Suisei is a space robot that was made by the Japanese space agency to explore something called Halley's Comet. A comet is like a big snowball that goes around the sun, and Halley's Comet is a famous one that comes by Earth every 76 years.
Suisei was launched into space on a big rocket and traveled for a long time to reach the comet. When it got there, it used special instruments to study the comet and send back information to scientists on Earth.
Suisei had to be very tough to survive in space because there is no air or water or food like on Earth. It had to use solar panels to get energy from the sun and keep all its electronic parts from getting too hot or too cold.
In the end, Suisei did a really good job and helped scientists learn a lot about Halley's Comet. And even though it's not flying around anymore, it's still an important part of space history!