PLATO Spacecraft: Assessment of Thermo-Elastic Stability of an Optical Bench Demonstrator



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2020 International Conference on Environmental Systems


PLATO (PLAnetary Transits and Oscillations of stars) aims to detect earth-like planets around sun-like stars. To do so, the light intensity of stars during occultation by the planet needs to be monitored with unprecedented accuracy over month-long periods. One important contribution to minimize the measurement noise is to keep the relative pointing of all cameras stable over a broad frequency range, with special focus on the μ-Hz area. Therefore, very stringent requirements are imposed on the optical bench assembly (OBA) thermo-elastic stability. Their verification constitutes one of the most challenging aspects in the spacecraft qualification. The paper focuses on the evaluation of the first breadboard test to assess the feasibility of the Thermo-Elastic Distortions (TED) verification plan that is being implemented. The verification of in-orbit performance is partly based on a combination of transfer functions between possible disturbance sources and the TED performance of the OBA. To assess the feasibility of predicting and testing such transfer functions, a demonstrator bread board model (DMBB) was built to represent a cut-out of the OBA, and tested with a high accuracy interferometry setup. The results of the test were compared to the predicted thermal and TED behavior, showing very good correlation. Measurement accuracy was shown to be in the ~0.1μm range, with relative deformations between camera support structures as low as 0.1 arcsec being measurable. A second test using a videogrammetric measurement setup has shown further correlation with the interferometry test results.


Jan Junker, Otto Hydraulic Bremen (OHB) System AG, DE
Carsten Reese, Otto Hydraulic Bremen (OHB) System AG, DE
Gerhard Bleicher, Otto Hydraulic Bremen (OHB) System AG, DE
Oliver Nicolay, Otto Hydraulic Bremen (OHB) System AG, DE
Ami Mottaghibonab, Otto Hydraulic Bremen (OHB) System AG, DE
ICES203: Thermal Testing
The proceedings for the 2020 International Conference on Environmental Systems were published from July 31, 2020. The technical papers were not presented in person due to the inability to hold the event as scheduled in Lisbon, Portugal because of the COVID-19 global pandemic.


Thermo-elastic distortion, Transfer function, Optical bench, Interferometry, Videogrammetry