1. AVAPS II DROPSONDE Overview
April 28th 2009
AVAPS Users Group Meeting
Terry Hock

2. NCAR/EOL Dropsonde Team
Kate Young
Dean
Lauritsen
LauraTudor
June Wang
Terry Hock
Nick Potts
Charlie Martin
Chip Owens
Clayton Arendt
Hal Cole
Mary Hansen
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Corporation for Atmospheric Research 2

3. 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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Corporation for Atmospheric Research

4. AVAPS II Size Sonde mass: Fall Rate
323 grams, ~18% less weight (RD g)
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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Corporation for Atmospheric Research

5. 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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Corporation for Atmospheric Research

6. 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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Corporation for Atmospheric Research

7. 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 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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Corporation for Atmospheric Research

8. Launch Detect Mechanism
Dropsonde
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.
Parachute
Chamber
CDS
Photo Detector
White
LED transmitter
Electronics
GPS Antenna
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Corporation for Atmospheric Research

9. Sonde Comparison RD-93 & AVAPS II Sonde
AVAPS II RD AVAPS II RD93
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Corporation for Atmospheric Research

10. 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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Corporation for Atmospheric Research

11. 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

12. 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
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Corporation for Atmospheric Research