Upper-air measurement

iMet-54Radiosonde

New-generation sensor technology. Simple sounding preparation. A robust data link, even in challenging urban environments.

80 g

Lightweight construction

> 180 min

Operating time

> 250 km

Maximum telemetry range

Concurrent GNSS

GPS, GLONASS, BDS, Galileo, QZSS

01 / Technology

Key features

Improved measurement techniques address evaporative cooling and humidity sensor icing.

Capacitive thin-film polymer humidity sensor with integrated heater for fast response at low temperature
Dynamic heating of the humidity sensor prevents saturation or ice formation on the sensor.
A very small mass glass bead thermistor facilitates extremely fast response to temperature changes. Reflective coating reduces the effects of solar radiation while a hydrophobic polymer counters evaporative cooling events
SI traceable sensor calibration
High sensitivity, multi-constellation GNSS receiver with unparalleled accuracy of wind and altitude measurement
ETSI certified telemetry transmitter provides error free data transmission without interference. Forward-error correcting techniques ensure fault correction for a highly robust telemetry link
Pre-installed dry lithium battery. Easy-to-use push-button controls power and pre-set transmission frequencies
User-selectable transmission frequency anywhere within the assigned meteorological frequency band
No pre-flight recalibration required – all sensors are factory calibrated
Compact and light weight: 235 x 70 x 30 mm and only 80 grams
Reduced environmental impact

02 / Technical data

Sensor performance, system characteristics and telemetry specifications.

System overview

GPS Receiver

Type	GNSS
Channels	99 Channels
GNNS Systems	GPS, GLONASS, BDS, Galileo, QZSS
Cold Start Acquisition Time	35 s (nominal)
Reacquisition Time	1 s (nominal)
Horizontal Position Accuracy	1.5 m (CEP)

Humidity

Type	Capacitive Thin Polymer
Range	0 % to 100 % RH
Resolution	0.01 % RH
Response Time
6 m/s, 1000 hPa, +20°C	< 0.4 s
6 m/s, 1000 hPa, 0°C	< 1 s
6 m/s, 1000 hPa, – 20°C	< 3.2 s
6 m/s, 1000 hPa, -40°C	< 20 s
Repeatability in Calibration	< 2 % RH
Uncertainty	< 4 % RH
Reproducibility	< 3 % RH

Temperature

Type	Bead Thermistor
Range	-100 °C to + 60°C
Resolution	0.01 °C
Response time (still air @ 1000 hPa)	< 2 s
Response time (6 m/s flow @ 1000 hPa)	< 0.5 s
Repeatability in Calibration	< 0.1 °C
Uncertainty > 100 hPa	< 0.3 °C
Uncertainty < 100 hPa	< 0.5 °C
Reproducibility > 100 hPa	< 0.1 °C
Reproducibility < 100 hPa	< 0.25 °C

Pressure (GNSS derived)

Telemetry

Transmission type	Synthesized
Maximum range	>250 km
Frequency band	400.15 – 406 MHz OR 1668.4 – 1690 MHz
Frequency stability	±2 kHz
Deviation (peak to peak)	4.8 kHz
Output power	200 mW
Emission Bandwidth	According to EN 302 054 for 403MHz model According to EN 302 454 for 1680MHz model
Sideband Radiation	According to EN 302 054 for 403MHz model According to EN 302 454 for 1680MHz model
Modulation	GFSK
Data rate	4800 bit/s
Frequency selection	Wireless or push button
Push button frequencies	402, 403, 404, 405 MHz OR 1676, 1678, 1680, 1682 MHz
Wireless frequency selection	400 – 406 MHz (10 kHz resolution) OR 1668.4 – 1690MHz (10kHz resolution)

Wind

Type	GNSS derived
Wind Speed Range	0 to 180 m/s
Wind Speed Resolution	0.1 m/s
Wind Speed Uncertainty	< 0.15 m/s
Wind Speed Reproducibility	< 0.1 m/s
Wind Direction Range	0 to 360°
Wind Direction Resolution	0.01°
Wind Direction Uncertainty	< 1°
Wind Direction Reproducibility	< 1°

Geopotential Height

Type	GNSS derived or optional Piezoresistive Sensor
Range	0 to 50 km
Resolution	0.1m
Uncertainty	< 8m
Reproducibility	< 5m

03 / Product options

403 MHz and 1680 MHz configurations, including pressure sensor options.

Product description	Product code
403Mhz GPS Radiosonde	IMET-54-AA
403MHz Radiosonde with pressure sensor	IMET-54-AB
403MHz encrypted Radiosonde	IMET-54-AC
1680Mhz GPS Radiosonde	IMET-54-BA
1680Mhz Radiosonde with pressure sensor	IMET-54-BB
1680Mhz RDF Radiosonde	IMET-54-BI