Modern Radar Technology for Efficient Detection of Landmines and UXO M. Peichl, E. Schreiber, A. Heinzel, S. Dill DLR, Microwaves and Radar Institute Oberpfaffenhofen, Germany

Colloquium „Improvised explosive devices and antipersonnel mines meeting the challenges“ RMA, Brussels, Belgium, 17 May 2016

Overview

Motivation / EU FP7 Project TIRAMISU

Theoretical considerations

Radar sensor TIRAMI-SAR

Proof of concept

Lessons learned

Mine/UXO clearance still a challenging problem.

Hence EU FP7 project TIRAMISU. Global goal: Provide a comprehensive

toolbox addressing the problem in all facets.

Project runtime: 01.01.2012 – 31.12.2015.

Example mine clearance in Cambodia

http://fp7-tiramisu.eu/

Motivation / EU FP7 Project TIRAMISU

http://fp7-tiramisu.eu/

3 main topics: o Planning tools – locate and define contaminated areas. o Tools for detection and clearance – neutralize threats and safe lives if operators. o Tools for training and education on risks.

26 partners from all over Europe + various consulting institutions. Main topics divide in 10 modules, one being close-in detection. Sensors Radars, Metal detectors, Prodders, chemical vapor sensors. DLR contribution – Large-area sensing synthetic aperture radar

TIRAMI-SAR.

Motivation / EU FP7 Project TIRAMISU

State of the art / improvement

Complexity of landmine/UXO problem makes close-in detection mandatory.

Many detection approaches exist, e.g. metal detectors MD, dogs, imaging sensors IR/GPR, chemical analyzers CA, spectroscopy SP – carried manually, on vehicles, on robots, airborne, …

Mostly they are slow and have to come very close to the contaminated area.

Detection preferably from stand-off – safe distance to dangerous area.

Requirement on scanning reliably large areas in short time.

Confirmation of detections by use of other sensors, e.g. MD, GPR, CA, SP, …

Synthetic Aperture Radar (SAR)

Sensor

Safe area Contaminated area

Large scan area

Suspicious objects

Radar reflection measurement

TX RX

Object

Radar principle

Material properties

ε1 µ1 Z1

ε2 µ2 Z2

Material transition

𝑟𝑟 = 𝑍𝑍1 − 𝑍𝑍2𝑍𝑍1 + 𝑍𝑍2

Z0 Z1

Z2

𝑟𝑟 = 𝑟𝑟(𝑥𝑥,𝑦𝑦, 𝑓𝑓,Θ, 𝑝𝑝) Material scanning

Electric ε, Magnetic µ, Impedance Z.

Partial reflection r,

Scattering.

Frequency f, Incidence angle Θ, Polarization p.

x

y

z

Requirements – special features

Sufficient penetration into soil.

Sufficient spatial resolution.

Discrimination of targets from background (soil, vegetation, etc.).

Stand-off / side-looking perspective.

In-situ imaging of large scenes.

Synthetic Aperture Radar – SAR

Sufficient spatial resolution <10 cm.

Stand-off / side-looking perspective ∼ 45° average incidence angle, few meters to target area.

In-situ imaging of large scenes swath width around 5 m, length 5…X m.

TIRAMI-SAR concept

Realized TIRAMI-SAR

TIRAMI-SAR at DOVO/SEDEE Bandwidth: 0.5 – 3 GHz Range res.: 5 - 10 cm in air Crossrange res.: 5 - 10 cm in air FoV: 5 m x 10 m (50 m² in 3 min) Channels: Independent 2 Tx and 4 Rx Tx mode: Arbitrary waveforms possible (12 Gs/s) Rx Mode: Sampling in time domain – full bandwidth at once (8 Gs/s) Polarisation: HH/VV/HV Processing: Coherent/Incoherent 3D imaging / interferometry

Proof of concept

Corner reflectors

DLR test area sand box along a rail track

SAR image – recorded by TIRAMI-SAR mounted on a rail trolley. All targets can be clearly detected, although background echoes (clutter).

Corner reflectors

Grass clutter

Sand clutter

Conclusions / lessons learned

Efficient detection of landmines/UXO still is a complex and challenging problem: Number and multitude of threat types. Time consuming and dangerous methods.

SAR appears to be a suitable tool to face such problems:

Scanning large areas in short time (e.g. 100 m2 in few minutes).

Multi-static und polarimetric sensing approach for clutter suppression is mandatory.

Diverse processing/visualization approaches useful.

TIRAMI-SAR is a valuable experimental platform. Potential yet still not fully exploited. Continuation of work is in progress.