Samus downloads the bomb data in Sector 2.
Data Rooms were a type of room found on the Biologic Space Laboratories research station. As its name indicates, Samus Aran used it during the events of Metroid Fusion to gain upgrades sent by the Galactic Federation. Many upgrades were successfully downloaded, but some, which were much more powerful, (such as the Plasma Beam) were secretly withheld by Samus's superiors to prevent her from seeking the SA-X's destruction. Some upgrades such as the Varia were successfully downloaded by the X, and integrated into their genome. But these abilities would still be available to Samus, as she could simply defeat these X and absorb the new abilities. Actually, quite a few upgrades were biologically absorbed by Samus without a need for a Data Room. This suggests some sort of link between these upgrades and Samus's body, and not just between the upgrades and the Fusion Suit.
Over the course of the game, the X either destroyed or impeded the paths to all the Data Rooms in an attempt to block Samus's recovery to full power, showing their considerable intelligence, as Samus's computer noted.
The Technology
The Data Room contains a terminal which Samus steps onto to begin the download. The new abilities that are downloaded are digitally transferred to Samus's body armor, and the Fusion Suit uses the data transferred to upgrade itself much like the Power Suit uses a material upgrade item. While the data is being downloaded, the Fusion Suit is surrounded by glowing white energy waves. Several upgrades were developed and sent for Samus's download. These included Missiles, Bombs, Super Missiles, Ice Missiles, Power Bombs,the Varia Suit, though Samus never succesfully downloaded the Varia Suit via the the terminal it was sent to, and instead had to defeat the X-Parasite that had stolen it. Diffusion Missiles were designed by the Federation for Samus to use, and later decided to withold it. However, they had already sent the data, and Samus managed to bypass security level 4 and find the download.
Trivia
- This hasn't been confirmed, but the visible technology of the Fusion Suit suggests that the data is downloaded through three diode-like objects mounted on the Fusion Suit's back.
- For some reason, Samus never uses the Data Room in the Operations Deck, even after Adam Malkovich restores power.