The mission of Operation IceBridge is to collect data on changing polar ice and maintain continuity of measurements between ICESat missions. The original ICESat mission launched in 2003 and ended in 2009, and its successor, ICESat-2, is scheduled for launch in late 2018. Operation IceBridge began in 2009 and is currently planned to continue until 2020 so it to overlaps with ICESat-2 to help scientists connect measurements from the two satellites.
Source: tatoeba (6478993)