| Name of Satellite, Alternate Names | DSP 21 (USA 159) (Defense Support Program) |
| Country of Operator/Owner | USA |
| Operator/Owner | Air Force |
| Users | Military |
| Purpose | Early Warning |
| Class of Orbit | GEO |
| Type of Orbit | |
| Longitude of GEO (degrees) | 69.48 |
| Perigee (km) | 35765 |
| Apogee (km) | 35810 |
| Eccentricity | 0.000533712862479986 |
| Inclination (degrees) | 3.68 |
| Period (minutes) | 1436.14 |
| Launch Mass (kg.) | 2380 |
| Dry Mass (kg.) | |
| Power (watts) | 1485 |
| Date of Launch | 06-08-2001 |
| Expected Lifetime | 7-9 yrs. |
| Contractor | TRW and Aerojet Electronics Systems |
| Country of Contractor | USA |
| Launch Site | Cape Canaveral |
| Launch Vehicle | Titan 4B |
| COSPAR Number | 2001-033A |
| NORAD Number | 26880 |
| Comments | Infrared sensors to detect heat from missile and booster plumes against Earth´s background; detection capability of smaller missiles; improved warning of attack by short-range missiles against U.S. and allied forces. |