Recent developments have seen a trend towards larger constellations of spacecraft, with some proposals featuring constellations of more than 10.000 satellites. While similar concepts for large ...constellations already existed in the past, traditional satellite deployments hardly ever feature groups of more than 100 satellites. This trend towards considerably larger satellite numbers originates from non-traditional design and operations of spacecraft by non-traditional space companies. The evolution in the space sector, precipitated by new players, is often referred to as “Space 4.0” or “New Space”. It necessitates a rethinking of the way satellites and satellite constellations are planned, designed, and operated. New operational paradigms are needed to enable automatic, optimal task definition, and scheduling in a holistic approach.
This is the second of two companion papers that investigate the operations of distributed satellite systems. This second article investigates the classification of distributed satellite systems and evaluates commercial tools for automated spacecraft operations, whereas the first article performed a survey of conventional and “new space”operations of spacecraft constellations.
Classification metrics for constellations are derived and evaluated with respect to their informative value concerning the operation, the automation, and the scalability of the constellation. The proposed classification system is applied to the Dove and RapidEye constellation and allows for a comparison between the presented automation approaches. Commercial tools for automated spacecraft operations are evaluated for several mission task elements, such as orbit control, orbit maintenance, and collision avoidance. Subsequently, the trends, benefits, and standardization needs for operational automation are identified.
Future human exploration missions require new concepts of operations since the international roadmap foresees stations with uncrewed periods (e.g. Lunar Gateway) and deep space missions with ...communication delays making real-time monitoring and control impossible (e.g. any vehicle on its way to or in orbit of Mars). As part of the commitment to achieve human presence in lunar orbit and prepare for missions to Mars, the goal for future operations is to become independent from ground and enable crews to live and work autonomously. However, as a first step towards on-board crew autonomy, the ground segment itself needs to be automated and its functions eventually transferred on-board. For this purpose, this paper introduces a novel tool, based on Columbus operations, conducted at the Columbus Control Center (COL-CC), allowing the interaction between scheduled activities and the commanding infrastructure, by automatically generating a command sequence, transferring the command sequence to the operators’ command interface for inspection and approval, and finally sending the commands to the receiver for execution. This tool is implemented as a ground prototype, in order to show how ground operations can be automated and how such a tool can ultimately lead to increased crew autonomy.
•Crewed deep-space missions cannot use real-time commanding, due to signal delays.•Real-time commanding is shifted from the ground controller to an on-board system.•An interface allows interaction between crew, mission timeline and command system.•The system is capable of automatically generating commands, based on constraints.•An activity database stores all necessary information for activity execution.
The Mars Express (MEX) spacecraft, operated by the European Space Agency (ESA), has been orbiting Mars for the past 18 years. During this period, it has provided unprecedented scientific data about ...the red planet, but it has also aged, and its batteries have degraded. Thus, MEX needs careful and accurate power modeling to continue its significant contribution without breaking, twisting, deforming, or failure of any equipment. The power consumed by the autonomous thermal subsystem, that keeps all equipment within its operating temperature in a difficult environment, is the only unknown variable in the spacecraft’s power budget. In this pilot study, we address the task of predicting the thermal power consumption (TPC) of MEX on all of its 33 thermal power lines, learning predictive models from the stream of its telemetry data, which is a task of multi-target regression on data streams. To analyze such data streams and to model the MEX power consumption, we consider both local and global approaches, i.e., predicting each target by a separate model and predicting all targets at once by a single model, respectively. Our evaluation of the considered approaches investigates their performance in predicting the MEX power consumption, the influence of the time resolution of the measurements of TPC on this performance, and the success of the methods in detecting and adapting to change.
•We learn online multi-target models for predicting spacecraft’s power consumption.•Global tree-based methods perform better than rule-based methods.•Local tree-based methods outperform global ones due to change detection/adaptation.•Effects of concept drift are visible at all time resolutions for all methods.
In June 2018, after 4 years of cruise, the Japanese space probe Hayabusa2 1-Watanabe S. et al.: Hayabusa2 Mission Overview. (2017) reached the Near-Earth Asteroid (162173) Ryugu. Hayabusa2 carried a ...small Lander named MASCOT (Mobile Asteroid Surface Scout) 2-Ho T. M. et al.: MASCOT-The Mobile Asteroid Surface Scout on-board the Hayabusa2 mission. (2017), jointly developed by the German Aerospace Center (DLR) and the French Space Agency (CNES), to investigate Ryugu's surface structure, composition and physical properties including its thermal behaviour and magnetization in-situ. The Microgravity User Support Centre (DLR-MUSC) in Cologne was in charge of providing all thermal conditions and constraints necessary for the selection of the final landing site and for the final operations of the Lander MASCOT on the surface of the asteroid Ryugu.
This article provides a comprehensive assessment of these thermal conditions and constraints, based on predictions performed with the Thermal Mathematical Model (TMM) of MASCOT using different asteroid surface thermal models, ephemeris data for approach as well as descent and hopping trajectories, the related operation sequences and scenarios and the possible environmental conditions driven by the Hayabusa2 spacecraft.
A comparison with the real telemetry data confirms the analysis and provides further information about the asteroid characteristics.
•Application of Thermal Mathematical Models for landing site selection.•Day-Night temperature is main criteria for landing site selection.•Pre-separation heating strategies will optimize science return.•Thermal models used not only for spacecraft design but also for planning mission phases.
This paper presents new perspectives on the application of Artificial Intelligence (AI) solutions to process Spacecraft (S/C) flight data in order to augment currently used operational S/C health ...monitoring and diagnostics systems. It captures the growing general interest in the usage of such techniques in the Space engineering domain and applications.
Jointly with the AI approach, the operational usage of S/C simulation models (referred to as “discipline models”) is also explored. During S/C development and testing activities, significant efforts are made by the discipline experts to build such models. However, using discipline-specific knowledge to support complex S/C operational activities (e.g., anomaly root cause analysis) remains a challenging task.
Based on the current needs of Space Agencies and Industry and by exploiting the advances in AI-based solutions and technologies, this paper proposes an operational S/C model-based diagnostics framework, which can serve as basis for future developments. Such framework combines AI-based techniques, S/C flight data information, and discipline models. Three main needs are addressed: S/C anomaly root cause analysis, S/C prediction behavior, and discipline model refinement. Concrete operational case studies from the Project for On-Board Autonomy (PROBA) satellite family are presented to show the applicability of the proposed framework.
During the satellite’s operations, simulation tools perform an important role in ensuring the space mission success. In this sense, the models implemented in the context of an operational satellite ...simulator that enables analysis of health status and maintenance during operations shall reflect the current satellite behavior with high fidelity. Moreover, it is complicated to obtain all analytical models of a satellite’s disciplines, considering its aging. This paper proposes an Artificial Neural Network (ANN) to reproduce the battery voltage behavior of a large sun-synchronous remote sensing satellite, the CBERS-4, currently in operation. Using the genetic algorithm to find the best network architecture of ANN, the neural model for this application presented an error of less than 1%, demonstrating its feasibility to obtain a high fidelity model for an operational simulator enabling extend analyses. The paper addresses advanced techniques aligned with the space industry’s future, increasing the ability to analyze a large amount of data and improve the space system’s operation.
Different drivers are nowadays leading spacecraft toward an increased level of on-board autonomy. In this paper, we survey model-based techniques as a vehicle to implement highly autonomous on-board ...capabilities for spacecraft mission planning and execution. In this respect, spacecraft reconfiguration approaches based on Markovian Decision Process are explored, and then compared with other model-based alternatives. The integration of planning systems and dynamic reprogramming capabilities into the on-board software is presented. Finally, operational concepts for mission planning and execution in recent European space projects as well as the implementation of in-flight adaptive mission operations via on-board control procedures are also analyzed.
Dawn is the first NASA mission to operate in the vicinity of the two most massive asteroids in the main belt, Ceres and Vesta. This double-rendezvous mission is enabled by the use of low-thrust solar ...electric propulsion. Dawn will arrive at Vesta in 2011 and will operate in its vicinity for approximately one year. Vesta's mass and non-spherical shape, coupled with its rotational period, presents very interesting challenges to a spacecraft that depends principally upon low-thrust propulsion for trajectory-changing maneuvers. The details of Vesta's high-order gravitational terms will not be determined until after Dawn's arrival at Vesta, but it is clear that their effect on Dawn operations creates the most complex operational environment for a NASA mission to date. Gravitational perturbations give rise to oscillations in Dawn's orbital radius, and it is found that trapping of the spacecraft is possible near the
1:1 resonance between Dawn's orbital period and Vesta's rotational period, located approximately between 520 and 580
km orbital radius. This resonant trapping can be escaped by thrusting at the appropriate orbital phase. Having passed through the
1:1 resonance, gravitational perturbations ultimately limit the minimum radius for low-altitude operations to about 400
km, in order to safely prevent surface impact. The lowest practical orbit is desirable in order to maximize signal-to-noise and spatial resolution of the Gamma-Ray and Neutron Detector and to provide the highest spatial resolution observations by Dawn's Framing Camera and Visible InfraRed mapping spectrometer. Dawn dynamical behavior is modeled in the context of a wide range of Vesta gravity models. Many of these models are distinguishable during Dawn's High Altitude Mapping Orbit and the remainder are resolved during Dawn's Low Altitude Mapping Orbit, providing insight into Vesta's interior structure. Ultimately, the dynamics of Dawn at Vesta identifies issues to be explored in the planning of future EP missions operating in close proximity to larger asteroids.
The aim of Dawn mission is the acquisition of data from orbits around two bodies (4) Vesta and (1) Ceres, the two most massive asteroids.
Due to the low thrust propulsion, Dawn will slowly cross and ...transit through ground-track resonances, where the perturbations on Dawn orbit may be significant. In this context, to safety go the Dawn mission from the approach orbit to the lowest science orbit, it is essential to know the properties of the crossed resonances.
This paper analytically investigates the properties of the major ground-track resonances (1:1, 1:2, 2:3 and 3:2) appearing for Vesta orbiters: location of the equilibria, aperture of the resonances and period at the stable equilibria. We develop a general method using an averaged Hamiltonian formulation with a spherical harmonic approximation of the gravity field. If the values of the gravity field coefficient change, our method stays correct and applicable. We also discuss the effect of one uncertainty on the C20 and C22 coefficients on the properties of the 1:1 resonance. These results are checked by numerical tests. We determine that the increase of the eccentricity appearing in the 2:3 resonance is due to the C22 and S22 coefficients.
Our method can be easily adapted to missions similar to Dawn because, contrarily to the numerical results, the analytical formalism stays the same and is valid for a wide range of physical parameters of the asteroid (namely the shape and the mass) as well as for different spacecraft orbits.
Finally we numerically study the probability of the capture in resonance 1:1. Our paper reproduces, explains and supplements the results of Tricarico and Sykes (2010).
► We study the properties of the major ground-track resonances around Vesta. ► The theory is general enough to be applied to a wide range of probes. ► We explain an increase of the eccentricity in the 2:3 resonance. ► We reproduce, explain and complete the results of Tricarico and Sykes (2010).
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