ESTCube-1 nanosatellite for electric solar wind sail in-orbit technology demonstration

Abstract

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.

Attitude determination and control for centrifugal tether deployment on the ESTCube-1 nanosatellite

“…For centrifugal tether deployment [29], the satellite is required to spin up: reach the angular velocity of ≈360 deg·s −1 around the axis of maximum moment of inertia (z-axis) and align its spin axis with the Earth's polar axis with a pointing error less than 3 • [30]. After tether deployment the spin rate will decrease to ≈20 deg·s −1 , which is an approximate spin rate during the experiment.…”

Design and pre-flight testing of the electrical power system for the ESTCube-1 nanosatellite

“…The satellite's expected deorbiting time from a 660 km sun-synchronous circular LEO is predicted to be 23 years and its designed operational lifetime 2 years [1].…”

“…The EPS has to power all of the other subsystems of the satellite using 3.3, 5, and 12 V voltage lines and has to be able to communicate with other subsystems over the Internal Communication Protocol (ICP) [1,18], a fault-tolerant communication system developed for the project that uses UART transceivers to form a faulttolerant communication network. The way all of the subsystems are connected together is shown in Fig.…”

“…The EPS harvests energy from solar panels, stores it in lithium-ion battery cells, and distributes it to other consumers. Since the mission [1] involves complicated and dynamic power conditions, such as high-power systems that need to be turned on during some mission phases for short durations, the satellite is continuously balancing between powernegative and power-positive modes. As an additional challenge, the satellite is required to spin fast (1 rotation per second) as a part of its mission and that causes complications for efficient solar power harvesting.…”

“…ESTCube-1 [1] is a 1-unit CubeSat [2] with the volume of roughly 1 liter and the mass of 1.05 kg. The satellite's main mission is a test of technologies required for the Electric Solar Wind Sail concept [3][4][5] that involves unreeling of a thin 10 m long conductive tether [1,6,7] in a circular sun-synchronous midday-midnight polar low Earth orbit (LEO) with the altitude of 660 km, charging it to a high voltage of 500 V, and measuring its interaction with atmospheric plasma.…”