www.vaisala.com Vaisala RD94

and the Vaisala RS92 use by the application in question. The family. Calibrations are traceable to AVAPS is not compatible with Vaisala the international standards. Accuracies and vice versa. have been validated e.g. in the WMO AVAPS can be configured to track up to comparisons. four at the same time. This The are measured using a is an essential ability in operations that commercial GPS receiver, which has are carried out with high-speed, high- a custom made firmware to ensure when dense horizontal proper measurement. The wind resolution of data is required. profiles from multiple simultaneous The AVAPS can be set to provide data dropsoundings show a good consistency. automatically for the aircraft data system for further use. The dropsonde Designed for Aircraft Use technology developer NCAR/EOL The Vaisala Dropsonde RD94 is provides ASPEN data post descent designed for aircraft use, and is processing software for dropsonde launched through the body of an users. aircraft. Specially designed launchers are used for both pressurized and Intellectual Property un-pressurized cabin aircrafts. The Rights and Development delayed deployment mechanism Vaisala Inc., USA, manufactures and ensures proper clearance from the markets the Dropsonde RD94 and aircraft, and allows the parachute to AVAPS Dropsonde Receiving System open safely. The specially designed under license to University Corporation parachute stabilizes the RD94 aligning for Atmospheric Research Foundation it properly for measurements, and (UCARF). The dropsonde and receiving its small gliding factor ensures The Vaisala Dropsonde RD94 is a system hardware and software have proper measurement of the wind meteorological measurement device been developed at the Earth Observing speed and direction. to be used in atmospheric profilings Laboratory (EOL) of the National from aircraft flight level to surface. The descent speed of the RD94 is Center of Atmospheric Research Descending through the atmosphere approximately 11 m/s at the sea level, (NCAR), in Boulder, Colorado, USA. by a parachute, it measures the and about 21 m/s at a 12 km altitude. profiles of (P), In strong convective situations the Vaisala Dropsonde (T), relative (U) and wind descent rate can vary a lot, and even References direction and speed from the point negative (descent) rates are measured. Since 1996, about 50,000 earlier of launch to the ground. It has been The RD94 measures the PTU twice and versions of the Vaisala Dropsonde used from low, 1500 ft, to high, 66 kft, and direction four times a RD93, have been used in eight altitude drops. The RD94 transmits second. This means that e.g. the last countries by various operators. data using a narrow bandwidth FSK measured pressure level is at maximum The main uses have been hurricane (Frequency Shift Key) modulation in about 5 - 6 meters above the surface. research, and data acquisition the 403 MHz meteorological band to the The robust design of the RD94 ensures over oceans as input for Numerical AVAPS (Airborne Vertical Atmospheric safe use of the legacy launchers and high Prediction (NWP) models. Profiling System) onboard the aircraft. speed deployment of the parachute. In addition, a large number of Vaisala Dropsonde RD93s, have been annually Proven Measurement Dropsonde Receiving used in various field campaigns Performance System to acquire data for meteorological The Vaisala Dropsonde RD94 sensors Onboard the aircraft the AVAPS research and for validation of other are calibrated using similar methods system receives, displays, stores, and airborne instrumentation. as with the Vaisala Dropsonde RD93 distributes dropsonde data for further Technical data

Vaisala Dropsonde RD94 Weight 350 g Size 7 cm in diameter, 41 cm in length Maximum deployment airspeed 250 kt IAS (= 125 m/s IAS) Shelf life 1 year from delivery

Transmitter - EN302054 Frequency range 400 MHz to 406 MHz Frequency stability ±1 kHz RF power output 100 mW Channel spacing Modulation FSK Harmonic & spurious output >50 dB below the carrier level Total modulation range with Relative humidity sensors (U) recommended receiving antenna 325 km Vaisala H-HUMICAP® thin film capacitor, twin-sensor design Battery Range 0 % to 100 %RH Type Three lithium CR-2 cells in series Resolution 1 %RH Voltage 9 V nominal Accuracy Current Max. 235 mA, 200 mA average repeatability * 2 %RH Life 2 hours (operating), 3 years (shelf) Response time (when used and measured in Vaisala Radiosonde RS92) 6 m/s, 1000 hPa, +20 °C < 0.5 s Pressure sensor (P) 6 m/s, 1000 hPa, –40 °C < 20 s Vaisala BAROCAP® silicon sensor Range 1080 hPa to 3 hPa Wind (horizontal) Resolution 0.1 hPa Commercial GPS receiver Accuracy Repeatability* 0.4 hPa Data rates Temperature sensor (T) PTU update rate 2 Hz Wind update rate 4 Hz Vaisala THERMOCAP® capacitive bead Range –90 °C to +60 °C Resolution 0.1 °C Descent Accuracy Descent speed ~11 m/s at sea level Repeatability * 0.2 °C Descent time Response time From 14 km ~15 mins (when used and measured in Vaisala Radiosonde RS80) From 7.5 km ~8 mins 6 m/s, 1000 hPa < 2 s *Standard deviation of differences between two successive repeated calibrations, k = 2 confidence level

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