Plants emit a faint glow during photosynthesis — a signal known as Sun-Induced Fluorescence (SIF). This signal, invisible to the naked eye, carries critical information about plant health, water stress, and carbon assimilation.
ESA's FLEX mission will capture this signal from orbit for the first time in history, enabling global monitoring of vegetation photosynthetic activity at 300 m resolution.
SpaFLEX-Exp maximises the scientific return of this landmark mission. Our consortium links the systematic implementation of Cal/Val protocols directly to the development of novel Level 2 and advanced Level 3/4 FLEX products for Earth system applications — from agriculture and water management to biodiversity conservation and climate modelling.
Spain offers unique advantages: high solar irradiance, stable atmospheric conditions, and a diverse range of ecosystems from Mediterranean wetlands to mountain forests and semi-arid shrublands.
// OVERALL OBJECTIVE
"Maximize the scientific return of the FLEX mission by linking the systematic implementation of Cal/Val protocols directly to the development of novel L2 and advanced L3/L4 FLEX products for Earth system applications."
SpaFLEX-Exp Consortium — 2024
// OVERALL OBJECTIVE
"Maximize the scientific return of the FLEX mission by linking the systematic implementation of Cal/Val protocols directly to the development of novel L2 and advanced L3/L4 FLEX products for Earth system applications."
SpaFLEX-Exp Consortium — 2024
02 - Why does it matter?
The Flex
Mission
ESA's FLuorescence EXplorer (FLEX) mission, flying in tandem with Sentinel-3, will revolutionise our ability to monitor the health and productivity of Earth's vegetation. Scheduled for launch in September 2026, it is the first satellite specifically designed to measure Sun-Induced Fluorescence from space at high spectral resolution.
MISSION
FLEX-S3
ESA Earth Explorer flying in tandem orbit with Sentinel-3
LAUNCH
2026
Scheduled September 2026, tandem orbit configuration
KEY VARIABLE
SIF
Sun-Induced Fluorescence — first global space measurement in history
RESOLUTION
300m
Global vegetation fluorescence and reflectance coverage
PRODUCTS
L2–L4
SIF, reflectance, GPP; ecosystem productivity and stress indicators
SPAIN'S ROLE
Cal/Val
ESA delegates L2 Cal/Val and advanced product development
03 - What we aim for
Project
Objectives
Six interconnected objectives drive SpaFLEX-Exp — from ground-level measurements to satellite-scale validation and scientific exploitation across Spain's diverse ecosystems.
// O1 — SYSTEMATIC VALIDATION
Cal/Val Plan Execution
Systematically execute the Cal/Val plan — including upscaling and intercomparison — to deliver the first traceable reference datasets for FLEX-S3 products.
// O2 — FRM COMPLIANCE
Data Management & FRM
Achieve formal Fiducial Reference Measurements (FRM) certification for Spain's Cal/Val network. Operate the SpaFLEX-Exp data center for validated L2 data delivery.
// O3 — NOVEL L2 PRODUCTS
Algorithm Development
Develop and improve FLEX Level 2 retrieval algorithms, including SIF, reflectance, and GPP products, with full end-to-end uncertainty budgets.
// O4 — ADVANCED L3/L4
Ecosystem Products
Develop predictive L3/L4 products for ecosystem productivity, stress detection, and carbon balance using FLEX data combined with ancillary observations.
// O5 — BIODIVERSITY & ECOSYSTEMS
Ecological Applications
Exploit FLEX products to link fluorescence with functional traits, biodiversity indicators, and ecosystem stability across diverse Spanish landscapes.
// O6 — CROSS-MISSION
Interoperability
Ensure methodologies are transferable to Sentinel-2, EnMAP, and CHIME — promoting consistency across current and future optical Earth observation missions.
// O1 — SYSTEMATIC VALIDATION
Cal/Val Plan Execution
Systematically execute the Cal/Val plan — including upscaling and intercomparison — to deliver the first traceable reference datasets for FLEX-S3 products.
// O2 — FRM COMPLIANCE
Data Management & FRM
Achieve formal Fiducial Reference Measurements (FRM) certification for Spain's Cal/Val network. Operate the SpaFLEX-Exp data center for validated L2 data delivery.
// O3 — NOVEL L2 PRODUCTS
Algorithm Development
Develop and improve FLEX Level 2 retrieval algorithms, including SIF, reflectance, and GPP products, with full end-to-end uncertainty budgets.
// O4 — ADVANCED L3/L4
Ecosystem Products
Develop predictive L3/L4 products for ecosystem productivity, stress detection, and carbon balance using FLEX data combined with ancillary observations.
// O5 — BIODIVERSITY & ECOSYSTEMS
Ecological Applications
Exploit FLEX products to link fluorescence with functional traits, biodiversity indicators, and ecosystem stability across diverse Spanish landscapes.
// O6 — CROSS-MISSION
Interoperability
Ensure methodologies are transferable to Sentinel-2, EnMAP, and CHIME — promoting consistency across current and future optical Earth observation missions.
04 - How we work
Work
Packages
WP1
Project Management & Coordination
Overall project coordination, ESA reporting, quality assurance, and communication between subprojects. Includes scientific dissemination and coordination with international Cal/Val networks.
LEAD: LEO-UVAL (SP1)
WP2
Cal/Val Protocol Development & Uncertainty Analysis
Standardised measurement protocols for SIF and reflectance. End-to-end uncertainty budgets following FRM and metrological best practices. Instrument characterisation and radiometric calibration.
LEAD: INTA (SP3)
WP3
Airborne & UAV Campaigns
Acquisition of hyperspectral airborne and UAV data over Cal/Val test sites. Integration of CFL SIF sensor into INTA's Airborne Hyperspectral System. Campaign coordination with satellite overpasses.
LEAD: INTA (SP3)
WP4
Operational Ground Cal/Val Network
Deployment and operation of ground instrumentation (FloX, eddy covariance towers, spectroradiometers) across Spanish Cal/Val test sites. Upscaling from field to satellite pixel.
LEAD: EBD-CSIC (SP2)
WP5
FLEX Product Development & Scientific Exploitation
Development of novel L2 algorithms and advanced L3/L4 products. Scientific exploitation for biodiversity, carbon, and water applications. Link with EU land management frameworks.
LEAD: LEO-UVAL (SP1) + EBD-CSIC (SP2)
WP6
Data Centre & Open Science Dissemination
Operation of the SpaFLEX-Exp data centre. Open data publication (FloX, eddy covariance, airborne datasets), outreach, and contribution to international Cal/Val initiatives and CEOS standards.
LEAD: INTA (SP3)
WP1
Project Management & Coordination
Overall project coordination, ESA reporting, quality assurance, and communication between subprojects. Includes scientific dissemination and coordination with international Cal/Val networks.
LEAD: LEO-UVAL (SP1)
WP2
Cal/Val Protocol Development & Uncertainty Analysis
Standardised measurement protocols for SIF and reflectance. End-to-end uncertainty budgets following FRM and metrological best practices. Instrument characterisation and radiometric calibration.
LEAD: INTA (SP3)
WP3
Airborne & UAV Campaigns
Acquisition of hyperspectral airborne and UAV data over Cal/Val test sites. Integration of CFL SIF sensor into INTA's Airborne Hyperspectral System. Campaign coordination with satellite overpasses.
LEAD: INTA (SP3)
WP4
Operational Ground Cal/Val Network
Deployment and operation of ground instrumentation (FloX, eddy covariance towers, spectroradiometers) across Spanish Cal/Val test sites. Upscaling from field to satellite pixel.
LEAD: EBD-CSIC (SP2)
WP5
FLEX Product Development & Scientific Exploitation
Development of novel L2 algorithms and advanced L3/L4 products. Scientific exploitation for biodiversity, carbon, and water applications. Link with EU land management frameworks.
LEAD: LEO-UVAL (SP1) + EBD-CSIC (SP2)
WP6
Data Centre & Open Science Dissemination
Operation of the SpaFLEX-Exp data centre. Open data publication (FloX, eddy covariance, airborne datasets), outreach, and contribution to international Cal/Val initiatives and CEOS standards.
LEAD: INTA (SP3)
Key Data
3
Subprojects & partner institutions
2026
FLEX-S3 launch
300m
Spatial resolution of FLEX-S3
5+
Cal/Val test sites across Spain
20+
Years of LEO-UVAL in FLEX mission design
L2–L4
Product levels addressed
05 - Who we are
The
Consortium
Three complementary subprojects form a complete, traceable Cal/Val pipeline — from ground measurements to satellite product validation and scientific exploitation at the European scale.
// SP1 — COORDINATION & CORE SCIENCE
LEO-UVAL
Laboratory of Earth Observation, University of Valencia
Scientific and coordination nucleus. 20+ years of involvement in FLEX mission foundational design. Prof. José Moreno currently chairs the FLEX Mission Advisory Group. Leads L3/L4 predictive modelling and ecological attribution studies.
Doñana Biological Station + Desertification Research Centre CSIC
Operational validation engine. Executes field campaigns, performs upscaling from ground to satellite. Leads scientific exploitation for biodiversity and ecosystem stability. CIDE specialises in water stress and Mediterranean degradation under climate change.
FIELD CAMPAIGNSUPSCALINGBIODIVERSITYWATER STRESS
// SP3 — METROLOGICAL & AIRBORNE
INTA
Remote Sensing Systems Area, National Institute of Aerospace Technology
Metrological backbone of SpaFLEX-Exp. Defines error propagation and uncertainty budgets. Operates Airborne Hyperspectral System with CFL SIF sensor. Manages FRM certification and operates the SpaFLEX-Exp data centre.
METROLOGYAIRBONE SIFFRM CERT.DATA CENTRE
// SP1 — COORDINATION & CORE SCIENCE
LEO-UVAL
Laboratory of Earth Observation, University of Valencia
Scientific and coordination nucleus. 20+ years of involvement in FLEX mission foundational design. Prof. José Moreno currently chairs the FLEX Mission Advisory Group. Leads L3/L4 predictive modelling and ecological attribution studies.
Doñana Biological Station + Desertification Research Centre CSIC
Operational validation engine. Executes field campaigns, performs upscaling from ground to satellite. Leads scientific exploitation for biodiversity and ecosystem stability. CIDE specialises in water stress and Mediterranean degradation under climate change.
FIELD CAMPAIGNSUPSCALINGBIODIVERSITYWATER STRESS
// SP3 — METROLOGICAL & AIRBORNE
INTA
Remote Sensing Systems Area, National Institute of Aerospace Technology
Metrological backbone of SpaFLEX-Exp. Defines error propagation and uncertainty budgets. Operates Airborne Hyperspectral System with CFL SIF sensor. Manages FRM certification and operates the SpaFLEX-Exp data centre.
