The Athena comes in two versions, Athena I and Athena II. The Athena I has two stages, the Thiokol Castor-120 first stage and a Pratt & Whitney ORBUS 21D upper stage, both powered by solid-fuel.
The Athena rocket comes in two forms: Athena I and Athena II.  Athena I has a Thiokol Castor-120 first stage and a Pratt & Whitney ORBUS 21D upper stage, both powered by solid fuel.