O T & E for ESM Systems and the use of simulation for system performance clarification Dr. Sue Robertson EW Defence Limited United Kingdom e-mail: sue@ewdefence.co.uk Tuesday 11 March 2014 EW Defence Limited Slide 1 of 52
Summary of Presentation Why ESM Testing is needed in an Operational Environment The Choice of a suitable Trials Area The simulation of Radar Pulses Analysis of Trials Data Example of the use of Trials Data to identify and solve ESM Performance Issues The use of trials data for ELINT database and ESM Emitter Library Population Tuesday 11 March 2014 EW Defence Limited Slide 2 of 52
Why OT&E is needed Although testing of ESM systems in a laboratory environment gives useful indications of system performance, testing in the real world is needed to determine how the system will work and to aid the optimisation of the system. Factors such as multipath reflections from the surface of the aircraft and from objects on the ground affect the performance of the system. Features of the ESM installation on an aircraft, such as the location of the antennas also affect system performance. Common problems with ESM systems such as multi-tracking for single radars, poor parameter measurement and errors in direction-finding can be identified and rectified by using test flights in an Operational setting. Tuesday 11 March 2014 EW Defence Limited Slide 3 of 52
Radar 1 Aircraft Route Radar 2 Radar 3 Tracks at correct DOA Fixes with Error Ellipses Ideal picture seen by an Electronic Surveillance System Tuesday 11 March 2014 EW Defence Limited Slide 4 of 52
Radar 1 Aircraft Route Radar 2 Radar 3 Tracks at correct DOA Extra Tracks at incorrect DOA Location Fixes with Error Ellipses Actual picture seen by an Electronic Surveillance System Tuesday 11 March 2014 EW Defence Limited Slide 5 of 52
Planning for a Trial Definition of Trials Objective E.g. To Test Direction Finding Accuracy To check the Performance of the pulse De-interleaver To make sure that intercepts are Created for radars that should be seen Selection of a Suitable RF Environment Ideally an area where the radar pulse density is low Gathering of Ground truth Find locations and types of land-based radars Build up a picture of shipping in the trials area Definition of Aircraft Route and Altitude Profile Simulation of Pulse Data for Comparison with Recorded Trials Data Tuesday 11 March 2014 EW Defence Limited Slide 6 of 52
Selection of a Suitable Trials Environment AIS Data Showing Ships in Malacca Straight and Singapore Tuesday 11 March 2014 EW Defence Limited Slide 7 of 52
Selection of a Suitable Trials Environment AIS Targets in South China Sea Tuesday 11 March 2014 EW Defence Limited Slide 8 of 52
Data for Ground Truth Air Traffic Control radars in East Malaysia 1. A 60 NM Primary Surveillance Radar (PSR) co-mounted with 200 NM monopulse SSR located on Bukit Kepayang, 1 NM NE of Kota Kinabalu International Airport (055638.7N 1160352.3E) 2. A 60 NM Primary Surveillance Radar (PSR) co-mounted with 200 NM monopulse SSR located in Kuching International Airport ( 012848.08 N 1102003.90 E) 3. A 60 NM Terminal Primary Approach Radar co-mounted with a 200 NM monopulse SSR located at Miri Airport (041929.8N 1135915.8E) 4. A 50 NM Terminal Approach Radar with co-mounted 250 NM conventional SSR located at Labuan Air Force Base (051526.9N 1150937.7E) Source: Malaysia Aeronautical Information Publication (AIP) Other Airfield radars in East Malaysia & Brunei Sibu (021523.2N 1115904.4E) Tawau (041415.4N 1180005.3E) Bandar Seri Bagawan (4.9442 N 114.9283E) Sibu Radar Tower Tuesday 11 March 2014 EW Defence Limited Slide 9 of 52
Weather Radars Data for Ground Truth There are 5 Weather Radars in East Malaysia Kota Kinabalu 5.76472N 116.058E 5 GHz Kuching 1.36472N 110.337E 5 GHz Miri 4.21528N 113.988E 3GHz Sandakan 5.90167N 118.048E 5 GHz Bintulu 3.12417N 113.019E 5 GHz Coastal Surveillance Radar in East Malaysia There are 3 coastal surveillance radars in East Malaysia provided as part of project 1206. Pulau Balambagan 7.283085N 116.92744E Pulau Gaya 6.022125N 116.02650E Pulau antanani 6.707025N 116.34932E Tuesday 11 March 2014 EW Defence Limited Slide 10 of 52
ATC Weather Radar Coastal Surveillance Radars in East Malaysia Tuesday 11 March 2014 EW Defence Limited Slide 11 of 52
Aircraft Flight Profile The best flight profile is one where a repeatable flight profile can be flown, for example a race track or a box route. The distance to be travelled on each straight track of the route will depend on the aircraft speed. Ideally. the aircraft should fly for about 10 minutes on a straight track before turning to allow the ESM picture to stabilise or to build up a new picture if the system is reset. Aircraft Speed (kts) Approx Distance (km) 80 25 120 40 200 60 300 90 500 150 1000 300 Tuesday 11 March 2014 EW Defence Limited Slide 12 of 52
Aircraft Flight Profile Altitude The altitude at which the trial is flown will determine how far the ESM can see. The radar range (R) is limited by the radar equation Power Received 1/R 4 The ESM only has to receive pulses that have been transmitted by the radar, so for the ESM Power Received 1/R 2 For example, a radar with a range of 60 nautical miles could be seen at a range of 3600 nm by an ESM, if is wasn t for the curvature of the earth. The radar horizon which increases with altitude is the real governing factor for the range at which the ESM can see the radar. Aircraft Altitude (ft) Radar Horizon(km) 200 32 1000 72 2000 102 5000 162 10000 230 20000 320 Tuesday 11 March 2014 EW Defence Limited Slide 13 of 52
Altitude 1000ft, horizon 75 km Altitude 2000ft, horizon 100 km Altitude 4500ft, horizon 150 km Altitude 12000ft, horizon 250 km ATC Weather Radar Coastal Surveillance Illustration of Radar Horizon Rings Tuesday 11 March 2014 EW Defence Limited Slide 14 of 52
Example of ESM Trial Trial Objectives To Test the De-interleaver using two of the same type of Coastal Surveillance Radar To check the creation of an intercept for a radar as it comes into the radar horizon To check that multi-tracking does not occur To Test DF performance Aircraft Parameters Speed = 200 kts, Maximum Altitude = 20000 ft Straight line route needed = 60 km Start of Route = 6.1 N 115.5 E End of Route = 6.5 N 116.0 E ESM Sensitivity - 60 dbmi Range to Radars of Interest Site Name Range at Route Start (km) Range at Route End (km) Pulau Gaya 60 53 Pulau Mantanani 115 44 Pulau Balambagan 205 134 Altitude = 5000 ft for radar horizon of 160 km Tuesday 11 March 2014 EW Defence Limited Slide 15 of 52
Aircraft Route to Test De-interleaver and Detection Range Tuesday 11 March 2014 EW Defence Limited Slide 16 of 52
Amplitude (dbmi) -20 What does the ESM see from each radar? The shape of the radar beam determines how many pulses are seen from the radar each time the radar scans past the ES system -25-30 -35 Range to Radar = 15nm 3 db Beamwidth = 1.5 o Sin(x)/x Beam Shape -40-45 -50 1 st Sidelobe Level = -23 db -55-60 ES Threshold -65-4 -3-2 -1 0 1 2 3 4 Azimuth Angle (degrees) Tuesday 11 March 2014 EW Defence Limited Slide 17 of 52
Simulation of Radar Beam Pattern The inputs to the calculation are the 3dB beamwidth of the radar and the first sidelobe level. A radiation pattern of the general form (sin(u)/u) 2 is generated, using the following equation for u: u = C p sin ( q ) B where: B is the 3dB beamwidth in radians C is a factor dependent on the level of the first sidelobe The factor C ranges from 0.885 when the first sidelobe level is -13.2 db to about 1.4 when the first sidelobe level is -40 db. For sidelobe levels other than -13.2 db (which is the default for a sin(u)/u pattern), the radiation pattern equation must be modified by the factor z to give a pattern with the required sidelobe levels. The actual equation used is: Power, A q = sin (u 2 - z 2 ) 2 (u 2 - z 2 ) The factor z ranges from 0 when the first sidelobe level is -13.2 db to about 5.4 when the first sidelobe level is -40 db. Tuesday 11 March 2014 EW Defence Limited Slide 18 of 52
Simulation of Radar Beam Pattern The radiation pattern is altered in two ways by the general equation which provides the power, A q. In addition to the suppression of the sidelobes, the main peak is enhanced in power. The power must be normalised by subtracting the power at the peak of the beam as follows to reduce the effects of the sidelobe generation to a zero gain: A = A 0 - A q where A 0 is the calculated power at the peak of the beam, i.e. q = 0. The final stage in the calculation of the emitter power is the correction for the peak ERP of the emitter at the particular range. Finally, the radar scan period and the pulse repetition intervals are needed to find the power of each pulse as the radar scans past the ESM. Tuesday 11 March 2014 EW Defence Limited Slide 19 of 52
Amplitude (db) Amplitude (db) Amplitude (db) -10 Beam Patterns for Different Ranges -20 50 nm -30 150 ms 0-40 -10-20 100 nm -50-30 66 ms -60-40 -70 0 50 100 150 200 250 300 350 Time (ms) -50-60 -10-20 -30-40 300 ms 25 nm -70 0 100 200 300 Time (ms) -50-60 -70-80 -90-100 0 50 100 150 200 250 300 350 Range Pulses % of Radar Duration Scan Time 200 nm 50 1.25 150 nm 50 1.25 100 nm 66 1.65 50 nm 150 3.75 25 nm 300 7.50 15 nm 1500 37.50 Time (ms) Tuesday 11 March 2014 EW Defence Limited Slide 20 of 52
Emitter in Scenario Time-line of All radars in trial 7 6 Labuan ATC 5 KK ATC 4 KK Weather 3 Palau Balambagan 2 Palau Mantanani 1 Palau Gaya 0 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 Time (ms) Tuesday 11 March 2014 EW Defence Limited Slide 21 of 52
Pulse Amplitude (db) -20-25 -30-35 -40-45 -50 KK Weather Radar KK ATC Labuan ATC Pulau Balambagan Pulau Mantanani Pulau Gaya -55-60 0 10000 20000 30000 40000 50000 60000 Time (ms) Predicted Amplitude of all radars Showing Pulse Density in one minute of flight (~ 4000 pulses from 6 radars) Tuesday 11 March 2014 EW Defence Limited Slide 22 of 52
Pulse Amplitude (db) -20-25 -30-35 -40-45 KK Weather Radar KK ATC Labuan ATC Pulau Balambagan Pulau Mantanani Pulau Gaya -50-55 -60 35000 36000 37000 38000 39000 40000 Time (ms) Detail of Predicted Amplitude Profiles Tuesday 11 March 2014 EW Defence Limited Slide 23 of 52
Pulse Amplitude (db) -20-25 -30-35 -40-45 KK Weather Radar KK ATC Labuan ATC Pulau Balambagan Pulau Mantanani Pulau Gaya -50-55 -60 37300 37400 37500 37600 37700 37800 37900 38000 Time (ms) Fine Detail of Predicted Amplitude Profiles Tuesday 11 March 2014 EW Defence Limited Slide 24 of 52
Analysis of Trials Data Visualisation / Playback of Operator s Screen Calculation and Plot of Correct DOA Profiles Graphical representation of Track Data Graphical Representation of Pulse Data Comparison of Pulse Data with Simulation Tuesday 11 March 2014 EW Defence Limited Slide 25 of 52
Visualisation of the Operator s Screen Tuesday 11 March 2014 EW Defence Limited Slide 26 of 52
Range (km) DOA (degrees) DOA and Range Profiles of Radars of Interest 210 180 150 120 90 Pulau Gaya Pulau Mantanani Pulau Balambagan 60 30 0 200 0 100 200 300 400 500 600 160 120 80 40 0 0 100 200 300 400 500 600 Time (seconds) Tuesday 11 March 2014 EW Defence Limited Slide 27 of 52
DOA (degrees) The analysis of ESM Track Data To see the DOA performance of the ESM the correct DOA of the radar is plotted (found by using navigation data from the trials platform) and the DOA of Track Updates created by the ESM are shown on the same graph. 200 180 53km 160 140 120 100 60km 80 Pulau Gaya Pulau Mantanani Pulau Balambagan 60 115 km 205 km40 44 km 134 km 20 0 0 100 200 300 400 500 600 Time (seconds) Tuesday 11 March 2014 EW Defence Limited Slide 28 of 52
DOA (degrees) The analysis of ESM Track Data This graph shows the tracks created for two of the radars, with the track for Palau Balambagan appearing as the radar comes into the radar horizon of the aircraft. 60 59 58 57 Palau Balambagan Palau Mantanani 56 55 54 53 52 51 50 300 310 320 330 340 350 360 370 380 390 400 Time (seconds) Tuesday 11 March 2014 EW Defence Limited Slide 29 of 52
DOA (degrees) The analysis of ESM Pulse Data Each of the updates to the ESM tracks is created from sets of pulses. In this plot the correct DOA of the radar is plotted and the DOAs of individual pulses are plotted on the same graph. 200 180 53km 160 140 120 100 60km 80 Pulau Mantanani Pulau Balambagan Pulau Gaya Pulau Gaya Pulau Mantanani Pulau Balambagan 60 115 km 205 km 40 44 km 134 km 20 0 0 100 200 300 400 500 600 Time (seconds) Tuesday 11 March 2014 EW Defence Limited Slide 30 of 52
DOA (degrees) The Detail of the Pulse Data In this graph the pulses from individual scans of each of the 3 radars can be seen. 160 60km 140 53km 120 100 80 Pulau Mantanani Pulau Balambagan Pulau Gaya Pulau Gaya Pulau Mantanani Pulau Balambagan 60 115 km 44 km 205 km 134 km 40 370 375 380 385 390 395 400 Time (seconds) Tuesday 11 March 2014 EW Defence Limited Slide 31 of 52
Amplitude (dbmi) Amplitude (dbmi) Comparison of Theoretical Beam Shape with Received Pulses -30-35 -40 Theoretical Amplitude Profile -45-50 -55-60 -65 Number of Pulses = 24 Range to Radar = 60 km 0 5 10 15 20 25 Time (ms) -30-35 -40-45 -50 Example of Amplitude Profile from Pulse Data -55-60 -65 Number of Pulses = 23 Range to Radar = 60 km 0 5 10 15 20 25 Time (ms) Tuesday 11 March 2014 EW Defence Limited Slide 32 of 52
Amplitude (dbmi) Amplitude (dbmi) Comparison of Theoretical Beam Shape with Received Pulses -40-42 -44-46 -48-50 -52-54 Number of Pulses = 11 Range to Radar = 160 km Theoretical Amplitude Profile -56 0 2 4 6 8 10 Time (ms) -40-42 -44-46 Example of Amplitude Profile from Pulse Data -48-50 -52-54 -56 Number of Pulses = 11 Range to Radar = 160 km 0 2 4 6 8 10 Time (ms) Tuesday 11 March 2014 EW Defence Limited Slide 33 of 52
Example of Use of Pulse Data to diagnose DF / Multi-tracking 3 4 2 radar 5 1 Route taken by aircraft in trial Tuesday 11 March 2014 EW Defence Limited Slide 34 of 52
3 2 4 1 radar 5 Track formation during the Trial Tuesday 11 March 2014 EW Defence Limited Slide 35 of 52
Pulse data during a single run of the flight trial Tuesday 11 March 2014 EW Defence Limited Slide 36 of 52
Single scans of an ATC Radar showing the slope in DOA across the main beam Tuesday 11 March 2014 EW Defence Limited Slide 37 of 52
ESM Antenna Installation on a Large Aircraft similar to the antenna configuration in the trial where the DOA spread was first seen Tuesday 11 March 2014 EW Defence Limited Slide 38 of 52
Amplitude Comparison DOA Measurement The assumption in the operation of an Amplitude Comparison ESM system is that the emitted pulse arrives with equal amplitude at all receiving antennas, but that the detected amplitude at each antenna depends on the receiver antenna beam shape. The DOA of the pulse can therefore be determined from the difference in amplitude of the receiving antennas. Typical ESM Receiver Antenna Beam Shapes with Activation Levels for a Correct DOA of 70 o The beam shape for the ESM antennas can be represented by a Gaussian model with a nominal 3dB beamwidth of about 70 o. The amplitude difference between the m th and either the (m+1) th port or the (m-1) th port can be used to estimate the direction of arrival of the signal. Tuesday 11 March 2014 EW Defence Limited Slide 39 of 52
Typical Beam Shape of an Air Traffic Control (ATC) Radar Tuesday 11 March 2014 EW Defence Limited Slide 40 of 52
Typical Beam Shape of an ATC Radar with overlay of Aircraft Azimuth Extent Tuesday 11 March 2014 EW Defence Limited Slide 41 of 52
DOA Errors across the main beam of a scanning radar as an aircraft with 30m ESM antenna separation moves past the radar at a range of 10 nm Tuesday 11 March 2014 EW Defence Limited Slide 42 of 52
DOA Error (degrees) Amplitude (dbmi) -30-35 -40-45 -50-55 -60-65 0 5 10 15 20 25 30 20 10 0-10 -20 0 5 10 15 20 25 30 Time (ms) Theoretical DOA Error Slope due to Antenna Separation Tuesday 11 March 2014 EW Defence Limited Slide 43 of 52
Using Trials Data for ELINT Databases Traditionally an Emitter Type would have been specified in the Emitter Libraries for ESM Systems, rather having specific parameters for individual Emitter sites. For example, A typical Air Traffic Control (ATC)Radar may have the following parameter ranges specified for it in the Emitter Library: RF = 2700 to 3100 MHz, PRI = 1000 to 2000 ms, PW = 1 to 2 ms A typical Marine Radar may have the following parameter ranges: RF = 3040 to 3065 MHz, PRI = 1200 to 1300 ms, PW = 0.7 to 1.2 ms Already we can see ambiguity... Tuesday 11 March 2014 EW Defence Limited Slide 44 of 52
pulse width (ns). 2500 Example of the Overlap in Parameter ranges for some ATC/Marine radars 2000 1500 1000 500 0 0 500 1000 1500 2000 2500 3000 PRI (ms) Tuesday 11 March 2014 EW Defence Limited Slide 45 of 52
Using Trials Data for ELINT Databases There is a trend towards using specific emitter parameters in Emitter Libraries. For example, two ATC radars of the same type would be specified individually in the library Radar at site A: Radar at Site B: RF = 2765 MHz, PRI = 1333ms, PW = 1.2ms RF = 2945 MHz, PRI = 1555ms, PW = 1.5ms Pulse data is needed to aid the specification and testing of the Emitter Library.. Tuesday 11 March 2014 EW Defence Limited Slide 46 of 52
Pulse Amplitude (dbmi) Interleaved Radar Pulses Here is an example of what pulses received from typical set of ship radars in 250 ms may look like even in a busy RF environment it is rare to get more than 3 or 4 radar pulse streams interleaved at any one time. -20-30 -40-50 -60-70 0 50 100 150 200 250 Time (ms) Tuesday 11 March 2014 EW Defence Limited Slide 47 of 52
Pulse Amplitude (dbmi) De-interleaved Radar Pulses It is therefore straightforward to de-interleave the radar pulses off-line from the trial and extract sets of pulses for individual radars for use in the ELINT database. -20-30 -40-50 -60-70 0 50 100 150 200 250 Time (ms) Tuesday 11 March 2014 EW Defence Limited Slide 48 of 52
Example of Pulses received from a Fixed PRI radar and corresponding ELINT data set Radar Pulses Pulse Amp 1 TOA 2 PRI 3 RF 4 PW 5 (dbmi) (ms) (ms) (MHz) (ms) 1-54.7 101.65 3045.1 0.70 2-52.5 102.98 1331.831 3045.1 0.70 3-48.5 104.32 1331.831 3045.2 0.71 4-48.5 105.65 1331.830 3045.0 0.71 5-47.0 106.98 1331.832 3045.2 0.70 6-46.2 108.31 1331.831 3045.2 0.70 7-47.0 109.64 1331.831 3045.1 0.70 8-48.5 110.98 1331.831 3045.3 0.70 9-49.5 112.31 1331.832 3045.2 0.70 10-52.5 113.64 1331.831 3045.3 0.71 11-54.0 114.97 1331.834 3045.2 0.70 12-57.0 116.30 1331.833 3045.2 0.70 13-59.5 117.63 1331.833 3045.2 0.72-20 -30-40 -50-60 -70 0 50 100 150 200 250 Time (ms) 1 Amplitude 2 Time of Arrival 3 Pulse Repetition Interval 4 Radar Frequency 5 Pulse Width Specific EmitterParameters RF = 3045 MHz PRI Type = Fixed PW = 0.7 (ms) PRI Element = 1331.83 (ms) Scan Period = 1.8 seconds 3dB beamwidth = 2 degrees Tuesday 11 March 2014 EW Defence Limited Slide 49 of 52
Radar Pulses Example of Pulses received from a Staggered PRI radar and corresponding ELINT data set Pulse Amp 1 TOA 2 PRI 3 RF 4 PW 5 (dbmi) (ms) (ms) (MHz) (ms) 1-59.0 215.20 9410.1 0.30 2-55.7 216.87 1673.232 9410.0 0.31 3-53.7 218.56 1685.516 9410.2 0.30 4-51.7 220.26 1697.217 9410.1 0.30 5-49.5 221.93 1673.232 9410.1 0.30 6-47.0 223.61 1685.516 9410.2 0.30 7-46.7 225.31 1697.217 9410.2 0.31 8-45.5 226.99 1673.233 9410.1 0.30 9-44.7 228.67 1685.516 9410.1 0.30 10-44.7 230.37 1697.217 9410.0 0.30 11-45.5 232.04 1673.232 9410.1 0.30 12-46.2 233.73 1685.516 9410.0 0.30 13-47.0 235.42 1697.217 9410.1 0.30 14-51.7 237.10 1673.232 9410.0 0.31 15-54.0 238.78 1685.517 9410.2 0.30-20 -30-40 -50-60 -70 0 50 100 150 200 250 Time (ms) 1 Amplitude 2 Time of Arrival 3 Pulse Repetition Interval 4 Radar Frequency 5 Pulse Width Specific Emitter Parameters RF = 9410 MHz PRI Type = Staggered PW = 0.3 (ms) PRI Elements =1673.232, 1685.516, 1697.217(ms) Scan Period = 1.5 seconds 3dB beamwidth = 1.8 degrees Tuesday 11 March 2014 EW Defence Limited Slide 50 of 52
Conclusions O T & E trials are needed to check aspects of ESM System performance, such as de-interleaving, detection range and DF accuracy in the real world. Use of simulation of radar beam shapes based on actual ground truth allows a comparison to be made with data recorded during a trial. Issues such as multi-tracking and DOA errors can be diagnosed by looking at recorded pulse data. Recorded radar pulse data can be used to populate ELINT databases and for the creation of ESM radar libraries containing specific Emitter Identities. Tuesday 11 March 2014 EW Defence Limited Slide 51 of 52
Nimrod MRA4 Dr Sue Robertson, e-mail: sue@ewdefence.co.uk Tuesday 11 March 2014 EW Defence Limited Slide 52 of 52