This merged session welcomes a broad range of presentations about future missions and instrumentation, and has a particular focus on small satellites. Recent advances in small platforms make it possible for small satellites, including CubeSats, to be considered as independent or complementary elements in planetary exploration missions, for example the small probes as part of the Hayabusa 2, DART and Hera mission. Presentations on Deep Space Planetary CubeSats, e.g. the small satellites accompanying the F-class ESA mission Comet Interceptor and those selected or proposed for the NASA SIMPLEX program are welcomed. Concepts for future mission may either be an augmentation to larger missions or as stand-alone missions of their own. We encourage presentations on new Planetary science mission architectures and associated technologies, as well as dedicated instrumentation that can be developed for these applications.
Orals: Wed, 21 Sep | Room Andalucia 1
The InSight mission (Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport mission; ) landed on Mars in November 2018 within a quasicircular depression called Homestead hollow  in the Elysium Planitia region. The InSight pressure sensor  is capable of acquiring data up to 20 Hz and operated continuously for long periods of time in order to support the interpretation of the seismological data. These InSight measurements have made infrasound observations on other planets possible for the first time [4-5].
Figure 1: The InSight lander. Credits: NASA/JPL-Caltech.
On February 18, 2021, the Perseverance rover landed on Mars, and two days after, the first sounds ever recorded on Mars were transmitted back to Earth . The SuperCam Microphone is not the first microphone to be implemented in a space mission, but it is the first to operate successfully and record sound on Mars . If the first sound recording of the Martian wind using the SuperCam microphone was a very important achievement in terms of outreach, the expected scientific return was mostly based on the assumption that the microphone would help constrain the physical properties of the rocks vaporized by the SuperCam Laser-Induced Breakdown Spectroscopy (LIBS) . However, microphones also have the capacity to provide data for new and important atmospheric investigations. Here we discuss the exciting potential of infrasound and sound recordings for studying planetary atmospheres and surface-atmosphere interactions in planetary exploration.
Figure 2: The SuperCam instrument. Credits: NASA/JPL-Caltech.
Studying atmospheric dynamics
Pressure fluctuations in the atmosphere tell us about boundary layer convection, convective cells, vortices, and the inertial and dissipative regimes. Compared with Earth, Martian daytime turbulence is characterised by a stronger radiative control, a lack of latent heat forcing and a reduced inertial range . Wind gustiness, convective vortex activity and the spectral slope of pressure, wind and temperature measurements can be used as indicators of turbulent motion in the atmosphere. These variables exhibit strong diurnal and seasonal variations (e.g., [10-12]). The InSight pressure measurements were at a higher frequency than any previous measurements and have shown unexpected behavior in the pressure fluctuations  and remarkable bursts of daytime vortices, and nighttime turbulence (including vortices) triggered by strong wind .
The SuperCam microphone with its high sampling frequency (up to 100 kHz), probes the Martian atmosphere at even higher frequencies than the InSight pressure sensor. More than one year on Jezero confirms that a microphone is indeed an extremely valuable tool for investigating key atmospheric properties, such as high frequency wind speed measurements, the wind gustiness, sound speed variations and turbulence profiles (Fig. 3). A synthesis of these findings is provided in .
Figure 3. SuperCam microphone (in Pa2/Hz over 167 s), MEDA pressure (in Pa2/Hz) and MEDA wind data (in (m/s)2/Hz). Mod. from .
Studying surface-atmosphere interactions
Several other objectives can be addressed also by planetary microphones, and more generally, through recording of pressure and acoustic waves on planetary surfaces : the recording of quake and meteoritic impacts , high frequency wind gust recordings , or the recording of saltation by the microphone . Such measurements can provide an estimation of the particle flux associated with saltation, a matter of crucial importance for aeolian research .
Forces imposed on planetary atmospheres can generate low frequency acoustic waves that may travel long distances. Sound-generating phenomena on planetary surfaces may include bolide airbursts and impacts , spacecraft entry, seismic activity, landslides, wind–mountain interactions, atmospheric turbulence, and convective vortices . In the case of having a pressure sensor and high-precision seismometer, three-axes ground deformations can complement pressure records in ascribing a given pressure perturbation to an infrasound phenomenon . This technique has been demonstrated with terrestrial quarry blast experiments  and has been applied to InSight data in the search for infrasound signals on Mars . Simultaneous seismic and pressure measurements can also be exploited to obtain the shallow subsurface properties using the atmosphere as seismic source [21-23].
Perspectives for Solar System exploration
With their high sampling frequency, microphones can be used to characterise planetary acoustic environments and atmospheric dynamics at high frequency. Such measurements, on previously inaccessible scales complement the lower frequency pressure and wind speed measurements fand provide a window into previously unexplored regimes of atmospheric science. From an acoustic recording perspective, Mars is probably one of the most challenging planetary atmospheres. Due both to the low pressure and to the specific absorption of carbon dioxide in the acoustic range, both the predicted  and measured  attenuation are high. We can therefore expect better performance for sound propagation on Venus and Titan (Fig. 4). Special attention should, however, be paid to the instrument design. Tunable gains as implemented for the Mars microphone, and a very rugged design able to cope with the rough planetary environment, are important. For Venus, a possible option would be to fly the above the clouds, where the temperature and pressure conditions are closer to terrestrial environment . For Titan, the challenge would be to cope with an external temperature of -180°C. For the Mars microphone, our design has been tested down to -120°C .
Figure 4. The Attenuation coefficient for planetary bodies with atmospheres .
 Banerdt et al., 2020;  Golombek et al., 2020;  Banfield et al., 2019;  Banfield et al., 2020;  Garcia et al., 2021;  Maurice et al., 2022;  Ksanfomaliti et al., 1982;  Maurice et al., 2020;  Spiga et al., SSR 2019;  Davy et al., 2010;  Ullan et al., 201;  Spiga et al., 2020;  Larsen et al., 2002;  Chatain et al., 2021;  Garcia et al., 2022 (submitted);  Newman et al., 2022;  Murdoch et al., 2022 (in prep.);  Kok et al, 2007 ;  Martire et al., 2020 ;  Garcia et al. 2020;  Garcia et al., 2020  Kenda et al., 2020 ;  Murdoch et al., 2021 ;  Petculescu & Lueptow, 2007 ;  Krishnamoorthy et al., 2019 ;  Mimoun et al., 2022 (submitted)
How to cite: Mimoun, D. and the SuperCam, MEDA and InSight Teams: From InSight to Perseverance, infrasound and sound recordings : investigating atmospheric science and surface-atmosphere interactions., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-94, https://doi.org/10.5194/epsc2022-94, 2022.
The Origo mission was submitted in response to the 2021 call for a Medium-size mission opportunity in ESA's Science Programme.
The goal of Origo is to inform and challenge planetesimal formation theories. Understanding how planetesimals form in protoplanetary disks is arguably one of the biggest open questions in planetary science. To this end, it is indispensable to collect ground truths about the physico-chemical structure of the most pristine and undisturbed material available in our Solar System. Origo seeks to resolve the question of whether this icy material can still be found and thoroughly analysed in the sub-surface of comets.
Specifically, Origo aims to address the following immediate science questions:
- Were cometesimals formed by distinct building blocks such as e.g. “pebbles”, hierarchical sub-units, or fractal distributions?
- How did refractory and volatile materials come together during planetesimal growth e.g. did icy and refractory grains grow separately and come together later, or did refractory grains serve as condensation nuclei for volatiles?
- Did the building blocks of planetesimals all form in the vicinity of each other, or was there significant mixing of material within the protoplanetary disk?
To answer these questions Origo will deliver a lander to a comet where we will characterise the first five meters of the subsurface with a combination of remote-sensing and payloads lowered into a borehole. Our instruments will examine the small scale physico-chemical structure. This approach will allow us to address the following objectives, each of which informs the respective science question:
- Reveal the existence of building blocks of a cometary nucleus from the (sub-)micron to metre scale by exploring unmodified material.
- Determine the physical structure of these building blocks, in particular, the size distribution of components and how refractory and volatile constituents are mixed and/or coupled.
- Characterise the composition of the building blocks by identifying and quantifying the major ices and refractory components.
Over the past decade, significant theoretical advances have been achieved in working out possible planetesimal formation scenarios.
The two leading hypotheses for how planetesimals formed from sub-micron dust and ice particles in the proto-planetary nebula can be classified into two groups:
- the hierarchical accretion of dust and ice grains to form planetesimals; and
- the growth of so-called pebbles, which are then brought to gentle gravitational collapse to form larger bodies by e.g. the streaming instability.
These competing theories only have indirect proof from observations.
Direct evidence, i.e. ground truths, about the building blocks of planetesimals remain hidden. Origo would challenge these theories by examining the physico-chemical structure of the most pristine material available in our Solar System. Though the proposal was not retained for step 2 we present our concept for community discussion.
How to cite: Marschall, R., Thomas, N., Ulamec, S., Hviid, S., Mottola, S., Vincent, J.-B., Ferri, F., Herique, A., Plettemeier, D., Kereszturi, Á., Lavagna, M., Prinetto, J., Dottori, A., Falke, A., and da Silva Pais Cabral, F.: Origo - an ESA M-class mission proposal to challenge planetesimal formation theories., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1127, https://doi.org/10.5194/epsc2022-1127, 2022.
Project Overview: Interest in Near-Earth Asteroids (NEAs) has rapidly grown in recent decades. The motivation is threefold: first, their proximity allows us to discover and investigate small bodies down to the metre-size, thus enhancing our understanding of the mechanisms underlying planetary formation; second, such information is also critical to mitigate their threat of collision with the Earth; third, their near-future exploitation can exponentially expand the natural resources available to humankind.
Ground-based observations of thousands of NEAs have revealed the striking diversity existing within this population in terms of physical properties. So far, only a handful of NEAs have been visited by space missions: each of them provided unexpected discoveries and huge steps forward in our understanding of planetary sciences.
Following the Near-Earth Space Trekker (NEST) proposal selected by ESA for the Phase 2 of the 2018 Call for a Fast mission, and the Asteroid Nodal Intersection Multiple Encounters (ANIME) proposal which passed the technical and financial screenings of the 2020 ASI Call for future CubeSat missions, here we propose to develop a flexible and modular concept, making use of smallsats and high-TRL available technology for the space exploration of several NEAs. Potential targets include Earth Trojan and other co-orbital asteroids, which are particularly appealing due to the low energetic cost to reach them. In particular, Earth Trojans represent a major gap in our inventory of near-Earth small bodies. Tracking their population size would put strong constraints on the dynamical and cosmochemical theories for the formation and evolution of the inner solar system.
International Context: Deep-space smallsats represent a new frontier for the solar system exploration. After the success of the NASA/JPL Mars Cube One (MarCO) mission in 2018 and the launch of ASI LICIACube in November 2021 (currently hosted as piggyback of the NASA DART spacecraft, which will impact the binary NEA Didymos in September 2022), several further deep-space smallsat missions will take place in the next few years, e.g. in the framework of ESA HERA and NASA ARTEMIS I projects.
Reference Scenario: Both CubeSat and larger SmallSat platforms are considered, which perfectly address the modularity and flexibility of the proposed mission concept. Multiple identical smallsats (to maximize mission return while minimizing costs and risks) can be launched profiting of the same or separate mission opportunities, and then reach their respective targets using electric propulsion and optimized interplanetary trajectories. Each smallsat will flyby and/or rendezvous multiple NEAs, with encounters at the nodal points.
A preliminary selection of the targets has been performed assuming a 12U platform and mission durations capped at 2-3 years, with total ΔV < 3 km/s. We stress that the existence of a large number of sequences with similar performances outlines the strong implementation flexibility of our concept. Indeed, the definitive choice of target NEAs can be easily updated even at relatively late project phases, also considering the exponential growth of NEA discoveries. This gives us a huge flexibility in terms of mission scenarios, which can be adapted to varying constraints in terms of, e.g., launch date, propulsion specifics, mission architecture and duration.
Example reference solutions that have been identified include the possibility to reach the Earth’s L4-L5 Lagrange points, using the smallsat payload for the discovery and characterization of Earth Trojan and co-orbital asteroids (especially those with a long synodic period relative to our planet, which are impossible to detect from Earth-based surveys), and to flyby already discovered Earth Trojan asteroids.
Considered scientific payload (whose final selection will depend upon the choice of the platform) includes an optical camera, a near-infrared spectrometer, a mass spectrometer and a neutral particle camera, while the onboard transponder will be used to acquire radio science data.
Technology Readiness: Mission architecture will rely on flight-proven (TRL 9) COTS and in-house components and scientific payload, using heritage from a number of ongoing (e.g., BepiColombo, LICIACube, …) or under development (e.g., Hera) space missions.
Potentially selected components that have flown in the Earth orbital environment only will be appropriately shielded to ensure radiation tolerance to deep-space environment for the whole mission duration.
Science and Technology Ambition: We aim to provide new insights into planetary science by characterizing several NEAs presenting peculiar and yet unexplored dynamical and physical properties. Noteworthy, such information will be also relevant for planetary protection purposes, as well as to assess a potential near-future exploitation of asteroid resources.
We also aim to validate critical technologies for the exploitation of smallsats in solar system exploration, benefiting from the deep knowhow already gained by our team in designing and managing space missions to NEAs.
Our mission concept relies on significant payload heritage and high-TRL available technology, based on our established consortium. Nevertheless, we will consider possible complementary contributions from further national and/or international partners willingly.
How to cite: Perna, D., Casalino, L., Cremonese, G., Dotto, E., Fulvio, D., Ieva, S., Ivanovski, S., Lavagna, M., Lucchetti, A., Mazzotta Epifani, E., Milillo, A., Palumbo, P., Pajola, M., Rossi, A., Tortora, P., and Zannoni, M.: SmallSat exploration of Near-Earth and co-orbital asteroids, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-605, https://doi.org/10.5194/epsc2022-605, 2022.
The ESA M7 Heavy Metal mission proposal is presented. The mission will provide detailed and ambitious science investigations to characterize the large M-class asteroid (216) Kleopatra and its two moons, and perhaps explore 1 or 2 additional M-type asteroids with the same mission.
The main goals of Heavy Metal, apart from characterising (216) Kleopatra with a broad science investigation, are to address the following specific science questions:
- What is the origin and evolutionary history of metallic (M-class) asteroids?
- Are the M-class asteroids the parent bodies of magnetized iron-nickel meteorites?
- Are the M-class asteroids the collisional remains of early protoplanetary dynamos?
- How does the potentially unique space environment around M-class asteroids work?
- How do contact binary asteroids form and evolve?
- What is the nature and origin of asteroid satellites?
The proposed investigation therefore provides a unique window into the early epochs of our solar system.
Our proposed mission profile allows a complete characterization of (216) Kleopatra. The combination of electromagnetic and gravity field (radio science) mapping by two spacecraft provides insight into its internal structure. Remote observations of the surface made in the visible, IR, UV, and radar wavelengths by the Main-craft will complement this by providing a geological context for the origin of any magnetization and its cause. We will address the possibility of remnant magnetization occurring in localized regions, or otherwise being ‘disordered’, by making electromagnetic and plasma measurements close to the surface to identify and remove space environment magnetic field variations.
Figure: Possible crustal field configurations of remnant magnetization, providing information of the evolutionary history of the magnetized material, as well as creating the magnetospheric structures around the asteroid.
A close approach (<10 km to the surface) with the main S/C is difficult, at least at the beginning of the orbital phase, due to the potentially complex gravity field and rapid rotation period of 5.4 hours of the irregularly shaped asteroid. We propose instead to use one Sub-craft to be inserted into a lower-altitude orbit for a duration of a month before the Sub-craft makes a controlled crash on the surface. This will facilitate near surface measurements of the electromagnetic and gravity fields, the composition of any volatile products ejected from the surface and produce truly high-resolution pictures of the surface, complementing the remote observations by the main S/C further away (20-200 km TBD). Additionally, simultaneous measurement of the space environment, including the electromagnetic fields, at both the Sub-craft and Main craft will allow a detailed study of the solar wind electromagnetic variations, and the induction of electrical currents in the partly conductive asteroid surface by the solar wind.
The Sub-craft is suggested to be released from low altitude orbit from the Main craft while having an estimated distance of < 200 km from the (216) Kleopatra surface. The Sub-craft will do flybys of the two moons, and approach (216) Kleopatra while doing science measurements and transferring data to the Main-craft. We hope to reach within a km from the surface of the two moons. At the end the Sub-craft can impact the polar surface of (216) Kleopatra.
High resolution hyperspectral imaging on a close flying Sub-craft will also be able to resolve cm-sized structures. This imaging will help us to decipher the grain size of the minerals, their textures, and the degree of brecciation of the surface to get a comprehensive interpretation about the nature of the regions spectroscopically analysed. These will allow us to determine if the asteroid is composed of relatively homogeneous iron- or rocky-iron-like materials, or more complex products of collisional gardening associated with chondritic impactors. The comparison of the detailed surface geology investigation by Heavy Metal with the terrestrial meteorite record will address the possible connections between metallic meteorites and the M-class asteroids. This investigation with a combined Main-craft and a Sub-craft will give a meaningful investigation for the cosmogony of this type of asteroids, and their relationship to meteoric magnetism. Likewise, an investigation of the composition, geology, and magnetization of the two sizable moons will give information regarding their origin, if coming from (216) Kleopatra or being captured.
How to cite: Wahlund, J.-E. and the Heavy Metal consortium: Heavy Metal, and ESA M7 mission proposal, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-668, https://doi.org/10.5194/epsc2022-668, 2022.
Introduction: We are pleased to announce that INAF (Istituto nazionale di Astrofisisca), POLIMI (Politecnico Milano), SkyLabs d.o.o., TU Delft, University of Maribor, University of Trent, joined in a consortium of research institutes, universities and industry, won the tender "Space Weather Monitor Nanosatellites" published by the European Space Agency (ESA) with a project proposal called CUBE (CME Catcher Carousel).
Our modern society has become increasingly dependent on reliable technology, such as communication, navigation, and electrical power systems, which can be vulnerable to the Sun's influence. The last USA Government research on the economic impact of the occurrence of another “once in a century'' severe geomagnetic storm (such as the 1859 “super storm”), shows potential costs on the Nation’s technological infrastructures (power grid, satellites, GNSS receivers etc.) of $15-20 trillion.
We propose multi-point, multi-in-situ measurements with a low-cost constellation of nano-satellites to monitor the Earth’s magnetospheric response, at magnetic reconnection sites and near the poles of the Earth, to various Space Weather phenomena directly associated to the solar activity, such as Coronal Mass Ejections (CME) and Solar Energetic Particle (SEP) events). This approach complies three main aspects of nowadays research - 1) advanced low-cost technology to study phenomena that can be investigated not only 2) at better spatial and temporal resolution but to be performed through 3) synergetic and simultaneous measurements.
Nano-satellites can be conveniently used to study Space weather events, because of both their short time of development, intrinsic modularity, flexibility, which allow them to cross different boundary regions characterized by rapid changes of the occurring key physical process, and of their relatively low cost, allowing possible deployment of constellation able to cover large spatial scales .
Scientific Objectives: The objective of the ESA competition is to study and develop possible solutions for effective space weather monitoring and it’s hazards by developing dedicated small satellites as a foundation of a future constellation of satellites. The solar wind is the ultimate source of energy and is responsible for virtually all the magnetospheric dynamics. Describing and quantifying the solar wind energy transfer to the Earth's magnetosphere-ionosphere system is one of the fundamental questions in space physics. The main objective of the proposed future CUBE constellation is to identify incoming Coronal Mass Ejections (CME) and solar energetic particle (SEP) events, measure them at different magnetospheric locations and altitude to quantitatively understand the energy transport toward the Earth. One of the objectives is also to study the SEP penetration in the magnetosphere, ionization of the ionosphere, and oscillations of the magnetic field during SEP events.
Fig. 1 The CUBE (CME Catcher Carousel) mission concept.
Rogue events are much rarer than standard CMEs, but are also much more energetic, thus representing a great threat for both space and Earth based infrastructures. Being rare, in-depth studies on these events are scattered and unsystematic. This uncomfortable situation could be alleviated by exploiting the new capabilities offered by nano-satellites. The scientific requirements for systematically studying CME and rogue events and the transport of energy from the reconnection sites to Earth can be achieved by a constellation of nano-satellites hosting magnetometers and sensitive particle monitors. Such a constellation could monitor four key sites (Fig. 1): the three main reconnection X-line locations, namely, near the subsolar points (1), magnetospheric flanks up to the cusp regions (2), the magnetotail (3), and the low altitude, high latitude sites where the manifestation of aurora brightening occurs (4). These are the target points for measurement of particle spectra and velocity. Such configuration will allow monitoring the response of the Earth’s ionospheric and upper atmosphere to the magnetic reconnection events in the magnetopause that brings energy through the Field Aligned Currents. For alert purposes, in order to better tune forecasting models, it is pivotal that constellation data would be received at Earth in nearly real time.
State of the art technology and developments needed for TRL advancement
We will perform a trade-off study using payloads already at TRL9 (for example the Next Generation Radiation Monitor), and developing a dedicated payload based on the experience matured for the HERMES pathfinder payload (currently at TRL 6, planned to reach TRL 9 in one year from now) and CSES-Limadou project .
Reference mission scenario
The baseline mission analysis, to be confirmed during the study, includes two 6U spacecraft on circular SSO and six 12U spacecraft on a highly energetic circular orbit, ~60000 km radius, phased 60 degrees away from one another. All units will be equipped with magnetometers, plasma analyzer, and particle monitors capable of measuring magnetic field strength of a few nT, proton spectra from a few tens keV to a few hundred MeV, and electron spectra up to a few hundred keV. The preliminary analysis of the mission suggests a three-year period for deploying in orbit the constellation of 6-8 nano-satellites of the 6-12U class.
Scientific and technological spin-offs
There is accumulating evidence that our technology is becoming more susceptible to space weather hazards, especially spacecraft since their payloads are becoming more sophisticated. The presented mission concept will be focused on the following space weather effects: 1) radiation damage to spacecraft electronics and other materials from radiation belt and solar energetic particles; 2) drag by the upper atmosphere, which is subject to changes in solar radiation and magnetospheric particle input; 3) interference with electromagnetic signals due to the response of the ionosphere to changes in solar input, geospace storms, and charged particle precipitation.
The mission study began in April 2022 with an estimated duration of 10 months, which means completion by the beginning of February 2023.
 https://space-env.esa.int/r-and-d/instrumentation/ngrm-next-generation-radiation-monitor/  http://cses.roma2.infn.it/instruments
How to cite: Ivanovski, S. L., Fiore, F., Lavagna, M., Piersanti, M., Laurenza, M., Iuppa, R., Battiston, R., Danzeca, S., Diego, P., Gacnik, D., Kramberger, I., Menicucci, A., and Vilona, V.: CUBE (CME Catcher Carousel) - creating groundwork for future ESA space weather activities, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-721, https://doi.org/10.5194/epsc2022-721, 2022.
Two 3-unit cubesats, FORESAIL-1 and ESTCube-2 soon to be launched (2022), both accommodate an electrostatic tether that can be charged to a high voltage with respect to the ambient ionospheric plasma in low-Earth orbit. The high voltage sheath around the tether serves as an electrostatic obstacle that perturbates the plasma ram flow causing Coulomb drag and a net braking force to reduce the orbital speed of the tether-spacecraft system.
According to the theory and particle-in-cell computer simulations, the Coulomb drag is a promising candidate for propellantless and continuous low-thrust propulsion in the solar wind with the plasma flow speeds typically being 440 km/s. In this presentation, we review its applications both to interplanetary missions as in ESA call for ideas, 2016, a 50-cubesat fleet to the main belt asteroids, and to space debris mitigation as in ESA cleansat building block 15, electrostatic tether plasma brake, 2017.
The key components of our payloads are a reeling system for the tether deployment and a high voltage power system: FORESAIL-1 (-1 kV); and ESTCube-2 (-1 kV, +0.5 kV, and +1.0 kV). In this presentation, we describe these payloads in further detail: The reeling system is such that the tether reel is supported by a ceramic bearing and rotated by a stepper motor and associated driver electronics. The 60-metre long tether is manufactured by knitting out of four thin aluminium wires with individual wire thickness of 50 micrometre. The multi-wire structure is required for redundancy against micrometeoroids. The tether is deployed by the centrifugal force provided by an end mass at the tip of the tether. During the launch, the reel and the end mass are secured by launch locks. The high voltage contact to the tether reel is realised by a slider connector. The payload electronics also contain the control electronics and electric power system. All this is miniaturised in order the payload spatial sizes to be less than that of one cubesat unit.
Concerning the high voltage polarity, the positive (negative) tether naturally collects electron (ion) current from the ambient plasma as electrons (ions) tend to neutralise the positive (negative) tether bias. Thus the high voltage system has to maintain the selected tether bias. In the solar wind, it is preferable to use the positive bias as it can be maintained by using electron emitters that are much simpler than the ion emitters. In the ionosphere, the plasma number density is large enough, and no ion emitter is required as an electron collecting surface as a conducting part of the spacecraft can be incorporated instead. For this reason, the payload on board ESTCube-2 has two electron emitters to enable the testing of the positive polarity high voltage system and the electron emitters for future development of the Coulomb drag propulsion in the solar wind. As a third topic of our presentation, the basics of the Coulomb drag propulsion are shortly covered.
Our tether payloads have been designed and built to measure the braking force caused by the Coulomb drag to the electrostatic tether in a low-Earth orbit plasma environment. It is a cornerstone measurement in the roadmap of evaluating Coulomb drag as space propulsion. On our roadmap, we are already developing a 6-unit cubesat (FORESAIL-2) for experiments in geostationary transfer orbit and further envisioning FORESAIL-3 and ESTCube-3, for example in lunar transfer orbit to measure the Coulomb drag in the solar wind.
How to cite: Toivanen, P., Janhunen, P., Kivekäs, J., Haslam, S., Polkko, J., and Iakubivskyi, I.: Cubesat experiments for Coulomb drag propulsion for interplanetary missions and space debris mitigation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-896, https://doi.org/10.5194/epsc2022-896, 2022.
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Posters: Thu, 22 Sep, 18:45–20:15 | Poster area Level 1
We study rover-regolith interactions in low-gravity environments by conducting soft-sphere discrete element method (SSDEM) simulations with a simplified rover wheel and a bed of spherical particles. The simulations reveal that rover performance scales according to the Froude number, or a dimensionless parameter which accounts for the size of the wheel, the rotational velocity of the wheel, and gravity. This relationship provides valuable insight into how to operate rovers and analyze wheel-regolith interactions during future rover missions.
Wheeled-rovers are useful tools for identifying the surface material properties of planetary surfaces [1-3]. The sinkage and traction of a rover can be used to assess the bearing strength of a material, and the tracks left behind by a rover’s wheels can provide information regarding the density, the friction angle, and the cohesion of the regolith . To maximize the scientific return from a rover mission, however, the vehicle must first be able to drive on a granular terrain in a reduced-gravity environment. Parabolic flight experiments and numerical simulations have shown that, as gravity decreases, wheel slip increases and rover traction decreases [4-6]. At the same time, wheel sinkage remains comparable for different gravity levels, at least for certain types of materials . While a few models have been proposed to help explain these findings [7,8], an explicit scaling relationship between rover performance and gravity has yet to be established.
In this work, we analyze rover-regolith interactions on Earth versus a small moon, Phobos. Based on the findings of  and , we hypothesize that rolling behavior scales with gravity according to the dimensionless Froude number, Fr = Lω^2/g, where L is a characteristic length (e.g., the radius of a rover wheel), ω is the rotational velocity of the wheel, and g is gravity.
We conducted SSDEM simulations using a simplified rover wheel and the MULTICORE module of the open-source code CHRONO [10, 11]. The rover wheel is 214 mm in diameter and 53 mm in width and has 9 thin grousers that are equally spaced around a cylindrical hub. The wheel rotates at a constant speed through a bed of spherical grains and can translate freely in the horizontal and vertical directions. The grains are 6 +/- 0.5 mm in diameter and are contained within a 800x250x150 mm box. Simulations were performed using different material cases (e.g., glass beads, rough glass beads, and rough glass beads with cohesion), two gravity levels (g = 9.81 and 0.006 m/s2), and several wheel speeds (ω = 0.065-2.65 rad/s). Fig. 1 provides a snapshot of a typical simulation. We evaluate driving performance by comparing the travel distance of the wheel Δx as a function of its angular displacement Δθ. We also compare the static and dynamic sinkage of the wheel for the different simulation cases.
Fig. 1: Snapshots from a simulation where gravity is 9.81 m/s2 and the rotational velocity is 0.65 rad/s. The container is filled with 6 +/- 0.5 mm spherical particles which are colored by their vertical positions at the start of the simulation .
We find that static wheel sinkage is independent of gravity for simulations with cohesionless materials. Like previous works, we also find that driving performance decreases as gravity decreases for configurations with similar driving speeds (Fig. 2a). We also observe, however, that rover performance is comparable for configurations with similar Froude numbers (Fig. 2b). This means that driving on a cohesionless granular material on Earth at 0.2 m/s is like driving on the same material at 0.005 m/s on Phobos.
Fig. 2: Travel distance Δx by angular displacement Δθ for a wheel rotating through rough glass beads on Earth and Phobos. Plot (a) shows results for similar wheel speeds and plot (b) shows results for similar Froude numbers .
To understand these findings, we consider wheel-regolith interactions in terms of granular regimes. When a wheel initially sinks into a granular material, the system is in a quasi-static state. Sinkage is independent of gravity, because the reduced strength of the material is offset by the reduced weight of the wheel [4,7]. Then, as the wheel turns, the grains become fluidized, and above a certain velocity, the system enters the inertial regime. For similar wheel velocities, the system might be in a quasi-static state on Earth but in an inertial regime on Phobos. This explains why traction decreases as gravity decreases. For similar Froude numbers, however, the system will be in the same regime regardless of gravity level. Fig. 3 illustrates this point further by comparing the velocity fields of the particles in the different simulations. Overall, we demonstrate how the Froude relationship can be a powerful tool for planning rover operations and for interpreting surface interactions during future rover missions.
Fig.3: Velocity field of the particles beneath a rover wheel for simulations in rough glass beads on Earth and Phobos. Plots (a) and (b) show results for similar wheel speeds and plots (c) and (d) show results for similar Froude numbers.
This work was funded by ISAE-SUPAERO and CNES through a PhD research grant. The simulations were conducted using HPC resources from CALMIP under grant 2019-P19030. NM acknowledges funding support from CNES.
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How to cite: Sunday, C., Murdoch, N., Tardivel, S., and Michel, P.: Froude scaling for rovers on small body surfaces , Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-525, https://doi.org/10.5194/epsc2022-525, 2022.
Mutual impedance experiments are active electric instruments that provide in situ diagnostic in space plasmas, such as the plasma density and electron temperature. The instrumental technique is based on the coupling between electric antennas embedded in the plasma, and characterizes the local properties of the plasma dielectric.
Different versions of mutual impedance instruments are present onboard past and future planetary missions, such as Rosetta, BepiColombo, JUICE, and Comet Interceptor. Recently, the interest of the scientific community is shifting from large satellite platforms with single-point measurements concepts to small satellite platforms, to enable multipoint measurements for the spatial mappings of planetary outer environments. Therefore, instruments previously designed for large platforms are now miniaturized and adapted to small satellites. In this context, instrumental efforts are devoted to adapting mutual impedance experiments to small satellites, such as in the case of the CIRCUS CubeSat or the SPEED SmallSat missions projects.
Current state-of-the-art quantitative instrumental models of mutual impedance experiments are based on the assumption of an unmagnetized plasma. However, for planetary environments within which the magnetic field is not negligible, such as intrinsic planetary magnetospheres (e.g. Mercury, Ganymede) significant modifications of mutual impedance measurements are expected.
The goal of this work is twofold: (i) support the preparation of mutual impedance instruments for small satellites and (ii) extend current mutual impedance instrumental models to take into account the effects of the magnetic field on the plasma diagnostic.
This investigation is performed by combining two complementary approaches. First, numerical simulations are used to quantify the impact of the plasma magnetization on the mutual impedance measurements and, therefore, improve its diagnostic. In particular, we have developed and validated a new instrumental model, based on the numerical calculation of the electric potential emitted by an electric antenna in a magnetized, homogeneous, collisionless, Maxwellian plasma. This new instrumental model is used to compute synthetic mutual impedance spectra and assess the impact of electron magnetization on the instrumental response. Using this new model, we provide diagnostics for the plasma density, electron temperature, and magnetic field amplitude. Second, laboratory experiments are used to test and validate our numerical model. We use the controlled plasma environment of the PEPSO plasma chamber at LPC2E laboratory in Orléans. This plasma chamber offers the possibility to test the performances of space plasma instruments and CubeSats in realistic planetary ionospheric conditions. A model of CubeSat is present inside the plasma chamber, and is equipped with a set of electric antennas that are used to perform mutual impedance measurements in the same configuration as a CubeSat. The measurements obtained by this setup are compared with the instrumental model, to validate the plasma diagnostic of the instrument prototype on a CubeSat.
How to cite: Dazzi, P., Henri, P., Bucciantini, L., Lavorenti, F., Wattieaux, G., and Califano, F.: Mutual impedance experiments as a diagnostic for magnetized space plasmas, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1091, https://doi.org/10.5194/epsc2022-1091, 2022.
LaRa is a radio-science instrument that is ready to fly and was part of the science payload of the surface platform of the ExoMars mission. Now that ExoMars is suspended, LaRa will need to find another mission to go to the Martian system (or elsewhere in the inner Solar System). The LaRa instrument consists of an X-band transponder accompanied by a set of three antennas and three RF cables. This instrument is designed to measure with a couple of mHz of accuracy the Doppler shift induced by the variations in Mars rotation and orientation on a direct-to-Earth round-trip radio link. The main scientific objective of the LaRa experiment is to constrain the interior structure of Mars by precisely measuring the precession and nutations of the planet’s spin axis. LaRa’s measurements can also be used to refine the rotation model of Mars, including the polar motion, and infer constraints on the dynamic of its atmosphere.
The LaRa Instrument
The radio-science experiment enabled by LaRa provides two-way Doppler measurements corresponding to the line-of-sight velocity variations between the lander on Mars and the Earth tracking stations. Here is a description of the LaRa instrument (see detailed description of LaRa in Dehant et al. (2020)):
- LaRa consists in a transponder box and 3 antennas that are interconnected via 3 coaxial cables.
- The electronic transponder box dimensions are 25x8x8 cm
- This electronic box weights 1.5 kg while the total weight of LaRa is 2.15 kg.
- LaRa instrument uses at most 42 W (nominal power provided by the platform) to produce a radio frequency output power of about 5 W.
- LaRa works at X-band (channel 24) in a two-way mode (because not equipped with an ultra-stable-oscillator). LaRa’s bandwidth for the uplink is center on 7173.871143MHz, and that of the downlink is centered on 8428.580248 MHz.
- The coherent transponder can lock and maintain the lock for more than one hour on an uplink signal with a level ≥ -140 dBm
- LaRa uses one antenna (Rx) for receiving the signal transmitted by the Earth and two antennas (to ensure redundancy of the SSPA just prior to the transmitting antennas (Tx) in the transponder output chain) for retransmitting the signal back to Earth (see detailed description of LaRa's antennas in Karki et al. (2019)).
- The antennas radiate conical patterns with a maximum gain of about 5 dBi (antenna gain in dB w.r.t. an isotropic radiator) with a main lobe in the [30º, 55º] range of elevation and with a right-hand circular polarization.
- The frequency stability ensured by the coherent detector inside the electric transponder box is characterized by an Allan deviation lower than 10-13 at 60s integration time. The resulting thermal noise of LaRa is of the order of 10-2 mm/s at 60-s for LaRa.
- The accuracy of LaRa’s data is expected to be better than 2.8mHz at 60-s (i.e. <0.05mm/s@60s)
- The LaRa instrument has been designed to operate over at least one Martian year (687 Earth days)
- LaRa Technological Readiness Level is TRL 9
- LaRa Flight model is currently installed on the Russian surface platform located in TAS-I, but LaRa will certainly be soon disassembled from the platform and repatriated to Belgium, where it will be stored and awaiting a new host.
Scientific objectives of LaRa
The main objectives of LaRa are (see details in Dehant et al. (2020)):
- Help positioning precisely and fast the lander, right after landing on the planet (see detailed description of the method in Le Maistre 2016)
- Measure variations in rotation and orientation of the planet, which gives information about deep interior and atmosphere dynamics
- Could be used to probe planet’s atmosphere if any and interplanetary medium
Designed to establish a two-way radio link between Mars and the Earth, LaRa would be perfectly suitable for missions landing on Phobos, Deimos or for any mission that would visit a body of the inner Solar System. Indeed, if 70m-dish deep space stations are always available and used to track LaRa, one could in theory use LaRa to explore asteroids of the main belt for instance.
This work was financially supported by the Belgian PRODEX program managed by the European Space Agency in collaboration with the Belgian Federal Science Policy Office.
 V. Dehant, S. Le Maistre, R.-M. Baland, Ö. Karatekin, M.-J. Péters, A. Rivoldini, T. van Hoolst, M. Yseboodt, M. Mitrovic, the LaRa team, The radioscience LaRa instrument onboard ExoMars 2020 to investigate the rotation and interior of Mars. Planetary and Space Science, 180, 104776 (2020).
 Karki, S., Sabbadini, M., Alkhalifeh, K., Craeye, C., 2019. Metallic monopole parasitic antenna with circularly polarized conical patterns. IEEE Trans. Antennas Propag. 67 (8), 5243–5252.
 Le Maistre S., InSight coordinates determination from direct-to-Earth radio-tracking and Mars topography model. Planetary and Space Science, 121, 1-9, 2016.
 S. Le Maistre, M.-J. Péters, J.-C. Marty, and V. Dehant. On the impact of the operational and technical characteristics of the LaRa experiment on the determination of Mars’ nutation. Planetary and Space Science, 180:104766, 2020.
How to cite: Le Maistre, S., Dehant, V., Baland, R.-M., Beuthe, M., Caldiero, A., Filice, V., Goli, M., Péters, M.-J., Steenput, B., Rivoldini, A., Ümit, E., Van Hoolst, T., and Yseboodt, M.: LaRa, an X-band coherent transponder ready to fly, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1169, https://doi.org/10.5194/epsc2022-1169, 2022.
JUICE is the first large mission chosen in the framework of ESA’s Cosmic Vision 2015-2025 program.
The focus of JUICE is to characterize the conditions that might have led to the emergence of habitable environments among the Jovian icy satellites, in particular Europa, Callisto and Ganymede. In addition, JUICE will also perform a multidisciplinary investigation of the Jupiter system as an archetype for gas giants.
To address those key science objectives, the spacecraft payload consists of 10 state-of-the-art instruments (and one experiment that use the spacecraft telecommunication system with ground-based instruments) that will perform remote and in-situ measurements of Jupiter, its moon and their environment.
From a trajectory’s point of view, the mission calls for a three-year orbital survey of the Jupiter System designed as a sequence of 67 orbits around the planet of different periods and inclinations, and includes 35 flybys of Europa (2), Ganymede (12) and Callisto (21). The second part of the mission will devote an additional 9 months in orbit around Ganymede for an in-depth characterization of Ganymede as a planetary object and possible habitat.
By its touring nature and due to the diversity of science targets and different disciplines involved in the mission, the development of an observation plan will often face conflicting observations opportunities, also limited in resources as a consequence of the large helio- and geo-centric distances at play.
The Science Operations Center, together with the Project Scientist and the Science Working Team, are in charge of setting up and developing a science planning strategy for the mission to ensure that the prime science objectives of the mission are addressed while remaining compatible with the mission constraints.
The JUICE Science Planning Process for the Jupiter tour consists of two main pillars:
- Segmentation of the trajectory. Based on the Cassini heritage, this activity relies on the analysis of all science opportunities along the tour to subsequently support the decision on selecting a prime scientific objective that will get priority in terms of resources (data volume, power and pointing) for a specific time window (a.k.a segment). Taking into account known operational activities’ constraints (navigation, wheel off-loading etc) and high-level resources’ estimate, an analysis of the expected scientific coverage and resource status along the tour is performed, and several iterations between the different disciplines experts (through the science working groups) take place to converge towards a plan that should ensure that prime science objectives of the mission are fulfilled within the operational constraints of the mission.
- Detailed sizing case analysis for science operations: For specific operationally of scientifically challenging sections of the segmentation, in-depth analysis is needed in order to refine resources assumptions (attitude, power and data volume) made at segmentation level. Those detailed analysis, performed down to observation level, is done in collaboration with the instrument teams.
The present work will describe the different steps and groups involved in the science planning, the current status of the segmentation, and the detailed analysis of the first JUICE Europa flybys will be presented.
How to cite: Vallat, C., Altobelli, N., Lorente, R., Munoz, C., Witasse, O., Cavalié, T., Fletcher, L., Masters, A., Modolo, R., Roatsch, T., Tobie, G., Tosi, F., and Van Hoolst, T.: The Science Planning Process for the JUICE mission, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1236, https://doi.org/10.5194/epsc2022-1236, 2022.
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