Nanosatelliidi Anatoomia Analüüs: ESTCube Teine Põlvkond

Any object that has been launched into orbit has experienced statical and dynamical loads during its travel through the atmosphere. The loads are of random nature and cannot be fully predicted as per real conditions. The structural requirements for ESTCube-2 have been determined as for the worst-case scenario, since the launch vehicle was not known at that stage of the project. A three-unit CubeSat will be subject to high-level sine and random vibration as well as shock response spectrum loading. Before physical testing, structural simulations were made and stresses were analysed in order to confirm the structural reliability and margins. Margins are essential in the design process due to uncertainties in the predicted vibration environment. In addition, the thesis presents the design of primary and secondary structures. As a result of this thesis, a final materials selection, topography optimisation, and manufacturing of the structure will be made. Moreover, the simulation results obtained here will be the subject of comparison with the physical testing results in the later stage of the ESTCube project. ESTCube-2 will be launched in the first half of 2019, and will serve as a testbed for the ESTCube-3 mission in the solar wind environment

Nanosatelliide kasutamine demonstratsioon- ja teadusmissioonidel

Väitekirja elektrooniline versioon ei sisalda publikatsiooneKosmost on vaadeldud ja uuritud aastatuhandeid, kuid kosmosemissioonid lubasid seda esimest korda kohapeale uurima minna alles 64 aastat tagasi. Satelliidid võimaldavad teha toiminguid, mis maapealsete uuringutega on võimatud, näiteks maanduda teistele taevakehadele, tuua Maale neilt võetud proove vaadelda lähedalt komeete, ja asteroide ning saada paremaid vaatlusandmeid galaktikate, päikesesüsteemide, eksoplaneetide ja muude objektide kohta.. Ajalooliselt korraldasid kosmosemissioone suured riiklikud kosmoseagentuurid, kuid viimase 20 aasta jooksul on valdkond avanenud ka väikeettevõtetele, ülikoolidele ja pea kõigile teistele, kes on satelliidi kosmosesse saatmisest huvitatud. See on saanud võimalikuks tänu kuupsatelliitide standardiseerimisele. Tavaliselt peame kuupsatelliitide all silmas 1–10 kg nanosatelliite. Selle väitekirja autor on aidanud kaasa planeedimissioonide ja -instrumentide miniaturiseerimisele, töötades välja missioone ja missioonikontseptsioone ning arendades selliseid koormused ja simulatsioonivahendeid, mis aitaksid kaasa pikaajalisele eesmärgile uurida kosmost nanosatelliitidega. Lõputöö esimene osa keskendub uuenduslikule kosmosereiside tehnoloogiale: Coulomb Drag Propulsionile. Seda saab kasutada, et madalalt Maa orbiidilt kosmoseprügi eemaldada (plasmapidur) või kosmoses liikuda, kandmata Maalt kaasa võetud raketikütust (elektriline päiksepuri). Kõnealune tõukejõutehnoloogia on paigaldatud satelliitidele ESTCube-2 ja FORESAIL-1, mis peagi kosmosesse lennutatakse. Samuti analüüsib doktoritöö ideed külastada elektrilise päiksepurje juhitava kuupsatelliidilaevastikuga sadu asteroide. Lõputöö teises osas antakse ülevaade jätkuvast protsessist eesmärgiga arendada kaamera Euroopa Kosmoseagentuuri (ESA) ja Jaapani Kosmoseuuringute Agentuuri (JAXA) ellu viidavale Komeedipüüduri (Comet Interceptor) missioonile. Missiooni sondid viib 2029. aastal kosmosesse rakett Ariane 6. Kaamera on varustatud periskoobiga, et kaitsta seda ohtliku keskkonna eest, mistõttu kannab see nime Optical Periscopic Imager for Comets või OPIC. Nimi viitab ühtlasi Eesti astronoomile Ernst Öpikule, kes pakkus esimesena välja, et Päikesesüsteemi ümber asub kauge komeedipilv, mida tänapäeval tuntakse Öpiku–Oorti pilvena. OPIC-u väljatöötamist toetab spetsiaalselt selleks arendatud simulatsioonitööriist SISPO, mida kirjeldatakse doktoritöö viimases osas.Humans have been observing and exploring the cosmos for millennia, yet space missions enabled in-situ examination only during the last 64 years. Artificial satellites enable opportunities unfeasible for ground-based studies, such as landing on other planetary bodies, sample return, close observations of comets and asteroids, and improved observations of galaxies, solar systems, exoplanets, etc. Historically, space missions were operated by large space agencies, but in the last twenty years, the field expanded to small enterprises, universities and practically anyone interested in launching a satellite. This was partially enabled by the standardisation of cubesats, typically 1–10 kg nanosatellites. The author of this dissertation has contributed to the miniaturisation of planetary missions and instruments by developing missions, mission concepts, payloads and simulation tools that commit to the long-term aims of cosmic exploration with nanospacecraft. The first part of the thesis focuses on innovative technology for space travel – Coulomb Drag Propulsion. It can be utilised to remove space debris from Low Earth Orbit (named plasma brake) or travel in space without carrying the propellant from the Earth (named E-sail). This propulsion is accommodated on the ESTCube-2 and FORESAIL-1 satellites, to be launched soon. The dissertation also analyses the concept of visiting hundreds of asteroids with a fleet of cubesats driven by E-sail. The second part of the thesis presents an ongoing camera development for the ESA-JAXA Comet Interceptor mission to be launched in 2029 by the Ariane 6 rocket. The camera is equipped with a periscope to protect it from a hazardous environment. It is therefore named Optical Periscopic Imager for Comets or OPIC shortly, also referring to the Estonian astronomer Ernst Öpik, who was the first to propose the existence of a distant comet cloud around the Solar System, known today as the Öpik–Oort cloud. The development of the OPIC instrument is supported by a custom-made open-source simulation tool called SISPO, described in the last part.  https://www.ester.ee/record=b547253

Optical Periscopic Imager for Comets (OPIC) Instrument for the Planned Comet Interceptor Mission

This poster presents an update on the development of the Optical Periscopic Imager for Comets (OPIC) instrument [1], which will be hosted on one of three spacecraft making up the Comet Interceptor ESA-JAXA mission [2]. OPIC is a compact ( \u3c 0.5 kg) monochromic camera for taking images of the nucleus and coma of either a long-period or dynamically new comet, or an interstellar object for mapping, reconstruction and localisation purposes. The camera will operate in a harsh environment with continuous dust impacts throughout its multi-day operation; therefore, the instrument is equipped with a periscope, which protects optics from high-velocity impacts. The probe is spin-stabilised at 4-15 RPM and will be parked in Lagrange point L2 (launched with ARIEL telescope) and depart at a suitable time to intercept a target at velocity 10-70 km/s. The closest approach is approximately 400 km

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with -1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.Peer reviewe

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with - 1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.</p

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

Aspects of nanospacecraft design for main-belt sailing voyage

We present a detailed mechanical and thermal analysis of a stand-alone nanospacecraft that performs asteroid flybys in the main asteroid belt (2.75 AU) and one Earth flyby at the end of the mission to return the gathered data. A fleet of such nanospacecraft (10 kg) has been proposed as part of the Multi-Asteroid Touring mission concept, a nearly propellantless mission where the electric solar wind sail (E-sail) is used for primary propulsion. The fleet makes flybys of thus far poorly characterised asteroid populations in the main belt and downlinks scientific data during the returning Earth flyby. The spacecraft size is close to a three-unit cubesat with a mass of less than 6 kg. The spacecraft is designed for a 3.2-year round trip. A 20-km-long E-sail tether is used. A remote unit is attached to the tether’s tip and stowed inside the spacecraft before the E-sail commissioning. The remote unit is slightly smaller than a one-unit cubesat with a mass of approximately 750 g. With an electrospray thruster, it provides angular momentum during tether deployment and spin-rate management while operating the E-sail. The selection of materials and configurations is optimised for thermal environment as well as to minimise the mass budget. This paper analyses the main spacecraft and remote-unit architectures along with deployment and operation strategies from a structural point of view, and thermal analysis for both bodies.Peer reviewe

PELE: the Planetary Analogs & Exobiology Lava Tube Expedition

Lava tubes on Earth represent some of the most enticing Martian analog environments when investigating the possibility of past or present life on Mars. Lava tubes provide stable, sheltered environments which are isolated and protected from the radiation on the surface. The microbial mats in these caves further regulate the environment for life, allowing various microbial communities with different metabolisms to coexist. This adaptation is so successful, one could imagine it might occur on other planets, with other biologies, and perhaps with other fundamental chemistries [1]. The PELE team has investigated lava caves on Terceira Island, the Azores, and in Iceland. The project aims to correlate biological and mineralogical data to describe the interactions between the microbes and their geological substrates, to identify microbe-specific speleothems as biosignatures (Figure 1), to map the gradients of light, nutrients, and biodiversity, and to develop a sampling technique in these fragile environments. This is achieved with a combination of DNA sequencing, mass spectrometry, and XRF, XRD, and Raman spectroscopy. The work will serve as an indication of what kind of life, or remnants of life, we might expect to find in lave tubes on Mars

SISPO: Space Imaging Simulator for Proximity Operations

Publisher Copyright: © 2022 Public Library of Science. All rights reserved.This paper describes the architecture and demonstrates the capabilities of a newly developed, physically-based imaging simulator environment called SISPO, developed for small solar system body fly-by and terrestrial planet surface mission simulations. The image simulator utilises the open-source 3-D visualisation system Blender and its Cycles rendering engine, which supports physically based rendering capabilities and procedural micropolygon displacement texture generation. The simulator concentrates on realistic surface rendering and has supplementary models to produce realistic dust- and gas-environment optical models for comets and active asteroids. The framework also includes tools to simulate the most common image aberrations, such as tangential and sagittal astigmatism, internal and external comatic aberration, and simple geometric distortions. The model framework’s primary objective is to support small-body space mission design by allowing better simulations for characterisation of imaging instrument performance, assisting mission planning, and developing computer-vision algorithms. SISPO allows the simulation of trajectories, light parameters and camera’s intrinsic parameters.Peer reviewe