Radiomeetriliselt kalibreeritud miniatuurse maavaatluskaamera optiline ülesehitus

Magistritöö raames töötati välja radiomeetriliselt kalibreeritud miniatuurse multispektraalse maavaatluskaamera difratksiooniga piiratud optiline ülesehitus ning viidi läbi selle kvaliteedi analüüs. Kaamera eesmärk on kolmeaastase eluea vältel Maa-l¨ahedasel orbiidil jäädvustada kvantitatiivseid kaugseire andmeid, mille radiomeetriline täpsus on 5%. Kaamera optiline ülesehitus põhineb optilistel ja radiomeetrilistel nõuetel, mis tulenevad projekti esialgsest kirjeldusest ning radiomeetrilise eelarve analüüsist. Eelarve tingis nõuded ka teistele optika komponentidele, mis valiti välja selle töö käigus. Optilisele disainile tehti ka tolerantsianalüüs, mis põhines kaamera valmistamisel ning kokkupanekul tekkivatel määramatustel. Analüüs näitas, et kaamera disain vastab algupärastele nõuetele ning sellest lähtuvalt ehitatakse prototüüp Euroopa Kosmoseagentuuri jaoks.In this thesis a diffraction limited optical design for a radiometrically calibrated miniature multispectral Earth observation imager is proposed and its performance analysed. The goal of the imager is to capture quantitative data for remote sensing with a radiometric accuracy of 5% during a three year lifetime in Low Earth Orbit. The design is based on optical and radiometric requirements that were derived from a radiometric budget analysis and the requirements from the original proposal. The budget also set requirements for different optical components which were chosen as part of this work. A tolerance analysis was performed on the optical design taking into account the uncertainties from manufacturing and assembly. It was found that instrument design fulfills the original requirements and it will be used to build a prototype instrument for the European Space Agency

Ülijuhtivuse fluktuatsioonide ajaline korrelatsioon kahetsoonilises süsteemis

http://www.ester.ee/record=b4683175*es

Design of a Scientific-Grade Multispectral Imager for Nanosatellites

Applications in agriculture, land-cover change, and vegetation phenology, to name a few, would benefit from more frequent high-quality remote sensing data. However, ”Landsat-class” satellites are too expensive for such applications. Therefore, there is a need to augment larger Earth observation satellites with nanosatellites that use scientific-grade imaging instruments. This paper presents the design for the scientific-grade multispectral imager Theia. It is designed for a 5% radiometric accuracy at a ground sampling distance of 33 m at a 650 km orbit while keeping the modulation transfer function above 0.13 at the Nyquist frequency. The camera has reflective optics with an aluminium optomechanical design to mitigate stress from thermal expansion. Furthermore, the optical path is covered with a mix of black anodization and Acktar Magic Black to suppress stray-light. The sCMOS sensor is back-side illuminated to increase the radio metric quality of the instrument. Furthermore, the imager has a post-launch calibration system for continuous monitoring of the instrument’s quality. The performance is achieved while fitting inside 0.6 CubeSat Units and weighing about 600 g. However, a trade-off between the modulation transfer function and radio metric quality is presented. Such an imager, when deployed on numerous nanosatellites, can enable new kinds of missions that are otherwise too costly. The project is funded by the European Space Agency

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

Interplanetary Student Nanospacecraft: Development of the LEO Demonstrator ESTCube-2

Nanosatellites have established their importance in low-Earth orbit (LEO), and it is common for student teams to build them for educational and technology demonstration purposes. The next challenge is the technology maturity for deep-space missions. The LEO serves as a relevant environment for maturing the spacecraft design. Here we present the ESTCube-2 mission, which will be launched onboard VEGA-C VV23. The satellite was developed as a technology demonstrator for the future deep-space mission by the Estonian Student Satellite Program. The ultimate vision of the program is to use the electric solar wind sail (E-sail) technology in an interplanetary environment to traverse the solar system using lightweight propulsion means. Additional experiments were added to demonstrate all necessary technologies to use the E-sail payload onboard ESTCube-3, the next nanospacecraft targeting the lunar orbit. The E-sail demonstration requires a high-angular velocity spin-up to deploy a tether, resulting in a need for a custom satellite bus. In addition, the satellite includes deep-space prototypes: deployable structures; compact avionics stack electronics (including side panels); star tracker; reaction wheels; and cold–gas propulsion. During the development, two additional payloads were added to the design of ESTCube-2, one for Earth observation of the Normalized Difference Vegetation Index and the other for corrosion testing in the space of thin-film materials. The ESTCube-2 satellite has been finished and tested in time for delivery to the launcher. Eventually, the project proved highly complex, making the team lower its ambitions and optimize the development of electronics, software, and mechanical structure. The ESTCube-2 team dealt with budgetary constraints, student management problems during a pandemic, and issues in the documentation approach. Beyond management techniques, the project required leadership that kept the team aware of the big picture and willing to finish a complex satellite platform. The paper discusses the ESTCube-2 design and its development, highlights the team’s main technical, management, and leadership issues, and presents suggestions for nanosatellite and nanospacecraft developers