What types of radiosondes are used by the NWS?
NWS currently uses two types of GPS radiosondes:
LMS-6 built by Lockheed Martin
RS92-NGP built by Vaisala
Note: The Mark IIA Radiosonde was phased out of the NWS weather balloon network in early 2015.
Further reading
NWS sounding - A virtual tour on preparing and launching a NWS GPS radiosonde.
Network Maps - Maps showing station locations of NWS offices that take radiosonde observations.
History - History of upper-air observations.