ESA's activities in space-borne Imaging Spectroscopy for Earth Observation CHII, June 2016, Graz, Austria

Transcription

1 ESA's activities in space-borne Imaging Spectroscopy for Earth Observation CHII, June 2016, Graz, Austria Michael Rast, ESA

2 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 Spectral radiance l x l 2D detector Imager Grating Collimator Slit Telescope Satellite motion during integration time provides spatial sampling in along-track (ALT) direction Three-dimensional hypercube is assembled by stacking two-dimensional spatial images, each corresponding to a particular narrow spectra channel Threedimensional hypercube Spectral channels

3 Courtesy R.Green, JPL

4 Future spaceborne imaging spectroscopy EO missions Launch and life time University of Hawaii, USA Roscosmos, Russia DLR, Germany/ Teledyne, USA 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 ESA HiakaSat Resurs-P No.3 CCRSS DESIS Resurs-P No.4 PRISMA Sentinel-2A GISAT Resurs-P No.5 ECOSTRESS HySpecIQ CartoSat-3 Sentinel-3A EnMAP HISUI / ISS Shalom FLORIS HyspIRI HYPXIM-P

5 ESA Earth Observation Programmes Imaging spectrometer meteosat meteosat-3 meteosat-4 meteosat-2 meteosat mtg-s meteosat mtg-i meteosat-7 ers-1 ers-2 msg-1 msg-2 msg-3 msg-4 metop-sg metop-a metop-b metop-c envisat goce cryosat biomass flex smos swarm earthcare adm-aeolus sentinel-1 sentinel-2 sentinel-3 sentinel-5p sentinel-5 sentinel-4 sentinel-6 jason-cs IPD-HO-ESA-516 FLEX - J.-L. Bézy - ESA Space Technology Workshop, 14 APR 2016 Slide 5

6 Imaging Spectrometers in ESA E.O. Missions dl: nm Radiom. Error 1 % (2021 -) dl: nm Radiom. Error 0.1 %

7 Earth Explorer 8: FLEX Mission Objectives FLEX will quantify actual photosynthetic activity of terrestrial ecosystems FLEX will provide physiological indicators for vegetation health status by direct measurements of vegetation fluorescence at relevant spatial scales

8 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 O 2 B O 2 A FLEX Mission: provide fluorescence emitted with 10% accuracy

9 FLEX: Low and High Resolution Spectrometers

10 FLEX/Sentinel-3 Formation Flying for Vegetation Health Water deficit Freezing Chilling Heat Nutrient deficit Salinity Pests Elevated CO2 Photosynthetic Strain Weeds / FLEX Herbicides Pollutants Insecticides Acid rain FLEX: Global estimates of the actual photosynthetic activity at the field scale UV Heavy metal toxicity Ozone High light

11 FLEX Driving Observation Requirements Requirement Specification Comment Swath width 150 km Optical design Spatial Sampling Distance 300 m Same as OLCI Spectral band coverage Spectral Resolution Spectral Sampling 500 nm 780 nm 0.3 nm (HR) 2 nm (LR) 0.1 nm (HR) 0.65 nm (LR) ISRF knowledge 1% Signal to noise ratio > 115 at 761 nm Straylight sensitivity 1% (Level 0) HR: High Resolution LR: Low Resolution Stable opto/mechanical concept On ground characterisation Pupil size (80 mm), mass and volume Efficient detector & gratings 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 Spatial co-registration <0.1 SSD and keystone Accurate alignment of detector Absolute radiometric On board calibration device 5 % accuracy On ground characterisation Polarisation sensitivity < 1% Polarisation Scrambler

12 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)

13 Imaging Spectrometers in Future EO Programme Operational European carbon dioxide (CO 2 ) mission Earth Explorer 9 31 letters of intent received 9 missions proposed with imaging spectrometer

14 International Cooperation NASA CWIS F/1.8 VSWIR Imaging Spectrometer EnMAP Flight Model on Ground Support Equipment Sept. 2015

15 Technology development way forward Imaging spectrometers for future E.O. missions are relying on cuttingedge technology Technology development shall not only address key instrument components (detectors, gratings,..) but also efficient OGSE for onground calibration Enabling technology for future imaging spectrometers have been well captured in the TRP Work Plan Straylight characterisation ISRF characterisation Straylight characterisation Straylight mitigation Straylight mitigation Large format detector for (e.g.) CO2 mission

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

17 Conclusion Thank you for your attention