66 Performance Improvement of Electro-Optic Search and Track System for Maritime Surveillance Manvendra Singh #,@,* , Sudhir Khare #,@ , and Brajesh Kumar Kaushik @ # DRDO-Instruments Research and Development Establishment, Dehradun - 248 008, India @ Indian Institute of Technology, Roorkee - 247 667, India * E-mail: manvendra@irde.drdo.in ABSTRACT Surveillance of maritime domain is absolutely vital to ensure an appropriate response against any adverse situation relating to maritime safety or security. Electro-optic search and track (EOST) system plays a vital role by providing independent search and track of potential targets in marine environment. EOST provides real-time images of objects with details, required to neutralise threats. At long range, detection and tracking capability of EOST degrades due to uncertainty in target signatures under cluttered scenario. Image quality can be improved by using suitable sensors and enhancement using the target/background signature knowledge. Robust tracking of object can be achieved by optimising the performance parameters of tracker. In the present work, improvement in the performance of EOST subsystems such as sensor, video processor and video tracker are discussed. To improve EOST performance in terms of detection and tracking, sensor selection criterion and various real time image processing techniques and their selection criteria for maritime applications have been also discussed. Resultant improvement in the quality of image recorded under marine environment has been presented. Keywords: Maritime surveillance; Electro optic search and track; EOST; MWIR; LWIR; Video tracker; Contrast enhancement; Detection 1. InTROduCTIOn Electro-optic search and track (EOST) systems operate in passive mode and are similar to surveillance radar. They allow passive detection and identifcation with precise line-of- sight target tracking. Low jamming susceptibility makes EOST system a popular choice for maritime surveillance. It can also be efciently used for surveillance at night and navigational support under very low ambient light. Typically, EOST system detects the potential target on the basis of diferential contrast w.r.t. background or discontinuity being sensed by the imaging sensor. The available imaging sensors for maritime surveillance operate in wavelength bands from visible band, short wave InfraRed (SWIR), medium wave InfraRed (MWIR), long wave InfraRed (LWIR) 1 . To collect complementary information, combinations of imaging sensors operating in two or three diferent wavelength bands are used. The target signature gets attenuated due to atmospheric absorption and scattering phenomena 2 . The degradation afects the quality of information being collected through EOST system. Several image processing modules are available to improve the image quality; however the efectiveness of the same heavily depends on the cause and type of degradation. Therefore, before implementing the mitigation plan to overcome these degradations, detailed study to examine the cause of degradation 3 . 2. COnfIguRATIOn Of EOST SySTEM EOST system has three main components namely, a set of electro optic (EO) sensors mounted on stabilised electro optic director and system control electronics. The system electronics is comprised of operator control console (OCC), video processor (VP) and video tracker (VT). Block diagram of a typical EOST system considered for the present case study is as shown in Fig. 1. For 24x7 maritime surveillance, a set of two sensors each operating in diferent bands are used. High resolution visible band sensor is the primary choice for better detection, however the performance is limited to clear day-time. To supplement this limitation, additional sensors operating in InfraRed band either MWIR or LWIR are used. VT enables operator to automatically follow the target of interest by updating its position continuously. The image collected through the EO sensor is a primary input to the VT. It eases the process of dealing with the threats in an efective manner and also improves the accuracy of the neutralisation mechanism, if integrated with fre control system. The factors afecting the performance of VT and suggested improvements are discussed in the following sections. 3. MWIR Vs LWIR In MARITIME SuRVEILLAnCE For night-time surveillance, sensors operating in MWIR and LWIR are natural choice. These sensors are not used together as it makes system costlier and bulky. Due to the higher Defence Science Journal, Vol. 70, No. 1, January 2020, pp. 66-71, DOI : 10.14429/dsj.70.13824  2020, DESIDOC Received : 04 November 2018, Revised : 21 April 2019 Accepted : 21 May 2019, Online published : 10 February 2020