Tao was one of the early Prospectors and he was affiliated with the ICA. The ICA campaign missions Doing the Work and Project Fireball explore his backstory.
Personality
Tao is implied to be a man that cares about other people, specifically people within the ICA. This fits within the Factions' ideology. It is also implied he likes to joke around, as it is stated ' it's something he joked about in case he ever got stranded' (referring to the SOS sign).
Timeline
Before prospecting became popular
Toa disappears. Some believed he just made it big and sneaked off to another system.
A long time later
Toa leaves an SOS sign near Water Facility; Toa leaves a Sign of Life from stranded Prospector inside the power facility store room at Water Facility. Toa goes to North Uplink and collects uplink data for at least a year. Toa dies at North Uplink.
Player gets involved
During Doing the Work the player visits the SOS Sign, Water Facility, and then North Uplink. At North Uplink the player finds Tao's body lying in bed, as well as writing on the wall, stating 'Tell Marie I tried - and take care of our people' .