CHII, 15-16 June 2016, Graz, Austria

Michael Rast, ESA

ESA's activities in space-borne

Imaging Spectroscopy for Earth

Observation

Observation Principle of Imaging Spectrometer

• The telescope images the ground scene on

the entrance slit

• The slit projection on ground defines the

swath width in across-track (ACT) direction

• The light is spectrally dispersed by a

diffraction grating and imaged onto a 2D

array detector

• Detector pixels represent image elements

sampled spatially in the ACT and spectrally

in the ALT

• Satellite motion during integration time

provides spatial sampling in along-track

(ALT) direction

Telescope

Slit

Collimator

Grating

Imager

2D detector

x

Spectral radiance

l

l

Spectral channels

Three-dimensional

hypercube

• Three-dimensional hypercube is assembled

by “stacking” two-dimensional spatial images,

each corresponding to a particular narrow

spectra channel

Courtesy R.Green, JPL

Future spaceborne imaging spectroscopy EO

missions – Launch and life time

ESA

28 29 30

EnMAP

PRISMA

HISUI / ISS

GISAT

FLORIS

Sentinel-3A

Shalom

CCRSS

Resurs-P No.4

Resurs-P No.5

ECOSTRESS

HySpecIQ

CartoSat-3

HYPXIM-P

2000 01 02

University of Hawaii, USA

Roscosmos, Russia

Sentinel-2A

… 14 15 16 17 18 19 20

HiakaSat

Resurs-P No.3

21 22 23 24 25 26 27

China

Roscosmos, Russia

ASI, Italy

ISRO, India

Roscosmos, Russia

JPL, USA

HySpecIQ/ Boeing, USA

ISRO, India

DLR, Germany

JAXA, Japan

ASI, Italy/ISA, Israel

ESA, UK

CNES, France

NASA/JPL, USA

DLR, Germany/ Teledyne, USA DESIS

HyspIRI

ESA Earth Observation Programmes

1980

1990

2000

2010

2020

sentinel-1

sentinel-2

sentinel-3

sentinel-5p

sentinel-4

sentinel-5

sentinel-6 jason-cs

envisat

earthcare

ers-1 ers-2

goce smos

cryosat swarm

biomass

flex

adm-aeolus

msg-1

meteosat-1

meteosat-2

meteosat-4

meteosat-3

meteosat-5

meteosat-6

msg-2 metop-a

metop-c

metop-b

msg-4

msg-3

metop-sg mtg-i

mtg-s

meteosat-7

Imaging spectrometer

Slide 5 IPD-HO-ESA-516 FLEX - J.-L. Bézy - ESA Space Technology Workshop, 14 APR 2016

Imaging Spectrometers in ESA E.O. Missions

dl:1.5-10 nm Radiom. Error ≈1 %

dl:0.1-0.5 nm Radiom. Error ≈ 0.1 %

(2021 -)

Earth Explorer 8: FLEX Mission Objectives

by direct measurements of vegetation fluorescence at

relevant spatial scales

FLEX will quantify actual photosynthetic activity of terrestrial ecosystems

FLEX will provide physiological indicators for vegetation health status

O2A O2B

Fluorescence Signal

The FLEX mission will accommodate an imaging spectrometer with a very high spectral-resolution (0.1 nm), to measure fluorescence within two oxygen bands, a second spectrometer to derive additional atmosphere and vegetation parameters

FLEX Mission: provide fluorescence emitted with 10% accuracy

FLEX: Low and High Resolution Spectrometers

FLEX/Sentinel-3 Formation Flying for Vegetation Health

/ FLEX FLEX: Global estimates of the actual

photosynthetic activity at the field scale

Pests

Elevated CO2

Salinity

Insecticides

Herbicides

Nutrient deficit

Pollutants

Acid rain

UV

Ozone

High light

Heat

Freezing Chilling Water deficit

Photosynthetic Strain

Weeds

Heavy metal

toxicity

FLEX Driving Observation Requirements

Requirement Specification Comment

Swath width 150 km Optical design

Spatial Sampling Distance 300 m Same as OLCI

Spectral band coverage 500 nm – 780 nm

Spectral Resolution 0.3 nm (HR) – 2 nm (LR) HR: High Resolution

LR: Low Resolution

Spectral Sampling 0.1 nm (HR) – 0.65 nm (LR)

ISRF knowledge 1% Stable opto/mechanical concept

On ground characterisation

Signal to noise ratio > 115 at 761 nm

Pupil size (80 mm), mass and

volume

Efficient detector & gratings

Straylight sensitivity 1% (Level 0)

Low roughness of optical surface

Low level of PAC Contamination

On ground characterisation

Spectral co-registration <0.1 SSI Good optical design with low smile

and keystone

Accurate alignment of detector Spatial co-registration <0.1 SSD

Absolute radiometric

accuracy 5 %

On board calibration device

On ground characterisation

Polarisation sensitivity < 1% Polarisation Scrambler

Enabling “Technology” for Imaging spectrometer

• Large 2D detectors

• Gratings with high efficiency, low sensitivity to

polarisation and low straylight level

• Optics with low level of straylight

Low surface roughness

Low PAC contamination level

• Spectrometer slit (planar or 1D homogenizer)

• Efficient polarisation scrambler

• Accurate on ground calibration (straylight, spectral

response function)

Imaging Spectrometers in Future EO Programme

Operational European carbon

dioxide (CO2) mission

Earth Explorer 9

• 31 letters of intent received

• 9 missions proposed with

imaging spectrometer

International Cooperation

EnMAP Flight Model on Ground Support Equipment Sept. 2015

NASA CWIS F/1.8 VSWIR Imaging Spectrometer

Technology development – way forward

Imaging spectrometers for future E.O. missions are relying on cutting-

edge technology

Technology development shall not only address key instrument components (detectors, gratings, ..) but also efficient OGSE for on-ground calibration

Enabling technology for future imaging spectrometers have been well

captured in the TRP 2016-2017 Work Plan

Straylight characterisation

Straylight characterisation

ISRF characterisation

Straylight mitigation

Straylight mitigation

Large format detector for (e.g.) CO2 mission

Images can raise many questions spectra can answer them -Rob Green

Conclusion

Thank you for your attention