Depends on whether you prefer direct romanization of the katakana letters, or to "translate" it back to English. In general, I prefer "Spica" (because if you don't make that clear, a lot of times this word gets mis-romanized as "Speaker" wtf wtf wtf that would be supiikaa) but it's really up to you. In case you didn't know, it's referring to the constellation
Spica.