Small Target Detection Techniques

The present times are trying times for any nation and army. The threat from non state actors’ is all pervading and requires preparations in order to meet the security challenges. These elements make use of unconventional techniques and medium to challenge the authority of the state and cause damage to innocent civilian and vital state assets. The challenge from sea and infiltration by small groups is omnipresent and needs to be tackled at the national level. Thus there is a requirement to enhance our technological knowhow pertaining to the small target detection techniques. The topic for contemplation in Radar community is a recent addition and poses a challenge to all concerned especially in the scientific community.

The technique for small target detection is of vital importance both in war and peace times. In addition to the threats mentioned above, in conventional wars, the UAVs of all hue with smaller and smaller sizes are making the battlefield challenging and more versatile. It is challenging because a nano UAV can simply hover 500 m near strategic radar and jam it without the knowledge of any other radar deployed to detect any such intrusion. In the 9^th International Radar Symposium held at Bangalore the technique of small target detection was discussed and the various issues connected with it were brought to the knowledge of the concerned people. The size of the target gives a technological challenge to the engineers and scientists. The size of the target being a small UAV or a small boat is such that it practically merges with the clutter that normal Radar comes across as the biggest challenge since the separation of the chaff from the wheat only can help in combating the threat. Since the very nature of the target is such ,the conventional radar technology is not geared to tackle it. If this be so in order to manage an active border and coast running into thousands of kilometer requires mastering of this technology.

The latest technology which is taking baby steps in this regard involves the ‘Track before Detect Algorithms’. These Algorithms are capable of detecting targets at lower Signal to Noise Ratio. Even this is also highly non linear in view of the size and the clutter available on the radar screen. The answer to this phenomenon is the birth of Particle Filters. These themselves are in very nascent stage and are going to take time to evolve. These Particle filters are capable of taking sample of these signals and the images of the echoes are computed in order to track the intruder and detect it.  In view of the prevailing scenario and the size of the intruder it is important that scan integration and correlation techniques are employed for coastal and land border management .

Similarly the challenge posed by these threats also entails distributed Sensor deployment in order to ensure that any intrusion by air, land or sea is handled immediately before the intruder can cause harm to the nation. The distributed sensor deployment will entail viewing the target from various aspect angles in order to arrive at the correct   location and multiple sensors ensuring total coverage. The netted radars will provide a wall of defence against such intrusions. This will have the inherent advantage of mono static and bi static radars setup in multiple locations to handle the small targets intruding in the borders and coastlines.

Thus there is a need to develop this technology and also  gradually deploy these radars to detect intrusion by small targets, it demands full attention from the technologist and planners. The developments of UAVs to detect enemy activities have another aspect of the enemy using advanced technology to defeat of own systems. The recent trend of small target detection and particle filters needs to be followed up in right earnest in order to build potent platforms for meeting the challenges posed by the small targets in the present scenario.

Lt Col Rajiv Tewari is posted at LRDE,DRDO,Bangalore

Views expressed are personal