| AstronautID | GivenName | FamilyName | DateEnlisted |
|---|---|---|---|
| A401 | Elena | Rostova | 2018-02-15 |
| A402 | Marcus | Vance | 2019-06-10 |
| A403 | Elena | Tanaka | 2019-11-01 |
| A404 | Sean | Vance | 2021-03-24 |
| AssignmentID | AstronautID | LaunchDate | Role |
|---|---|---|---|
| M901 | A401 | 2020-04-12 | Commander |
| M902 | A401 | 2021-10-15 | Pilot |
| M903 | A403 | 2022-03-05 | Mission Specialist |
| M904 | A402 | 2022-08-18 | Commander |
State the name of the field from the Astronaut table that is the most suitable to use as the primary key.