iMet-54 Radiosonde

The iMet-54 is a low cost, high accuracy GPS radiosonde operating in the 403MHz frequency band:

Advanced Sensor Technology:

  • Capacitive Polymer Humidity with integrated heater for short response at low temperature/high altitude.
  • The humidity is immune to icing
  • Micro Glass Bead Thermistor Temperature – very small mass for extremely fast response. Reflective hydrophobic coating for immunity to solar radiation and super cooling.
  • SI traceable sensor calibration
  • Highly sensitive GPS provided unparalleled accuracy of wind and altitude reporting.
  • ETSI certified telemetry transmitter provides error free data transmission without interference. Forward-error correcting including interleaving provides fault correction for virtually 100% data transmission.

Extremely Simple use:

  • Enclosed dry lithium battery does not need prior connection. A simple on switch activates the radiosonde
  • Unlimited transmission frequency within the meteorological band (400 to 406 MHz)
  • No pre-flight recalibration required – all sensors are 100% factory calibrated.
  • Auto launcher ready
  • Compact and light weight – 65x30x245mm and only 80grams.
  • Reduced environmental impact

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System Overview

Operating Principle GPS or RDF Wind Finding
Nominal Frequencies 403MHz
Range >250km*
Altitude >30km*
Battery Lithium
Operating time > 3 hours
Weight 80 grams
Calibration Stabilioty 2 years
Power control WIreless or Push button


Tuning Range 400 – 406MHz
Output Power 200mW
Data rate 4800 bit/s
Frequency selection Wireless or push button (defaults, 402, 403, 404 & 405MHz)
Emission Bandwidth According to
EN 302 054
Sideband Radiation According to
EN 302 054
Frequency Stability ±2 kHz

GPS receiver

Type GNSS, 99 Channel
GNNS Systems GPS, GLONASS, Galileo, QZSS
Cold Start Acquisition Time 35 s (nominal)
Acquisition Time Reacquisition Time 1 s (nominal)
Horizontal Position Accuracy 3 m (CEP)


Type Bead Thermistor
Range -90°C to +60°C
Accuracy ±0.2°C
Resolution 0.01°C
Response time (still air)
Response time (6 m/s flow)
<2 s @ 1000hPa
0.7 s @ 1000hPa
Repeatability in Calibration 0.1°C
Uncertainty > 100 hPa
Uncertainty < 100 hPa
Reproducibility> 100 hPa
Reproducibility< 100 hPa


Type Thin Polymer Capacitive
Range 0% to 100% RH
Resolution 0.1% RH
Response Time
6 m/s, 1000 hPa, > 0°C
6 m/s, 1000 hPa, > -20°C
6 m/s, 1000 hPa, > -40°C
<1 s
3.2 s
20 s
Repeatability in Calibration 3% RH
Uncertainty 4% RH
Reproducibility 3% RH


Wind Speed Range GNSS derived
Wind Speed Resolution 0 to 150 m/s
Wind Speed Uncertainty 0.1 m/s
Wind Speed Reproducibility <0.5 m/s
Wind Direction Range 0 to 360°
Wind Direction Resolution 0.01°
Wind Direction Uncertainty
Wind Direction Reproducibility

Pressure (GNSS derived)

Type GNSS derived
Range 1080 to 3 hPa
Accuracy 0.5 hPa
Resolution <0.01 hPa
Response Time <1.0 seconds

Pressure (optional sensor)

Type Piezo-resistive sensor
Range 1200 to 10 hPa
Accuracy ±0.15hPa
Resolution <0.13 hPa
Response Time <8.22 milliseconds

Geopotential Height

Type GNSS derived or optional Piezoresistive
Range 0 to 50 km
Resolution 0.1m
Uncertainty 15m
Reproducibility 6m

Ordering Information

Ordering Information:
Stock Number Product Code Frequency Product Description
5506000400 IMET-54-AA.02 403MHZ GPS radiosonde
5506000300 IMET-54-AB.01 403MHZ GPS radiosonde with added pressure

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