Browsing by Author "Ehrpais, Hendrik, supervisor"

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Development of ESTCube-2 side panels
(Tartu Ülikool, 2018) Parelo, Aleksander; Ilbis, Erik, supervisor; Ehrpais, Hendrik, supervisor; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Tehnoloogiainstituut
This thesis covers the design of ESTCube-2 nanosatellite sidepanels, the thesis focuses mainly on the design and testing of two side panel components: Sun sensors and magnetorquers. Rest of the side panel design is covered in less detail. The main goals of this work are to develop and test the magnetorquer electronics, the magnetic coils and to develop software for and test the Sun sensor. In this work an overview of ESTCube-2 and the side panels is given, then side panel requirements are set. Based on these requirements two modules for the side panels are developed and tested. The Sun sensors requirements are set, then a prototype sensor is presented that is based on these requirements. The software is developed, and the prototype sensor is tested in an optics laboratory to verify that they meet the requirements. Requirements are set for the coils and the coil driving electronics and designs are developed based on these requirements. The magnetorquers are tested to verify the designs.
Optical Design of a Radiometrically Calibrated Miniature Earth Observation Imager
(Tartu Ülikool, 2019) Kivastik, Joosep; Ehrpais, Hendrik, supervisor; Voznesenskiy, Nikolay, supervisor; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Tehnoloogiainstituut
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.
Using Star Identification Algorithms on ESTCube-2 Star Tracker
(Tartu Ülikool, 2019) Schumann, Sandra; Ehrpais, Hendrik, supervisor; Eenmäe, Tõnis, supervisor; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Tehnoloogiainstituut
This thesis estimates the feasibility and determines the expected performance characteristics of a star tracker for ESTCube-2 student satellite. It measures limiting magnitude for the ESTCube- 2 star tracker hardware and estimates the decrease in signal-to-noise ratio due to the spacecraft’s rotational motion using geometric modelling. The acquired limiting magnitude is used to determine the optimal parameters to use with the pattern recognition algorithms for star identification purposes. The work also develops a way of creating and structuring a reference database in an effective way. Test results indicate that using the acquired parameters, the star tracker will be able to determine spacecraft’s attitude for cases of slow rotation up to 5 degrees per second. Results also indicate capability of attitude determination up to 10 times per second. The spacecraft’s mission also contains a phase of fast rotation, during which the star tracker will no longer be able to produce accurate attitude estimates at all times. With the algorithm configurations recommended in the thesis the ESTCube-2 star tracker could still provide a valuable contribution to the attitude and orbital control subsystem while experiencing angular velocities greater than 5 degrees per second. Thus it may outperform state-of-the-art commercial nanosatellite star trackers in that particular situation.