{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T11:11:44Z","timestamp":1768993904941,"version":"3.49.0"},"reference-count":23,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2022,10,27]],"date-time":"2022-10-27T00:00:00Z","timestamp":1666828800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Solar-Terrestrial Center of Excellence (STCE)"},{"name":"Interreg (Fotonica Pilootlijnen, NWE758)"},{"name":"Flanders Make"},{"name":"Methusalem and Hercules Foundations"},{"name":"OZR of the Vrije Universiteit Brussel (VUB)"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Wide field-of-view imaging optics offer a huge potential for space-based Earth observation enabling the capture of global data. Reflective imaging telescopes are often favored, as they do not show chromatic aberrations and are less susceptible to radiation darkening than their refractive counterparts. However, the main drawback of reflective telescopes is that they are limited with respect to field-of-view while featuring large dimensions. We propose the use of freeform optics to maximize the field of view while maintaining diffraction-limited image quality and minimizing system dimensions. In this paper, we present a novel freeform wide field-of-view reflective telescope, starting from the optical design, and continuing to tolerancing analysis and manufacture, towards a proof-of-concept demonstrator. The novel telescope features a full field-of-view of 120\u00b0 while showing an exceptional spatial resolution of 2.6 km and fitting within 1 CubeSat unit. To the best of our knowledge, this is the widest field-of-view that has ever been realized for a space-based telescope, nearly reaching Earth observation from limb to limb from an altitude of about 700 km. We hope this design paves the way for future space missions enabling improved Earth observation and leading to enhanced monitoring of climate and climate change.<\/jats:p>","DOI":"10.3390\/s22218233","type":"journal-article","created":{"date-parts":[[2022,10,27]],"date-time":"2022-10-27T22:36:17Z","timestamp":1666910177000},"page":"8233","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Freeform Wide Field-of-View Spaceborne Imaging Telescope: From Design to Demonstrator"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6191-7822","authenticated-orcid":false,"given":"Luca","family":"Schifano","sequence":"first","affiliation":[{"name":"Brussels Photonics (B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"},{"name":"Royal Meteorological Institute of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7096-7477","authenticated-orcid":false,"given":"Michael","family":"Vervaeke","sequence":"additional","affiliation":[{"name":"Brussels Photonics (B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"},{"name":"Flanders Make, Pleinlaan 2, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0476-197X","authenticated-orcid":false,"given":"Dries","family":"Rosseel","sequence":"additional","affiliation":[{"name":"Brussels Photonics (B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"},{"name":"Flanders Make, Pleinlaan 2, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jef","family":"Verbaenen","sequence":"additional","affiliation":[{"name":"Brussels Photonics (B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"},{"name":"Flanders Make, Pleinlaan 2, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0483-0960","authenticated-orcid":false,"given":"Hugo","family":"Thienpont","sequence":"additional","affiliation":[{"name":"Brussels Photonics (B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"},{"name":"Flanders Make, Pleinlaan 2, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Steven","family":"Dewitte","sequence":"additional","affiliation":[{"name":"Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0822-233X","authenticated-orcid":false,"given":"Francis","family":"Berghmans","sequence":"additional","affiliation":[{"name":"Brussels Photonics (B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"},{"name":"Flanders Make, Pleinlaan 2, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2431-1052","authenticated-orcid":false,"given":"Lien","family":"Smeesters","sequence":"additional","affiliation":[{"name":"Brussels Photonics (B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"},{"name":"Flanders Make, Pleinlaan 2, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"46","DOI":"10.1016\/j.spacepol.2016.05.005","article-title":"A Review of Applications of Satellite Earth Observation Data for Global Societal Benefit and Stewardship of Planet Earth","volume":"36","author":"Kansakar","year":"2016","journal-title":"Space Policy"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1080\/10095020.2017.1333230","article-title":"Earth Observation in Service of the 2030 Agenda for Sustainable Development","volume":"20","author":"Anderson","year":"2017","journal-title":"Geo-Spat. 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