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

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

5. APEX Timeline Pre–Phase A Phase A Phase B Phase C/D Phase E Post–Phase E Feasibility Study of APIS and AMIRIS 1/967/968/962/9810/983/004/01(?)6/03(?)6/036/086/13 Feasibility Study of APEX and Critical Design Review (CCN2) Detail Specifica- tions and Breadboards 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) ParameterRequirement Field of View (FOV)± 14 deg Instantaneous Field of View (IFOV)0.5 mrad Flight altitude4,000 - 10,000 m.a.s.l. (7,500 m nominal) Spectral channelsVIS/NIR: 124; SWIR: 176 Spectral range400 – 2500 nm Spectral sampling interval600 – 780 nm: < 5 nm 400 – 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) ParameterRequirement Bad pixelsNone (requirement after electronics) Scanning mechanismPushbroom Absolute radiometric calibration accuracy 2% Storage capacity on board (online)> 50 GByte Dynamic Range16 bit Positional knowledge20% of the ground pixel size (DGPS required) Attitude knowledge20% of IFOV (accelerometers, gyros, inertial navigation system required) Navigation system, flight line repeatability± 5% of FOV Positional and attitude dataRecording of data onto a housekeeping channel Reliability99 % successful data acquisitions for all flights during each year of operation Optical head dimensionsMust 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. The PAF Processing Levels data download and segregation Level 2B/C orthorectification system correction calibration linking parameters: view angle, view distance, terrain height atmospheric and radiometric correction Level 1D Level 2A Level 0B Level 3 laboratory and in-flight calibration data in-flight auxiliary data DEM, flightpath meteorological measurements application processing

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