From Bulbapedia, the community-driven Pokémon encyclopedia.
The Mossdeep Space Center is located in Mossdeep City. This destination was chosen because of Mossdeep's ideal weather, clear and sunny with stable winds. The Space Center successfully sends rockets into space, though specifics of the space missions are unknown. There is a white rock outside which holds a special meaning to the people at the space center; it is a symbol of their wish for their rockets to fly safely.
In the games
Many scientists work here and are dedicated to the rocket launches' success. The Space Center contains many blueprints of rockets, machines and computers, and has two accessible floors. The Mossdeep Space Center has little to do with the storyline in Pokémon Ruby and Sapphire, while in Emerald, it plays a larger part.
In the game, a man by the window will reveal the number of successful launches there have been. Another person in the Space Center will give the player a Template:Evosto.
In Pokémon Emerald
The Space Center in Mossdeep plays a much larger role in Pokémon Emerald. After failing to take control of Groudon, Team Magma tries to obtain the rocket fuel there to use to make Mt. Chimney erupt. Team Magma sends a letter to the Space Center, informing them that Team Magma will take the rocket fuel and causing a panic. After defeating the Mossdeep Gym, Team Magma attacks the center, and the player must enter the Space Center and defeat all of the Team Magma grunts on the first floor in order to go to the second floor. On the second floor, the player meets up with Steven Stone and pairs up with him to double battle against Maxie and Tabitha.
During the attack, a man on the 1st floor gives the player a Sun Stone.
1st Floor Trainers
2nd Floor Trainers
Rumors
In the game, a man by the window will reveal the number of successful launches there have been; the number is determined by the number of weeks since the saved game was begun. Many rumors have been spread about this number and its relation to Jirachi and Deoxys. Many believe that if the man reaches a certain number, the player will be able to ride a rocket into space and battle Jirachi. Like the truck rumors of Generation I, this rumor is false.
In the anime
In It's Still Rocket Roll to Me!, Ash and co. visit the Space Center in search of the Mossdeep Gym Leaders, Liza and Tate, but they find that a rocket is about to launch. Meanwhile, Team Rocket tries to steal a rocket from the Space Center, but their plan is stopped by the help of Liza and Tate.
In the anime, the Space Center contains many training machines for astronauts, such as a moon walker to simulate walking on the moon in low gravity and the MAT (multi-axis trainer) that spins people around.