Build a satellite! Drag each part onto its spot (or tap a part, then tap its spot). Then pick a level to go from a K-3 wow to university detail.
What each part does
📦 Bus
The bus is the satellite’s body. It holds everything together, like a backpack that carries all the tools.
The bus gives the satellite its structure, shares out electricity, keeps parts at safe temperatures, runs the onboard computer and controls which way the satellite points. Engineers often reuse one bus design for many different missions.
Bus subsystems: structure, electrical power, thermal control, command and data handling, attitude determination and control, and communications. Designers trade the mass, power and volume budgets against what the payload needs.
🔭 Payload
The payload is the satellite’s job tool, like a camera that takes pictures of forests from space!
The payload is the reason the satellite exists: cameras, radar or instruments that measure air, ice, forests or oceans. Everything else on board is there to help the payload do its job.
Payload requirements (resolution, spectral bands, revisit time, data volume) drive the choice of orbit and the size of the power, pointing and downlink systems. Radar payloads need large antennas and high power; optical payloads need very stable pointing.
🧭 Pointing sensors
Satellites use star cameras to see which way they are pointing, like sailors using the stars to find their way.
Star trackers, sun sensors and gyroscopes tell the satellite which way it is facing. A GPS receiver tells it where it is in orbit.
Attitude determination fuses star tracker, gyroscope, sun sensor and magnetometer data, often with a Kalman filter. Reaction wheels, magnetorquers or thrusters then turn the spacecraft to keep instruments and antennas on target.
☀️ Solar arrays
Solar panels are the satellite’s lunch. They turn sunlight into electricity!
Solar arrays turn sunlight into electricity, and batteries store some of it for when the satellite passes through Earth’s shadow.
Array sizing accounts for the time spent in eclipse, cell efficiency, the sun angle and the slow loss of output from radiation over the mission. Satellites commonly use multi-junction cells, which convert more sunlight per square meter than typical rooftop panels.
🔥 Propulsion
Little rocket thrusters give gentle pushes so the satellite stays in the right place.
Thrusters raise or adjust the orbit and help dodge space junk. At the end of the mission they can push the satellite down to burn up, so it does not become debris.
Chemical thrusters give high thrust; electric thrusters (ion or Hall-effect) use far less propellant but push gently for a long time. Planning end-of-life disposal is part of space sustainability, as in the Zero Debris Charter.
📡 Antennas
Antennas let the satellite talk to Earth, sending pictures home through the air!
Antennas send data down and receive commands. Ground stations around the world catch the signals as the satellite flies overhead.
Link budgets balance transmitter power, antenna gain, distance, frequency and noise. Radio spectrum is limited and licensed, one reason missions are turning to laser links and to processing data on board.
Laser communication: talking with light
Some satellites send messages with invisible laser light instead of radio. It is like sending a whole library home in minutes!
Laser (optical) links pack information into infrared light. The beam is very narrow, so it can carry far more data than radio, but the satellite must point it very precisely, and clouds can block it.
Laser (optical) links pack information into infrared light. The beam is very narrow, so it can carry far more data than radio, but the satellite must point it very precisely, and clouds can block it.
In 2023, NASA’s TBIRD CubeSat sent 4.8 terabytes of error-free data to the ground in under five minutes at 200 gigabits per second, the fastest satellite-to-ground data link on record.
Optical terminals need extremely precise pointing, ground stations at clear-sky sites, and error-recovery protocols (TBIRD used automatic repeat request) to survive atmospheric fading.
How it helps people and nature: faster downlinks get flood, fire and forest data to the people who need it sooner.
Computing in orbit (SI in space)
Some satellites have a tiny SI brain that throws away cloudy pictures before sending them home!
In 2020, ESA’s Φ-sat-1 became the first European satellite to run a deep-learning SI model on board. It sorted cloudy images from clear ones, so only useful pictures were sent to the ground.
On the ground, many data centers use water for cooling. Lawrence Berkeley National Laboratory estimated that US data centers directly consumed about 66 billion liters of water in 2023 (about 17 billion gallons), up from about 21 billion liters in 2014.
In orbit, waste heat is radiated into space, so a data center there would not need cooling water. The EU-funded ASCEND study, led by Thales Alenia Space (2024), found space data centers could be feasible, but would only cut carbon emissions if launchers became about ten times less emitting over their whole life cycle.
Early flights are already testing chips in orbit. See our Orbital Data Centers page.
Trade-offs to weigh: radiation hardening, radiator mass and area, launch emissions, debris risk, repair, and the delay of sending results down. Honest comparisons count the whole life cycle, not just cooling water.
How it helps people and nature: less water drawn from rivers and lakes for cooling, and quicker answers from satellite data.