Long-wave infrared imaging spectroscopy from small satellite and UAV platformsRobert Wright, Paul Lucey, Sarah Crites, Mark Wood, Harold Garbeil, Eric Pilger

Hawai'i Institute of Geophysics and Planetology, University of Hawai'i at Mānoa

Overview• Thermal infrared (3-5 µm

and 8-14 µm) imagingspectroscopy allows you toquantify the chemicalcomposition of solid andgaseous targets remotely, aswell as their thermo-physical characteristics

• Imaging interferometry hasthe potential to characterizethese targets at highspectral resolution, withhigh signal-to-noise

• HIGP has active programsaimed at making suchremote sensing instrumentssmall enough, light enough,and with low enough powerrequirements, to be flownon micro-satellites and UAVs

Methane leak, Los Angeles Dust cloud, Iraq

HIGP-developed TIRCIS instrument

CH4SiO2

• HIGP designs, builds and tests thermal infrared imaging spectrometers, with a focus on high spectral resolution and high sensitivity (signal-to-noise)

• In line with the growing importance of small satellites and UAV platforms, these instruments are designed to be compact, low mass, with modest power requirements

• To satisfy these (seemingly) mutually exclusive goals we have focused on two key technologies:

• Uncooled microbolometer detector arrays to detecting the light• An Interferometric approach to resolving the spectral composition of the light

Small-sat/UAV compatible sensors built at HIGP

Thermal Infrared Compact Imaging Spectrometer (TIRCIS)

Space Ultra-Compact Hyperspectral Imager (SUCHI)

Thermal Hyperspectral Imager (THI)

Thermal Infra-Red Compact Imaging Spectrometer(TIRCIS)

• Funded by NASA (2014-2017)• Goal is to design, build and test a prototype

for a small-satellite compliant thermal infrared imaging spectrometer

• Advance from TRL 4 to TRL 6

Calibration

Uncooled microbolometer

Fabry-Perot interferometer

Lenses

Spectral imaging using a Fabry-Perot interferometer

Interferometer

Uncooled microbolometer

Primary radiometric calibration

Secondary radiometric calibration

and flat-field correction

Lenses

Electronics

Structure

TIRCIS instrument design

2.4 kg

0.2 kg

TIRCIS spatial resolution: 120 m ground resolution from 500 km

i) Interferometer #1 = 44 cm-1 ~ 15 samples between 8-14 µmii) Interferometer #2 = 8.7 cm-1 ~60 samples between 8-14 µmiii) Interferometer #3 = 6.5 cm-1 ~90 samples between 8-14 µm

0.1 kg

TIRCIS spectral resolution: 15 to 90 wavebands between 8-14 µm

Wedge angle equates to samples in the interferogram

5 mrad slope = 44 cm-1 15 mrad slope = 8.7 cm-1

TIRCIS structure: stress and deformation

StressMaximum = 5000 psi (yield strength of material = 8000 psi)

DeformationMaximum displacement = 0.05 mm (primary calibrator) and 0.02

mm for optical elements (camera)

Mode shape 1: 222.98 Hz Mode shape 2: 352.48 Hz

ASD vs frequency for 55 kg micro-satellite(derived from NASA GEVS-SE, RevA, 1996)

TIRCIS performance model: signal-to-noise predictions

Two 8” aperture NIST-traceable blackbody calibration standards (-40 °C to 120 °C)

Instrument test facilities: blackbody standards

Instrument test facilities: collimator/target projector

Collimator, target projector (with spectral calibration capability)

Instrument test facilities: high resolution FTIR spectrometer

Design and Prototypes Model 102 FTIR spectrometer• 4 cm-1 spectral resolution• 2-14 µm spectral range

120 m GRE from 500 km60 channels (8-14 µm)SNR ~200-400:1Mass = 5 kgPeak power = 20 WDimensions = 28 cm × 36 cm × 56 cm

TIRCIS instrument summary

Space Ultra-Compact Hyperspectral Imager (SUCHI)

• Design funded by NASA (2010-2014)• Goal was to design, build and test a flight

unit for a thermal infrared imaging spectrometer, as the primary payload for the ORS-4 mission

SUCHI instrument design

Onboard calibration shutters

Sealed vessel houses non-space-qualified components

SUCHI electronics, designed and fabricated in house

SUCHI in the cleanrooms

SUCHI undergoing vibration testing

Thermal-Vacuum test chamber

SUCHI undergoing T-VAC testing

SUCHI instrument summary

250 m GRE from 500 km20 channels (8-14 µm)SNR ~200-400:1Mass = 10 kgPeak power = 7 WDimensions = 10 cm × 11 cm × 36 cm

SUCHI was launched onboard ORS-4 in October 2015

Thermal Hyperspectral Imager (THI)

Calibrated gas measurements with THI

Field gas measurements with THI

• HIGP designs, builds and tests thermal infrared imaging spectrometers, with a focus on high spectral resolution and high sensitivity (signal-to-noise)

• In line with the growing importance of small satellites and UAV platforms, these instruments are designed to be compact, low mass, and with modest power requirements

• HIGP has facilities to design, fabricate and test the instruments in house

Thermal Infrared Compact Imaging Spectrometer (TIRCIS)

Space Ultra-Compact Hyperspectral Imager (SUCHI)

Thermal Hyperspectral Imager (THI)

Summary