G. Tachell was a Human Starfleet officer in the 22nd century.
In 2151, he was named as an Imaging and sensor technologies officer on the dedication plaque of the Enterprise NX-01. (ENT: "Broken Bow", dedication plaque)
In January of 2155, he was named as an ODIN officer on the directory placards at the Fleet Operations Center, Sol Sector. His office was in room #1323. (ENT: "Demons", directories)