Flight Results of ESTCube-1 Attitude Determination System

Abstract

This paper presents the characterization and in-orbit validation of the ESTCube-1 attitude determination system (ADS). ESTCube-1 is a one-unit CubeSat built by students and launched on May 7, 2013 to a Sun-synchronous, 700 km, polar low Earth orbit. Its primary mission is to centrifugally deploy a tether as a part of the first in-orbit demonstration of electric solar wind sail (E-sail) technology. The ADS uses magnetometers, gyroscopic sensors, Sun sensors and an Unscented Kalman Filter for attitude determination. Here we share the performance of commercial off-the-shelf (COTS) sensors and results from tuning the system-re-calibration, software and Kalman Filter adjustments. We validate the system by comparing the attitude determined by the on-board ADS with the attitude determined from on-board camera images. Uncertainty budgets for both attitude determination methods are estimated. The expanded uncertainty of comparison (95% confidence level, k=2) is 1.75 • and the maximum difference between attitudes determined by both methods is 1.43 • .

Optimized Design and Thermal Analysis of Printed Magnetorquer for Attitude Control of Reconfigurable Nanosatellites

“…For magnetic field modeling, the International Geomagnetic Reference Field (IGRF) [9] is typically used; and for sun direction modeling, the method described in Montenbruck and Pfleger (1994) is used. Having the estimate of the current attitude, the controller issues torque commands for desired orientation [9], [21], [22]. The closed loop feedback ensures the maintenance of desired attitude control by repeating the torque command until the desired orientation is achieved [23], [24], [25], [26].…”

In-Orbit Results and Attitude Analysis of the SNUGLITE Cube-Satellite

“…The attitude systems of the RAX-1 and RAX-2 CubeSats were quantified by the state error covariance of the estimation filter without reference attitude [8]. Camera images were utilized to generate the reference attitude [6,9]. However, the number of image samples (less than 15 samples) was not sufficient to evaluate the attitude estimation performance.…”

“…Analyses indicate that the attitude estimation of the SNUGLITE CubeSat has achieved an in-orbit real-time pointing accuracy with a root mean square of 6.1 • . mission 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.…”

“…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. The SNUGLITE CubeSat was successfully launched and settled in orbit on December 03, 2018, and it has broadcast its status data continuously for more than a year, with signals being received worldwide, both at the SNUGLITE ground station and at amateur ground stations [13].…”

“…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].…”