The Solar Upper Transition Region Imager (SUTRI) onboard the Space Advanced Technology demonstration satellite (SATech-01), which was launched to a Sun-synchronous orbit at a height of ∼500 km in 2022 July, aims to test the on-orbit performance of our newly developed Sc/Si multi-layer reflecting mirror and the 2k×2k EUV CMOS imaging camera and to take full-disk solar images at the Ne vii 46.5 nm spectral line with a filter width of ∼3 nm. SUTRI employs a Ritchey–Chrétien optical system with an aperture of 18 cm. The on-orbit observations show that SUTRI images have a field of view of ∼ 41.′6 × 41.′6 and a moderate spatial resolution of ∼8″ without an image stabilization system. The normal cadence of SUTRI images is 30 s and the solar observation time is about 16 hr each day because the earth eclipse time accounts for about 1/3 of SATech-01's orbit period. Approximately 15 GB data is acquired each day and made available online after processing. SUTRI images are valuable as the Ne vii 46.5 nm line is formed at a temperature regime of ∼0.5 MK in the solar atmosphere, which has rarely been sampled by existing solar imagers. SUTRI observations will establish connections between structures in the lower solar atmosphere and corona, and advance our understanding of various types of solar activity such as flares, filament eruptions, coronal jets and coronal mass ejections.

/pdf/the-solar-upper-transition-region-imager-sutri-onboard-the-443yjqt9.pdf

The Solar Upper Transition Region Imager (SUTRI) Onboard the SATech-01 Satellite

Spacecraft are subjected to a harsh and complex dynamic environment during launch and on-orbit operation, necessitating the use of vibration isolation techniques to protect the onboard components and the payload from harmful vibration. Moreover, the stringent requirements for modern spacecraft’s payload stability and pointing accuracy have fueled research for higher-performance vibration isolation. Consequently, a number of vibration isolation systems based on active, passive, semi-active, and hybrid isolation methods have been proposed. This study employed a systematic literature review methodology to examine the most recent methods for vibration isolation in spacecraft, taking into account both whole-spacecraft vibration isolation (WSVI) and microvibration isolation (MVI) and primarily referencing works published in the literature between 2012 and 2022. The review highlighted current research trends in vibration isolation methods and implementation strategies reported in the literature, as well as the status of research on WSVI and MVI. The findings suggest that more research was conducted in the domain of MVI compared to WSVI, with passive techniques accounting for about 42% of the articles reviewed. This could be attributed to the advances made in smart materials, metamaterials, and the quasi-zero-stiffness concept to address the shortcomings of traditional passive isolators. To this end, remarks on the limitations of the current studies and future prospects were highlighted. 

Vibration isolation methods in spacecraft: A review of current techniques

The CHASE satellite is designed based on the novel ultra-high pointing accuracy and stability levitated-body satellite platform, which breaks the traditional idea of rigidly connecting the satellite platform and payload. When operating in orbit, the platform and payload are non-connected and spatially levitated. By separately arranging the “noisy” and “quiet” devices, the complicated influence of platform vibration on the payload pointing direction is effectively avoided. Using the novel master-slave collaborative control method, the pointing accuracy and stability of the payload are improved considerably. In this paper, the basic principles, overall scheme, control method, and engineering implementation of a levitated-body satellite platform are discussed. Combined with the CHASE mission in-orbit data, the actual attitude pointing precision and stability of a levitated-body satellite platform are analyzed and evaluated. 

https://link.springer.com/content/pdf/10.1007/s11433-022-1924-3.pdf

Levitated-body ultra-high pointing accuracy and stability satellite platform of the CHASE mission

Solar filaments often exhibit rotation and deflection during eruptions, which would significantly affect the geoeffectiveness of the corresponding coronal mass ejections (CMEs). Therefore, understanding the mechanisms that lead to such rotation and lateral displacement of filaments is a great concern to space weather forecasting. In this paper, we examine an intriguing filament eruption event observed by the Chinese Hα Solar Explorer and the Solar Dynamics Observatory. The filament, which eventually evolves into a CME, exhibits significant lateral drifting during its rising. Moreover, the orientation of the CME flux rope axis deviates from that of the pre-eruptive filament observed in the source region. To investigate the physical processes behind these observations, we perform a data-constrained magnetohydrodynamic simulation. Many prominent observational features in the eruption are reproduced by our numerical model, including the morphology of the eruptive filament, eruption path, and flare ribbons. The simulation results reveal that the magnetic reconnection between the flux rope leg and neighboring low-lying sheared arcades may be the primary mechanism responsible for the lateral drifting of the filament material. Such a reconnection geometry leads to flux rope footpoint migration and a reconfiguration of its morphology. As a consequence, the filament material hosted in the flux rope drifts laterally, and the CME flux rope deviates from the pre-eruptive filament. This finding underscores the importance of external magnetic reconnection in influencing the orientation of a flux rope axis during eruption.

pdf/understanding-the-lateral-drifting-of-an-erupting-filament-3it0w8pq3f.pdf

Understanding the Lateral Drifting of an Erupting Filament with a Data-constrained Magnetohydrodynamic Simulation

Abstract Partial filament eruptions have often been observed; however, the physical mechanisms that lead to filament splitting are not yet fully understood. In this study, we present a unique event of a partial filament eruption that undergoes two distinct splitting processes. The first process involves vertical splitting and is accompanied by brightenings inside the filament, which may result from internal magnetic reconnection within the filament. Following the first splitting process, the filament is separated into an upper part and a lower part. Subsequently, the upper part undergoes a second splitting, which is accompanied by a coronal blowout jet. An extrapolation of the coronal magnetic field reveals a hyperbolic flux tube structure above the filament, indicating the occurrence of breakout reconnection that reduces the constraining field above. Consequently, the filament is lifted up, but at a nonuniform speed. The high-speed part reaches the breakout current sheet to generate the blowout jet, while the low-speed part falls back to the solar surface, resulting in the second splitting. In addition, continuous brightenings are observed along the flare ribbons, suggesting the occurrence of a slipping reconnection process. This study presents, for the first time, the unambiguous observation of a two-stage filament-splitting process, advancing our understanding of the complex dynamics of solar eruptions. 

Observation of Two Splitting Processes in a Partial Filament Eruption on the Sun: The Role of Breakout Reconnection

The Chinese Hα Solar Explorer (CHASE), dubbed “Xihe”—Goddess of the Sun, was launched on October 14, 2021 as the first solar space mission of China National Space Administration (CNSA). The CHASE mission is designed to test a newly developed satellite platform and to acquire the spectroscopic observations in the Hα waveband. The Hα Imaging Spectrograph (HIS) is the scientific payload of the CHASE satellite. It consists of two observational modes: raster scanning mode and continuum imaging mode. The raster scanning mode obtains full-Sun or region-of-interest spectral images from 6559.7 to 6565.9 Å; and from 6567.8 to 6570.6 Å with 0.024 Å pixel spectral resolution and 1 min temporal resolution. The continuum imaging mode obtains photospheric images in continuum around 6689 Å with the full width at half maximum of 13.4 Å. The CHASE mission will advance our understanding of the dynamics of solar activity in the photosphere and chromosphere. In this paper, we present an overview of the CHASE mission including the scientific objectives, HIS instrument overview, data calibration flow, and first results of on-orbit observations. 

https://link.springer.com/content/pdf/10.1007/s11433-022-1893-3.pdf

The Chinese Hα Solar Explorer (CHASE) mission: An overview

Clock error prediction is of vital importance for the distributed netted systems’ regular operation, like netted satellites, netted radars, etc. Aiming at the problem of predicted length could not get beforehand in some conditions, we put forth a combined clock error method under uncertain predicted length. We estimate the predicted length based on the clock error data quality factor in advance. Then, we operate clock error prediction based on the combination method. If the time synchronization has reestablished earlier than the predicted length, we stop prediction immediately. And if time synchronization has not reestablished when the clock error prediction reaches the predicted length, we re-estimate the predicted length and continue prediction until time synchronization reestablishes. From examples analyses, we could get 0.3–0.5 ns around precision for one-day long precision and 0.9–1.1 ns for 2 days and 1.2–1.4 ns for 1 week. Besides, we could conclude that the combination method could flat the differences of the clocks and the difference of sole algorithms, improving the robustness of the algorithm. The combination clock error prediction method could be both applied in satellites’ clock error prediction and in other distributed netted system, especially in the condition that the predicted length could not be known before predicting, being vital to the whole systems’ performance.

Research on Combination Clock Error Prediction Under Uncertain Predicted Length

The invention discloses a short-term combined clock correction forecasting method under a condition of uncertain forecasting duration. The method comprises the following steps that: obtaining an original clock correction sequence, and carrying out differential processing; according to the original clock correction sequence, calculating a clock correction data quality factor, and determining the forecasting duration; adopting at least two types of clock correction forecasting methods to carry out forecasting learning; calculating the weight value of each clock correction forecasting method; according to the forecasting learning results of various clock correction forecasting methods and the corresponding weight value, calculating a combined clock correction forecasting value; judging whether time synchronization is established again or not at any time in a forecasting process; if the time synchronization is established, stopping forecasting immediately, and otherwise, continuously forecasting until the forecasting duration is achieved; if the time synchronization is still not established after the forecasting duration is achieved, prolonging the duration of the original clock correction, estimating the forecasting duration again, and repeating the above steps until the step of clock correction is established again; and after the clock correction forecasting is finished, carryingout differential inverse operation on the clock correction forecasting result, and obtaining a final clock correction forecasting sequence. The method aims at a situation that the forecasting duration is uncertain, and forecasting robustness is good.

Short-term combined clock correction forecasting method under condition of uncertain forecasting duration

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The Chinese Hα Solar Explorer (CHASE) mission: An overview

Research on Combination Clock Error Prediction Under Uncertain Predicted Length

Short-term combined clock correction forecasting method under condition of uncertain forecasting duration