Payloads in satellites are the scientific instruments carried by a satellite to fullfill its scientific objectives. For example, a cubesat payload can be an imaging sensor carried to perform Earth observation tasks. In cubesats, the payload must be small due to the volume, mass and power constraints of cubesats. Hence, the big challenge remains in the integration of the satellite subsystems in a confined volume. Their low cost also means that they are designed to last for a few months or years.
CubeSats rely on solar cells, arrays and panels to generate power for the payload and satellite electronics. The solar power is stored in Lithium-Ion or Lithium-Polymer batteries for satellite operation during eclipse. The solar cells are assembled on the external walls of the cubesat with additional power demands provided using deployable solar arrays. The power subsystem provides the energy needed for the operation of all other subsystems and can comprimise up to one-third of the satellite's mass.
Attitude & Orbit Control is a crucial subsystem to control the orientation of a satelite for satellite pointing during telecommunication, Earth observation, orbital maneuvers or deep space imaging. Many CubeSats employ AOCS sensors including, earth sensors, sun sensors, gyros, magnetometers and star trackers to determine their attitude and attitude rate, and use actuators such as, magnetorquers, thruster and miniature reaction wheels to control their attitude.
Communication subsystem is an essential part of the spacecraft. It provides a link for transmission of data and telemetry to Earth station, recieve commands from Earth station and relay information to one another. A transciever is normally used to recieve and transmit telemetry and command sequences. Many different communication bands can be used for cubesats communication including, UHF, VHF, L-band, S-band, K-band and laser communications.
Propulsion subsystem transfers CubeSats into their operational orbit and provides the neccessay thrust for attitude control and orbit corrections. The strict mass, power and volume limitations imposed by nano-satellite requirements restrict the amount of propellant that can be carried which limits the delta-v budget that can achieved. This led to the development of unique micro-propulsion systems in recent years to extend the capabilities of CubeSat platforms. Cubesat propulsion technologies include cold gas, chemical propulsion, electrical propulsion, green propellants and solar sails.