The LappiSat Space Program - Expanding Observatory Quality Geophysical Measurements to Orbits

For more than 100 years, the Sodankylä Geophysical Observatory (SGO) has produced a continuous stream of measured data and conducted top-tier research on various topics on space and geophysics. The main research areas include magnetic disturbances, geomagnetic activity, ionospheric composition and disturbances, radio science, seismic activity, and cosmic rays. The observatory’s location in Finnish Lapland (Lappi in Finnish), 120 kilometers north of the Arctic Circle, has made it an ideal site for auroral studies and related geophysical research. It has been a time-honored tradition at SGO to design, develop and construct the observatory\u27s most critical measurement instruments in-house. SGO’s instrument network includes over 70 instruments in 27 locations–reaching from Svalbard to Antarctica. The next step in further enhancing SGO\u27s measurement capabilities is to expand its instrument network to low Earth orbits. The LappiSat space program aims at establishing a space technology center in Sodankylä, Finland. As the center\u27s first assignment, the first satellite LappiSat-1 shall be built together with the required ground infrastructure. The LappiSat-1 will carry multiple in-house built geophysical instruments, including auroral imagers, an auroral photometer, and a CubeSat compatible scientific grade magnetometer. The optical and system design of the imagers (i.e. auroral cameras) are optimized for auroral imaging, providing enough spatial resolution and sensitivity for low intensities to enable meaningful scientific observations of the shape and location of the auroral oval. Further information of the polarlights is obtained with the on-board photometer, designed to take narrow-band measurements at the most significant emission wavelengths of the aurorae. Simultaneous fluctuations in the geomagnetic field are recorded with the on-board magnetometer CubeMag. In addition to the instruments required to complete its scientific mission, the LappiSat-1 is expected to contain various features that are tested for future missions. These may include propulsion (also used for hastened re-entry of LappiSat-1), partial radiation shielding and use of radiation-hardened components, and telecommunication links for fast communication. The missions following LappiSat-1 are intended to reach orbits past LEO –with the subsequent goal being the Moon and beyond

Electric solar wind sail applications overview

We analyse the potential of the electric solar wind sail for solar system space missions. Applications studied include fly-by missions to terrestrial planets (Venus, Mars and Phobos, Mercury) and asteroids, missions based on non-Keplerian orbits (orbits that can be maintained only by applying continuous propulsive force), one-way boosting to outer solar system, off-Lagrange point space weather forecasting and low-cost impactor probes for added science value to other missions. We also discuss the generic idea of data clippers (returning large volumes of high resolution scientific data from distant targets packed in memory chips) and possible exploitation of asteroid resources. Possible orbits were estimated by orbit calculations assuming circular and coplanar orbits for planets. Some particular challenge areas requiring further research work and related to some more ambitious mission scenarios are also identified and discussed.Comment: 18 pages, 3 figures, accepted for publication in ESTCube-1 special issue of Proceedings of the Estonian Academy of Science

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

Optisen tehon mittaukset: sovellukset kuituoptiikassa ja ultraviolettialueen radiometriassa

The work described in this thesis has concentrated on development and characterization of detectors, measurement setups and measurement methods for the needs of optical metrology in the fields of fiber optics and ultraviolet (UV) radiometry. A straightforward detector design for fiber optic power measurements, consisting of a single InGaAs photodiode, has been introduced. The simple and cost effective detectors were found applicable in high-precision measurements at <1-mW level with a combined measurement uncertainty of 0.9% (k=2). Another detector type for fiber optic power measurements, consisting of an integrating sphere and an InGaAs photodiode, has been characterized for measurements at power levels up to 200 mW. Further characterizations have extended the power range up to 650 mW. The measurement uncertainty of the detector is 0.8% at 1-mW level and 1.3% at 100-mW level (k=2). The capability for accurate measurements of fiber optic power at 100-mW level has been found useful in studying the non-linear properties of optical fibers. A high-intensity spectral comparator facility for measurements of spectral irradiance responsivity s(λ) at UV is presented. The setup consists of a single grating monochromator and intense xenon source. The high power levels are needed to obtain sufficient levels in narrow-band (1 nm) spectral measurements with broadband UV detectors. The power levels obtained were high enough even for measurements at UVB region (280-315 nm). A sophisticated method for calibration of broadband detectors was tested. The method is based on the measured s(λ) of the detector. This method enables the irradiance responsivity of the detector to be calculated for any source whose spectral shape is known. The consistency between this method and the widely used spectroradiometric method was show. A novel method for inter-comparisons of calibration facilities of broadband UV detectors is introduced. The method is based on the known s(λ) and angular response of the detector. The applicability of the method was verified with a successful inter-comparison between five laboratories.Tässä väitöskirjassa kuvatussa tutkimustyössä on keskitytty kuituoptiikassa ja ultraviolettialueen (UV) radiometriassa tarvittavien tehomittarien (detektorien), mittausjärjestelmien ja mittausmenetelmien kehittämiseen. Tässä työssä on kuvattu yksinkertainen ja edullinen, pelkästä InGaAs-fotodiodista koostuva, kuituoptinen detektori. Tarkat karakterisointimittaukset osoittivat detektorin käyttökelpoiseksi mittanormaaliksi kuituoptisiin tarkkuustehomittauksiin <1 mW tehotasoilla. Detektorin mittausepävarmuus on 0.9% (k=2). Olemme karakterisoineet integroivasta pallosta ja InGaAs-fotodiodista koostuvan pallodetektorin, ja osoittaneet, että detektori kykenee luotettaviin kuituoptisen tehon mittauksiin aina 200 mW tehotasoille asti. Myöhemmät laboratoriossamme tehdyt mittaukset ovat vielä entisestään laajentaneet tehoaluetta 650 mW asti. Mittausepävarmuus 1 mW tasolla on 0.8% ja 100 mW tasolla 1.3% (k=2). Korkeiden tehotasojen (∼100 mW) tarkkuusmittaukset ovat huomattavasti edesauttaneet laboratoriossamme tehtäviä kuitujen epälineaarisia ominaisuuksia käsitteleviä tutkimuksia. Työssä on esitelty suuritehoinen mittausjärjestelmä UV-alueen detektorien spektrisen irradianssivasteen s(λ) mittaamiseen. Järjestelmä koostuu yksihilaisesta monokromaattorista ja suuritehoisesta ksenonlampusta. Korkeat tehotasot edesauttavat laajakaistaisten UV-mittarien spektrisiä mittauksia kapeilla 1 nm kaistoilla. Tehotasot todettiin riittäviksi jopa lyhytaaltoisella UVB-alueella (280-315 nm). Kokeilimme myös uutta menetelmää laajakaistaisten UV-mittarien kalibrointiin. Menetelmä perustuu s(λ):n mittaamiseen. Tätä menetelmää käyttäen voidaan mittarin vaste määrittää mille tahansa lähteelle, jonka spektrimuoto tunnetaan. Osoitimme myös yhtäpitävyyden tämän menetelmän ja laajalti käytetyn spektroradiometrisen menetelmän välillä. Esittelemme lisäksi uuden menetelmän kansainvälisiin laajakaistaisten UV-mittareiden vertailuihin. Menetelmä hyödyntää mitattua s(λ):aa, lisäksi tarvitaan mittarin mitattu kulmavaste. Menetelmän toimivuus on todennettu järjestämässämme kansainvälisessä pilottivertailussa, jonka tulokset esitetään tässä väitöskirjassa.reviewe