| Name of Satellite, Alternate Names | UFO-8 (USA 138, UHF F/O F8) "UHF Follow-On" |
| Country of Operator/Owner | USA |
| Operator/Owner | US Navy |
| Users | Military |
| Purpose | Communications |
| Class of Orbit | GEO |
| Type of Orbit | |
| Longitude of GEO (degrees) | 172.28 |
| Perigee (km) | 35772 |
| Apogee (km) | 35794 |
| Eccentricity | 0.000260954143240102 |
| Inclination (degrees) | 5.24 |
| Period (minutes) | 1435.94 |
| Launch Mass (kg.) | 3206 |
| Dry Mass (kg.) | 1545 |
| Power (watts) | 3,800 (EOL) |
| Date of Launch | 16-03-1998 |
| Expected Lifetime | 4 yrs. |
| Contractor | Boeing Satellite Systems |
| Country of Contractor | USA |
| Launch Site | Cape Canaveral |
| Launch Vehicle | Atlas 2 |
| COSPAR Number | 1998-016A |
| NORAD Number | 25258 |
| Comments | Ultra-High Frequency (UHF) communications and Super-High Frequency (SHF) antijam command and broadcast capabilities through four pairs of geosynchronous satellites and one spare; tactical application. |