The STIX Aspect System (SAS): The Optical Aspect System of the Spectrometer/Telescope for Imaging X-Rays (STIX) on Solar Orbiter

Warmuth, A.; Önel, H.; Mann, G.; Rendtel, J.; Strassmeier, K. G.; Denker, C.; Hurford, G. J.; Krucker, S.; Anderson, J. M.; Bauer, Svend‐Marian; Bittner, Wilbert; Dionies, Frank; Paschke, J.; Plüschke, D.; Sablowski, D. P.; Schüller, F.; Pavai, V. Senthamizh; Woche, M.; Casadei, D.; Kögl, S.; Arnold, N. G.; Gröbelbauer, H.-P.; Schori, D.; Wiehl, H. J.; Csillaghy, A.; Grimm, O.; Orleański, P.; Skup, Konrad; Bujwan, Waldemar; Rutkowski, K.; Ber, Kamil

doi:10.1007/s11207-020-01660-w

Cited by 23 publications

(13 citation statements)

References 9 publications

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“…The roll-angle value used for the rotation is provided by the SPICE as-flown attitude kernel 2 . As for the offset issue, for the events considered in this study, the Solar Orbiter was too far (outside 0.75 AU) from the Sun for the STIX Aspect System to be able to provide absolute pointing information (Warmuth et al., 2020 ). In order to superimpose the reconstructed hard X-ray sources on the UV ribbons, we therefore performed a manual shift of the reconstructed and rotated STIX maps.…”

Section: Stix Images Of May 2021 Eventsmentioning

confidence: 99%

First Hard X-Ray Imaging Results by Solar Orbiter STIX

et al. 2022

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The Spectrometer/Telescope for Imaging X-rays (STIX) is one of six remote sensing instruments on-board Solar Orbiter. The telescope applies an indirect imaging technique that uses the measurement of 30 visibilities, i.e., angular Fourier components of the solar flare X-ray source. Hence, the imaging problem for STIX consists of the Fourier inversion of the data measured by the instrument. In this work, we show that the visibility amplitude and phase calibration of 24 out of 30 STIX sub-collimators has reached a satisfactory level for scientific data exploitation and that a set of imaging methods is able to provide the first hard X-ray images of solar flares from Solar Orbiter. Four visibility-based image reconstruction methods and one count-based are applied to calibrated STIX observations of six events with GOES class between C4 and M4 that occurred in May 2021. The resulting reconstructions are compared to those provided by an optimization algorithm used for fitting the amplitudes of STIX visibilities. We show that the five imaging methods produce results morphologically consistent with the ones provided by the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory (SDO/AIA) in UV wavelengths. The $\chi ^{2}$ χ 2 values and the parameters of the reconstructed sources are comparable between methods, thus confirming their robustness.

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Section: Stix Images Of May 2021 Eventsmentioning

confidence: 99%

First Hard X-Ray Imaging Results by Solar Orbiter STIX

et al. 2022

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“…The roll-angle value used for the rotation is provided by the SPICE as-flown attitude kernel 4 . As for the offset issue issue, for the events considered in this study, Solar Orbiter was too far (outside 0.75 AU) from the Sun for the STIX Aspect System to be able to provide absolute pointing information (Warmuth et al 2020). In order to superimpose the reconstructed hard X-ray sources on the UV ribbons, we therefore performed a manual shift of the reconstructed and rotated STIX maps.…”

Section: Location Of the Stix Reconstructionsmentioning

confidence: 99%

“…During the official science window, Solar Orbiter will be close enough to the Sun to allow precise measurements of STIX pointing by means of the Aspect System. We expect the error in the location of STIX reconstructions to be better than 4 arcsec (Warmuth et al 2020) once the corrections based on these measurements are implemented.…”

Section: Location Of the Stix Reconstructionsmentioning

confidence: 99%

First hard X-ray imaging results by Solar Orbiter STIX

Massa,

Battaglia,

Volpara

et al. 2022

Preprint

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Context. The Spectrometer/Telescope for Imaging X-rays (STIX) is one of 6 remote sensing instruments on-board Solar Orbiter. It provides hard X-ray imaging spectroscopy of solar flares by sampling the Fourier transform of the incoming flux. Aims. To show that the visibility amplitude and phase calibration of 24 out of 30 STIX sub-collimators is well advanced and that a set of imaging methods is able to provide the first hard X-ray images of the flaring Sun from Solar Orbiter. Methods. We applied four visibility-based image reconstruction methods and a count-based one to calibrated STIX observations. The resulting reconstructions are compared to those provided by an optimization algorithm used for fitting the amplitudes of STIX visibilities.Results. When applied to six flares with GOES class between C4 and M4 which occurred in May 2021, the five imaging methods produce results morphologically consistent with the ones provided by the Atmospheric Imaging Assembly on-board the Solar Dynamic Observatory (SDO/AIA) in UV wavelengths. The χ 2 values and the parameters of the reconstructed sources are comparable between methods, thus confirming their robustness. Conclusions. This paper shows that the current calibration of the main part of STIX sub-collimators has reached a satisfactory level for scientific data exploitation, and that the imaging algorithms already available in the STIX data analysis software provide reliable and robust reconstructions of the morphology of solar flares.

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“…At a heliocentric distance of 0.87 au, the STIX Aspect System (Warmuth et al, 2020) is not functional, and therefore the exact position of the X-ray sources is not known precisely. However, we have applied an average image displacement obtained from other events observed from the cruise phase where aspect information was available.…”

Section: Flare Observationsmentioning

confidence: 99%

The eruption of 22 April 2021 as observed by SolarOrbiter, STEREO and Earth bound instruments

Rodriguez

Warmuth

Andretta

et al. 2022

Preprint

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The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter ob-served an eruption through both of its channels (17.4/30.4 nm) of its Full Sun Imager, on 22 April 2021. At the time, the spacecraft was at 0.87 au from the Sun,and 98◦ east of the Sun-Earth line. The eruption was slightly back-sided, emerging close to the southwest limb, starting at 04:24 UT, with the source located at S20W103 from the Solar Orbiter perspective. The Solar Orbiter coronagraph, Metis, observed the CME at 06:05 UT. The Spectrometer/Telescope for Imaging X-rays (STIX) on Solar Orbiter sampled the associated X-ray flare, which was partially occulted. This allowed the characterization of both the thermal plasmaand any potential contribution of non-thermal electrons in the tenuous coronal source. The X-ray source location is compared to the extreme ultraviolet coronal structures seen by EUI, and it is established that STIX imager only sees the top part of the flaring loops, while most of the flare – in particular the non-thermal foot points – remain occulted. From the Earth’s perspective the eruption source region was observed at S20W05 (close to disk centre), the Atmospheric Imaging Assembly (AIA), onboard the Solar Dynamics Observatory (SDO) and the Sun Watcher using Active Pixel System detector and Image Processing (SWAP), onboard the PRoject for OnboardAutonomy (PROBA2) observed dimmings and an associated large-scale coronal wave starting around 04:07 UT. The Extreme Ultraviolet Imager (EUVI) on the Solar-TErrestial RElations Observatory (STEREO-A), located 53◦ east of the Sun-Earth line at the time, observed similar signatures of an eruption starting around 04:17 UT, on-disk at S20W50. The corresponding CME was observedas a partial halo CME shortly after (∼06:00 UT) by the C2 Large Angle and Spectrometric Coronagraph (LASCO), from the Earth perspective onboard the SOlar and Heliospheric Observatory (SOHO), and by the STEREO-A/COR2 coronagraph as a clear structured CME around 05:23 UT. The corresponding ICME arrived at Earth on 24 April 2021, it was driving ashock and created minor geomagnetic storm conditions. We simulate the CMEwith the 3D MHD heliospheric model EUHFORIA. We provide an analysis ofthe eruption as observed by these various instruments from different vantage points. The combination of data from Solar Orbiter as well as other space-based assets with numerical modeling clearly showcases the scientific potential for the science phase of Solar Orbiter, and the unique observations available.

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The STIX Aspect System (SAS): The Optical Aspect System of the Spectrometer/Telescope for Imaging X-Rays (STIX) on Solar Orbiter

Cited by 23 publications

References 9 publications

First Hard X-Ray Imaging Results by Solar Orbiter STIX

First Hard X-Ray Imaging Results by Solar Orbiter STIX

First hard X-ray imaging results by Solar Orbiter STIX

The eruption of 22 April 2021 as observed by SolarOrbiter, STEREO and Earth bound instruments

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