000003589 001__ 3589
000003589 005__ 20190108113652.0
000003589 0247_ $$2DOI$$a10.1051/0004-6361/201732386
000003589 037__ $$aSCART-2018-0063
000003589 100__ $$aShestov, S. V.
000003589 245__ $$aInfluence of misalignments on the performance of externally occulted solar coronagraphs
000003589 260__ $$c2018
000003589 520__ $$aASPIICS is a novel externally occulted coronagraph that will be launched onboard the PROBA-3 mission of ESA. The external occulter (EO) will be placed on one satellite ~150 m ahead of the second satellite with an optical instrument. During part of each orbit, the satellites will fly in a precise formation, constituting a giant externally occulted coronagraph. Large distance between the EO and the primary objective will allow observations of the white-light solar corona starting already from ~1.1RSun. We analyze influence of shifts of the satellites and misalignments of optical elements on diffracted light. Based on the quantitative influence of misalignments on diffracted light, we will provide a "recipe" for choosing the size of the internal occulter (IO) to achieve a trade-off between the minimal height of observations and sustainability to possible misalignments. We implement a numerical model of the diffracted light and its propagation through the optical system, and compute intensities of diffracted light throughout the instrument. Our numerical model extends axi-symmetrical model of Rougeot et al. 2017 to non-symmetrical cases. The computations fully confirm main properties of the diffracted light obtained from semi-analytical consideration. Results: relative influences of various misalignments are significantly different. We show that: the IO with R=1.1RSun is large enough to compensate possible misalignments in ASPIICS, apodizing the edge of the IO leads to additional suppression of the diffracted light. Conclusions: the most important misalignment is the tilt of the telescope WRT the line connecting the center of the EO and the entrance aperture. Special care should be taken to co-align the EO and the coronagraph, i.e. co-aligning the diffraction fringe from the EO and the IO. We suggest that the best orientation strategy is to point the coronagraph to the center of the EO.
000003589 536__ $$a3PRODPROBA3/$$c3PRODPROBA3/$$f3PRODPROBA3
000003589 594__ $$aSTCE
000003589 700__ $$aZhukov, A. N.
000003589 773__ $$cA82$$nJanuary$$pAstronomy&Astrophysics$$v612$$y2018
000003589 8560_ $$fsergei.shestov@observatoire.be
000003589 85642 $$ahttps://www.aanda.org/10.1051/0004-6361/201732386
000003589 905__ $$apublished in
000003589 980__ $$aREFERD