DISCOVERER 21
| Launched | 17 February 1961 |
| Flight ended | 19 April 1962 |
| Status | Decayed |
| Launch site | Air Force Western Test Range, California, USA |
| Owner | United States |
| NORAD ID | 84 |
| COSPAR ID | 1961-006A |
| Observing |
DISCOVERER 21
| Launched | 17 February 1961 |
| Flight ended | 19 April 1962 |
| Status | Decayed |
| Launch site | Air Force Western Test Range, California, USA |
| Owner | United States |
| NORAD ID | 84 |
| COSPAR ID | 1961-006A |
| Observing |