FLEX (satellite)

FLEX
Mission typeEarth observing satellite
OperatorESA
COSPAR ID2026-209A Edit this at Wikidata
SATCAT no.100689Edit this on Wikidata
Websitehttps://earth.esa.int/eogateway/missions/flex
Mission duration3.5 years (planned)
Spacecraft properties
BusMyriade
ManufacturerThales Alenia Space
Launch mass425 kilograms (937 lb)
Power700W
Start of mission
Launch date15 September 2026, 1:21 UTC
RocketVega-C
Launch siteKourou ELV
ContractorArianespace
Orbital parameters
Reference systemGeocentric
RegimeSun-synchronous
Altitude814 km
Inclination98.64°
Repeat interval27 days

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The FLuorescence EXplorer (FLEX) is a satellite developed by the European Space Agency (ESA) for monitoring the global steady-state chlorophyll fluorescence in terrestrial vegetation. FLEX is the eighth mission in the Earth Explorer series of Earth observation satellites, part of ESA's FutureEO programme. The mission was selected for funding in November 2015 and was launched on a Vega C rocket from Guiana Space Centre on 15 September 2026 together with another European Earth observation satellite, Sentinel-3C.

Science

The mission's goal is 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 nm. Fluorescence is a sensitive indicator of photosynthesis in both healthy and physiologically perturbed vegetation that can be used to monitor croplands and forests.

Fluorescence provides information on overall photosynthetic performance with implications for related carbon sequestration. The 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.

Timeline

Development

On 19 November 2015, ESA selected FLEX as the agency's eighth Earth Explorer mission. In November 2016, ESA selected Italian company Leonardo to build the main instrument (FLORIS) for the FLEX satellite. In January 2019, ESA selected Thales Alenia Space as the prime contractor for the satellite and to oversee the development of the FLORIS instrument by Leonardo. In January 2022, ESA signed a contract with Arianespace for a launch of FLEX 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.

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 summer 2019, the second FLEXSense campaign took place, with operations closely following the 2018 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. By mid-April 2026, FLEX has completed its functional and environmental tests and was ready for transport to Guiana Space Centre for launch. The satellite, together with other two European Earth observation satellites, Sentinel-3C and MTG-I2, was presented at a media event hosted by Thales Alenia Space in Cannes.

Launch campaign

FLEX and Sentinel-3C satellite launched together aboard a Vega-C rocket

In early July 2026, FLEX and Sentinel-3C departed Cannes aboard MN Colibri for French Guiana. The satellites arrived at Pariacabo, the port of Kourou, on 12 July 2026. On 21 July 2026, FLEX was removed from its container packaging at Kourou. In late August 2026, the satellite's tanks were fully filled with 30 kg of fuel. On 2 September 2026, both FLEX and Sentinel-3C were enclosed within the Vega-C fairing; FLEX inside the Vespa secondary payload adapter and Sentinel-3C on top of it. On 7 September 2026, the two satellites inside their launch fairing were transported to the launch tower and later hoisted atop the Vega-C rocket. The launch took place as planned on 15 September at 1:21 UTC. Both satellites successfully separated and started communicating. This was the second space launch operated by Avio independently from Arianespece. The satellite completed its Launch and Early Orbit Phase (LEOP) on 18 September 2026.

See also

References

  1. ↑ "Fluorescence Explorer (FLEX) – Facts and Figures". ESA. Retrieved 3 January 2020.
  2. 1 2 3 4 Amos, Jonathan (19 November 2015). "Flex satellite will map Earth's plant glow". BBC News. Retrieved 2015-11-20.
  3. 1 2 "FLEX (Fluorescence Explorer)". www.eoportal.org. Retrieved 2022-12-28.
  4. ↑ de Selding, Peter B. (25 September 2015). "Panel Endorses Vegetation Fluorescence Mapper for ESA's Earth Explorer Program". Spacenews. Retrieved 3 October 2015.
  5. ↑ Kraft, S; Del Bello, U; Bouvet, M; Drusch, M; Moreno, J (2012). "FLEX: ESA's Earth Explorer 8 candidate mission". 2012 IEEE International Geoscience and Remote Sensing Symposium. pp. 7125–7128. doi:10.1109/IGARSS.2012.6352020. ISBN 978-1-4673-1159-5. S2CID 7603157.
  6. ↑ Kraft, S; Bézy, J.-L; Del Bello, U; Berlich, R; Drusch, M; Franco, R; Gabriele, A; Harnisch, B; Meynart, R; Silvestrin, P (2013). "FLORIS: Phase a status of the fluorescence imaging spectrometer of the Earth Explorer mission candidate FLEX". In Meynart, Roland; Neeck, Steven P.; Shimoda, Haruhisa (eds.). Sensors, Systems, and Next-Generation Satellites XVII. Vol. 8889. pp. 88890T. doi:10.1117/12.2032060. S2CID 128624334.
  7. ↑ Drusch, Matthias; Moreno, Jose; Del Bello, Umberto; Franco, Raffaella; Goulas, Yves; Huth, Andreas; Kraft, Stefan; Middleton, Elizabeth M; Miglietta, Franco; Mohammed, Gina; Nedbal, Ladislav; Rascher, Uwe; Schuttemeyer, Dirk; Verhoef, Wout (2017). "The FLuorescence EXplorer Mission Concept—ESA's Earth Explorer 8". IEEE Transactions on Geoscience and Remote Sensing. 55 (3): 1273–1284. Bibcode:2017ITGRS..55.1273D. doi:10.1109/TGRS.2016.2621820. S2CID 5267592.
  8. ↑ Stoll, M.P; Buschmann, C; Court, A; Laurila, T; Moreno, J; Moya, I (2003). "The FLEX-Fluorescence Explorer mission project: Motivations and present status of preparatory activities". IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477). Vol. 1. pp. 585–587. doi:10.1109/IGARSS.2003.1293850. ISBN 978-0-7803-7929-9. S2CID 56932583.
  9. ↑ Rascher, Uwe; Gioli, Beniamino; Miglietta, Franco (2008). "FLEX — Fluorescence Explorer: A Remote Sensing Approach to Quantify Spatio-Temporal Variations of Photosynthetic Efficiency from Space". Photosynthesis. Energy from the Sun. pp. 1387–1390. doi:10.1007/978-1-4020-6709-9_299. ISBN 978-1-4020-6707-5.
  10. ↑ Harnisch, Bernd; Kraft, Stefan; Bézy, Jean-Loup; Drusch, Matthias; Bouvet, Marc; Del Bello, Umberto (2017). "Fluorescence imaging spectrometer concepts for the Earth explorer mission candidate flex". International Conference on Space Optics — ICSO 2012. p. 72. doi:10.1117/12.2309086. ISBN 9781510616172. S2CID 125313615.
  11. ↑ "FLEX and Sentinel-3C launched". www.esa.int. Retrieved 2026-09-15.
  12. ↑ "ALTIUS - ESA's ozone mission". ESA. Retrieved 4 May 2024.
  13. ↑ Evolution, Satellite (2022-01-11). "Arianespace to launch with Vega C Flex & Altius, two ESA programmes at the service of environment". Satellite Evolution. Retrieved 2025-12-31.
  14. ↑ "Announcement of opportunity for FLEX cal/val".
  15. ↑ "Fluorescence explorer (FLEX): A new technique for the observation of global vegetation photosynthesis". juser.fz-juelich.de. Retrieved 2026-04-16.
  16. ↑ "New satellite to measure plant health". www.esa.int. Retrieved 2025-03-31.
  17. ↑ "Deal signed for FLEX's fluorescence finder". www.esa.int. Retrieved 2025-03-31.
  18. ↑ "Thales Alenia Space leads the build of photosynthesis mission". www.esa.int. Retrieved 2025-03-31.
  19. ↑ "Ride into space on Vega-C secured for FLEX and Altius". www.esa.int. Retrieved 2025-03-31.
  20. ↑ "Thales Alenia Space selects the UK's National Satellite Test Facility for FLEX satellite 1st test – SatNews". news.satnews.com. Retrieved 2025-03-31.
  21. 1 2 "New FLEX-related campaign datasets released - Earth Online". earth.esa.int. Archived from the original on 2024-07-11. Retrieved 2025-03-31.
  22. ↑ "SPIE Photonics West: Fraunhofer IOF presents high-precision double slit for space spectrometer". Fraunhofer Institute for Applied Optics and Precision Engineering IOF. Retrieved 2025-04-02.
  23. ↑ "FLEX instrument meets its satellite". www.esa.int. Retrieved 2025-08-16.
  24. ↑ "Three ESA-built satellites on show in France". www.esa.int. Retrieved 2026-04-16.
  25. ↑ "FLEX and Sentinel-3C bound for launch site". www.esa.int. Retrieved 2026-07-03.
  26. ↑ "FLEX and Sentinel-3C arrive at Europe's Spaceport". www.esa.int. Retrieved 2026-08-04.
  27. ↑ "FLEX removed from container". www.esa.int. Retrieved 2026-08-04.
  28. ↑ "ESA's photosynthesis satellite fuelled". www.esa.int. Retrieved 2026-08-24.
  29. ↑ "FLEX and Sentinel-3C sealed within Vega-C fairing". www.esa.int. Retrieved 2026-09-03.
  30. ↑ "FLEX and Sentinel-3C being hoisted into the launch tower". www.esa.int. Retrieved 2026-09-14.
  31. ↑ "FLEX and Sentinel-3C ready for liftoff on Vega-C". www.esa.int. Retrieved 2026-09-14.
  32. ↑ "FLEX and Sentinel-3C launched". www.esa.int. Retrieved 2026-09-15.
  33. ↑ "Avio launches pair of climate monitoring European spacecraft to study plants, oceans and atmospheric changes – Spaceflight Now". Retrieved 2026-09-15.
  34. ↑ Wall, Mike; today, Copernicus-3C spacecraft lifted off at 9:21 p m ET (2026-09-14). "Vega C rocket launches 2 European Earth-observing satellites to orbit from South America". Space. Retrieved 2026-09-15.{{cite web}}: CS1 maint: numeric names: authors list (link)
  35. ↑ Parsonson, Andrew (2026-09-15). "Avio Launches Second Successful Vega C Flight of 2026". European Spaceflight. Retrieved 2026-09-15.
  36. ↑ "ESA Operations (@operations.esa.int)". Bluesky Social. 2026-09-18. Archived from the original on 2026-09-25. Retrieved 2026-09-25.