NCAR has developed many generations of the GPS dropsondes:
The NCAR Research Dropsonde NRD41 is electrically equivalent to the RD41 dropsonde, but has been designed to work with automatic or manual launchers using the smaller form factor.
The NRD41 dropsondes incorporate a pressure, temperature, humidity sensor module (RSS421) designed by Vaisala, Inc. for their RS41 radiosonde, and a GPS receiver module independent of the sensor module. The specifications are shown in the following table.
xRD41 Sensor Specifications
|Pressure||1080-100 hPa||± 0.5 hPa||0.01 hPa|
|Temperature||-90 to +60 C||± 0.2 C||0.01 C|
|Horiz Wind||0-200 m/s||± 0.5 m/s||0.01 m/s|
Older sonde models
The RD41 is the last of the larger form factor produced dropsondes. It is the same physical size as the older models RD94 and RD93 but uses the PTU sensor module of the Vaisala RS41 radiosonde. Electronically it is identical to the smaller NRD41 dropsonde, but uses a the older ribbon delayed parachute release. It can only be used in manual launchers.
The NCAR Research Dropsonde NRD94 is electrically equivalent to the RD94 dropsonde, but has been designed to work with automatic or manual launchers using the smaller form factor. It was in used between 2010 and 2018.
The RD94 was produced between 2009 and 2018 and was the first dropsonde to incorporate a code correlating GPS for improved wind and position measurements.
The Miniature In situ Sounding Technology (MIST) dropsonde was used for driftsonde projects between 2006 and 2008. It was the first dropsonde in the 1.75"x12" form factor.
The RD93 was designed in the mid 90's and was used until 2010. It was the first dropsonde to use the GPS navigation system for wind finding.
Dropsondes have been designed and built at NCAR since the 1960s. These include the Omega DropWindsonde (ODW), the Lightweight Loran Digial Dropsonde (L2D2) and the Lightweight Omega Digital Dropsonde (LOD2), which were in use between 1980 and 1995 and used the Omega and LORAN radio navigation systems.
Overview of NCAR GPS dropsonde models
|Dropsonde Type||Diameter (cm)||Length (cm)||Weight (g)||Parachute size
(cm x cm)
|NRD41||4.5||30.5||169||20 x 20||Manual/Automatic||Currently in production at NCAR and licensed for production to Vaisala|
|RD41||7.0||40.6||323||30 x 30||Manual||Produced from 2018-2023|
|RD94||7.0||40.6||320||30 x 30||Manual||Produced 2009-2018|
|NRD94||4.5||30.5||167||20 x 20||Manual/Automatic||Produced by NCAR for automatic launchers on NASA Global Hawk and NSF/NCAR G-V|
|MIST||4.5||30.5||184||20 x 20||Gondola only||Produced for Driftsonde in 2010|
|RD93||7.0||40.6||400||30 x 30||Manual||Produced 1996-2009|
UCAR has licensed Vaisala Inc. of Louisville, Colorado to build the NCAR GPS Dropsonde RD41.