CubeSat

Overview

A CubeSat is a small satellite built to a standardised cubic unit, where one "U" measures 10 centimetres on a side. The 3U class stacks three such units into a single elongated body, a popular size for low-Earth-orbit missions because it balances available volume against launch cost. Standardisation lets CubeSats ride as secondary payloads in a deployer, sharing a launch with larger spacecraft. Despite its size, a CubeSat carries every subsystem of a full satellite in miniature.

The spacecraft is built up from a rigid frame and a stack of functional subsystems. The Aluminum Structure is the anodised aluminium chassis that defines the 3U envelope and protects the deployer rails. The Electrical Power System generates power from solar cells, stores it in a battery, and distributes regulated rails to the bus. The Onboard Computer runs flight software and sequences commands, the Attitude Determination & Control points the spacecraft, the Communications subsystem links to the ground, and the Imaging Payload camera performs the mission. The Thermal Control subsystem holds every component within its temperature limits.

How it works

After release from the deployer, the Separation Switch kill switches close and power the bus. Stowed solar arrays and antennas deploy by burn-wire release, and the attitude control system first detumbles the spacecraft using magnetorquers that push against Earth's magnetic field, then spins up reaction wheels for fine three-axis pointing aided by a star tracker.

In sunlight the triple-junction solar cells charge the lithium-ion pack through a peak-power-tracking controller, sizing the energy budget so the satellite survives each eclipse. During an imaging pass the onboard computer slews the spacecraft to point the payload optics at the target, captures imagery, and buffers it in flash. Over a ground station the S-band transmitter downlinks the data at high rate, while the UHF/VHF radio handles low-rate telemetry and command.