APEX - Airborne Prism EXperiment

1. APEX - Airborne Prism EXperiment • Walter Debruyn • Vito/TAP • Boeretang 200 • B-2400 Mol • walter.debruyn@vito.be • http://www.apex-esa.org

2. Scope of APEX • APEX is a hyperspectral airborne simulator for the support and development of future hyperspectral spaceborne missions. • APEX will be able to • Simulate, • Calibrate, and • Validate • the planned European imaging spectrometer missions (ESA Land Mission, CHRIS/PROBA, MERIS/ENVISAT). • APEX will foster the use of imaging spectrometer data in Europe and will support the application development of imaging spectroscopy products. • APEX is the first European perspective of an imaging spectrometer covering the full solar reflected range.

3. Earth Explorer Mission(s) Technology Demonstrator Science Demonstrator & Data Simulator LSPIM (Phase A) Further advancement of the Land Mission CHRIS on PROBA New Land Mission Radiometric Transfer Standard (MERIS, CHRIS, etc.) APEX in the Context of ESA • Partial Simulation Capabilities Only

4. APEX Setup (Phase B) National Entities Institutes Industry Industrial Con- sultant Alcatel Space France Belgian PRODEX Office Co–Investigator Industrial Subcontr. DSS–OIP Belgium PRODEX Office Industrial Prime Alcatel Space Switzerland Principal Investigator Industrial Subcontr. SF Switzerland Swiss PRODEX Office Industrial Consultant DLR / DFD Germany Technical Directorate Earth Observation Scientific Consultancy Group (SCG) Swiss PRODEX Committee (PPK)

5. APEX Timeline 1/96 7/96 8/96 2/98 10/98 3/00 4/01(?) 6/03(?) 6/03 6/08 6/13 Pre–Phase A Phase A Phase B Feasibility Study of APIS and AMIRIS Phase C/D Feasibility Study of APEX and Critical Design Review (CCN2) Phase E Detail Specifica- tions and Breadboards Post–Phase E Hardware Construction and Implementation ESA Operation and Exploitation

6. APEX Optimization Scheme • Optimization Priorities • Signal to noise, • Transmission of optical design • Pushbroom principle • Minimizing noise of detectors and electronics • Spectral uniformity, • Coregistration of spectral channels and bands • Minimizing geometric abberation (‘frown’ and ‘smile’) • Stability, and • Pressure/temperature controlled environment • Pre and post flight on board calibration • Repeatability. • Laboratory and vicarious calibration • Navigational system (Positional and attitude recording system)

7. APEX Specifications (1 of 2) • Parameter Requirement • Field of View (FOV) ± 14 deg • Instantaneous Field of View (IFOV) 0.5 mrad • Flight altitude 4,000 - 10,000 m.a.s.l. (7,500 m nominal) • Spectral channels VIS/NIR: 124; SWIR: 176 • Spectral range 400 – 2500 nm • Spectral sampling interval 600 – 780 nm: < 5 nm400 – 600 nm and 780 – 1050 nm: < 10 nm; optimized for SNR • 1050 – 2500 nm: < 10 nm • Spectral sampling width < 1.5 * Spectral sampling interval • Center wavelength accuracy < 0.2 nm • Spectral sampling width accuracy < 0.02 * Spectral sampling width • PSF (Point Spread Function) PSF  1.75 * IFOV • Smile < 0.1 pixel • Frown < 0.1 pixel

8. APEX Specifications (2 of 2) • Parameter Requirement • Bad pixels None (requirement after electronics) • Scanning mechanism Pushbroom • Absolute radiometric calibration accuracy 2% • Storage capacity on board (online) > 50 GByte • Dynamic Range 16 bit • Positional knowledge 20% of the ground pixel size (DGPS required) • Attitude knowledge 20% of IFOV (accelerometers, gyros, inertial navigation system required) • Navigation system, flight line repeatability ± 5% of FOV • Positional and attitude data Recording of data onto a housekeeping channel • Reliability 99 % successful data acquisitions for all flights during each year of operation • Optical head dimensions Must fit in standard mount

9. Signal To Noise Levels

10. Simulated APEX Spectral Response

11. APEX - Airborne Prism Experiment

12. APEX Blockdiagram Processing and Archiving Facility Data storage Pre-processing Processing Data Distribution

13. APEX raw data simulation • Simulated raw sensor data as acquired by the APEX system, including dark current and internal integrating sphere measurements. This cube contains all data acquired for one imaging section (simulation based on HYMAP measurements).

14. atmospheric and radiometric correction The PAF Processing Levels in-flight auxiliary data data download and segregation laboratory and in-flight calibration data Level 0B system correction calibration DEM, flightpath Level 1D orthorectification linking parameters: meteorological measurements Level 2A view angle, view distance, terrain height Level 2B/C application processing Level 3

15. APEX (near) future • Phase C/D operational organization • Scientific Team : RSL • Operations Team : Vito • 2000 : Calibration test site studied : HYMAP and CASI flight campaigns • 2001: AVIRIS flight campaigns throughout Europe (ESA initiative, Vito operations)

16. APEX Outlook • Completing the - instrument - processing and archiving facility - calibration home base in Spring 2003 is achievable • Additional ESA study (detectors, calibration) [institutes]and breadboarding of critical components [industry]are ongoing • Hardware construction and implementation (phase C/D) will start ASAP