| Prime contractor | NEC (with Hughes as major subcontractor) |
| Platform | HS-378 |
| Mass at launch | 682 kg |
| Mass in orbit |
#1:
304 kg #2: 268 kg #3 & 4: 303 kg #5: 312 kg |
| Diameter | 2.16 m |
| Height | 3.45 m (except GMS 1: 2.7 m) |
| Stabilization | Spin stabilized |
| DC power | 291 W |
| Design lifetime | 5 years |