The SPERO as shown in-game.

SPEROs [1] (pronounced as 'spare-oh', or sparrow) are probes sent by the Koppaites to search for a planet with edible sustenance on it in order to save their planet Koppai, as seen in the opening sequence of Pikmin 3.  SPERO 3 is the last one searching and is the one that finds PNF-404a planet with bountiful food to sustain Koppai's population.

Mission Mode

SPEROs are used as a storage device for the fruit collected in Pikmin 3's Mission Mode, comparable to the Ship's Research Pod in underground areas in Pikmin 2. 

Trivia

  • SPERO also means "I hope" in italian. Given the probe's mission, it seems fitting.
  • As SPERO is written in all caps, it probably is an acronym, but what SPERO stands for is never mentioned in the game. 

Gallery

References