An article in Science (7 April 2006) notes that weather balloons have always been the "gold standard" of atmospheric sensors, used to calibrate spaceborne instruments and initialize forecast models. GPS-RO is many times more accurate than balloon measurements and may soon be used to calibrate weather balloon data. Recent studies in Europe (Healy and Thépaut, 2006) indicate that a GPS-RO profile has up to 100 times the information content of a similar profile from a conventional spaceborne weather sensor, such as AIRS, MODIS and AMSU. Conventional sensors, moreover, can cost up to 1000 times more than a GPS-RO receiver.