Gulfstream HALO IHALO Gulfstream airplane model. The High ALtitude Observatory (HALO), is an instrumented Gulfstream IIb twin engine jet aircraft maintained by the United States Army Space and Strategic Defense Command as an optical data collection platform. Capable of operating above 50,000 feet, the HALO's diverse and flexible sensor suite has provided infrared, optical and ultraviolet data on numerous SDIO, NASA and DOD test programs. The HALO contains three