Micro Hyperspectral Systems For UAVs If a picture is worth 1000 words, a hyperspectral image is worth almost 1000 pictures RSPSoc and NERC Cluster UAV Workshop University of Durham, 7-8 June 2011 Dr John P Ferguson Photonics & Analytical Marketing Ltd

TOPICS TO BE COVERED Headwall Photonics Explanation of Hyperspectral Imaging Some applications The Headwall Micro Hyperspec Imaging from UAVs

HEADWALL PHOTONICS INC 1976 - American Holographic, Inc. 2000 - Agilent Technologies acquisition 2003 – Headwall Photonics launched Currently 40 employees Factory in Fitchburg, Massachusetts, USA Producers of imaging spectrometers, OEM spectral engines, original holographic gratings

Applications of Headwall Technology Hyperspec V10 – Marine Ocean Buoy Project (MOBY) Hyperspec VS30 – NRL airborne requirement for remote sensing and ocean color monitoring Hyperspec VS15 – USAF airborne mine detection in littoral zones Hyperspec VS15 – USN Predator-based project for Project Warhorse Hyperspec VS15 – NRL Ocean PHILLS sensor Hyperspec VS15 – AFRL LWIR sensor for polarimetric sensing for battlefield surveillance Hyperspec VS25 – Selected by NASA for International Space Station deployment Hyperspec VS25 – First UAV deployment Hyperspec VS – Custom UV/MCP unit deployed for AFRL missile plume tracking Hyperspec VS50 – Airborne SWIR sensor Micro-Hyperspec VNIR and NIR – Introduced in 2006 for UAV and SUGV deployment Hyperspec-VNIR – NASA deployment for AVIRIS project augmentation Hyperspec-VNIR, Hyperspec-NIR, Hyperspec-SWIR – integrated instruments for commercial applications Micro-Hyperspec – UAV remote sensing

Applications of Headwall Hyperspectral Systems Space Piloted UAV Ground-based Handheld Small Satellite Multiple Platforms Base protection Reconnaissance

WHAT IS HYPERSPECTRAL IMAGING? Collection of high resolution spectral detail over a large spatial and broad wavelength region from within each pixels instantaneous field of view Also known as imaging spectroscopy, chemical sensing Chemical/spectral imaging within spatial dimension Many definitions Common requirement = > ~ 100 spectral bands No definition has explained spatial requirements

Example – Airborne remote sensing Image Source: BAE Systems

THE VISIBLE LIGHT SPECTRUM

What information can the spectrum tell us?

The type of building material used

The type of vegetation

The rock strata

The type of ground

How does it work?

AN OUTLINE OF HYPERSPECTRAL IMAGING

A TYPICAL SCENE

THE CAMERA’S VIEW

THE VIEW THROUGH A SLIT - PIXELS IN ROW 7

PIXELS IN ROW 11

PIXELS IN ROW 17

THE HYPERSPECTRAL DATA

CLOSER TO REALITY

A HYPERSPECTRAL DATA CUBE

Some technical stuff

Hyperspectral Design Options Prism-Grating-Prism Transmission-based grating system Aberration-Corrected Concentric All-reflective system Three reflective surfaces Headwall’s imager design optimized for … Imaging performance – Aberration-corrected Minimal stray light High signal-to-noise High dynamic range High spectral/spatial resolution Efficiency across total spectral range Deployment in harsh environments Ruggedized & durable Small, compact size Minimal thermal expansion

THE HEADWALL PATENTED SPECTROGRAPH DESIGN Attributes - Integrated spectrometer solution - High spectral/spatial resolution - Very tall image slit - Very low image distortion - Low stray light, high signal-to-noise Small package size Flight hardened no moving parts Entrance Slit Original holographic high efficiency convex grating Detector Plane

Hyperspec© Concentric Design Advantages - selection of concentric design … Extremely compact nature Image quality (spectral/spatial resolution) Superior aberration-correction characteristics Lower F number All reflective design Additionally, Headwall sensors offers additional benefits … Balanced spectral performance across range Lower stray light Tall image slits - Spectral & spatial performance off-axis Performance in lower VIS / blue region

THE SALES PITCH Key Imaging Spectrograph Risks: Fore-optics  Imaging Spectrograph  Detection Electronics Key Imaging Spectrograph Risks: Keystone (spatial distortion) Smile (spectral distortion) Vignette Scatter (transmissive materials, poor surface qualities, replicated optics) Stray Light (overfilled optics, secondary diffracted orders, inadequate baffeling) Chromatic Aberrations and Astigmatism Low Optical Dynamic Range

CAMERA CONSIDERATIONS Fore-optics  Imaging Spectrograph  Detection Electronics Key Detection Electronics Risks: Base chip dynamic range - pixel full well capacity / (dark current + read noise) A/D bit depth Pixel resolution (spatial and spectral) Spectral band sensitivity Readout speed Readout method Second order detection

Traditional Hyperspectral Imaging Deployments Remote Sensing Military/Defense Ocean Monitoring Surveillance Search & Rescue Geological Mapping Target Identification & Tracking Spectral Tagging Environmental Analysis Photos: Courtesy of NRL, Space Computer, BAE, General Atomics

Micro-Hyperspec™ for UAVs Design goals: Very small size, form factor Less than 1 lb pounds Excellent imaging and S/N performance Aberration-corrected optics Low-power CCD/CMOS sensor Modular for variety of input & detector options Spectral Ranges VNIR - 400-1000nm NIR - 900-1700nm

Micro-Hyperspec in Agriculture

Micro-Hyperspec for Airborne Turrets & Gimbals Fully integrated – sensor, GPS/INS, processor board Designed for integration into UAV turrets & gimbals Single attachment point

Micro-Hyperspec – Small Tier UAVs Mounting Options Tier 2 UAV Hyperspectral mounting options Micro-Hyperspec within Payload Bay Payload bay or forward turret

Micro-Hyperspec – Payload Bay Mounting Tier II UAV

Fiber-Optic-Downwelling Irradiance Sensor (FODIS) In-flight calibration of Hyperspec© sensor Fully reflective FODIS module allows frame-by-frame real-time tracking of the solar Irradiance allowing

High Efficiency Sensors Three spectral ranges – Ext VNIR (600-1700nm), NIR (900-1700nm), & SWIR (900– 2500nm) Extremely high optical efficiency Lightweight for airborne missions Athermal design for measurement accuracy and stability Tall image slit for wide field of view, swath path efficiency Custom designed fore-optics High Efficiency sensors offer peak efficiency greater than 90%, minimum 70%

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