Control electronics for tuneable Fabry-Perot interferometers in hyperspectral imagers
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School of Electrical Engineering |
Doctoral thesis (article-based)
| Defence date: 2025-06-13
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Language
en
Pages
73 + app. 87
Series
Aalto University publication series Doctoral Theses, 116/2025
Abstract
Hyperspectral imaging has been rapidly evolving during the last decades. In hyperspectral imaging, a contiguous spectrum is acquired for each pixel in an image. Typically, a hyperspectral camera covers part of the wavelength range from the near ultraviolet to the mid-infrared in tens to hundreds of wavelength channels. This capability enables identifying and analysing materials and substances based on their spectral characteristics. Hyperspectral imagers or hyperspectral cameras have been used in satellites for various purposes, including environmental monitoring, atmospheric studies, and solar and astronomic research. A tuneable Fabry-Perot interferometer can be used as a scanning optical bandpass filter in a spectral imager. The transmitted wavelengths depend on the distance between the mirrors of the interferometer. In order to achieve the required spectral stability and repeatability, the mirror gap has to be controlled with sub-nanometre precision. The performance must remain unchanged over a wide operating temperature range. This thesis presents the control of the Fabry-Perot interferometers used in the hyperspectral imagers of the nanosatellites Aalto-1 and PICASSO. The electronics of the controller for the Fabry-Perot interferometers of the ultraviolet channel in the ALTIUS spectral imager are described in some detail. The ALTIUS instrument and satellite, currently under construction, are part of the European Space Agency’s Earth Watch programme.Hyperspektral avbildning har utvecklats snabbt under de senaste decennierna. Hyperspektral avbildning ger ett kontinuerligt spektrum för varje element i en bild. Med en hyperspektralkamera kan man typiskt täcka en del av våglängdsområdet från närultraviolett till kortvågsinfrarött i totals eller hundratals våglängdsband. Kameran gör det möjligt att identifiera och analysera material och ämnen på basen av deras spektrala egenskaper. Hyperspektralkameror har använts i satelliter för olika ändamål, inklusive miljöövervakning, atmosfäriska studier och sol- och astronomisk forskning. En ställbar Fabry-Perot interferometer kan användas som ett svepande optiskt bandpassfilter i en spektralkamera. De genomsläppta våglängderna beror på avståndet mellan interferometerns speglar. För att uppnå tillräcklig spekral stabilitet och repeterbarhet måste spegelavståndet regleras med subnanometer precision. Prestanda måste bevaras över ett brett temperaturområde. Denna avhandling presenterar elektroniken för styrningen av Fabry-Perotinterferometrarna som används i hyperspektralkamerorna i nanosatelliterna Aalto-1 och PICASSO. Elektroniken för styrenheten till Fabry-Perot-interferometrarna i ultraviolettkanalen i ALTIUS spektralkamera beskrivs i detalj. ALTIUS-instrumentet och -satelliten, som för närvarande byggs, är en del av Europeiska rymdorganisationens Earth Watch-program.Description
Supervising professor
Praks, Jaan, Assoc. Prof., Aalto University, Department of Electronics and Nanoengineering, FinlandThesis advisor
Rissanen, Anna, Dr., Aalto University, OtaNano, FinlandOther note
Parts
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[Publication 1]: Heikki Saari, Ville-Veikko Aallos, Altti Akujärvi, Tapani Antila, Christer Holmlund, Uula Kantojärvi, Jussi Mäkynen, and Jyrki Ollila. Novel miniaturized hyperspectral sensor for UAV and space applications. In SPIE Remote Sensing 2009, Sensors, Systems, and Next-Generation Satellites XIII,, Proc. SPIE Vol. 7474, pp. 74741M-1–74741M-12., September 2009.
DOI: 10.1117/12.830284 View at publisher
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[Publication 2]: Rami Mannila, Antti Näsilä, Kai Viherkanto, Christer Holmlund, Ismo Näkki, Heikki Saari. Spectral imager based on Fabry-Perot interferometer for Aalto-1 nanosatellite. In Imaging Spectrometry XVIII, SPIE Optical Engineering + Applications, San Diego, United States, pages, Vol. 8870, pp. 887002-1–887002-8, September 2013.
DOI: 10.1117/12.2023299 View at publisher
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[Publication 3]: Heikki Saari, Antti Näsilä, Christer Holmlund, Rami Mannila, Ismo Näkki, Harri J. Ojanen, Didier Fussen, Didier Pieroux, Philippe Demoulin, Emmanuel Dekemper, Filip Vanhellemont. Visible spectral imager for occultation and nightglow (VISION) for the PICASSO mission. In SPIE Remote Sensing 2015, Sensors, Systems, and Next-Generation Satellites XIX, Toulouse, France, Vol. 9639, pp. 96391M-1–96391M-10, October 2015.
DOI: 10.1117/12.2193557 View at publisher
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[Publication 4]: Antti Näsilä, Christer Holmlund, Rami Mannila, Ismo Näkki, Harri J. Ojanen, Altti Akujärvi, Heikki Saari, Didier Fussen, Didier Pieroux, Philippe Demoulin. PICASSO VISION instrument design, engineering model test results, and flight model development status. In SPIE Remote Sensing 2016, Remote Sensing of Clouds and the Atmosphere XXI, Edinburgh, United Kingdom, Vol. 10001, pp. 1000109-1–1000109-14, October 2016.
DOI: 10.1117/12.2241956 View at publisher
- [Publication 5]: Christer Holmlund, Antti Näsilä, Jussi Mäkynen. Control electronics for high wavelength accuracy in a nanosatellite hyperspectral imager. Journal of Small Satellites, Vol. 9, No. 2, pp. 911–920, June 2020
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[Publication 6]: Christer Holmlund, Roberts Trops. Implementation of a controller for a space-grade, piezo-actuated Fabry-Perot interferometer. IEEE Access, Vol. 10, pp. 83664–83677, August 2022.
DOI: 10.1109/ACCESS.2022.3197284 View at publisher