Project Areas
The Collaborative Research Center 1667 ATLAS encompasses 17 distinct scientific subprojects, which are organised into three project areas, respectively addressing the problem of sustainable VLEO flight at different levels. Each of these project areas in turn comprises two project sub-clusters indicating a common focus area and a particulary close collaboration between research partners.
Project Area A: Gas-Surface Interactions
Project Area A focuses on tools and methods required for a fundamental understanding and mastering of gas-surface interactions from both experimental and numerical modelling point of views, further covering different relevant scales in time and space.
The interactions between atomic oxygen and metals or oxides are studied at the atomistic level (ab initio / molecular dynamics based on density functional theory and machine learning techniques). The fractions of reflected, adsorbed, and chemically reacting atoms, as well as energy and momentum transfer, are determined as a function of material, incident energy and angle, roughness, and temperature, among other factors. Adsorption energies and diffusion paths of oxygen at the surface, in the material and along metal-oxide interfaces are also calculated.
Project Leaders: Johannes Kästner (itheoc), Johannes Roth (FMQ)
A detailed gas-surface interaction model with surface chemical reactions will be developed and implemented in the gas kinetic DSMC code PICLas, using microscopic data from A01. This will enable more accurate predictions of drag and lift coefficients, bridging the gap between microscopic approaches and the required macroscopic values for entire satellites. Furthermore, methods from "Uncertainty Quantification" are investigated and implemented to account for uncertainties from flow boundary conditions and satellite design.
Project Leaders: Andrea Beck (IAG), Marcel Pfeiffer (IRS)
A novel, experimentally well characterized ground test facility will be realised in this project based on a plasma wind tunnel adapted with a skimmer. The development will be accompanied by detailed simulations with the DSMC code PICLas. The associated methodology for combined experimental and numerical investigations of gas-surface interactions will be established and evaluated. This will particularly allow for an experimental validation of physical models developed and used in the numerical tools in this and other projects.
Project Leaders: Georg Herdrich (IRS), Stefanos Fasoulas (IRS)
Project A04 will develop and refine diagnostic methods required for the quantitative measurement of atomic oxygen in the ground test facility of Project A03 and for future measurements in the actual VLEO environment. The measurement methods are based on a combination of optical diagnostics, mass spectrometry, and solid-state electrolyte sensors that have been or are being used in various experiments on sounding rockets, the International Space Station, and satellites.
Project Leader: Stefan Löhle (IRS)
Novel algorithms for satellite attitude control are developed that take aerodynamic forces and moments into account. For this purpose, two strategies are pursued in parallel, which are based on the measurement of disturbances and on data-driven approaches, respectively. For validation, verification methods are derived that combine nonlinear system theory with stochastic methods. The sensitivity of the control and verification to uncertainties in the environmental parameters will also be assessed.
Project Leaders: Torbjørn Cunis (iFR), Walter Fichter (iFR)
A simulation tool for planning manoeuvres considering the acting aerodynamic forces, the associated uncertainties and thrusts will be developed and investigated. The tool will provide the possibility to identify optimal manoeuvre strategies, e.g. with minimum thrust requirements, or to evaluate the effects of satellite design. In particular, aerodynamic lift, which has often been neglected so far, will be taken into account, as it is essential for three-dimensional orbit control.
Project Leader: Stefanos Fasoulas (IRS)
Project Area B: Enabling Subsystems
Realising platforms capable of efficient, sustained, controlled and safe VLEO operations requires fundamental technological advances for a variety of spacecraft subsystems. Project Area B focuses therefore on solutions with breakthrough potential towards attaining sustainable VLEO utilisation.
Electric propulsion systems that use the residual atmosphere as propellant represent a key technology for the exploitation of VLEO. In this project, Helicon-mode Inductive Plasma Thrusters (IPT/HPT) and potential alternative concepts are investigated. The use of IPT/HPT as an electrode/gridless concept circumvents the problem of degradation due to exposure to atomic oxygen. The project will experimentally gain a deeper understanding of propellant trapping, ionization, and plasma acceleration.
Project Leader: Georg Herdrich (IRS)
An improved collector efficiency for atmosphere-breathing electric propulsion systems can be achieved by using porous structures. The occurring rarefied non-equilibrium flows and sorption processes within porous structures will be described in detail microscopically using the particle-based DSMC code PICLas. Based on these findings, methods for efficient scaling to macroscopic structures will be developed and evaluated, realizing effective relationships between networks of pore bodies with a fast but faithful surrogate model.
Project Leaders: Bernd Flemisch (IWS), Marcel Pfeiffer (IRS), Martin Schneider (IWS)
The potentials for drag compensation and attitude control using asymmetric emission of solar radiation and the internal waste heat of a satellite are investigated. The focus is on investigating the applicability of the occurring effects by means of analytical methods, ray tracing simulations and experiments. A quantitative design tool for the optimised use of thermo-radiative pulses for the purpose of drag reduction will be implemented and essential influencing parameters are evaluated.
Project Leaders: Grazia Lamanna (ITLR), Rico Poser (ITLR)
Novel, micrometre-thick, highly efficient perovskite solar cells produced by a printing process on very thin and flexible glass or polymer films are developed and characterised. The degradation behaviour of such solar modules in the chemically aggressive environment of the VLEO will be investigated theoretically and experimentally to improve their resilience. Further optimisation of the area-specific energy yield by superimposing several solar cells with different absorption bands will also be investigated.
Project Leaders: Stephanie Essig (ipv), Michael Saliba (ipv)
Miniaturised, modular integrated photonic chips are being developed and investigated, which represent key elements for future quantum technology applications in space. This includes components such as integrated single photon sources and elements for information processing. These will be combined to form communication chips that will allow the potential of integrated photonics for quantum communication to be evaluated in an exemplary manner. The main focus will be to test and explore these chips under VLEO-typical environmental conditions.
Project Leader: Stefanie Barz (FMQ)
Project Area C: Mission-related Challenges
Ultimately striving towards VLEO operations justified by the prospect of notably improved or novel scientific application scenarios. Aside the potentials of single satellites or formations, a likely deployment scenario will be that of larger constellations. While bearing the full variety of applications in mind, Project Area C will concentrate on the challenges associated with a specific set of utilisation scenarios, namely the scientific investigation of the thermosphere and gravity field, as this exemplarily allows to consider single satellites, formations and even small constellations on a focused level.
Requirements and design principles for ground and space segments are investigated for the operation of individual satellites, formations and constellations in VLEO. It will explore how existing operational methods need to be combined and to what extent new methods need to be implemented to achieve a sufficient level of automation for reliable VLEO operations. Consideration must be given to the sensitivity of the predicted ground track and alignment accuracy, which affect the typically short communication windows.
Project Leader: Sabine Klinkner (IRS)
A new method for precise orbit and attitude determination based on the chirp pulse compression (CPC) method of laser radiation in the near-infrared spectral region will be developed and tested at DLR's Johannes Kepler Observatory. The approach promises a significant increase in achievable efficiency and signal-to-noise ratio compared to conventional laser-based techniques for distance measurement. Furthermore, the ability of the developed CPC method to detect the orientation, shape and material of objects in VLEO will be investigated and tested.
Project Leaders: Gerd Wagner (DLR-TP), Thomas Dekorsy (DLR-TP)
To address the increasing demands for vertical and horizontal data traffic of individual satellites, formations and constellations in VLEO, the use of communication techniques with extremely high data rates in the high millimetre-wave frequency range between 40 and 110 GHz will be investigated. The research questions in this project include the dynamic calculation of link budgets, an evaluation of the boundary conditions in operation, the achievable performance of key components and a comparison with laser-based transceivers.
Project Leader: Ingmar Kallfass (ILH)
Project C04 is dedicated to the investigation of fundamental models and methods for a self-organising, safety-critical and distributed autonomous computing platform for VLEO satellites and their ground segment infrastructure. Self-organisation algorithms for automatic function allocation in a dynamically changing computing topology will be developed. Possible methods are compared on the basis of generated application scenarios. The models will be evaluated and validated in parameter studies with regard to their general and mission-specific performance indicators.
Project Leader: Björn Annighöfer (ILS)
Algorithms for precise attitude and orbit determination are developed using novel parameter estimates that receive input from global navigation satellites and from on-board systems. These will not only provide the most accurate satellite orbits, but also estimates of atmospheric density and other parameters relevant to applications and satellite operations in VLEO. Another aspect covers the challenges and potentials of implementing a VLEO navigation satellite system.
Project Leader: Thomas Hobiger (INS)
Based on developments in inertial sensor and ranging technologies, this project aims to systematically investigate all factors relevant to the design of a future multi-satellite mission to measure the gravitational field with a VLEO constellation. Such a mission must, for example, meet requirements from hydrology and atmospheric research in terms of accuracy, spatial resolution and lifetime. Research questions include the sampling properties of constellations, the use of formations and the development of multi-scale spatio-temporal processing strategies.
Project Leader: Nico Sneeuw (GIS)
Support Projects
The research program is supported by three support projects, respectively focusing on the central management, public and educational outreach, as well as the data management and software engineering aspects of the Collaborative Research Center.
This project encompasses all activities related to public relations and science communication, both online and offline. One focus is an annual one-week Satellite Design Workshop (SDW) for (inter)national students and young scientists, in which possible VLEO mission scenarios are analysed using the latest findings from the CRC ATLAS.
Project Leaders: Sabine Klinkner (IRS), Stefanos Fasoulas (IRS)
The objective of this project is to ensure that the research data obtained from experiments and simulations, as well as the software developed, follows FAIR principles, i.e. that they are Findable, Accessible, Interoperable and Reusable. In this sense, this project also serves to optimise knowledge transfer within the CRC between successive generations of doctoral researchers.
Project Leaders: Bernd Flemisch (IWS), Stefan Löhle (IRS)
This project encompasses all the central tasks of administration and scientific coordination.
Project Leaders: Stefanos Fasoulas (IRS), Sabine Klinkner (IRS)