FLEX (satellite)

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title: "FLEX (satellite)" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["fluorescence", "ecological-metrics", "earth-observation-satellites-of-the-european-space-agency", "2026-in-spaceflight", "proposed-satellites", "spectrometers"] description: "Planned ESA Earth observation satellite" topic_path: "philosophy" source: "https://en.wikipedia.org/wiki/FLEX_(satellite)" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Planned ESA Earth observation satellite ::

::data[format=table title="Infobox spaceflight"]

Field	Value
name	FLEX
names_list
	image
image_size
mission_type	Earth observing satellite
operator	ESA
website	https://earth.esa.int/eogateway/missions/flex
mission_duration	3.5 years (planned)
spacecraft_type
spacecraft_bus	Myriade
manufacturer	Thales Alenia Space
launch_mass	425 kg
BOL_mass
dry_mass
payload_mass
dimensions
power	700W
	launch_date
launch_rocket	Vega-C
launch_site	Kourou ELV
launch_contractor	Arianespace
	orbit_reference
orbit_regime	Sun-synchronous
orbit_longitude
orbit_slot
orbit_semimajor
orbit_eccentricity
orbit_altitude	814 km
orbit_periapsis
orbit_apoapsis
orbit_inclination	98.64°
orbit_period
orbit_RAAN
orbit_arg_periapsis
orbit_mean_anomaly
orbit_mean_motion
orbit_repeat	27 days
orbit_velocity
orbit_epoch
orbit_rev_number
apsis	gee
programme	FutureEO
previous_mission	HydroGNSS
next_mission	FORUM
::

| name = FLEX | names_list = | image = ESA’s photosynthesis mission ESA515347.jpg | image_caption = | image_size = | mission_type = Earth observing satellite | operator = ESA | COSPAR_ID = | SATCAT = | website = https://earth.esa.int/eogateway/missions/flex | mission_duration = 3.5 years (planned) | spacecraft_type = | spacecraft_bus = Myriade | manufacturer = Thales Alenia Space | launch_mass = 425 kg | BOL_mass = | dry_mass = | payload_mass = | dimensions = | power = 700W

| launch_date = 2026 (planned) | launch_rocket = Vega-C | launch_site = Kourou ELV | launch_contractor = Arianespace

| orbit_reference = Geocentric | orbit_regime = Sun-synchronous | orbit_longitude = | orbit_slot = | orbit_semimajor = | orbit_eccentricity = | orbit_altitude = 814 km | orbit_periapsis = | orbit_apoapsis = | orbit_inclination = 98.64° | orbit_period = | orbit_RAAN = | orbit_arg_periapsis = | orbit_mean_anomaly = | orbit_mean_motion = | orbit_repeat = 27 days | orbit_velocity = | orbit_epoch = | orbit_rev_number = | apsis = gee | programme = FutureEO | previous_mission = HydroGNSS | next_mission = FORUM

The FLuorescence EXplorer (FLEX) is a planned mission by the European Space Agency to launch a satellite to monitor the global steady-state chlorophyll fluorescence in terrestrial vegetation. FLEX was selected for funding on 19 November 2015 and will be launched on a Vega C rocket from Guiana Space Centre in September 2026 together with another European Earth observation satellite, Sentinel-3C.

Overview

The FLuorescence EXplorer (FLEX) mission is the eighth mission in the Earth Explorer programme, (part of ESA's Living Planet Programme). It comprises a satellite for the global monitoring of steady-state chlorophyll fluorescence in terrestrial vegetation. Leaf photosynthesis releases energy not required in the biochemical process in the form of light in wavelength between 640 and 800 nanometres.

After more than 70 years of basic and applied research in chlorophyll fluorescence, it is now established that fluorescence is a sensitive indicator of photosynthesis in both healthy and physiologically perturbed vegetation that can be used to monitor croplands and forests.

Fluorescence is a powerful non-invasive tool to track the status, resilience, and recovery of photochemical processes, and provides important information on overall photosynthetic performance with implications for related carbon sequestration. The early responsiveness of fluorescence to atmospheric, soil and plant water balance, as well as to atmospheric chemistry and human intervention in land usage, makes it a useful biological indicator in improving the understanding of Earth system dynamics.

FLEX will encompass a three-instrument array for measurement of the interrelated features of fluorescence, hyperspectral reflectance, and canopy temperature. ::figure[src="https://upload.wikimedia.org/wikipedia/commons/4/47/ESA-developed_Earth_observation_missions_ESA19415147_(cropped).jpeg" caption="ESA-developed Earth observation missions"] ::

The program will involve a space and ground-measurement program of 3-years duration and will provide data formats for research and applied science.

Timeline

Development

• In November 2015, ESA has selected FLEX as the agency's eighth Earth Explorer mission.
• In November 2016, ESA has selected Italian company Leonardo to build the main instrument (FLORIS) for the FLEX satellite.
• In 2018, during the first FLEXSense campaign, the OLCI instruments of the Sentinel-3B satellite was reprogrammed to operate in a mode simulating the future cooperations with FLEX and a parallel aerial campaign used aircraft-based observations to demonstrate aspects of the FLORIS instrument functionality.
• In January 2019, ESA has selected Thales Alenia Space as the prime contractor for the satellite and to oversee the development of the FLORIS instrument by Leonardo.
• In summer 2019, the second FLEXSense campaign took place, with operations closely following the 2018 campaign.
• In January 2022, ESA has signed a contract with Arianespace for a joint launch of FLEX and Altius on Vega C.
• In December 2023, Thales Alenia Space selected the UK’s National Satellite Test Facility for the satellite's first comprehensive assembly, integration and test campaign.

Construction

• In 2024, the Fraunhofer IOF in Jena was exhibiting the double-slit assembly, which it had developed for the FLORIS instrument, at SPIE Photonics West in San Francisco.
• In August 2025, the FLORIS instrument has been joined to the FLEX satellite platform at Thales Alenia Space in Cannes.

References

References

1. "Fluorescence Explorer (FLEX) – Facts and Figures". [[ESA]].
2. "ALTIUS - ESA's ozone mission". ESA.
3. Amos, Jonathan. (19 November 2015). "Flex satellite will map Earth's plant glow". BBC News.
4. (25 September 2015). "Panel Endorses Vegetation Fluorescence Mapper for ESA's Earth Explorer Program". Spacenews.
5. (2012). "2012 IEEE International Geoscience and Remote Sensing Symposium".
6. (2013). "Sensors, Systems, and Next-Generation Satellites XVII".
7. (2017). "The FLuorescence EXplorer Mission Concept—ESA's Earth Explorer 8". IEEE Transactions on Geoscience and Remote Sensing.
8. (2003). "IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477)".
9. (2008). "Photosynthesis. Energy from the Sun".
10. (2017). "International Conference on Space Optics — ICSO 2012".
11. Evolution, Satellite. (2022-01-11). "Arianespace to launch with Vega C Flex & Altius, two ESA programmes at the service of environment".
12. "Announcement of opportunity for FLEX cal/val".
13. "FLEX (Fluorescence Explorer)".
14. "New satellite to measure plant health".
15. "Deal signed for FLEX's fluorescence finder".
16. "New FLEX-related campaign datasets released - Earth Online".
17. "Thales Alenia Space leads the build of photosynthesis mission".
18. "Ride into space on Vega-C secured for FLEX and Altius".
19. "Thales Alenia Space selects the UK's National Satellite Test Facility for FLEX satellite 1st test – SatNews".
20. "SPIE Photonics West: Fraunhofer IOF presents high-precision double slit for space spectrometer".
21. "FLEX instrument meets its satellite".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::