{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T19:15:46Z","timestamp":1771701346000,"version":"3.50.1"},"reference-count":36,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2020,1,13]],"date-time":"2020-01-13T00:00:00Z","timestamp":1578873600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The preliminary design and validation of a novel, high accuracy horizon-sensor for small satellites is presented, which is based on the theory of attitude determination from ellipsoid observations. The concept consists of a multi-head infrared sensor capturing images of the Earth limb. By fitting an ellipse to the imaged limb arcs, and exploiting some analytical results available from projective geometry, a closed form solution for computing the attitude matrix is provided. The algorithm is developed in a dimensionless framework, requiring the knowledge of the shape of the imaged target, but not of its size. As a result, the solution is less sensitive to the limb shift caused by the atmospheric own radiance. To evaluate the performance of the proposed method, a numerical simulator is developed, which generates images captured in low Earth orbit, including also the presence of the atmosphere. In addition, experimental validation is provided due to a dedicated testbed, making use of a miniature infrared camera. Results show that our sensor concept returns rms errors of few hundredths of a degree or less in determining the local nadir direction.<\/jats:p>","DOI":"10.3390\/s20020433","type":"journal-article","created":{"date-parts":[[2020,1,13]],"date-time":"2020-01-13T04:05:51Z","timestamp":1578888351000},"page":"433","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Attitude Sensor from Ellipsoid Observations: A Numerical and Experimental Validation"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1517-3938","authenticated-orcid":false,"given":"Dario","family":"Modenini","sequence":"first","affiliation":[{"name":"Department of Industrial Engineering, University of Bologna, 47121 Forl\u00ec, Italy"}]},{"given":"Alfredo","family":"Locarini","sequence":"additional","affiliation":[{"name":"Department of Industrial Engineering, University of Bologna, 47121 Forl\u00ec, Italy"}]},{"given":"Marco","family":"Zannoni","sequence":"additional","affiliation":[{"name":"Department of Industrial Engineering, University of Bologna, 47121 Forl\u00ec, Italy"}]}],"member":"1968","published-online":{"date-parts":[[2020,1,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/0005-1098(71)90082-3","article-title":"High precision attitude determination by sensing the earth and lunar horizon in the infrared","volume":"7","author":"Astheimer","year":"1971","journal-title":"Automatica"},{"key":"ref_2","unstructured":"Jalink, A., Davis, R.E., and Dodgen, J.A. 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