Frequently asked questions about
the NWS Radiosonde Observations Program


(1) What is a radiosonde and how are the data it provides used?

NWS has been using balloon-borne radiosonde instruments since the late 1930s. The data they provide are critical for weather forecasting and research.  Click here to learn more.

(2) I found a radiosonde.  Is it dangerous?  Does the National Weather Service want it back?

If you found a radiosonde follow the instructions here: Found Radiosonde Instructions

(3) What types of radiosondes does the NWS use in its network?

Lockheed Martin Sippican (LMS) MarkIIA GPS radiosonde, LMS B2 radiosonde, and the LMS-6 radiosonde (used only at Wallops Island)

(4) What types of ground equipment does NWS use to track the radiosonde?

Most stations use GPS radiosondes operating at 1680 MHz that is tracked with a dish antenna system.  Check out the Radiosonde Replacement System (RRS) page for more information.  A small number of stations use  a radiotheodolite  (see photograph below) to track the radiosonde as it ascends and receive the radiosonde signals.   These systems are now obsolete (date to the 1950s) and are being replaced with the RRS. 

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NWS Radiotheodolite with the fiberglass radome removed.

(5) How are radiosonde data checked for quality?

Quality control of radiosonde data is done at the upper-air station and national centers such as the NOAA National Centers for Environmental Prediction (NCEP) and at the National Climatic Data Center (NCDC).  Click here to learn more.

(6) Why does NWS still use radiosondes? Isn't there another observing system available that can provide the same data?

At the present time, there is no single observing system (e.g., satellites, aircraft observations, and ground-based remote sensors) that can match the vertical data resolution (about 30 meters or less) and height coverage (more than 30 km) obtained with radiosondes.  NOAA is involved in developing new, cost-effective technologies and methods for obtaining upper-air data to meet future data needs.

(7) What is the difference between a "radiosonde" and a "rawinsonde" observation?

A radiosonde observation provides only pressure, temperature, and relative humidity data. When a radiosonde is tracked so that winds aloft are provided in addition to the pressure, temperature, and relative humidity data, it is called a rawinsonde observation. Most stations around the world take rawinsonde observations. However, meteorologists and other data users frequently refer to a rawinsonde observation as a radiosonde observation.

(8) Who do I contact if I have further questions?

Please send an email to   We will answer your questions as soon as possible.

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