US Air Force (USAF) SENIOR AIRMAN (SRA) Kevin Cain (left) and SRA Bill Cacek, from the 90th Space Wing (SW), F.E. Warren Air Force Base (AFB), Wyoming (WY), works on his unit's equipment for the pneudraulics event at Vandenberg Air Force Base (AFB), California (CA). Guardian Challenge, the world's premier space and missile competition, is a four-day event hosted annually at Vandenberg AFB