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

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



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)



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



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.



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. . .



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



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



Sonde Comparison RD-93 & AVAPS II SondeAVAPS II RD93 AVAPS II RD93



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



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



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

Documents

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