The ATLAS missions, ACRIM II, and the Six Pack in the vacuum chamber on the tracker at the Table Mountain Observatory/Solar Test Facility (TMO/STF) . (The top of the vacuum chamber is removed.) The Six Pack has six openings for reference sensors that are used in the calibration process for the instruments. The tracker can point the vacuum chamber at the sun. This co-calibration took place in June, 1990 before ACRIM II was shipped for integration into the UARS spacecraft.