Advances in Space Research

Journal: Advances in Space Research

Abbreviation

Adv. Space Res.

Publisher

Elsevier

ISSN

0273-1177
1879-1948

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Publications 1 - 10 of 39

Heliophysics Great Observatories and international cooperation in Heliophysics: An orchestrated framework for scientific advancement and discovery
Kepko, Larry; Nakamura, Rumi; Saito, Yoshifumi; et al. (2024)
Advances in Space Research
We suggest that the next era of Heliophysics should focus on the Sun–Heliosphere and Geospace as each a system-of-systems, and recommend a coordinated, deliberate, worldwide scientific effort to answer long-standing questions that will remain unanswered without a unified program. Many of the biggest unanswered science questions that remain across Heliophysics center around the interconnectivity of the different physical systems and the role of mesoscale dynamics in modulating, regulating, and controlling that interconnected behavior. Heliophysics has made key progress understanding both the large-scale dynamics and the microphysical processes that occur in these dynamic systems. Such understanding grew out of a systematic approach to study both limits of the system, from global, with the coordinated missions of the International Solar Terrestrial Physics (ISTP) program, to micro, with largely uncoordinated (albeit coincident) missions such as Cluster, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes, Magnetospheric Multiscale (MMS), Parker Solar Probe, and Solar Orbiter. We suggest that the international Heliophysics community should embark on a grand program to study these system-of-systems holistically, with coordinated, multipoint measurements. We particularly recommend an emphasis on resolving the mesoscale dynamics that links micro to global, and a whole-of-science approach that includes ground-based measurements and advanced numerical modeling. In effect, we propose a mesoscale ISTP type program that would consist of a system of Great Observatories capable of revealing the connections among systems from the solar interior to the top of Earth's atmosphere. The paradigm and specific approaches outlined in this paper could serve as a strategic imperative and overarching theme that binds our Solar and Space Physics communities together under a common scientific objective. By its very nature, the type of program we argue for would be large, with several coordinated elements, and international in scope. It would include space-borne missions and coordinated ground-based observatories, artificial intelligence/machine learning (AI/ML) methods of analyzing large and complex datasets, and next-generation numerical modeling. The need to coordinate and integrate these different elements is independent of any specific mission implementation. Hence, we suggest the Heliophysics community organize around an ISTP-type program, ISTPNext, with associated Heliophysics “Great Observatories”.
The FLUKA code for space applications
Andersen, V.; Ballarini, F.; Battistoni, G.; et al. (2004)
Advances in Space Research
Micro-events in the active and quiet solar corona
Benz, A. O.; Grigis, P.C. (2003)
Advances in Space Research
Exodus: A mission proposal to explore exoplanet evolution through understanding atmospheric escape
Bruce Rosete, Citlali Bruce; Leon Dasi, Mireia Leon; Boyd, Mark R.; et al. (2026)
Advances in Space Research
Understanding the variety of system architectures and formation histories of planetary systems remains a major challenge. Current detection methods are strongly biased towards short-period bodies, leaving a gap in the exoplanet population demographics. This paper outlines Exodus, a mission proposal to study the largely unexplored range of sub-Neptune to Jupiter-sized exoplanets with orbital periods greater than 100 days. The focus of the mission lies in the detection of these planets and characterisation of atmospheric escape to constrain their evolutionary pathways. For this, Exodus will directly image exoplanets with radii above 1.5R_earth and measure signatures of the helium triplet at 1083nm. Furthermore, the activity of the host star is monitored in the ultraviolet (UV) wavelengths to distinguish between two mechanisms of atmospheric escape: UV-driven mass loss and core-powered mass loss. The proposed mission design consists of a space telescope which requires a Lissajous orbit around H₂. The primary instrument uses an Integral Field Unit (IFU) optimised for direct imaging of exoplanetary systems in the near-infrared (NIR) domain. Simultaneous monitoring of the parent star is conducted via photometric observations of the H_α emission. In addition to the necessary instrumentation, we present a comprehensive spacecraft design considering important budgets like mass, power, and propulsion, as well as a thermal design. The mission described in this paper was developed during the Alpbach Summer School 2023, which focused on the theme ”Exoplanets: Understanding alien worlds in diverse environments.”.
Past, present and future measurements of the solar diameter
Thuillier, Gérard; Sofia, Sabatino; Haberreiter, Margit (2005)
Advances in Space Research
In-flight testing of the injection of the LISA Pathfinder test mass into a geodesic
Bortoluzzi, Daniele; Ferraioli, Luigi; Giardini, Domenico; et al. (2021)
Advances in Space Research
LISA Pathfinder is a technology demonstrator space mission, aimed at testing key technologies for detecting gravitational waves in space. The mission is the precursor of LISA, the first space gravitational waves observatory, whose launch is scheduled for 2034. The LISA Pathfinder scientific payload includes two gravitational reference sensors (GRSs), each one containing a test mass (TM), which is the sensing body of the experiment. A mission critical task is to set each TM into a pure geodesic motion, i.e. guaranteeing an extremely low acceleration noise in the sub-Hertz frequency bandwidth. The grabbing positioning and release mechanism (GPRM), responsible for the injection of the TM into a geodesic trajectory, was widely tested on ground, with the limitations imposed by the 1-g environment. The experiments showed that the mechanism, working in its nominal conditions, is capable of releasing the TM into free-fall fulfilling the very strict constraint imposed on the TM residual velocity, in order to allow its capture on behalf of the electrostatic actuation. However, the first in-flight releases produced unexpected residual velocity components, for both the TMs. Moreover, all the residual velocity components were greater than maximum value set by the requirements. The main suspect is that unexpected contacts took place between the TM and the surroundings bodies. As a consequence, ad hoc manual release procedures had to be adopted for the few following injections performed during the nominal mission. These procedures still resulted in non compliant TM states which were captured only after impacts. However, such procedures seem not practicable for LISA, both for the limited repeatability of the system and for the unmanageable time lag of the telemetry/telecommand signals (about 4400 s). For this reason, at the end of the mission, the GPRM was deeply tested in-flight, performing a large number of releases, according to different strategies. The tests were carried out in order to understand the unexpected dynamics and limit its effects on the final injection. Some risk mitigation maneuvers have been tested aimed at minimizing the vibration of the system at the release and improving the alignment between the mechanism and the TM. However, no overall optimal release strategy to be implemented in LISA could be found, because the two GPRMs behaved differently.
Inclusion of data uncertainty in machine learning and its application in geodetic data science, with case studies for the prediction of Earth orientation parameters and GNSS station coordinate time series
Kiani Shahvandi, Mostafa; Soja, Benedikt (2022)
Advances in Space Research
Data uncertainty plays an important role in the field of geodesy. Even though deep learning is becoming increasingly important for geodetic applications due to its high accuracy, it typically does not consider the data uncertainty. As we demonstrate in this study, we propose to include the uncertainty of data in deep neural network architectures to achieve a better generalization. This is advantageous for big data applications as well as for small datasets. Inspired by weighted and total least squares, we formulate the problem for both input and target uncertainties, and combine it with the Bayesian learning method. This results in a new form of the loss function in machine learning. As an alternative approach, we consider data uncertainties by including them as additional features. For comparison purposes, we use models without the consideration of data uncertainty as a benchmark. To show the efficacy of the proposed method, we apply it to the prediction of Earth Orientation Parameters (EOPs, namely polar motion, dUT1, and LOD) and Global Navigation Satellite System (GNSS) station coordinate time series. We demonstrate that the least-squares-inspired method outperforms both the benchmark and the feature-inspired method for both the studies. In the EOPs study, the improvement can be more than 50% in the study interval. In the study of GNSS station coordinate time series, which is presented for 1000 stations across the globe, the improvement on an average basis is around 12%. The results demonstrate the advantage of using uncertainty information in the machine learning algorithms, when applied to geodetic time series.
Role of shielding in modulating the effects of solar particle events
Ballarini, F.; Biaggi, M.; De Biaggi, L.; et al. (2004)
Advances in Space Research
Real-time navigation solutions of low-cost off-the-shelf GNSS receivers on board the Astrocast constellation satellites
Müller, Lukas; Chen, Kangkang; Möller, Gregor; et al. (2024)
Advances in Space Research
With the ever-increasing number of small satellites launched into space, on-board orbit determination is becoming more and more important. Precise satellite positions are needed for constellation maintenance, formation flying, communication optimization, collision avoidance and Earth observation. In addition, accurate time information is required for the functioning of the instruments on board. Low-cost off-the-shelf Global Navigation Satellite System (GNSS) receivers and antennas, adapted to the small size and weight of the satellite, allow precise on-board orbit determination and time synchronization for even the smallest satellites. We analysed more than one year of on-board navigation solutions (NAVSOL) from 8 Astrocast CubeSats, which are equipped with our multi-GNSS single-frequency payload. Based on the residuals from a dynamic orbit fitting, we found that the quality of the NAVSOL from the Astrocast satellites varies strongly both over time and between satellites, with an RMS ranging from a few meters to several tens of meters. In this study, we focus on three main effects that influence the quality of the NAVSOL from the Astrocast satellites: (1) The orbit-fit residuals show a positive radial offset in the range of about 6 m to 15 m, which is caused by ionospheric refraction. Our data show that GNSS signals at negative elevations are very strongly affected by the ionospheric refraction and thus account for the major part of the radial offset. (2) Discrepancies between the NAVSOL positions and velocities, and simulations with a GNSS signal generator show a once-per-revolution periodicity in the out-of-plane component, with amplitudes of 2 m and 5 cm/s in position and velocity, respectively. This effect is probably due to an inappropriate dynamic model used in the real-time navigation algorithm of the GNSS receiver. (3) Depending on the location of the GNSS antenna on board the satellite, the noise level varies by a multiple. This is assumed to be due to the antenna orientations, interference of the GNSS signals with electromagnetic waves coming from the satellite platform, signal attenuation during the transmission from the antenna to the receiver and differences in the soldering or tuning of the individual GNSS antennas. These findings help us refine hardware configurations and firmware settings in preparation for future Astrocast satellites or other nanosatellite missions. By eliminating or minimizing the mentioned effects, we expect to consistently achieve an accuracy on the level of a few meters for the real-time navigation solution of commercial off-the-shelf single-frequency GNSS receivers in space.
RHESSI and radio imaging observations of microflares
Kundu, M.R.; Trottet, G.; Garaimov, V.I.; et al. (2005)
Advances in Space Research

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