From Halopedia, the Halo wiki
Teller Station was constructed atop Site 17, a planetesimal that contained a Forerunner complex considered to be one of the most promising artifact sites in the whole system. The station's complement included a xenoarchaeology team including Dr. Daniels and several other scientists, who had spent several years carefully excavating and studying the site, as well as a defense and security force.
In the summer of 2552, after WINTER CONTINGENCY had been declared on Reach, the decision was made to withdraw and abandon the station after one final dig. This last dig successfully extracted a Forerunner object from the site, but also activated several dormant Forerunner systems due to haste. This alerted the Covenant to the station's location, necessitating the intervention of a UNSC battle group to allow the station's personal to evacuate. This was successfully accomplished, although at the cost of irreplaceable UNSC ships and lives.
List of appearances