What is a satellite made of?

It has been two years since TakeMe2Space was founded and around four since this team started working on satellites. None of us from that early-stage team were space engineers. In a way it helps not knowing what you cannot do when starting up. 

Today we’re planning to build multi-kW, multi-ton satellites with GPUs at automotive scale manufacturing volumes. However, the basics remain the same. In this article we’ll cover most of the subsystems that make up a satellite.

TakeMe2Space's 6U cubesat bus with subsystems.

A cubesat or any low earth orbit (LEO) satellite will need the following:

Structures: The chassis (like that of an automobile) that bears the mechanical loads, especially during launch.

Power: All satellites need power. Unless you’re launching a deep space mission (like Voyager), solar is the way to go for power generation. We use Li-ion batteries for storage and then there’s the corresponding electrical circuit for power conditioning, power distribution, safety, sensor integration and so on – collectively called the electrical power subsystem or EPS. If the power system fails, the satellite is essentially a brick floating in space.

Communications: Possibly the most critical function for a satellite (once it survives launch and generates power). If the satellite can’t talk to you and you to it, it becomes a brick with electricity (which is also why affordable in-orbit servicing can be a huge game changer). Today satellites use radio waves to communicate with us on Earth. The amount of data it can send back to us depends on the frequency used (higher frequencies need more energy), the power you can give it, and the modulation. The usual bands are UHF/VHF, S band, and X band. Depending on the use cases, Ka, Ku, L, V, and E band could also be used.

ADCS: The Attitude Determination and Control System is probably the most complex satellite subsystem. This system of sensors, actuators, controllers, and logic helps orient the satellite in the desired direction – panels towards the sun to charge the batteries, imager/radios towards the Earth for payload operations – and also helps when firing the satellite’s torquers to stop tumbling when ejected from the deployer. The ADCS typically includes sun sensors, spectral sensors, star trackers, magnetic torquer coils, reaction wheels, and a control board.

OBC: The on-board computer is the orchestrator, or the brain, of the satellite. Your satellite code, so to speak, rests in the OBC which reads data from sensors, takes commands received from the ground station on Earth, and fires actuators or triggers payloads.

Additional subsystems:

Propulsion: All satellites lose altitude over time, even at 500km or even at 36,000km (GEO) for that matter. Propulsion is what keeps it in the intended orbit. Propulsion is also used for orbit-raising/orbit-change (especially useful for defence satellites, but expensive), de-orbiting at end of life, and increasingly for collision avoidance given the number of satellites being launched. Propulsion itself comes in many forms – the most common being chemical and electric with many more new technologies and approaches being explored. 

Compute: Our favourite topic.  By compute we mean high performance compute, GPUs, and the like. Not your 6W edge compute that can detect clouds. Along with data storage. Traditional satellites have been designed as data capture and transmission devices precisely because adding compute was expensive. With the vast improvements in specifications of automotive or MIL grade equipment (broadly fall under COTS or commercial off the shelf) and reduction in costs, and with TM2S’ proprietary radiation shielding coating, satellites today are becoming much smarter. This is also one of the reasons why orbital data centres are becoming viable.

Payloads: The satellite is the vehicle (also called a satellite ‘bus’) that is meant to carry a payload to achieve an objective. The payload could be a camera (telescope or imager), broadcasting equipment, broadband provider, or one or more of the multitude of snooping sensors.

Where can you buy satellite buses and subsystem?

If you're looking to buy a satellite bus, CubeSat, or satellite subsystems, SatSearch is a good place to start. There are many aggregators, marketplaces and product discovery platforms today. Unfortunately, a majority of the satellite hardware market is opaque when it comes to product specifications, availability and pricing. TakeMe2Space isn't. 

If you're looking for CubeSat components, satellite subsystems, LEO satellite buses, onboard computers, ADCS, communications systems, power systems or AI compute, explore the TM2Space satellite hardware catalogue.