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 has two variants: Athena I and Athena II.  Athena I utilizes a Thiokol Castor-120 first stage and a Pratt & Whitney ORBUS 21D upper stage, both of which are powered by solid fuel.