Northern Watch Air Surveillance with a Rutter 100S6 Radar System – Trials Analysis and Results
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Northern Watch Air Surveillance with a Rutter 100S6 Radar System – Trials Analysis and Results Dan Brookes DRDC Ottawa . Defence R&D Canada – Ottawa Technical Memorandum DRDC Ottawa TM 2013-152 November 2013 Northern Watch Air Surveillance with a Rutter 100S6 Radar System - Trials Analysis and Results Dan Brookes DRDC Ottawa Defence R&D Canada – Ottawa Technical Memorandum DRDC Ottawa TM 2013-152 November 2013 Principal Author Original signed by Dan Brookes Dan Brookes Defence Scientist Approved by Original signed by Rahim Jassemi Rahim Jassemi Acting Head, Space and ISR Applications Section Approved for release by Original signed by Chris McMillan Chris McMillan Chair, Document Review Panel © Her Majesty the Queen in Right of Canada, as represented by the Minister of National Defence, 2013 © Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale, 2013 Abstract …….. This document describes an initial assessment of the Rutter 100S6 marine radar system’s ability to perform a useful function as a limited air surveillance asset at a remote test site on Devon Island, overlooking Barrow Strait and Lancaster Sound. As part of the assessment, a set of trials was performed in the Ottawa-Gatineau area to measure the radar system’s ability to detect and track aircraft of opportunity in a land-based setting. The aircraft were of various types and sizes ranging from small general aviation aircraft (fixed and rotary wing) to large commercial jet airliners. Ground-truth of the aircraft classification, identification and course information was provided by a combination of visual means (i.e. naked eye, binoculars, and camera imagery) and, when available, Automatic Dependent Surveillance-Broadcast (ADS-B) reports. Only a few days of actual data collection was accomplished, which was performed intermittently over the period from 29 July to 19 September 2010. The outcome of the assessment was that this radar system has the potential to provide a useful, though limited, air surveillance role as long as the system constraints are respected. It was also determined that a more capable tracker would be needed if automatic surveillance of aircraft, with minimal analyst intervention, is required. The current alpha-beta tracker provided with radar system has difficulty initiating a track or maintaining track continuity on high speed (over 100 kph) manoeuvring targets, especially given their tendency for scintillation. Résumé …..... Ce document décrit une première évaluation de la capacité d'un système de radar de marine, le Rutter 100S6, pour remplir une fonction utile comme un atout pour la surveillance limitée des avions sur un site de test à distance sur l'île Devon, avec une vue sur les détroits de Barrow et de Lancaster. Dans le cadre de l'évaluation, une série d'essais a été réalisée dans la région d'Ottawa- Gatineau pour mesurer la capacité du système de radar pour détecter et suivre les avions d'occasion dans un cadre terrestre. Les avions étaient de différents types et tailles allant de petits avions de l'aviation générale (fixe et à voilure tournante) aux grands avions de ligne commerciaux. Rez-de-vérité de l'information pour la classification, l'identification et trajectoires de vol des aéronefs a été fourni par une combinaison de moyens visuels (à savoir l'œil nu, des jumelles, et l'imagerie de la caméra) et, lorsqu'il est disponible, la surveillance dépendante automatique en mode diffusion (ADS-B) rapports. Seulement un peu de jours de collecte de données réelles ont été accomplies; ils ont été réalisés par intermittence au cours de la période allant du 29 Juillet au 19 Septembre 2010. Le résultat de l'évaluation était que ce système radar a le potentiel de fournir un utile, bien que limité, le rôle de surveillance de l'air à condition que les contraintes du système sont respectées. Il a également été déterminé qu'un plus capable algorithme de poursuite serait nécessaire si la surveillance automatique des avions, avec un montant minimal de l'intervention par l'analyste, est nécessaire. Le courant traqueur alpha-bêta fourni avec le système radar a difficulté à initier une piste ou le maintien de la continuité de la piste pour les cibles de manœuvre à grande vitesse (plus de 100 km), en particulier en raison de leur tendance à scintiller. DRDC Ottawa TM 2013-152 i This page intentionally left blank. ii DRDC Ottawa TM 2013-152 Executive summary Northern Watch: Air Surveillance with a Rutter 100S6 Radar System- Trials Analysis and Results Brookes, D.; DRDC Ottawa TM 2013-152; Defence R&D Canada – Ottawa; November 2013. Introduction or background: In 2008, at the beginning of the implementation phase of the Northern Watch (NW) Technology Demonstration Program (TDP) project, a Rutter 100S6 maritime navigation radar was purchased. Its main purpose was to be used as an all-weather sensor capable of detecting, localizing, and tracking both cooperative and non-cooperative surface vessels as part of an integrated suite of complementary above water and underwater sensors for local maritime surveillance. The objective of the integrated suite was to be able to detect, track, classify and possibly identify sub-surface, and surface vessels as well as provide limited surveillance of aircraft. Since the Rutter 100S6 was designed for detecting and tracking marine surface vessels, its effectiveness as an air surveillance asset for Northern Watch needed to be assessed. In order to perform this assessment, experimental trials were performed (over land) at the Gatineau Executive Airport (GEA), in Gatineau, Quebec, during the late summer of 2010. Results: The following observations and conclusions can be made about the ability of the Rutter 100S6 radar system to detect and track aircraft over land in good weather conditions. 1) The aircraft usually needs to be within the volume scanned by the main beam of the radar (i.e. a vertical angle between -12° and 12° relative to the horizontal boresight, and azimuth angle between 0° and 360°) to be detected and tracked. 2) The detection range of the aircraft depends on the type, size and aspect angle: a. Small low winged aircraft can be detected and tracked to a maximum range of about 15 km when viewed tail-on. b. Larger aircraft the size of the PBY-5A Canso or the Lancaster Mark X can be detected and tracked to a range of just over 30 km when viewed tail-on. c. Large commercial airliners like the Boeing 737-300 can be seen for brief periods at ranges of up to 50 km when viewed at an optimal angle of broadside, and within the main beam of the radar antenna (i.e. up to 36000 ft). At other times it can usually be detected and tracked to ranges between 30 and 35 km. d. Very large aircraft such as the Boeing 767 and Airbus A320 or A330 can usually be detected to a range of 40 km and to altitudes up to 36000 ft (within the 12°) regardless of aspect angle and up to 50 km when seen broadside. DRDC Ottawa TM 2013-152 iii 3) Unless the aircraft maintains a relatively straight bearing, the alpha-beta tracker that comes with the radar system has difficulty maintaining a track lock. This is expected since the radar was originally intended as a marine navigation aid to detect and track relatively slow moving marine targets. The aircraft observed in these trials had airspeeds that usually exceeded 150kph and went as high a 600kph. At such speeds, manoeuvring aircraft are difficult to track because the radar only has a maximum update rate of about 1.3 seconds between rotational scans (48 rpm). These problems are exacerbated when the aircraft is at a range and aspect where there are a significant number of missed detections conflicting with the required tracking criteria (e.g. M-of-N detection parameter). A more advanced tracking algorithm would probably provide better results, especially if the tracking was not required to be in real-time. 4) With the current signal processing and tracker, initiating a track in heavy ground clutter (especially in Long Range mode) near the radar site is generally not possible. This can limit the tracking capability to ranges beginning at more than a kilometre from the radar site, in reasonably flat terrain. In general, ground clutter is highly terrain dependent but may be reduced by suitably locating the radar on a summit. 5) Maintaining a track through areas of heavy ground clutter can be problematic, and depends on the speed of the aircraft and the width of the clutter with respect to the track. 6) The results obtained in these experiments are consistent with the prediction software (SIESTA) that a high-winged aircraft the size of a DHC-6 Twin-Otter might be seen by the 100S6 radar to a distance of over 30 km, as long as it is broadside to the radar beam. It was found that one method of obtaining ground truth course information for the radar, i.e. ADS-B reports from aircraft, was not always acccurate. During the trials, at least one Air Canada B767-38E(ER) passenger aircraft had a positional offset of over 12 km to the West, and 1 km to the South of the true route. Significance: Based on the outcomes of these experiments, and of ADS-B reports collected from aircraft flying in the vicinity of Cape Liddon during NW sensor trials in August of 2008, the density of trans-polar flights might be great enough for the 100S6 to detect and track several aircraft per week, at least for brief periods of time, depending on their aspect, range and altitude. Future plans: It would be useful to apply more sophisticated tracking algorithms to the Rutter 100S6 data recorded during the GEA trials to determine whether significantly better performance might be achieved for tracking aircraft.