GRAW - Model DFM-09 - Radiosonde Systems
Extremely Low Weight GRAW’s latest state-of-the-art radiosonde, the DFM-09, is currently the smallest and lightest synoptic radiosonde available on the market today. The DFM-09 has dimensions of 200mmx42mmx60mm and weighs just 90 grams (Ready to Fly)! The DFM-09 has already proven itself to many customers worldwide - delivering excellent perform-ance, ease of use, and high reliability.
- All sensors are delivered Ready to Fly - 100 % factory calibrated and with no additional ground calibration necessary prior to launch
- The temperature and humidity sensor boom ensures precise measurements during ascent, it is unaffected by any thermal influences of the sondes housing
- A mirrored surface reduces errors due to solar radiation
- A ceramic temperature sensor delivers a fast response due to its low mass and low thermal capacity
- Fast, capacitive polymer humidity sensor
Function and Design
The DFM-09 radiosonde is designed to reliably measure the atmospheric profile of pressure, temperature, humidity, wind speed, and wind direction from the surface to an altitude of 40 kms. Continuous data sets are sent to the groundstation by a high quality radio-telemetry link.
High-Power Lithium Battery
- Shelf storage life of several years
- Simple activation, just a small on/off switch
- No special preparation
- Environmentally friendly
- Fulfills all transportation and storage regulations
Differential C/A-Code GPS for Wind Finding
The GRAW radiosonde family has a standard on-board C/A code-correlated GPS receiver. The sonde’s positional information is transmitted to the groundstation where it is corrected with the groundstation’s differential GPS system. The resulting data is used to accurately calculate the wind speed and direction of the sonde’s ascent - at all heights. Fully coded GPS allows the groundstation to be used on the move, such as launching from a vehicle or from a ship.
High Quality Telemetry
Each sonde contains a high specification telemetry transmitter. The radio transmission from the sonde meets demanding radio requirements and can cope with long slant ranges, even as far as 300 km. The use of code-spreading, a method where link-errors can be readily detected and corrected and other modern digital radio techniques such as interleaving which minimises the effect of burst errors, ensures that the data is reliably received at the distant groundstation.
The continuous on-board measurements of all sensors and transmission of their data is performed in a time-window of less than one second. Additionally, in a spare channel, diagnostic information from the sonde’s on-board Built In Test (BIT) systems are transmitted, thus ensuring the data sent is reliable during the ascent.
All important functions of the radiosonde are controlled by an on-board, low power microprocessor. The microprocessor controls the radiosonde initilisation, sensor measurements, communication, and in flight data quality control.
Freely Programmable Frequency
Each radiosonde can transmit in a narrow channel anywhere within the meteorological band (400 to 406 MHz). The sonde uses an on-board frequency synthesiser, which is automatically set to the desired transmission channel during initialisation.
The highly-sensitive groundstation receiver system does not require a steered antenna and can receive valid data from sondes up to 300 km slant range using its compact dual antenna set.
Quick and Easy Initialisation
Prior to launch, a simple cable connection starts up the sonde, sets its frequency and downloads the calibration data for the sensors from its on-board non-volatile memory. During this rapid and simple initialisation phase, the sonde is also checked and tested by the groundstation. The sonde is now ready for immediate release.