1. Fiber-optic Temperature Profiler for Long Duration Balloon Missions
High Resolution Temperature Measurements of the Tropical Tropopause Layer
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Lars Kalnajs – LASP /University of Colorado
Sean Davis – NOAA ESRL Chemical Sciences Division
Planetary Science • Space Physics • Solar Influences • Atmospheric Science • Engineering • Mission Operations & Data Systems

2. Concept
High resolution temperature profile measurements covering ~4km below balloon (from ~13 – 17km)
Measurement region spans the Tropical Tropopause Layer
Laser based sensor to measure the temperature along ~4km of fiber suspended below balloon
Profile temperature at rates up to 1/min for the entire duration of the flight
Vertical resolution of 2m and temperature precision better than 1C
Photo: Sean Davis
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

3. Instrument Overview
Measures the temperature of a standard multi-mode communications fiber. Based on the intensity of the Stokes and Anti-Stokes Raman scattering spectrum. Ratio of Stokes (+10nm) to anti-stokes (-10nm) gives temperature, time of flight gives position. FPGA based sampling at very high rates (107 samples s-1), coherent averaging (105 points) gives high precision End-of-Fiber unit determines position, pressure and temperature at bottom end of fiber.
Spectra from
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

4. Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs
Prototype Instrument
Motor/Gear Box
Optical Bench
Fiber Reel
GPS + Data Acquisition
Motion Controller
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

5. Optical Fiber 50/125 μm Multimode Optical Fiber
240 μm polyamide coating
Human Hair
125 μm glass cladding
50 μm glass core
150 grams / kilometer
<2Kg Practical Breaking
Strain
High Albedo Coating
600 μm Liquid Crystal Polymer Coating
50/125 μm Optical Fiber
400 grams / kilometer
>20 Kg Breaking Strain
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

6. Instrument Performance
1-σ temperature accuracy: 1°C Spatial resolution: 2m (1/e change) Scan speed: 100 meters / second Raw Data rate : 5 bytes/meter/scan Power: 10W continuous, 4W 10 profiles/hour Weight: 7 Kg (prototype) 4 Kg (expected flight model)
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

7. Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs
Tower Tests
Image: Sean Davis
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

8. Flight Tests Click to add image credit info
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

9. Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs
Flight Tests
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

10. Further Work Re-print fiber reel to allow 2km of 600 μm LCP fiber
Quantify daytime radiative bias on measured temperature.
Test fiber coatings to minimize and correct for radiative bias.
Establish wavelength division multiplexing for communication from EOF -> 1550nm
Build low power End of Fiber unit with GPS, pressure sensor, and precision thermistor
Test self deploying fiber spool
Further test flights this summer!
Image: linden photonics
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

11. Science Questions for Stratéole 2
Provide a precise, high frequency measurements of the thermal structure of the Tropical Tropopause Layer
Greatly increase the density of high resolution measurements over current radiosonde based data
Investigate the location and temperature evolution of the cold point tropopause
Obtain unprecedented detail of gravity wave propagation through the TTL on scales unresolved by satellite sounders
High frequency profiles will provide direct measurement of gravity wave phase speed spectrum
Validate and improve atmospheric wave parameterizations in GCMs
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

12. Acknowledgements
This work has been supported by an NSF EAGER award # and a CU/CIRES Research and Development Grant.
Thanks to:
Sean Davis (NOAA ESRL)
Terry Deshler (U. Wyoming)
Joan Alexander (NWRA)
Greg Wright (LASP)
Edge of Space Science
Click to add image credit info
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs

13. Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs
QUESTIONS?
Fiber Temperature Profiler - Strateole Workshop; Lars Kalnajs