March 8, 2005 Calibration and Operation of the Stepped Frequency Microwave Radiometer during the 2005 Hurricane Season Ivan PopStefanija Mark Goodberlet ProSensing Inc. 107 Sunderland Rd. Amherst, MA USA, Hurricane season

December 25, 2015December 25, 2015December 25, 2015 SFMR 2005 accomplishments May 2005: Delivery of the third SFMR, S/N US003 June 2005: Delivery of the retrofitted SFMR, S/N US002 July 2005: Successful testing of upgraded SFMR (implementation of the “cold” calibration load) August 2005: Validation of the new SFMR for wide range of environmental conditions (TS to CAT 5) in comparison with the original “IWRS” SFMR August 2005: First time deployment of two SFMR’s operating on N43RF ( SFMR- US003 ) and N42RF ( SFMR-US002 ) 2005 July-November: Spare SFMR (US001) available (down time for replacement – about 4 hours) 2005 June-November: Flawless operation of SFMR Hardware

December 25, 2015December 25, 2015December 25, 2015 SFMR Development History [1970s] Concept of airborne measurements of ocean surface winds developed at NASA Langley [1970s] Concept of airborne measurements of ocean surface winds developed at NASA Langley [ ] Prototype SFMR, designed by the University of Massachusetts, tested by NOAA HRD and AOC [ ] Prototype SFMR, designed by the University of Massachusetts, tested by NOAA HRD and AOC [ ] SFMR-HRD built by ProSensing (formerly Quadrant Engineering) funded by OFCM through IWRS program [ ] 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) [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 [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 [2004] Real-time wind estimates provided by SFMR impact NHC hurricane forecasts SFMR-HRD (IWRS) SFMR-AOC

December 25, 2015December 25, 2015December 25, 2015 SFMR AOC Validation SFMR AOC Validation SFMR-IWRS and SFMR #US003 installed on N43RF for simultaneous and independent operation SFMR-IWRS and SFMR #US003 installed on N43RF for simultaneous and independent operation Comparative operation and data collection through Katrina flights capturing the full range of environmental conditions: TS,CAT1, 3, 4,and 5 Comparative operation and data collection through Katrina flights capturing the full range of environmental conditions: TS,CAT1, 3, 4,and 5 TS CAT 3CAT 5CAT 4 SFMR 2005 accomplishments

December 25, 2015December 25, 2015December 25, 2015 SFMR Theory of Operation The Stepped Frequency Microwave Radiometer is designed to measure blackbody electromagnetic radiation of the scene at six frequencies (4 to 6 GHz) 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) Measured power is expressed as brightness temperature which is a function of the physical temperature of the scene and its emissivity (0<emissivity<1) The frequency dependence of the brightness temperature is used to estimate wind speed and rain rate The frequency dependence of the brightness temperature is used to estimate wind speed and rain rate

December 25, 2015December 25, 2015December 25, 2015 SFMR Theory of Operation Measured T B is affected by a variety of environmental factors Measured T B is affected by a variety of environmental factors –Extra terrestrial radiation –Atmospheric vapor and liquid –Ocean Salinity –Sea surface temperature –Physical temperature of ocean and atmosphere –Ocean surface roughness

December 25, 2015December 25, 2015December 25, 2015 Components of T b as Measured by SFMR

December 25, 2015December 25, 2015December 25, 2015 SFMR Calibration A “two-load” technique is used to achieve a calibrated measurement of T a A “two-load” technique is used to achieve a calibrated measurement of T a Measurement accuracy is unaffected by changes in the radiometer receiver characteristics Measurement accuracy is unaffected by changes in the radiometer receiver characteristics Internal calibration tracks short term SFMR drifts (performed 100 times per second) Internal calibration tracks short term SFMR drifts (performed 100 times per second) Internal loads do not account for changes in antenna characteristics (i.e., it is a receiver-only calibration). Internal loads do not account for changes in antenna characteristics (i.e., it is a receiver-only calibration).

December 25, 2015December 25, 2015December 25, 2015 SFMR Calibration with External Loads External loads, viewed via the radiometer antenna, are used for a “total system” (receiver + antenna) calibration 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 is primarily used to characterize antenna characteristics External calibration at factory is performed once a year External calibration at factory is performed once a year

December 25, 2015December 25, 2015December 25, 2015 SFMR factory calibration Calculation of T b Calculation of T b Table of calibration constants Table of calibration constants SFMR US003 F GHz F GHz F GHz F GHz F GHz F GHz a a a a a a

December 25, 2015December 25, 2015December 25, 2015 Flight Calibration In-flight calibration of SFMR is performed by flying over a buoy or by using dropsondes. 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) 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 are reported to AOC Measurement bias is estimated and adjustments are reported to AOC 2005 calibration flight on July 18 in TS Irene 2005 calibration flight on July 18 in TS Irene

December 25, 2015December 25, 2015December 25, 2015 SFMR Pod Effects It is desirable to eliminate the need for in-flight calibration It is desirable to eliminate the need for in-flight calibration In-flight test should only be used as a pre-season system check In-flight test should only be used as a pre-season system check ProSensing built a mock-up pod to determine the effects of the pod on SFMR data ProSensing built a mock-up pod to determine the effects of the pod on SFMR data

December 25, 2015December 25, 2015December 25, 2015 SFMR Pod effect

December 25, 2015December 25, 2015December 25, 2015 Measurement of Wing Pod Effects on SFMR data Antenna beam patterns showed negligible change Antenna beam patterns showed negligible change Calibration with external loads (with and without pod mock up) showed significant difference of about 0.7 K Calibration with external loads (with and without pod mock up) showed significant difference of about 0.7 K Difference in the actual configuration could be higher. Difference in the actual configuration could be higher. Recommendation: re-design bottom plate of the wing pod Recommendation: re-design bottom plate of the wing pod

December 25, 2015December 25, 2015December 25, 2015 Proposed “Zero-Zero” calibration Flight calibration conditions Flight calibration conditions –Wind speed < 5 m/s –No precipitation –Cloudless sky –Night flight – no possibility of sun glint (up to 12 K bias) – Fly over buoy at multiple altitudes

December 25, 2015December 25, 2015December 25, 2015 Future SFMR Work Test and debug the newly-developed SFMR 2005W rack mounted computer and interface box Test and debug the newly-developed SFMR 2005W rack mounted computer and interface box SFMR software upgrades to improve operation robustness: SFMR software upgrades to improve operation robustness: –Real time input data [T b ] quality check –Real-time land mask to eliminate reporting of invalid data –Real-time check of the RMS error of the wind retrieval model –In flight self-calibration with minimal operator involvement Analyze 2005 Hurricane season data to improve wind retrieval model in some ranges of operation Analyze 2005 Hurricane season data to improve wind retrieval model in some ranges of operation –Low wind speed (<15 m/s) –Rain height estimate (important at wind speeds lower then 20 m/s) –Analyze high wind conditions (above 50 m/s) [HRD: Uhlhorn, Black]

December 25, 2015December 25, 2015December 25, 2015 SFMR