# In-Orbit Results and Attitude Analysis of the SNUGLITE CubeSatellite
## 1 Introduction  
A cube-satellite (CubeSat) standard has been developed for the design of pico-satellites and nano-satellites, with the objectives being to reduce cost and development time, increase accessibility to space, and sustain frequent launches [1]. The CubeSat platform allows students to conceive, design, implement, test, and operate a complete spacecraft in space, often using commercial off-the-shelf (COTS) components for educational purposes [2; 3], and it also allows developers to test payloads and platforms in orbit at a reasonable price. Various missions and projects have been performed using CubeSats for scientific, private and government purposes, and the number of launches and operations is on the rise [4]. MinXSS-1 CubeSat's science objective is to measure the soft x-ray energy distribution from the sun [5]. The primary mission goal of CSTB1 was to accelerate the maturity of components and subsystems, as well as to accelerate the infrastructure and operations of the CubeSat platform [6]. The primary objective of the Radio Aurora Explorer (RAX) mission is to study the formation of magnetic field-aligned plasma irregulars in the polar lower ionosphere [7; 8]. The mainmission of the ESTCube-1 CubeSat is to conduct the first in-orbit electric solar wind sail experiment [9]. Presently, industrial companies, such as Planet Labs Inc. [10] and Spire [11], have started to open commercial services, including the use of CubeSat constellations. Planet Labs Inc. operates more than a hundred CubeSats for Earth-imaging, and Spire's missions are ship tracking and weather forecasts. The statistics of the CubeSat missions show that while it has been primarily Earth-imaging and science missions that have been conducted, technical demonstrations, communications, education, and military missions have also been performed [4]. According to the mission or telecommunication with the ground station, the attitude system of the CubeSat is required to point to the target area or ground station. Legacy full-scale satellite attitude systems are large and expensive to install on the CubeSat-class platform, where mass, size, and power are limited [12]. To achieve accurate and precise attitude, an attitude system using a star-tracker was developed and applied on the CubeSat platform, and its in-orbit validation was performed [5]. It should be noted, however, that applying a star-tracker on the CubeSat platform is very expensive at present. Attitude systems that use low-cost sensors have been developed [6; 7; 8; 9; 12], taking advantage of the relative cost-effectiveness of the CubeSat platform in allowing access to space. The RAX-1 and RAX-2 CubeSats use COTS magnetometers, as well as coarse sun-sensors (photodiodes), micro electro mechanical systems (MEMS)-rate gyroscopes, and an extended Kalman filter (EKF). The in-orbit performance of attitude estimation was analyzed with the error covariance of the filter, which uses onboard calibration [7; 8]. Boeing's CSTB1 also used low-cost sensors for attitude estimation, and its performance was validated using onboard camera images taken at the time of attitude estimation [6]. The attitude determination system of ESTCube-1 was also validated by comparing 15 samples of the onboard camera image and estimated attitude [9]. We developed the SNUGLITE (Seoul National University Global navigation satellite system Laboratory satellite) CubeSat with these objectives in mind: (1) to monitor the disturbance of the ionosphere and the Earth's magnetic field that is caused by seismic events, (2) to develop and verify the in-orbit operation of the linear quadratic Gaussian (LQG)-based attitude system, and (3) to provide a technical demonstration of the own-developed dual-frequency Global Positioning System (GPS) receiver for the CubeSat platform.