 CryoSat @-@ 2 was built as a replacement for CryoSat @-@ 1 , whose Rokot carrier rocket was unable to achieve orbit . Compared to its predecessor , CryoSat @-@ 2 features software upgrades , greater battery capacity and an updated instrument package . Its main instrument is an interferometric radar range @-@ finder with twin antennas , which measures the height difference between floating ice and open water . 
