The Ultra Long-Duration Balloon (ULDB) Project is a project, managed by Goddard Space Flight Center, to fly balloons on missions lasting up to 100 days at the edge of space. The pumpkin-shaped ULDB is the largest single-cell, sealed balloon ever flown, with a fully-inflated diameter of 58.5 meters and a height of 35 meters. It is designed to inflate gradually as it approaches its cruising altitude of 35 kilometers – above 99% of Earth's atmosphere-and then circumnavigate the globe while taking measurements with its scientific payload. NASA sees the ULDB as offering a cheap alternative to certain kinds of low-Earth-orbiting satellite missions.