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12/05/2010
APEX Status: Instrument Performance, Operations and Product GenerationKoen Meuleman VITO, Mol, Belgium
APEX – Airborne Prism Experiment
12/05/2010 2© 2010, VITO NV
Airborne Prism EXperiment – APEX
» Background» The Instrument» Instrument Calibration» Processing and Archiving Facility» Measurements and Products» Conclusions
12/05/2010 4© 2010, VITO NV
Airborne Imaging SpectrometersGERIS, 1982AISAVIRIS
CASIDAIS7915ROSIS
SFSIHYDICEHYMAP
12/05/2010 7© 2010, VITO NV
Pushbroom Principle
12/05/2010 8© 2010, VITO NV
Image Cube
12/05/2010 10© 2010, VITO NV
Spectral Data Richness0.15
0.10
0.05
0.00
L s [W
/(m
2 sr
nm)]
24002200200018001600140012001000800600400Wavelength [nm]
0.15
0.10
0.05
0.000.15
0.10
0.05
0.000.15
0.10
0.05
0.00
Total Radiance at Sensor (MODTRAN 4)
Imaging Spectrometer (10 nm FWHM)
Landsat 7
SPOT 4
12/05/2010 11© 2010, VITO NV
APEX – Project Background» APEX is a joint Swiss/Belgian project funded by ESA PRODEX with support
from ESA Earth Observation.
» APEX is an airborne pushbroom dispersive spectrometer for the support and development of future spaceborne Earth Observation systems, supported by a Processing and Archiving Facility (PAF) and a Calibration Home Base (CHB).
» APEX is able to simulate, calibrate, and validate existing and planned spaceborne optical missions.
» APEX will foster the use of imaging spectrometer data and will support the application development for imaging spectroscopy products.
12/05/2010 12© 2010, VITO NV
Background1991 APEX was initiated by Klaus I. Itten, following the MacEurope campaign
1994 ESA identified as funding agency
1996 Belgium was asked to join the project , VITO joined the APEX team
1997 First APEX paper (Itten, K.I., Schaepman, M.E., De Vos, L., Hermans, L., Schlaepfer, H., & Droz, F. (1997). APEX - Airborne PRISM Experiment: A New Concept for an Airborne Imaging Spectrometer. In Third International Airborne Remote Sensing Conference and Exhibition (pp. 181-188). Copenhagen: ERIM)
1998 First instrument concept identified
2001 Phase A: Requirements, specifications, feasibility studies
2003 Phase B: Breadboarding activities (detectors, optical parts)
2006 Phase C/D: Critical Design Review
2007 … instrument prototype realized
2008 Spring: contamination due to cooling liquid leakage» Autumn: first tests at full system level, first test flight
2009 Acceptance flight campaign in June Performance assessment, acceptance procedures2010 SWIR detector failure: recovery action ongoing. New accpetance flights in June 2010
2011-2016 Phase E: Exploitation Operations
12/05/2010 13© 2010, VITO NV
Institutes Phase C/D
Industry Phase C/D
Delivery
Characterization &
Testing activities
Acceptance
Review 2Acceptance Flight Campaign FRR2
PAF End to End
Testing and Finalisation
Today
2009 2010
Phase E(5+5 years)
2011
Oct. 2010
SWIR detector replacement
FRR
Recovery action
System Tests
Test Flight
Supporting Industry Activities
AR
Performance
Assessment
Characterization
& Testing Activities
Performance
AssessmentSupporting Industry Activities
Acceptance Flight Campaign 2
Calibration and Characterisation
First Data delivery
APEX Schedule as of April 2010
12/05/2010 14© 2010, VITO NV
Airborne Prism EXperiment – APEX
» Project Background» The Instrument» Instrument Calibration» Processing and Archiving Facility» Measurements and Products» Conclusions
12/05/2010 15© 2010, VITO NV
Schaepman, M.E., Schläpfer, D., & Müller, A. (2002). Performance requirements for airborne imaging spectrometers. In M.R. Descour & S.S. Shen (Eds.), Imaging Spectrometry VII (pp. 23-31). San Diego: SPIE
APEX Performance Definition
12/05/2010 17© 2010, VITO NV
Schläpfer, D., & Schaepman, M.E. (2002). Modeling the noise equivalent radiance requirements of imaging spectrometers based on scientific applications. Applied Optics, 41, 5691-5701
APEX Performance Definition
12/05/2010 18© 2010, VITO NV
APEX PerformanceSpectral Performance VNIR SWIR Spectral Range 380.5 – 971.7 nm 941.2 – 2501.5 nm Spectral Bands Up to 334 (default: 114) 198 (number of VNIR spectral rows programmable via binning
pattern upload) Spectral Sampling Interval 0.5 ÷ 8 nm 5 ÷ 10 nm (default: 11 ÷ 8 nm) Spectral Resolution (FWHM) 0.6 ÷ 6.3 nm 6.2 ÷ 11 nm Spatial Performance Spatial Pixels (acrosstrack) 1000FOV 28° IFOV 0.028° (ca 0.5 mrad) Spatial Sampling Interval (across track) 1.75 m @ 3500 m AGL Sensor Characteristics Type CCD (Si) CMOS (HgCdTe) Dynamic Range 14 bit encoding 13 bit encoding Pixel Size 22.5 μm x 22.5 μm 30 μm x 30 μm Smile
Average, less than 0.35 pixel
Keystone (Frown) 0.35 pixel Co‐Registration 0.55 pixel Other Information Data Capacity 500 GB on SSDData Transfer Spectral frames 30 MB/s via Optical Link Housekeeping Data 20 kB/s via Serial Cable Data rate for default configuration 0.4 GB/km (1250 km max)
12/05/2010 19© 2010, VITO NV
APEX Optical Sub-Unit
VNIR Detector(380 -
1000 nm)
SWIR Detector(940 -
2500 nm)
SWIR Cryo-Cooler
Beam Splitter
(dycroic
layer)
Ground imager,
slit and spherical
mirror
Main CollimatorSWIR
OpticsVNIR
Optics
folding mirror
12/05/2010 20© 2010, VITO NV
HgCdTe CMOS from SOFRADIR (F)* •
hybridized on multiplexer,•
1024 x 256 square pixels (used: 1000x199)•
Pixel pitch 30 μm x 30 μm •
addressable readout, fast operation,•
Integrated in cryostat cooler assembly, •
wavelength range: 0.94 – 2.50 μm,•
QE: > 70 % average, Top. : 150 K•
13 bit encoding
CCD 55-30 from E2V Technologies (GB)» Frame transfer mode, » 1252 x 1152 pixels (used: 1000 x 335)» Pixel pitch 22.5 µm x 22.5 µm, » fill factor 100%,» Back illuminated,» Read out frequency 7 MS/s,» 14 bit encoding
Detector TechnologyDetector Technology
Dewar Cooler
Sapphire Window
Cold finger
Detector with Cryostat/Dewar Assembly
*custom development under ESA-EOP contract
12/05/2010 21© 2010, VITO NV
VNIR FWHM and Binning
12/05/2010 22© 2010, VITO NV
SWIR FWHM
12/05/2010 24© 2010, VITO NV
APEX Aircraft Installation
Thermal Control Unit (TCU)
Optical Subsystem Unit (OSU)
Stabilising Platform (Leica PAV30)
Environmental Thermal Control (ETC) Box
12/05/2010 25© 2010, VITO NV
Navigation Sub-System (Applanix POS/AV)
Main Control Computer (CSU)
Storage Unit (SSD and tape)
Operator’s Interface Flight Management System (FMS, TrackAir)
Power Distribution Unit
APEX Aircraft Installation
12/05/2010 26© 2010, VITO NV
SWIR Detector Failure
Failure of the SWIR detector in November 2009Root cause:Lost vacuum tightness detector dewar
Impact on sensor:- Operating temperature not reachable- Condensation on the detector housing- possible contamination of the HgCdTe matrix due to partial air content on the FPA
Impact on schedule: 5 months delay- Failure identification by Sofradir- Handling/substitution under French military regulations
- Partial sensor realignment- Instrument validation (characterization, calibration, flight validation) to be partially repeated
12/05/2010 27© 2010, VITO NV
System improvementsBy means of IFC, spectral and geometric performance have been traced back on differential pressure and environmental conditions
>> to avoid mechanical stress induced by pressure differences during flight maintaining a nitrogen environment, a new pressure regulation system is under implementation
>> to avoid thermo- mechanical stresses and condensation/frosting induced by the flight environment, the climate system effectectiveness of the ETC box must be increased
3D CAD model of the pressure regulator 3D CAD model of the pressure regulator to be integrated on the aircraftto be integrated on the aircraft
APEX Test 3 (04.11 - 04.11.2009)
-20.0
-10.0
0.0
10.0
20.0
30.0
40.0
50.0
0:00:00 1:12:00 2:24:00 3:36:00 4:48:00 6:00:00
ETC top/frontETC on STP levelMIP interface 3MIP interface 4MIP interface 6Inside baffleOutside baffleChamber
FEM model to investigate frosting/FEM model to investigate frosting/ condensation in flight conditionscondensation in flight conditions
Climate chamber tests of the new climate systemClimate chamber tests of the new climate system
12/05/2010 28© 2010, VITO NV
Airborne Prism EXperiment – APEX
» Project Background» The Instrument» Instrument Calibration» Processing and Archiving Facility» Measurements and Products» Conclusions
12/05/2010 30© 2010, VITO NV
APEX - Calibration Approaches
» CHB – Calibration Home Base (DLR Oberpfaffenhofen (GER))» Calibration and characterization activities are time consuming» A full spectral calibration for each pixel takes 110 measurements, each requiring
slight parameter adaptations (overall calibration matrix: 1000 x 534 pixels + temporal component)
» IFC – In-flight Characterization» Allowing reference measurements before and after each data take during flight
» Vicarious calibration activities» Field reference targets, also including directional characterization
Spectral Calibration for 1 pixel: 2’30”
Overall Laboratory session: 10 days
12/05/2010 31© 2010, VITO NV
The Calibration Home Base @ DLR München*
* Developed under ESA-EOP Contract; Status: Acceptance review successful in Jan. 2007
6 ton granite optical bench
APEX
Mono- chromatorCollimator
Folding mirror assembly
Relative radiometric calibration
1.6 m Integrating Sphere0.5 m Integrating Sphere
Seismic Platform (max displacement 0.3 um)
Absolute radiometric calibration
12/05/2010 32© 2010, VITO NV
In-Flight Characterization Facility
Stabilised IFC QTH lamp
Spectrometer optical path
Filter wheel
IFC light path (glass fiber)
Shutter for standard imaging operations
Entrance Baffle
Spectral filters:• 3 Bandpass (color) filters• 1 Rare Earth Material (NIST) filter• 1 Neutral Density (grey) filter
The IFC is a tool designed to investigate the overall instrument (radiometric, spectral, geometric) stability during flight.
liding mirror
12/05/2010 34© 2010, VITO NV
Airborne Prism EXperiment – APEX
» Project Background» The Instrument» Instrument Calibration» Processing and Archiving Facility» Measurements and Products» Conclusions
12/05/2010 35© 2010, VITO NV
Schematic APEX Processing Flow
Calibration ParametersCube
Calibration Coefficients Preparation
Level 0 ImageData DC Data
BIL2BSQ
Level 1CCalibrated ImageCubeBSQ/BIL
Linear Dark Current Correction
Smear correction
Bad Pixels replacement
SWIR
VNIR
SWIR
Spectral/Spatial Misregistration Resampling Process
Radiometric Calibration
VNIR VNIR/SWIR cube merging
Quality Layer Generation
CalibrationCoefficients
Flight data
Rad GainRad Offset
Across center WVL
Bad Pixels
HK Data
Spectral shiftmodelling
Post Calibration Destriping Module
Level 1CCalibrated, Destriped Image Cube
BSQ/BIL
QISP (Quality Indicator SPatial)
QIFR (Quality Indicator FRame)
Instrument modelProducts
12/05/2010 36© 2010, VITO NV
Processing and Archiving Facility (PAF)
InstrumentData Stream
APEX PAFLevel 0 - 1CProcessor
CalibratedImageCubes
Level 2A-2C Products
Level 3A-3B Products
Geolocated/AtmosphericallyCorrected cube
Level 1C Product
APEX PAFLevel 2A – 2CProcessor
Higher Order Products
APEX PAFLevel 3A – 3BProcessors
PAF Version Evolution
(HCRF-BRDF-BHR)
1 empirical BRDF
2 NBAR
3 DHR/BHR/BHRiso
PAF HW hosted @ VITO (Mol, B)PAF HW hosted @ VITO (Mol, B)
12/05/2010 39© 2010, VITO NV
Airborne Prism EXperiment – APEX
» Project Background» The Instrument» Instrument Calibration» Processing and Archiving Facility» Measurements and Products» Conclusions
12/05/2010 40© 2010, VITO NV
Target Areas
BelgiumBelgium
-- Sea coasts (Oostende)Sea coasts (Oostende)
-- Scheldt river (Antwerpen)Scheldt river (Antwerpen)
SwitzerlandSwitzerland
-- inland water (Lake Konstanz)inland water (Lake Konstanz)
-- urban area (Basel)urban area (Basel)
-- vegetation/crops (Vordemwald)vegetation/crops (Vordemwald)
-- mixed (Lmixed (Läägeren, Holderbank)geren, Holderbank)
APEX Acceptance Campaign 2009 – Similar in 2010
Flight Window: CW24Flight Window: CW24--26 26 (8(8--24 June 2009)24 June 2009)
-- Objective: Investigation of APEX performances in Objective: Investigation of APEX performances in view of ESA Final Acceptanceview of ESA Final Acceptance
-- Instrument responsibility and property: Industrial Instrument responsibility and property: Industrial PrimePrime
-- Base Airfield: DLR Base Airfield: DLR OberpfaffenhofenOberpfaffenhofen (D)(D)
-- Aircraft: DLR DoAircraft: DLR Do--228 D228 D--CFFUCFFU
-- Ground support: extensive vicarious calibration Ground support: extensive vicarious calibration campaigncampaign
12/05/2010 41© 2010, VITO NV
12/05/2010 42© 2010, VITO NV
12/05/2010 43© 2010, VITO NV
VIS
CIR
CHC cellulose hydrocarbon canopy structureTCARI/ OSAVIPRI photochemical reflectance index
12/05/2010 44© 2010, VITO NV
CABCDM CIRCWLAI
12/05/2010 45© 2010, VITO NV
Aircraft
» APEX is currently certified to fly on DLR’s DO- 228.
» Current activities are to certify APEX on several other platforms (CAE Aviation – Cessna; DLR Halo – Gulfstream; RUAG – DO-228NG; etc.).
» EUFAR – European Facility for Airborne Research offers aircraft and APEX within a EC FP7 project.
» Airworthiness certification costs per aircraft range from approx. 10 -100 kEUR depending on type and rules.
» Export licence rules apply for the operation of APEX in certain countries.
12/05/2010 46© 2010, VITO NV
Airborne Prism EXperiment – APEX
» Project Background» The Instrument» Instrument Calibration» Processing and Archiving Facility» Measurements and Products» Conclusions
12/05/2010 47© 2010, VITO NV
Conclusions
» APEX is scheduled to be finalized in September 2010.
» Preliminary flight data from 2009 are delivered to selected customers.
» APEX is currently undergoing a hardware upgrade and revision (exchange of SWIR detector, upgrade of flight management system, improvement of thermal and environmental stability, etc.).
» A full recalibration and acceptance test is scheduled for June 2010, including the coverage of a variety of test sites across Europe.
» A structured programme will be available 2011 onwards for APEX flights to interested parties.
.
12/05/2010 48© 2010, VITO NV
Perspectives
» APEX is the first airborne imaging spectrometer of ESA available to the user community from 2011 onwards.
» APEX will be operated by VITO & RSL on behlaf of ESA for 5 years.» RSL and VITO are cooperating during the exploitation phase of
APEX.
» National funding (B & CH) and operations will secure APEX operations in the first period.
» Interested parties or contact:» [email protected]» [email protected]
12/05/2010 49© 2010, VITO NV
APEX – Airborne Prism Experiment
Thank you for your attention!
© K. Meuleman, M.E. Schaepman, S. Adriaensen, M. Jehle, J. Bieseman, B. Bomans, A. Damm, F. Dell'Endice, P. D’Odorico, D. Raymaekers, A. Hueni, K. Itten, S. Kempanaers, Z. Malenovsky, Rezaei, F. Seidel, D. Schläpfer, S. Sterckx, J. Weyermann, 2010