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Bread Board Development of a Telescope with a Steerable Line of Sight (OSTEELOS BB)



Prime contractor
Organisational Unit
19 June 2024

Duration: 18 months


A new type of telescope is proposed for a laboratory proof-of-concept study, allowing persistent video Earth observation missions with high ground resolution by applying a constellation of picosats at VLEO. The tescope is calles OSTEELOS (Optical telescope with Steerable Line of Sight). It is the first telescope known, realizing a steerable line of sight over a large angular range without a frontal scanning mirror. An optical concept, operating in TIR (8-13µm) and VIS wavelength range was studied on optical concept level in a previous ESA activity (Contract 4000138490/22/NL/AR/zk). The proposed telescope will be diffraction limited in the thermal infrared and presents an optical resolution of 2.8 m at Nadir in the visible spectral range. It achieves of an angular scanning range of more than +/-18 degrees. The concept follows a novel way of achieving the angular scanning: The innovative and novel all-reflective freeform telescope is working with two freeform mirrors which move relative to each other on translation stages to provide the angular steering function. A freeform stabilization mirror on a tip/tilt stage and a freeform germanium beam splitter for the spectral channel separation are also part of the concept and are needed to achieve the required performance. The application of translating optical components enable a significantly reduced cross-section which allows a reduction of the drag and such increase the lifetime of the satellites in VLEO. Such a concept also leads to a performance increase and a cost decrease at system level. The manufacturability and alignment of the components can be challenging, as well as the mechanisms needed for the translation in terms of range, accuracy and resolution. To tackle these challenges a bread board laboratory demonstrator is now necessary to proof the concept and fully validate the working principle with a hardware demonstrator. By that the Technology Readiness Level shall be raised from TRL2 to TRL3.

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Bread Board Development of a Telescope with a Steerable Line of Sight (OSTEELOS BB)