The Inter-Continental Radiosonde Sounding System (ICARUSS), also called Driftsonde, is a proposed new atmospheric sounding system for use during the upcoming THORPEX experiment in 2003 or 2004.

The ICARUSS concept uses a thin polyethylene balloon (0.35 mil) with a volume of 268 cubic meters to lift a payload (< or =40 kilograms) of 24 dropsondes or modified radiosondes to an altitude of about 100 to 75 mb ((53,000 - 60,000 feet) and maintain that altitude for 5-6 days. The altitude of the balloon can be adjusted over a limited range to take advantage of the most favorable upper-level westerly wind flow.

Simulations using 1999 wind data over the Atlantic and Pacific oceans (Figure 1, Figure 2) show that balloons launched from coastal radiosonde sites (eastern U.S. or Asian) will travel across the oceans in approximately 5-6 days. The distribution of soundings over the oceans is shown in these two slides if a dropsonde is released every 6 hours from an individual balloon and a new balloon is launched every 12 hours. The dropsonde would telemeter the measured profile data back to the balloon where it would be received, processed, and stored. A compressed data set (e.g. WMO message or 10 second data) would be sent through a Low Earth Orbiting satellite (e.g. OBCOM) to a ground station and on to the THORPEX control center for further processing and/or input into the Global Telecommunications System (GTS).

The balloon gondola would house 24 dropsondes, a telemetry receiver card, PTH and GPS wind processing cards, a single board computer card for data processing and ballast control, a satellite transceiver card, a lithium battery power supply and a passive thermal control system to maintain the electronics above -10 deg C. During the nighttime transition period when the balloon volume decreases due to radiational cooling of the helium, ballast would be dropped to maintain altitude. An additional natural rubber balloon may be required during rain, wind and snow conditions to tow the ICARUSS balloon and payload through the severe weather. The rubber balloon would be jettisoned above the severe weather.

Presentation (27 November 2000)
Preliminary Design Presentation (19 January 2000)