avaps ii dropsonde overview april 28 th 2009 avaps users group meeting terry hock
TRANSCRIPT
AVAPS II DROPSONDEOverview
April 28th 2009 AVAPS Users Group Meeting
Terry Hock
2 © 2009 Copyright University
Corporation for Atmospheric Research
NCAR/EOL Dropsonde Team
Dean LauritsenLauraTudor
Kate Young
June WangTerry Hock
Chip Owens
Nick Potts
Hal Cole
Clayton Arendt
Charlie Martin
Mary Hansen
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Corporation for Atmospheric Research
AVAPS II Functionality
• Sensors– Pressure, Temperature, Humidity
• Vaisala RSS-921 PTU module (Standard part)• Pressure sensor – no change from RD-93• Humidity sensors – no change from RF-93• Temperature sensor – new fast response sensor
– Winds and Position via GPS receiver• U-Blox TIM-5H receiver, latest generation from u-Blox
– (RD-93 used TIM-LF, TIM-4P)
• Date Rate– PTU 2 Hz Data (0.5sec)– Position 2 Hz (0.5 sec)– Winds 4 Hz (0.25 sec)
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AVAPS II Size
• Sonde mass: – 323 grams, ~18% less weight (RD-93 395g)
• Fall Rate– ~10.5 m/s at sea surface
• ( ~11.5 m/s RD-93)
– Same size parachute as RD-93– Same case size 2.75” x 16” as RD-93– Same sensor and parachute bulkheads
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AVAPS II Operations
• Pre-Flight– Umbilical cable
• Set 400MHz transmitter frequency • Umbilcal cable has no other required functions
– RD-93 required upload of PTH sensor coefficients to PC
– If sonde frequency is preset, there is no need for use of umbilical cable
– Sonde has a 2nd serial port through umbilical cable to u-Blox GPS receiver.
• Optional - Upload GPS ephemeris data for quick satellite acquisition, still under investigation for dropsonde use in an aircraft, all ground tests are very promising.
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AVAPS II Sonde Design• 3 lithium batteries, nominal 8 volts,
– Minimum voltage required is 6 volts • 2 microcontrollers PIC18F….FLASH easily to update firmware
– Vaisala PIC• measure PTU sensor frequencies• Calculate Pressure, Humidity, Temperature in sonde
– Main Sonde PIC• Controls Vaisala PIC• Controls GPS receiver• Controls 400 MHz transmitter• Creates telemetry data message• Interface configuration during manufacturing
• U-Blox TIM-5H GPS receiver– 4 Hz update rate– 50-channel engine with over 1 million correlators– Improved sensitivity, -160dBm– “Improved GPS satellite acquisition time”– L1 only receiver– FLASH EEPROM easy to upgrade firmware
• Sensor expansion capability for other sensors, i.e. ozone, electric field strength. . .
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AVAPS II Sonde Design (cont)• 400 MHz Transmitter uses a RF ASIC
– Fractional Synthesizer for fine frequency resolution– Spectral purity same as RD-93– RF Bandwidth ~20kHz– Operates in 400-406 MHz Meteorological band– Eliminated manual adjustments during manufacturing, cost reduction (RD-93 had
2 required adjustments)– Same antenna design
• New Modulation Scheme– Frequency Shift Keying (FSK) modulation (RD-93 had 2 modulation signals)– 2400 Baud data rate– Manchester encoding– PTU and GPS data all embedded in same data stream– Telemetry errors should be similar between PTU and GPS
• Electronic Components are all “ROHS”– AVAPS II Dropsonde 170 electronic parts (~20% fewer electronic parts)– RD-93 Dropsonde 214 electronic parts
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Launch Detect Mechanism• Goals for new system
– Reliable– Low Cost– Simple to implement
• Optical– Light beam
• Electronics in parachute compartment
• Packed parachute block beam
• Low cost• No Mechanical parts
• RD-93 Sonde is a shorting pin attached to the parachute riser line via a string
• Drop tests have shown 100% reliability.
Electronics
ParachuteChamber
WhiteLED
transmitter
CDSPhoto Detector
GPS Antenna
Dropsonde
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Sonde Comparison RD-93 & AVAPS II SondeAVAPS II RD93 AVAPS II RD93
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Summary of Cost reductions
• Single PCB assembly vs 2 PCB assemblies• No manual tuning adjustments required of transmitter• Simplified launch detector, removal of shorting pin/string• Removal of bunchee cord assembly in parachute riser
line• Reduction of electronic parts by 20%• 2 layer PCB vs 4 layer PCB• Next generation of production test software
– uses bar code reader to simplify process• Reduced the number of cells in battery pack from 6-cells
to 3-cells– cost, weight, safety, shipping
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Summary Performance Changes
• Faster response temperature sensor• Improved telemetry for GPS wind data• Improved reliability of launch detect• Possibility of no GPS re-radiation required (pre
loading GPS ephemeris data)• 4 Hz (0.25 sec) GPS Wind Data !! • System easily adapted to adding other sensors
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Corporation for Atmospheric Research
AVAPS II Development Roles
• NCAR– Development; New Dropsonde, Telemetry chassis
modifications and AVAPS Software, production of prototypes Dropsonde and telemetry cards.
– Drawing package– Support Dropsonde production– Data analysis
• NOAA/AOC– Flight testing: prototype dropsondes, telemetry chassis
and AVAPS Software– Technical engineering input– Flight Operations input– Data analysis