PROBA-3 is a mission devoted to the in-orbit demonstration (IOD) of precise formation flying (F2) techniques and technologies for future ESA missions. The mission includes two spacecrafts. One of them will act as an external occulter for scientific observations of the solar corona from the other spacecraft, which will hold the ASPIICS coronagraph instrument, under CSL (Centre Spatial de Liège) responsibility. The ASPIICS instrument on PROBA-3 looks at the solar corona through a refractive telescope, able to select 3 different spectral bands: Fe XIV line @ 530.4nm, He I D3 line @587.7nm, and the white-light spectral band [540;570nm]. The external occulter being located at ~ 150 meters from the instrument entrance, will allow ASPIICS to observe the corona really close to the solar limb, probably closer than any internally or externally occulted coronagraph ever observed. CSL is responsible for the optical design, integration, testing and validation of the complete ASPIICS instrument. The instrument qualification model (QM) underwent a full qualification campaign at CSL, providing confidence and assuring the performances of the coronagraph design. During the year 2021, the flight model (FM) was also successfully integrated and tested at CSL. The calibration performed at INAF during September 2021 was the last step to achieve before the instrument delivery to ESA end of 2021. This paper will present the results of the qualification campaign, the optical performances of the flight instrument and the calibration campaign. Several challenges were faced during these campaigns, amongst which are detailed the alignment of the focal plane, the alignment measurement during environmental testing and setup constraints during the calibration. The successful validation of the instrument and its final acceptance is demonstrated.
The Comet Interceptor mission was selected by ESA in June 2019 as ESA's new fast-class mission in its Cosmic Vision Programme. Comprising three spacecraft, it will be the first to visit a Long Period Comet (LPC) or even an interstellar object that is only just starting its journey into the inner Solar System. The RMA, under CSL responsibility, is a mechanism rotating a mirror which ensures that the comet is kept within the FoV of the CoCa instrument during the closest part of the approach. The RMA is composed of the Scanning Mirror Assembly (SMA), including a protection baffle, and the associated electronics (SME). The technical role of CSL is to design, develop, build and verify the SMA to be finally delivered to ESA as part of the RMA. This paper introduces the current activities on the RMA development with a deeper insight on the design steps and the preliminary results of the performed breadboard tests (mechanism actuation and coating impact tests). Additional presentation content can be accessed on the supplemental content page.
The Centre Spatial of Liege (CSL) is involved from more than 10 years in the BTDF/BRRDF metrology of large Lambertian diffusers used for on-board calibration on space instrumentation. In this context, a dedicated automatized BSDF calibration facility has been developed, suitable for calibration of all types of diffusers (from industry to space applications). Accurate calibration of such systems induces constraining requirements on the calibration bench: manipulate large diffusers and mechanisms in class ISO5 environment; incidence beam divergence close to the Sun divergence; large spectral range coverage; measurement of very low diffused signals (highly stable, with low noise, straylight free set-up), high accurate measurement of attenuator and a high knowledge of all calibration properties for BSDF modelling. Based on previous heritage, recent improvements have been implemented in order to correct some defaults like mechanical stabilities (complete new design), specimen alignment (new iterative procedure), absolute error (super stable light bulb, improved filters wheel repeatability, optics to limit diffraction effects in UV, incidence beam non-uniformity compensation …). This paper presents the design of the improved bench, highlights critical parameters for BTDF/BRDF calibration and relates main improvements to reach todays performances. The current bench performances are illustrated by calibration campaigns results performed at CSL for Sentinel 2, Sentinel 3 and Sentinel 4 calibration assemblies.
The Centre Spatial of Liege (CSL) is involved from more than 10 years in the BTDF/BRRDF metrology of large Lambertian diffusers used for on-board calibration on space instrumentation. In this context, a dedicated automatized BSDF calibration facility has been developed, suitable for calibration of all types of diffusers (from industry to space applications). Accurate calibration of such systems induces constraining requirements on the calibration bench: manipulate large diffusers and mechanisms in class ISO5 environment; incidence beam divergence close to the Sun divergence; large spectral range coverage; measurement of very low diffused signals (highly stable, with low noise, straylight free set-up), high accurate measurement of attenuator and a high knowledge of all calibration properties for BSDF modelling. Based on previous heritage, recent improvements have been implemented in order to correct some defaults like mechanical stabilities (complete new design), specimen alignment (new iterative procedure), absolute error (super stable light bulb, improved filters wheel repeatability, optics to limit diffraction effects in UV, incidence beam non-uniformity compensation …). This paper presents the design of the improved bench, highlights critical parameters for BTDF/BRDF calibration and relates main improvements to reach todays performances. The current bench performances are illustrated by calibration campaigns results performed at CSL for Sentinel 2, Sentinel 3 and Sentinel 4 calibration assemblies.
PLATO (PLAnetary Transits and Oscillation of stars) is a medium-class space mission part of the ESA Cosmic vision program. Its goal is to find and study extrasolar planetary systems, emphasizing on planets located in habitable zone around solar-like stars. PLATO is equipped with 26 cameras, operating between 500 and 1000nm. The alignment of the focal plane assembly (FPA) with the optical assembly is a time consuming process, to be performed for each of the 26 cameras. An automatized method has been developed to fasten this process. The principle of the alignment is to illuminate the camera with a collimated beam and to vary the position of the FPA to search for the position which minimizes the RMS spot diameter. To reduce the total number of measurements which is performed, the alignment method is done by iteratively searching for the best focus, decreasing at each step the error on the estimated best focus by a factor 2. Because the spot size at focus is similar to the pixel, it would not be possible with this process alone to reach an alignment accuracy of less than several tens of microns. Dithering, achieved by in-plane translation of the focal plane and image recombination, is thus used to increase the sampling of the spot and decrease the error on the merit function.
This paper presents the recent achievements in the development of ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), a solar coronagraph that is the primary payload of ESA’s formation flying in-orbit demonstration mission PROBA-3. The PROBA-3 Coronagraph System is designed as a classical externally occulted Lyot coronagraph but it takes advantage of the opportunity to place the 1.4 meter wide external occulter on a companion spacecraft, about 150m apart, to perform high resolution imaging of the inner corona of the Sun as close as ~1.1 solar radii. Besides providing scientific data, ASPIICS is also equipped with sensors for providing relevant navigation data to the Formation Flying GNC system. This paper is reviewing the recent development status of the ASPIICS instrument as it passed CDR, following detailed design of all the sub-systems and testing of STM and various Breadboard models.
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