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:» Koen.Meuleman@vito.be» Michael.Schaepman@geo.uzh.ch

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