Evaluation of the 2007 Hurricane Season Deployment of Operational SFMR Instruments on the Hurricane Hunter C-130J Fleet

1. Evaluation of the 2007 Hurricane Season Deployment of Operational SFMR Instrumentson the Hurricane Hunter C-130J Fleet Ivan PopStefanija popstefanija@prosensing.com Mark Goodberletgoodberlet@prosensing.com ProSensing Inc. 107 Sunderland Rd. Amherst, MA 01002 USA,www.prosensing.com

2. SFMR 2007 Accomplishments • Delivered 10 + 3 spare SFMR systems • between September 2006 and January 2008 • Six units operated during the Hurricane Season 2007 • Continuous coverage of major hurricanes Dean and Felix • Hurricane Dean: completed 6 missions for total of 40 hours of wind evolution coverage. Including 56 maximum wind speed measurements from 56 eye wall penetrations • Presented us with operational challenges • Prepared and implemented a major software revision in the middle of the hurricane season (first week of September 2007.) All operational SFMR units updated with no down time. • Delivery of High Altitude SFMR for G-IV aircraft (NOAA) • Larger antenna; new radome 62nd Interdepartmental Hurricane Conference

3. SFMRTheory of Operation • The Stepped Frequency Microwave Radiometer is designed to measure blackbody electromagnetic radiation of the scene at six frequencies (4 to 6 GHz) • Measured power is expressed as brightness temperature which is a function of the physical temperature of the scene and its emissivity (0<emissivity<1) • Frequency diversity of the SFMR measurement helps distinguish wind speed effects from those of rain rate. 62nd Interdepartmental Hurricane Conference

4. SFMR Theory of Operation • Measured TB is affected by a many environmental factors: • Extra terrestrial radiation • Atmospheric vapor and liquid • Ocean Salinity • Sea surface temperature • Physical temperature of ocean and atmosphere • Ocean surface roughness 62nd Interdepartmental Hurricane Conference

5. SFMR Factory Calibration with External Loads • External loads, viewed via the radiometer antenna, are used for a “total system” (receiver + antenna) calibration • Warm Load: Absorber box with continuously monitored physical temperature • Cold Load: Cloudless sky at night • External calibration is primarily used to characterize antenna characteristics • External calibration at factory is performed once per year 62nd Interdepartmental Hurricane Conference

6. SFMR Calibration • A “two-load” (cold and warm) technique is used to achieve a calibrated measurement of TB . A hot load is available as backup. • Measurement accuracy is unaffected by changes in the radiometer receiver characteristics • Internal calibration tracks short term SFMR drifts (performed 2x per second) • Internal loads do not account for changes in antenna characteristics (i.e., it is a receiver-only calibration). 62nd Interdepartmental Hurricane Conference

7. SFMR Calibration File • Calculation of TB • Table of typical calibration constants 62nd Interdepartmental Hurricane Conference

8. “Zero-Zero” calibrationin flight • Flight calibration conditions: • Wind speed < 8 m/s [ 10 m/s acceptable] • No precipitation • Cloudless sky • Night flight – no possibility of sun glint (up to 12 K bias) • Fly over buoy at multiple altitudes: • 20,000 feet • 10,000 feet  reconnaissance flight level • 5,000 feet • 1,000 feet 62nd Interdepartmental Hurricane Conference

9. Flight Calibration • In-flight calibration of SFMR is performed by flying over a buoy or by using dropsondes. • In-flight calibration is needed to account for biases due to reflections and emissions from external objects (i.e. instrument pod, aircraft engine) • Measurement bias is estimated and adjustments to calibration constants are entered into the new release calibration file • Latest version of the calibration file SFMR3.cal is 1.28 62nd Interdepartmental Hurricane Conference

10. Before CalibrationFlights After Adjustments on the order of less then 1K 62nd Interdepartmental Hurricane Conference

11. SFMR in Hurricane Dean data dropouts • Alert! SFMR reported data invalid during the eye wall passes • Wind speed estimates = 20 m/s ???? • Fix was modification to the wind retrieval algorithm: • change of the initial conditions to improve the convergences in cases of high wind conditions • use of the previous value as initial condition (miscommunication between ProSensing and HRD /AOC ) • Change of the RMS error calculation 62nd Interdepartmental Hurricane Conference

12. Wind retrieval Algorithm Fix Change of initial condition Before At wind speeds higher then 64 m/s algorithm did not converge After No 10 sec averaging of wind speeds 62nd Interdepartmental Hurricane Conference

13. Wind retrieval algorithm Fix Before After 62nd Interdepartmental Hurricane Conference

14. Wind Retrieval Algorithm FixRMS error RMS error and Data Valid flag occurrences 62nd Interdepartmental Hurricane Conference

15. Problem with SFMR S/N US008small frequency drift SFMR S/N US008 • Reported to ProSensing from Keelser AFB: “ TB values are flipping!!! Winds do not look good. ” SFMR S/N US007 62nd Interdepartmental Hurricane Conference

16. Problem with SFMR S/N US008small frequency drift • Frequency drift for all six channels • Frequency drift was as much as 5MHz for some frequencies [< 0.1%] 62nd Interdepartmental Hurricane Conference

17. Problem with SFMR S/N US008Correction • Correction: • Modification of the receiver front-end to reduce TBdependence on frequency drift. Before After 62nd Interdepartmental Hurricane Conference

18. Operating and Storage Temperature range of SFMR • Operational testing (SFMR powered-on): • SFMR “survived” 24 hour operation per MIL-STD-810F temperature profile • Temperature range -52C to +43C • Re-calibration necessary after operation at -52C for 24 hours • Storage and cold-start temperature testing: • plan to test (spring 2008) storage and “cold start” at temperatures down to -52C 62nd Interdepartmental Hurricane Conference

19. Preparation for Hurricane Season 2008 • Setting up maintenance service contract with AFRC for SFMR units flown in 2007 hurricane season • Setting up a Long-Term Sustainment Contract with AFRC • Prevention of components obsolescence • Quick repair turnaround • Modification of the SFMR radiometer front end • Preliminary schedule workout with Keesler AFB to provide six SFMR with mod before June 2008 • Implementation of the new lower loss radome • New radome developed for High Altitude SFMR flying on NOAA G4 aircraft with significantly better performance • NRE design of the new radome for C-130J and WP-3D SFMR funded through grant from University of Massachusetts Center for Advanced Sensor and Communications Antennas (CASCA) • Implementation and evaluation of faster switching time for TB measurement (only for NOAA SFMR) • First flights with High Altitude SFMR – excepted June 2008 62nd Interdepartmental Hurricane Conference

20. SFMR Development History • [1970s] Concept of airborne measurements of ocean surface winds developed at NASA Langley • [1982-1995] Prototype SFMR, designed by the University of Massachusetts, tested by NOAA HRD and AOC • [1995-2001] SFMR-HRD built by ProSensing (formerly Quadrant Engineering) funded by OFCM through IWRS program • [2001] ProSensing developed a compact SFMR installed in an external aircraft pod (funded by NRL) • [2003] ProSensing delivered a wing-pod mounted SFMR to NOAA, funded by OFCM • [2004] Real-time wind estimates provided by SFMR impact NHC hurricane forecasts 62nd Interdepartmental Hurricane Conference