A novel hyperspectral imager based on microslice technology A novel hyperspectral imager based on microslice technology Ray Sharples, Danny Donoghue, Robert Content Colin Dunlop, David Nandi, Gordon Talbot Durham University UAV Workshop 7 th July 2011

Outline of Presentation Background Background Methods for simultaneous 3D spectroscopy Methods for simultaneous 3D spectroscopy Operating principles of a microslice hyperspectral imager Operating principles of a microslice hyperspectral imager First laboratory results from a CEOI- funded prototype sensor First laboratory results from a CEOI- funded prototype sensor Future Plans Future Plans

Project Background TelescopefocusSpectrographinput Lensletarray Fibrearray Imageslicer 1234 Both designs maximise the spectrum length and allows more efficient utilisation of detector surface. Only the image slicer retains spatial information within each slice/sample  high information density in datacube Overlaps must be avoided  less information density in datacube Spectrographoutput slit Fibres Pupil imagery slit Micro- mirrors x y Datacube Divides the field in two dimensions

Project Background

Fully exploit modern large-format 2D detectors to obtain faster survey speeds. Longer exposures in stare-mode to allow higher SNR in finer pixels for radiometry, meteorology & and atmospheric composition studies - particularly important for low reflectivity targets such as water, forestry and shallow marine environments. Enable smaller, more compact devices than other comparable platforms. Compact designs using state-of-the-art sensors to reduce mass/volume requirements. Step-change in the imagery available to assist in meeting NERC targets for Earth observation with applications in many areas: not in the least vegetation, geology and pollution monitoring. CEOI Seedcorn Project: budget £50k. A New Approach to Hyperspectral Imaging V km/sec xx Dwell time =  x/V

Instrument Concept: Microslice IFU

Instrument Layout CEOI Mid-Term Review Meeting 12 Jan 2011 Pick-off mirror Collimator Image slicer Fore-optics GRISM Camera Baseplate (cover omitted) Dimensions 33 cm x 15 cm x 12 cm Mass ~5 kg (excl baseplate)

Hyperspectral Imaging Using Microslice Technologies Novel application of microlens resampling optics to deliver unprecedented field-of-view sampling over multiple spectral channels simultaneously. Addresses current spectral resolution and sensitivity limitations with available airborne/spaceborne instruments. Enables high spectral resolution observations to characterise and quantify ecosystem and land/water surface properties. Allows spectral fingerprinting to be scaled up to address whole Earth system processes.

Prototype Microslice Spectrograph NERC Centre for Earth Observation Instrumentation Seedcorn Project started April x 20 “spaxels” (spatial pixels each giving a spectrum) so 6,600 spectra. Spectra 180 pixels long Resolution of 5-7 nm (slice images 3 pixel wide) over 400 nm to 700nm Dimensions 33 cm x 15 cm x 12 cm

Microslicer Assembly

Microslice Optical Performance

Foveon CCD

Flatfield Performance nm

Spectral Performance H beta H alpha Hg

Application Tests Lab set up Microslicer & ASD FieldSpec Pro Objectives: – Test spectral resolution – Test signal / noise ratio – Ability to extract spectra – Use Spectralon standard

Calibration and Testing

565 nm Fagus sylvatica leaf Calibration and Testing Source: David Nandi

Extracting spectra from datacube Source: David Nandi

Advantages of Microslice Hyperspectral Imagers Rapid survey speeds with options for multiple viewing geometries. High spatial resolution with no limitations due to scanning speed on a single overpass as with pushbroom techniques. High spectral and spatial resolutions. Longer exposures in stare-mode to allow higher SNR in finer pixels for radiometry, meteorology and atmospheric composition studies. Signal strength is also particularly important for low reflectivity targets such as water and shallow marine environments. Compact design using state-of-the-art sensors to reduce mass/volume requirements.

Summary Knowledge transfer from astronomy to remote sensing is opening up new concepts for hyperspectral imaging of the environment. Extreme multiplex microslice technologies offer a new approach to obtain high spatial and spectral resolution simultaneously over a 2D FoV. The use of step and stare modes offer the potential for 2-3 orders of magnitude increase in S/N compared with pushbroom or whiskbroom approaches and also allows monitoring of time-dependent processes. Further Details: Prof. Ray Sharples - Prof. Danny Donoghue -