Howard Philips was a citizen living on Titan Station; he left various messages throughout Chapter 7. Isaac eventually finds his corpse, and uses it to access restricted areas. From logs left behind by Philips, it appears that the AI for the solar collector facility where he works has either been corrupted or gone rogue, and will not permit him to leave. His corpse, or more accurately, his RIG, is needed to bypass the security door in order to enter the Solar Array proper.