Scaled-model guidelines for formation-flying solar coronagraph missions

Landini, Federico; Romoli, M.; Baccani, Cristian; Focardi, M.; Pancrazzi, M.; Galano, Damien; Kirschner, Volker

doi:10.1364/ol.41.000757

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…However, these defects would be purely mechanical, and it is probably easier to achieve a very good quality for the occulter itself, in comparison to what is required for the optics in the Lyot coronagraph. A comparison with an experimental approach would be of interest, as was reported by Landini et al (2016).…”

Section: Resultsmentioning

confidence: 94%

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Theoretical performance of serrated external occulters for solar coronagraphy

Rougeot

Aime

2018

A&A

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Context. This study is made in the context of the future solar coronagraph ASPIICS of the ESA formation-flying mission Proba-3. Aims. In the context of solar coronagraphy, we provide a comparative study of the theoretical performance of serrated (or toothed) external occulters by varying the number and size of the teeth, which we compare to the sharp-edged and apodized disks. The tooth height is small (a few centimeters), to avoid hindering the observation of the solar corona near the limb. We first analyze the diffraction pattern produced by such occulters. In a second step, we compute the umbra profile by integration over the Sun. Methods. We explored a few methods to compute the diffraction pattern. Two of them were implemented. The first is based on 2D fast Fourier transformation (FFT) routines and a multiplication by the Fresnel filter of the form exp(−iπλzu2). Simple rules were derived and discussed to set the sampling conditions. The Maggi–Rubinowicz representation is then proposed as an alternative method, and is proven to be very efficient for this study. Results. Serrated occulters tend to create a two-level intensity pattern, the inner being the darker, which perfectly matches a previously reported geometrical prediction. The diffraction in this central region is lower by two to four orders of magnitude when compared to the sharp-edged disk. The achieved umbra level at the center ranges from 10−4 to below 10−7, depending on the geometry of the teeth. Conclusions. Our study shows that serrated occulters can achieve a high rejection and can almost reach the performance of the apodized disk when very many teeth are used. We prove that shaped occulters must be preferred to simple disks in solar and stellar coronagraphy.

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Section: Resultsmentioning

confidence: 94%

“…Our results are therefore not comparable to their results. Finally, Landini et al (2016) presented an experimental study of the rejection of various external occulters, based on a reduced scale test bench.…”

Section: Introductionmentioning

confidence: 99%

Theoretical performance of serrated external occulters for solar coronagraphy

Rougeot

Aime

2018

A&A

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“…Following this analysis, some hypotheses and parameters can be refined to better fit with the reality: 1-To consider real BTDF measurement of lenses in the µroughness scattering model 2-To consider a contamination model (following Mie theory) that will add to the µroughness scattering 3-To add the propagation of the diffraction as calculated in [9] to the final straylight irradiance 4-To consider a way to use the real diffraction profile and compute the generated straylight…”

Section: Resultsmentioning

confidence: 99%

“…The propagation of the diffraction itself through the ASPIICS instrument was not performed at this time, but the diffraction signal itself should be added to this comparison to get a full overview of the in-FoV straylight. This calculation is being made through a numerical model presented in [9] and [11].…”

Section: Icso 2018 International Conference On Space Opticsmentioning

confidence: 99%

Straylight analysis on ASPIICS, PROBA-3 coronagraph

Galy

Thizy

Stockman

et al. 2019

International Conference on Space Optics — ICSO 2018

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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 spacecraft. 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 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. This paper will present the straylight model and analyses carried out by CSL. A first specificity of the analysis is that the scene on the useful Field of View (FOV) is the solar corona which has a brightness dynamic range as high as 10³ between the close corona, close to 1 solar radius (Rsun), and the "distant" corona around 3RSun. The specifications are very stringent for this type of instrument. A consensus was found and will be presented regarding the expected straylight within the FOV. It will also be shown that to achieve realistic estimations it is required to take into account the exact location of the created straylight as well as the entrance field.The second specificity that had to be analyzed is that the diffraction from the solar disk by the external occulter enters the instrument un-obstructed until the internal occulter, and with a brightness 100 times higher than the close corona (~1RSun) brightness. The simulation of this diffraction as well as its propagation inside the ASPIICS telescope creating additional straylight, had to be carefully established in order to give realistic results of its impact on the performances while being actually possible to compute.

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“…Thus Landini et al (2010) and Landini et al (2011) compared the efficiency of linear segments of various occulters, and thick occulters were again found to be more efficient, with the advantage being about factor of two. Later, Landini et al (2016Landini et al ( , 2017a developed an analytical model and showed how an ASPIICS-size configuration can be rescaled to a laboratory size (linear scaling for distances, and quadratic scaling for thicknesses) so that the experiments would be representative. However, in this case, the intensity of the diffracted light can be measured only in the entrance aperture plane and not in the detector plane, as otherwise the remaining optical system would be scaled down to an unrealistic size.…”

Section: Discussionmentioning

confidence: 99%

Expected performances of the PROBA-3/ASPIICS solar coronagraph: Simulated data

Shestov

Zhukov

Inhester

et al. 2021

A&A

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Context. The Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS) is a novel externally occulted solar coronagraph that will be launched on board the Project for On-Board Autonomy (PROBA-3) mission in 2023. The external occulter will be placed on the first satellite ∼ 150 m ahead of the second satellite, which will carry an optical instrument. During 6 hours per orbit, the satellites will fly in a precise formation and will constitute a giant externally occulted coronagraph. The large distance between the external occulter and the primary objective will allow observations of the white-light solar corona starting from extremely low heights of ∼ 1.1R ⊙ . Aims. Developing and testing of algorithms for the scientific image processing requires understanding of all the optics-related and detector-related effects of the coronagraph, development of appropriate physical and numerical models, and preparation of simulated images that include all these effects. At the same time, an analysis of the simulated data gives valuable information about the performance of the instrument, the suitable observation regime, and the amount of telemetry. Methods. We used available physical models of the instrument and implemented them as a software to generate simulated data. We analyzed intermediate and complete simulated images to obtain a better understanding of the performance of ASPIICS, in particular, to predict its photometric sensitivity, effect of noise, suitable exposure times, etc. Results. The proposed models and algorithms are used not only to create the simulated data, but also to form the basis for the scientific processing algorithms to be applied during on-ground ASPIICS data processing. We discuss the possible effect of noise and the uncertainty of the calibration factors on the accuracy of final data, and propose suitable exposure times.

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Scaled-model guidelines for formation-flying solar coronagraph missions

Cited by 6 publications

References 8 publications

Theoretical performance of serrated external occulters for solar coronagraphy

Theoretical performance of serrated external occulters for solar coronagraphy

Straylight analysis on ASPIICS, PROBA-3 coronagraph

Expected performances of the PROBA-3/ASPIICS solar coronagraph: Simulated data

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