PROBA3-ASPIICS Coronagraph - Alignment, Performance Tests and Calibration

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.