After mastering the techniques connected with solid-propellant motors manufacture - with INTA-100 and INTA 300 sounding rockets - the Spanish INTA undertook, in the beginning of the 1990s, the development of a launcher able to orbit mini-satellites (up to 100 kg) in LEO (up to 600 km).
It had to be a three-stage solid-rocket, measuring 18.2 m in length and 1 m in diameter (1st stage), with a takeoff mass of approximately 15 tons. The first stage motor, selected in June 1997, was a Thiokol Castor 4B (USA) already used for the Maxus sounding rocket. This motor, that delivers an average 450 kN thrust during 63 seconds, is equipped with a directional nozzle that authorizes the piloting of the rocket. The two upper stages were the Deneb, built in collaboration with Thiokol, and the Spanish designed Mizar. INTA was also responsible of the launcher guidance and control electronics as well as of the construction of a launch base on the island of El Hierro (27° North) in the Canaries archipelago.
A technological demonstrator designated Argo, 9.2 m in length and 0.83 m in diameter, had to allow to test the Capricornio upper stages composite. The first firing of Argo was planned for the winter 1998-99, but the program was cancelled some months earlier.