org/photos/f15a. jpghttp://www. aerospaceweb. org/aircraft/fighter/mig29/mig29_12. jpg
6. Post World Warfare II, there also has been a substantial upsurge in the speed of fighters employed in aerial battle. This fact as well as previously mentioned aspects makes visible identification a pass. The use of radars performed give some respite to the aerial fighters. Nevertheless the tool solution was still based on visual identification. With the introduction of BVRs, the necessity for alternate method of identification gained importance. Without this, the entire capability of BVR cannot be exploited.
7. To tackle this issue of target identification, some techniques like the IFF (Identify Good friend or Foe) have been developed so far. IFF systems derive from problem response system. The machine consists of a transponder fixed on the airplane which replies by means of suitable codes to any other IFF system. In case the rules match, the aeroplanes is declared friendly. However if the code be incorrect or in case of no response, the plane is declared hostile. It ought to be considered that response would not be possible in case of battle damage, loss of encryption keys, wrong encryption secrets, or equipment failure. Therefore the major drawback of the system was that it was imperative on the part of the friendly airplane to confirm that he is friendly. In the event of faulty transponder, there are chances of fratricide.
8. Therefore there is a need to have a standalone system capable of identifying and realizing aircraft to have timely reactive action and to prevent fratricide / firing down of neutrals.
CHAPTER III
HISTORY OF NCTR
"Know thy self applied, know thy foe. A thousand fights, one thousand victories. " - SUN TZU
1. Dependence on a Stand Alone System. As can be seen from the last chapter, the IFF systems possessed a major downside, that of needing contribution from the other aeroplanes. Inability to participate in the challenge response loop by other aeroplanes due to whatever reason was construed as 'Hostile' by the system. This has led to many fratricides in the past. A number of such fratricides anticipated to faulty IFF led to the necessity for a stand alone system. Some more circumstances of disasters anticipated to faulty IFF are enumerated below:-
(a) 1980. An Italian DC-9 passenger plane was taken down with a missile near Sicily. The missile was targeted in error because of incorrect IFF and discrimination of the type of plane. 81 passengers died.
(b) 1988. In the Persian Gulf, an Iranian Airbus was shot down by an SM-2 standard missile. The plane was erroneously recognized as an F-14 fighter aircraft. 298 people passed on.
(c) 2003. A glaring exemplory case of fratricide due to faulty IFF is that of two Royal Air Force Tornados returning after having a quest in Iraq, that have been taken down by US Patriot missiles on 22 Mar 03, in which both the crew were wiped out instantly. The looking into mother board attributed one of the complexities as faulty IFF probably divided due to ability failure.
2. These types of mishaps resulted in the requirement of experiencing a system that could identify aircraft minus the active involvement of the unidentified aeroplanes. The concept of NCTR goes back from the middle seventies. An application started out by the USAF code called 'Musketeer', introduced the idea of NCTR for the first time. In the program, the aeroplanes radar was used to count up the fan blades in the engine motor. This technology was later called as 'Jet Engine unit Modulation' which would discussed at length in the subsequent section. The radar signature was unique to each engine motor. Since most plane had different engines, this technique was exploited for identifying the kind of aircraft.
3. Though the concept was created in the mid seventies, the computational technology then was not satisfactory. The radar by itself only gathers data and the removal of useful information should be done by the radar pcs. Hence NCTR technology acquired to hold back till mid eighties for the computer technology to get up. Thereafter the USAF acquired incorporated NCTR methods in the An/APG - 63 radar of F-15 C aircraft. Through the Gulf war in 1990- 91, use of this technique was manufactured in conjunction with Airborne Warning And Control System (AWACS) for discovering hostile aircraft.
4. Post Gulf battle some progress was manufactured in Automatic Target Acknowledgement (ATR) systems. These systems didn't limit themselves to aeroplanes radars and were largely ground established systems using millimetric influx radars. The amounts of the radars were significantly less than airborne interception radars. While these radars were very different in terms of technology and functioning ranges, the essential principles were similar. However the computations involved with aerial target popularity was much higher than ground goals. Though many tests were conducted on ATR systems, the progress in NCTR was not at the same speed.
5. Post 1985, NCTR was tried and fixed on the USAF F-14, F-16 and F-18 aeroplanes. Furthermore, NCTR was also fixed on selected overseas F-15s (Israeli), English Tornados and French Mirage 2000-5s. Today, this year 2010, the technology has still not completely matured but still cannot be found in isolation for aerial target identification.
CHAPTER IV
PRINCIPLE OF OPERATION AND THE DIFFERENT PARTS OF NCTR
Principle of Operation
1. Now before proceeding further, it might be prudent to understand how NCTR concepts work. NCTR fundamentally relies on the returns from the target plane. Hence no energetic participation (as with IFF) is necessary from the target aeroplanes. Non Cooperative Focus on Acceptance like any other id process would in simple conditions consist of first sensing the mark. Then your relevant features of the prospective are extricated and weighed against a databases. Thus any NCTR system should essentially include a Sensor, a Feature Extractor and a Classifier.
2. The rule of procedure of NCTR is very similar to Optical Character Acknowledgement (OCR) just as computers. The info from the mark is gathered by the right sensor and relevant data extracted. This is set alongside the data existing in the library and then grouped based on the results of the comparison. And then for the success of the technique, a huge library of varied aircraft profiles is necessary as database for comparability. The steps involved with identifying the mark plane has been depicted in Fig 4. 1. The move chart of aim for recognition demonstrates the 'Acceptance Algorithm' might take two inputs namely measured target signature and signatures stored in the catalogue and gives aim for personality as the outcome. Identification Algorithms have been briefly described subsequently.
Fig 4. 1 : Flowchart of Goal Recognition
SENSOR
3. Selection of Sensor. Choice of sensor is an essential part of the identification process. Without proper or sufficient returns from the mark, it would be nearly impossible to accurately classify the airplane. For NCTR by itself, lots of sensors are available - Optical, Infra red, laser, acoustic and radar. Nevertheless the optical, IR and laser sensors are prone to adverse weather conditions like moisture, dust etc. Also the diagnosis ranges of these receptors are significantly smaller when compared with air to air weapon varies especially in a BVR environment. Radar as a sensor has significant advantages as compared to the other receptors for the following reasons :-
(a) Aircraft are usually created by radar reflective materials (even those with carbon composite have metallic parts that echo radar).
(b) Radar can be employed by day or night and is also not damaged by haze, fog, snow and rain.
(c) Radar ranges are higher than other detectors anticipated to reduced atmospheric propagation attenuation. .
(d) Radar has been one of the very most extensively used detectors for aerial security and the technology to create, receive and process radar signals has been continually refined for nearly 100 years.
Hence radar is the desired choice of sensor for NCTR on fighter aeroplanes. Moreover radars are already in place in all the modern generation fighters. Hence there would be no necessity to add a separate sub system on the aeroplanes.
4. Sensor Requirements. The radar potential required for the NCTR is specific. It really is misnomer that any radar can be made NCTR capable. Suited radar software is not the only thing that necessary for NCTR process. It's important that the radar design is suitable to the type of measurement that has to be performed and to provide the type of target personal required. To be able to obtain signatures of high integrity, the waveform must be carefully designed and the radar must support the transmission and reception of the indication without distortion. The radar must be made to minimize the effects of multiple reflections and clutter. The radar must also possess sufficient energy so that the returns from the mark contain enough data, necessary for the recognition process. Therefore it may well not be possible to update the existing radars with NCTR ability. Should it be possible, it may entail change of major components, which may well not be the most economical solution for preventing fratricides.
FEATURE EXTRACTOR
5. Function. The profits from the radar are simply just electromagnetic pulses. It really is useless unless, relevant data is extracted from them. This is done by the Feature Extractor. Feature removal is a process which happens inside the radar computer through suitable algorithms. These algorithms choose a specific feature and isolate them for evaluation. The algorithm for feature extraction would depend on the sort of NCTR technique being employed for target reputation. Types of NCTR techniques are discussed in detail in the next chapter.
6. Constraints. Feature removal is a highly complex problem due to highly strong nature of fighter airplane. The radar earnings from the aircraft are highly aspect centered. More the aspect, more and more robust the radar returns, hence better feature extraction Aspect position in simple terms is a way of measuring how a lot of the target aircraft is seen. When looked at from leading / rear minimum area is obvious which is 'Zero' aspect. When viewed from broad side, maximum section of the aircraft is visible. Now the aspect sides in 3D space are both in conditions of elevation as well as azimuth. Because of highly aspect based mostly characteristics of the dispersed signature, the process of feature extraction becomes even more complicated. Also credited to activity of the mark, the radar signatures get distorted which poses problems not only in feature extraction but also classification. These aspects are talked about in detail in Chapter 5.
7. Following the radar has transmitted the pulses, diagnosed and processed the return from the target of interest, the prospective signature is now ready for the acceptance process. In order to perform correct focus on recognition, a lot of information must be known about the mark. These information are contained in the form of a library in the radar computer. The facts of databases and database era are discussed in detail in Chapter 6.
CLASSIFIER
8. Classifier. The classifier within an NCTR system compares the extracted features of the target signature with the already existing collection of aircraft signatures. The assessment is made by making use of recognition algorithms. Recognition algorithms are mathematical techniques or formulae that compare the signatures which were measured with the numerical models of aeroplanes existing in the radar collection. The algorithms are made to analyse and assess how close a match a particular signature is to research signature within the library. By using these algorithms, the classifier now assigns the most appropriate and closest individuality to the mark. Shown in the fig 4. 2 is a target signature being compared with the three guide signatures. On close analysis though the focus on signature does not perfectly match any of the reference signatures, it is closest to 'Target C'. Which means classifier would it assign the assessed personal as 'Aim for C'.
Fig 4. 2 : Target Signature Assessment with Reference point Signatures
9. Goal signatures have to be measured, modelled and analysed, to allow the qualities used for recognition to be revealed. The techniques for reliably extracting these traits from the target have to be identified. Libraries of goal data have to be assembled, ordered, handled and updated as new goals emerge and much more target signature data becomes available. The introduction of reliable acceptance algorithms is evidently critical for creating a high-performance target recognition capability.
10. While a computer can simply identify various items based on the scale, shape, color etcetera, it could still lack the ability to identify things logically as the human brain does indeed. Till the neural and hereditary algorithms aren't fully developed, it would be difficult to boost NCTR for aerial recognition.
