Mary Keen, center, a facility modeling engineer, explains how Arnold Engineering Development Complex test facility operations are simulated in the Range Systems Support Lab to Maj. Gen. Evan Dertien, commander, Air Force Test Center, during Dertien's visit to Arnold Air Force Base, Oct. 14, 2021. Also pictured, from left, are Col. Robert Lance, director of the Test Support Division, and Scott Howard, Test Information Systems Section chief. (U.S. Air Force photo by Jill Pickett) (This image has been altered by obscuring screens and papers for security purposes.)