Earth Observation Technologies: Low-End-Market Disruptive Innovation

After decades of traditional space businesses, the space paradigm is changing. New approaches to more efficient missions in terms of costs, design, and manufacturing processes are fostered. For instance, placing big constellations of micro- and nano-satellites in Low Earth Orbit and Very Low Earth Orbit (LEO and VLEO) enables the space community to obtain a huge amount of data in near real-time with an unprecedented temporal resolution. Beyond technology innovations, other drivers promote innovation in the space sector like the increasing demand for Earth Observation (EO) data by the commercial sector. Perez et al. stated that the EO industry is the second market in terms of operative satellites (661 units), micro- and nano-satellites being the higher share of them (61%). Technological and market drivers encourage the emergence of new start-ups in the space environment like Skybox, OneWeb, Telesat, Planet, and OpenCosmos, among others, with novel business models that change the accessibility, affordability, ownership, and commercialization of space products and services. This chapter shows some results of the H2020 DISCOVERER (DISruptive teChnOlogies for VERy low Earth oRbit platforms) Project and focuses on understanding how micro- and nano-satellites have been disrupting the EO market in front of traditional platforms

A review of gas-surface interaction models for orbital aerodynamics applications

Renewed interest in Very Low Earth Orbits (VLEO) - i.e. altitudes below 450 km - has led to an increased demand for accurate environment characterisation and aerodynamic force prediction. While the former requires knowledge of the mechanisms that drive density variations in the thermosphere, the latter also depends on the interactions between the gas-particles in the residual atmosphere and the surfaces exposed to the flow. The determination of the aerodynamic coefficients is hindered by the numerous uncertainties that characterise the physical processes occurring at the exposed surfaces. Several models have been produced over the last 60 years with the intent of combining accuracy with relatively simple implementations. In this paper the most popular models have been selected and reviewed using as discriminating factors relevance with regards to orbital aerodynamics applications and theoretical agreement with gas-beam experimental data. More sophisticated models were neglected, since their increased accuracy is generally accompanied by a substantial increase in computation times which is likely to be unsuitable for most space engineering applications. For the sake of clarity, a distinction was introduced between physical and scattering kernel theory based gas-surface interaction models. The physical model category comprises the Hard Cube model, the Soft Cube model and the Washboard model, while the scattering kernel family consists of the Maxwell model, the Nocilla-Hurlbut-Sherman model and the Cercignani-Lampis-Lord model. Limits and assets of each model have been discussed with regards to the context of this paper. Wherever possible, comments have been provided to help the reader to identify possible future challenges for gas-surface interaction science with regards to orbital aerodynamic applications

A planning tool for optimal three-dimensional formation flight maneuvers of satellites in VLEO using aerodynamic lift and drag via yaw angle deviations

Differential drag is a promising option to control the relative motion of distributed satellites in the Very Low Earth Orbit regime which are not equipped with dedicated thrusting devices. A major downside of the methodology, however, is that its control authority is (mainly) limited to the in-plane relative motion control. By additionally applying differential lift, however, all three translational degrees-of-freedom become controllable. In this article, we present a tool to flexibly plan optimal three-dimensional formation flight maneuvers via differential lift and drag. In the planning process, the most significant perturbing effects in this orbital regime, namely the J2 effect and atmospheric forces, are taken into account. Moreover, varying atmospheric densities as well as the co-rotation of the atmosphere are considered. Besides its flexible and high-fidelity nature, the major assets of the proposed methodology are that the in-and out-of-plane relative motion are controlled simultaneously via deviations in the yaw angles of the respective satellites and that the planned trajectory is optimal in a sense that the overall decay during the maneuver is minimized. Thereby, the remaining lifetime of the satellites is maximized and the practicability and sustainability of the methodology significantly increased. To the best of the authors knowledge, a tool with the given capabilities has not yet been presented in literature. The resulting trajectories for three fundamentally different relevant formation flight maneuvers are presented and discussed in detail in order to indicate the vast range of applicability of the tool

Contribution of Vacuum-Ultraviolet Transitions of Molecular Nitrogen to Radiative Heat Flux During Aatmospheric Reentry

Within this work we investigate the radiative properties of molecular nitrogen with respect to the highly excited electronic states giving rise to radiative transitions occurring in the spectral range of Vacuum-Ultraviolet (VUV) radiation. This is done in order to shed light on the role of VUV radiation of molecular nitrogen in the radiative heat load encountered by a vessel during highspeed atmospheric reentry. The considered transitions bands are the Lyman – Birge – Hopfield, Birge – Hopfield I, Birge – Hopfield II, Caroll – Yoshino, Worley – Jenkins, Worley, and e'1Sigmau+ - X1Sigmag+ band. The approach to retrieve the relevant parameters for the line by line radiation simulation follows common methods of calculation, which are the reconstruction of the potential energy function via the Rydberg-Klein-Rees (RKR) method and subsequently solving the corresponding radial Schrödinger equation. Absorption and emission spectra are then calculated for a known equilibrium test condition of air plasma to illustrate the contribution of the VUV transitions to the radiation. The influence of the VUV radiation on the heat load experienced by a reentry vehicle is illustrated with an exemplary CFD calculation

A Method for the Experimental Characterisation of Novel Drag-Reducing Materials for Very Low Earth Orbits using the Satellite for Orbital Aerodynamics Research (SOAR) Mission

The Satellite for Orbital Aerodynamics Research (SOAR) is a 3U CubeSat mission that aims to investigate the gas–surface interactions (GSIs) of diferent materials in the very low Earth orbit environment (VLEO), i.e. below 450 km. Improving the understanding of these interactions is critical for the development of satellites that can operate sustainably at these lower orbital altitudes, with particular application to future Earth observation and communications missions. SOAR has been designed to perform the characterisation of the aerodynamic coefcients of four diferent materials at diferent angles of incidence with respect to the fow and at diferent altitudes in the VLEO altitude range. Two conventional and erosion-resistant materials (borosilicate glass and sputter-coated gold) have frst been selected to support the validation of the ground-based Rarefed Orbital Aerodynamics Research (ROAR) facility. Two further, novel materials have been selected for their potential to reduce the drag experienced in orbit whilst also remaining resistant to the detrimental efects of atomic oxygen erosion in VLEO. In this paper, the uncertainty associated with the experimental method for determining the aerodynamic coeffcients of satellite with diferent confgurations of the test materials from on-orbit data is estimated for diferent assumed gas–surface interaction properties. The presented results indicate that for reducing surface accommodation coefcients the experimental uncertainty on the drag coefcient determination generally increases, a result of increased aerodynamic attitude perturbations. This efect is also exacerbated by the high atmospheric density at low orbital altitude (i.e. 200 km), resulting in high experimental uncertainty. Co-rotated steerable fn confgurations are shown to provide generally lower experimental uncertainty than counter-rotated confgurations, with the lowest uncertainties expected in the mid-VLEO altitudes (~300 km). For drag coefcient experiments, confgurations with two fns oriented at 90¿ were found to allow the best diferentiation between surfaces with diferent GSI performance. In comparison, the determination of the lift coefcient is found to be improve as the altitude is reduced from 400 to 200 km. These experiments were also found to show the best expected performance in determining the GSI properties of diferent materials. SOAR was deployed into an orbit of 421 km × 415 km with 51.6¿ inclination on 14 June 2021. This orbit will naturally decay allowing access to diferent altitudes over the lifetime of the mission. The results presented in this paper will be used to plan the experimental schedule for this mission and to maximise the scientifc output.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

ADBSat: Verification and validation of a novel panel method for quick aerodynamic analysis of satellites

We present the validation of ADBSat, a novel implementation of the panel method including a fast pseudo-shading algorithm, that can quickly and accurately determine the forces and torques on satellites in free-molecular flow. Our main method of validation is comparing test cases between ADBSat, the current de facto standard of direct simulation Monte Carlo (DSMC), and published literature. ADBSat exhibits a significantly shorter runtime than DSMC and performs well, except where deep concavities are present in the satellite models. The shading algorithm also experiences problems when a large proportion of the satellite surface area is oriented parallel to the flow, but this can be mitigated by examining the body at small angles to this configuration (± 0.1°). We recommend that an error interval on ADBSat outputs of up to 3% is adopted. Therefore, ADBSat is a suitable tool for quickly determining the aerodynamic characteristics of a wide range of satellite geometries in different environmental conditions in VLEO. It can also be used in a complementary manner to identify cases that warrant further investigation using other numerical-based methods.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Business roadmap for the European Union in the NewSpace ecosystem: a case study for access to space

A business roadmap is a high-level strategic management tool that maps the actions to develop new industries. It serves as a guide to plan and forecast technological, market and product developments in a more operational way. Precisely, the business roadmap of this article highlights the main actions to be taken by the European Union (EU) space ecosystem with regards to Low Earth Orbit (LEO)—orbits from 450 to 2000 km—and Very Low Earth Orbit (VLEO)—orbits from 150 to 450 km. On the one hand, it is necessary to (1) develop industrial and technological space capabilities, (2) continue investing public funds in European Programs to develop new vehicle concepts of access to space, (3) improve testing, demonstration and exploration for faster the Technology Readiness Level (TRL) development, (4) promote an entrepreneurial and risk-taking culture, and (5) leverage the private investment to boost the development of advanced access to space technologies, attract talent, promote collaboration between public and private companies, and finance NewSpace Small–Medium sized Enterprises (SMEs). On the other hand, it should also strengthen its relationship with the European Space Agency (ESA) to foster its space capabilities and become a competitive player in the access to space market in the medium term (5–10 years). The implementation of these actions will help the EU to improve its international positioning, and adapt the technology to the needs and requirements of NewSpace demand, mobilizing around €40,500 million euros for the EU economy during the first 10–15 years of operations with an average Leverage Factor (LF) of 4Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

DISCOVERER: Final results and outcomes

The DISCOVERER project commenced in 2017 with the aim to advance the development of key technologies to enable the commercially viable, sustained operation of satellites in very low Earth orbits (VLEO). Funded by the European Commission through Horizon 2020, the project ends this month. This paper presents an overview of the key achievements and current status of the project. The project set out to advance the development of, and demonstrate, several technologies with the long-term aim of enabling the commercial use of VLEO. These technologies include: 1. aerodynamic materials which encourage specular scattering of the incoming flow to minimise drag and increase the performance of aerodynamic surfaces in the highly rarefied flows experienced in VLEO 2. aerodynamic attitude control methods to compensate for the dynamic flow environment, especially lower in the VLEO altitude range 3. atmosphere breathing electric propulsion (ABEP), combining an optimised atmospheric intake with advanced RF Helicon-based plasma thruster, for drag compensation DISCOVERER’s test satellite, the Satellite for Orbital Aerodynamics Research or SOAR, was deployed from the International Space Station in June 2021 and re-entered the atmosphere in March 2022. The primary aim was to measure the induced drag and lift on different aerodynamic materials candidates in VLEO by exposing panels, coated in various novel and control materials, to the flow at different orientations whilst observing the induced attitude and orbit perturbations produced. Early analysis of the results from the mission shows promising results for the novel materials developed as part of the project. Parallel studies on the long-term survivability of these materials to the space environment have been on-going through exposure tests on the exterior of the International Space Station through the MISSE programme. The project has also been developing a ground-based facility, the Rarefied Orbital Aerodynamics Research facility, to characterise the gas surface interaction properties of materials to atomic oxygen at orbital velocities. Characterisation of the facility itself is on-going. In support of ABEP technology, the experimental development and characterisation of an RF Helicon-based plasma thruster has been on-going, along with detailed computational modelling of aerodynamic intakes. Whilst the thruster has already been operated, current work focusses on the characterisation of its performance. Finally, work to place these technological developments into context has also been progressed. On overview of the overall achievements in this area is provided, including business modelling of the VLEO market ecosystem, which identifies the enormous market potential for VLEO missions.Peer ReviewedArticle signat per 30 autors: Peter C.E. Roberts, Nicholas H. Crisp, Steve Edmondson, Antonio Arcos, Georg H. Herdrich, Jonathan Skalden, Silvia Rodriguez-Donaire, Daniel Garcia-Almiñana, Alejandro Macario-Rojas, Katharine L. Smith, Ciara Mcgrath, Sarah J. Haigh, Vitor T.A. Oiko, Brandon E.A. Holmes, Luciana A. Sinpetru, Virginia Hanessian, Simon Christensen, Thomas Kauffman Jensen, Jens Nielsen, Morten Bisgaard, Francesco Romano, Stefanos Fasoulas, Constantin Traub, Konstantinos Papvramidis, Miquel Sureda, Dhiren Kataria, Badia Belkouchi, Alexis Conte, Simon Seminari, Rachel VillainPostprint (published version