Coral
From Halopedia, the Halo wiki
Coral may be the planet where the next book of Halo, Halo: Ghosts of Coral may set place if the title isn't changed. Rumour has it that that's where Dr.Catherine Halsey took Spartan-087, while she was sedated for healing on the ship Ascendant Justice/Gettysburg where they will meet up with Chief Mendez who is possibly training the Spartan IIIs.
