ESRL/GML Water Vapor

NOAA GML/OZWV Software Downloads

These software packages were developed by the NOAA Ozone and Water Vapor Group to assist with weather balloon launch planning, data collection/processing, and instrument setup. They are written for Windows (XP/Vista/7/8/10) and require the .NET Framework 4.0 or higher (typically already installed on modern computers). Contact Information:

Programmer: Allen Jordan allen.jordan@noaa.gov Design/QA/Testing: Emrys Hall emrys.hall@noaa.gov Supervisor/PI: Dale Hurst dale.hurst@noaa.gov

Disclaimer: The availability of these tools to the general public does not condone attempts to recover balloon payloads that land on private property, government property, or hazardous locations. Predicted trajectories and landing zones are only approximate, therefore active tracking is required to accurately locate launched payloads.

Balloon Prediction

This program forecasts weather balloon trajectories and landing locations, showing the resulting path on a map. Use this to help select safe launch days, avoiding airports, city centers, and other hazardous landing zones (though accurate results are not guaranteed).





Calculates weather balloon trajectories/paths and landing locations

Uses NOAA GFS model wind data, or NWS radiosonde soundings as input

Custom burst/turn altitude, launch locations, dates/times, and time zones

Adjustable rise rate tables for different balloons/payloads

Detailed mapping, selectable map sources

Google Earth KML output file for 3D trajectory viewing

Download Installer

Download User Manual

SkySonde Client/Server

A pair of programs for collecting and displaying Intermet iMet-1 and iMet-4 radiosonde data telemetry in real-time during a weather balloon flight, along with the NOAA Frostpoint Hygrometer (FPH), EN-SCI/DMT ECC Ozonesonde, and several other instruments.

NOTE: This program will NOT receive National Weather Service radiosonde data, as they use different radiosonde models/formats.





Parses, displays, and stores wireless data from iMet radiosondes

Support for the NOAA FPH and ECC Ozonesonde is built in

Extra instrument plugins included for the ETH COBALD, Anasphere SLWC, MetOne OPC, and NOAA POPS (contact Allen Jordan to add more)

Client/Server architecture. Can be run on the same computer or across a network (a server computer attached to the receiver, one or more client computers displaying and saving the data)

Audio input data from a receiver can be demodulated directly without a physical modem

NEW: Software-defined radio (SDR) receiver support for the RTL-SDR and all SDRplay models. This allows for high-quality affordable receiving systems to be setup with a minimum amount of equipment (see below). The digital filters used with SDR input were designed with genetic algorithms to be optimal for Intermet radiosondes.

Important: If using the SDRplay, download and install the latest "API/HW Driver – v3" available from this link or SkySonde Server might crash when using the device.

Download Server

Download Client

Download User Manual

Software-Defined Radio Receiving System

SkySonde Server now supports using software-defined radio (SDR) receivers directly through USB for receiving iMet radiosonde data. They are affordable, simple to setup, and work great even when compared to expensive commercial iCom receivers.



Many flight tests have proven SDR systems to work as well as traditional iCom receiver systems for balloon data collection. Often, the SDR will outperform the iCom receivers in low signal strength situations.

Antenna Option 1 Harsh/Synergetics 14A-N Antenna, ~$600 A durable omnidirectional outdoor antenna. Can be mounted on a tripod or mast with modification. Antenna Option 2 Laird YS3805 Yagi, ~$80 Cheaper yagi directional antenna with high gain, mast mounting brackets included. Antenna Option 3 Motorola HAE6011A, ~$55 Cheap whip-style antenna, but requires cutting cable short and crimping SMA male to RG-58 coax. Long ordering lead time. Requires mounting on metal box or vehicle roof. See doc below for more information. Antenna Option 4 home made 1/4 wave ground plane antenna, ~$5 Custom build your own antenna centered at ~404 MHz. This has proven surprisingly effective for receiving balloon data. Preamplifier Uputronics 403 MHz Radiosonde Filtered Preamp, ~$65 A good preamp, can be powered through coax from the SDRplay (if the model supports bias-t). Preamp Enclosure Mast Mountable Enclosure, ~$50 A weather-resistant enclosure for the preamp, important for outdoor use. For the cleanest mounting, it may also need a 15 cm (6 inch) SMA male to SMA female 90' extender (also from Uputronics). Coax Cables Coax cable assemblies Several coax cables are required depending on antenna choice, see doc below. LMR-400-UF coax is recommended for longer than 25 ft, otherwise LMR-240-UF works well for shorter sections. Software-Defined Radio Option 1 SDRplay RSPdx, ~$200 High gain and low noise, can power the preamp through coax (bias-t on ANT B). All SDRplay models are now supported, though only the RSP2 and RSPdx have been tested. Note that some older models don't have bias-t support. Software-Defined Radio Option 2 Any RTL-SDR USB dongle, ~$25 These SDRs are cheap and work surprisingly well, but they are flimsy for a permanent setup. Get one with a SMA female connector. The NooElec NESDR SMArt has been tested successfully. USB Cable Shielded USB-A Male to USB-B Male Cable, 6 Foot, ~$5 A standard short USB cable, ideally shielded to reduce noise. Only needed for the SDRplay. Computer Any modern windows computer (i5 processor or better) The SDR requires a fair amount of processing power, an Intel i5 or better processor is recommended. Windows 7 or higher is needed to run the software.

Good System Approximate Cost: omni antenna + preamp + enclosure + SDRplay + cables = $1100 (not including computer) Affordable System Approximate Cost: HAE6011A antenna + preamp + RTL-SDR + cables = $200 (not including computer) NOTE: Make sure there is only one preamp in the system, and it should be as close to the antenna as possible (less than 3 feet away).

Download SDR Setup Instructions

XDATA Radiosonde Protocol

The XDATA protocol was invented by Jim Wendell (jim.wendell@noaa.gov) for connecting external instruments to a radiosonde for wireless data transmission to a ground station. It is currently implemented in Intermet iMet-1-RSB radiosondes, and partially in Vaisala RS41 radiosondes. The documents below describe both the XDATA protocol for instrument to radiosonde communications, and the received data protocol for radiosonde to antenna/receiver communications.



Attach custom instruments to a radiosonde for wireless transmission, using only a standard UART module

Open protocol implemented on several radiosondes and used by multiple prominent weather balloon instruments

The received data protocol allows for writing custom telemetry programs similar to SkySonde

XDATA Protocol

Packet Example

Instrument ID Allocation

Protocol for Received Data

SkySonde Client Plugin System Documentation

SkySonde Client supports plugins for parsing and storing data from other XDATA instruments attached to an iMet radiosonde. Instructions for writing a custom plugin are provided below, along with source code for an example plugin (written in C# using Visual Studio 2013).



Make custom XDATA instruments that transmit through iMet radiosondes, and collect the data in SkySonde Client using a custom plugin

Customize the metadata collection and real-time data display

Output any data fields and calculations, will be matched with current radiosonde PTU/GPS measurements on the same CSV file row

Plugin Documentation

Plugin Example