| Official name | IUS R/B(1) |
| Alternative name | IUS first stage (Atlantis (OV-104)) |
| Cospar ID | 1991-054C |
| Norad ID | 21640 |
| Launch date | 1991-08-02 |
| Launch site | AFETR |
| Launch vehicle | Shuttle |
| RCS size | LARGE |
| Decay date | ON ORBIT |
| Period (min) | 476.1 |
| Inclination (deg) | 26.57 |
| Perigee (km) | 287 |
| Apogee (km) | 27351 |
| Eccentricity | 0.979231492872133 |
| Mean motion (revs. per day) | 3.02457466918715 |
| Semi-Major axis (km) | 20197.135 |
| Raan (deg) | 71.1859 |
| Arg of perigee (deg) | 277.3675 |
| Shape | Cyl |
| Mass (kg) | 1243.81 |
| Diameter (m) | 2.32 |
| Height (m) | 3.07 |
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