This paper presents the mission analysis, requirements, system design, system level test results, as well as mass and power budgets of a 1-unit CubeSat ESTCube-1 built to perform the first in-orbit demonstration of electric solar wind sail (E-sail) technology. The E-sail is a propellantless propulsion system concept that uses thin charged electrostatic tethers for turning the momentum flux of a natural plasma stream, such as the solar wind, into spacecraft propulsion. ESTCube-1 will deploy and charge a 10 m long tether and measure changes in the satellite spin rate. These changes result from the Coulomb drag interaction with the ionospheric plasma that is moving with respect to the satellite due to the orbital motion of the satellite. The following subsystems have been developed to perform and to support the E-sail experiment: a tether deployment subsystem based on a piezoelectric motor; an attitude determination and control subsystem to provide the centrifugal force for tether deployment, which uses electromagnetic coils to spin up the satellite to one revolution per second with controlled spin axis alignment; an imaging subsystem to verify tether deployment, which is based on a 640 × 480 pixel resolution digital image sensor; an electron gun to keep the tether at a high positive potential; a high voltage source to charge the tether; a command and data handling subsystem; and an electrical power subsystem with high levels of redundancy and fault tolerance to mitigate the risk of mission failure.

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This paper presents the design, development, and pre-launch characterization of the ESTCube-1 Attitude Determination and Control System (ADCS). The design driver for the ADCS has been the mission requirement to spin up the satellite to 360 deg·s −1 with controlled orientation of the spin axis and to acquire the angular velocity and the attitude during the scientific experiment. ESTCube-1 is a one-unit CubeSat launched on 7 May 2013, 2:06 UTC on board the Vega VV02 rocket. Its primary mission is to measure the Coulomb drag force exerted by a natural plasma stream on a charged tether and, therefore, to perform the basic proof of concept measurement and technology demonstration of electric solar wind sail technology. The attitude determination system uses three-axis magnetometers, three-axis gyroscopic sensors, and two-axis Sun sensors, a Sun sensor on each side of the satellite. While commercial off-the-shelf components are used for magnetometers and gyroscopic sensors, Sun sensors are custombuilt based on analogue one-dimensional position sensitive detectors. The attitude of the satellite is estimated on board using an Unscented Kalman Filter. An ARM 32-bit processor is used for ADCS calculations. Three electromagnetic coils are used for attitude control. The system is characterized through tests and simulations. Results include mass and power budgets, estimated uncertainties as well as attitude determination and control performance. The system fulfils all mission requirements.

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 • .

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Today, the near‐Earth space is facing a paradigm change as the number of new spacecraft is literally skyrocketing. Increasing numbers of small satellites threaten the sustainable use of space, as without removal, space debris will eventually make certain critical orbits unusable. A central factor affecting small spacecraft health and leading to debris is the radiation environment, which is unpredictable due to an incomplete understanding of the near‐Earth radiation environment itself and its variability driven by the solar wind and outer magnetosphere. This paper presents the FORESAIL‐1 nanosatellite mission, having two scientific and one technological objectives. The first scientific objective is to measure the energy and flux of energetic particle loss to the atmosphere with a representative energy and pitch angle resolution over a wide range of magnetic local times. To pave the way to novel model‐in situ data comparisons, we also show preliminary results on precipitating electron fluxes obtained with the new global hybrid‐Vlasov simulation Vlasiator. The second scientific objective of the FORESAIL‐1 mission is to measure energetic neutral atoms of solar origin. The solar energetic neutral atom flux has the potential to contribute importantly to the knowledge of solar eruption energy budget estimations. The technological objective is to demonstrate a satellite deorbiting technology, and for the first time, make an orbit maneuver with a propellantless nanosatellite. FORESAIL‐1 will demonstrate the potential for nanosatellites to make important scientific contributions as well as promote the sustainable utilization of space by using a cost‐efficient deorbiting technology.

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