The SS-520 is a two-stage rocket, the first stage of which comes from the
main booster of the S-520. It has a capability for launching a 140 kg payload
to an altitude of about 800 km.
The SS-520 aims at reaching 800 km altitude, and at the same time, carrying out technological experiments concerning the development of a mini-satellite launch vehicle by adding the third stage atop. The first stage is stabilized aerodynamically by use of tail fins like the S-520.
As the second stage is heavier than the head of S-520, the aerodynamic margin is secured more than ever. The whole motor case of the second stage is made of CFRP. The spin generated in the first stage is succeeded by the second stage, and it is utilized in the Rhumb-line control and spin stabilization.
The SS-520 debuted in January, 1998, and ISAS has a plan to launch it from Spitsbergen, Norway, to send a payload into the cusp region of the geomagnetosphere.