1. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 1 AGU/NASA booth San Francisco; December 16, 2008 The GeoSTAR Instrument and the PATH Mission National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Bjorn Lambrigtsen Shannon Brown, Todd Gaier, Linda Herrell, Pekka Kangaslahti, Alan Tanner Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California

2. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 2 Overview GeoSTAR is the sensor for the PATH mission “Geostationary Synthetic Thinned Aperture Radiometer” GeoSTAR is the first microwave sounder for GEO New instrument concept has developed/demo’d at JPL We have developed new cutting-edge technology We are ready to proceed to a space mission PATH is one of 15 NASA “decadal-survey” missions “Precipitation and All-weather Temperature and Humidity” First microwave sensor in geostationary orbit Weather & climate observations: clouds, storms & hurricanes Improve models re. the hydrologic cycle  Improved forecasts Improve hurricane intensity forecasts Check out PATH Townhall meeting, Thursday 7:30 pm in Rm. 2004

3. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 3 Models & observations Models used to predict weather & climate are deficient Cloud formation, convection & precipitation is not completely understood; “microphysics” is deficient Diurnal-cycle variations are not well modeled; storm life cycles are not well modeled Observations used to “feed” models are incomplete Most satellite sensors do not penetrate clouds nor observe the internal “microphysics” of clouds & storms Most satellites provide observations only brief snapshots twice a day, when the satellite passes overhead Therefore, we need… Continuous observations of the entire process: diurnal cycle, storm cycle, etc. Observations under all weather conditions  PATH/GeoSTAR! Develop Math model Assimilate Compare Obser- vations InitializeAdjust Forecast

4. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 4 Atmospheric sounding (MW) High attenuation  Opaque channel  T near top of atmosphere Low attenuation  Transparent channel  T near the surface Intermediate attenuation  T at intermediate altitudes All channels combined  T(z) vertical profile Temperature sounding channels

5. LambrigtsenNASA/AGU - San Francisco, December 16, 2008  Severe storms MW/soundings IR+MW IR-only soundings 0 10 1 10 2 10 3 10 4 10 0 1 Cloud fraction Particle size [microns]  Precipitation MW/precipitation Why we need microwave sounders Note: This is a 2-D view of a multidimensional world Additional dimensions include spatial and temporal scales

6. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 ? ? ? What’s Going On Below Those Clouds?

7. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 7 Great Plains MCS Floridadiurnalstorms Tornados NorthAmericanMonsoon East Pacific hurricanes North Atlantic hurricanes Northeast winter storms &Extratropicalcyclones Boundary of optimal antenna gain Storms, hurricanes, moisture flow

8. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 8 2 km 15 km A closer look at hurricanes - literally 3-D view of the convective structure of Hurricane Emily (2005) New method being developed. See poster #A41G-0206 Thursday morning

9. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 9 Microwave instruments Low-earth-orbiting MW sounder (AMSU) Antenna size is determined by distance and “spatial resolution” AMSU antenna is 6” in dia. and gives 40-km resolution from 705 km GEO orbit is ~37000 km ≈ 50 x 705 km AMSU-antenna must then be 50 x 6” to give 40-km res. from GEO This is 25 feet (8 meters)! Can’t be done! To get 50-km res. we need 20 feet. Still can’t be done Solution: Synthesize large antenna  GeoSTAR The antenna is the key

10. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 10 The GeoSTAR concept Aperture-synthesis concept –Sparse array employed to synthesize large aperture –Cross-correlations -> Fourier transform of Tb field –Inverse Fourier transform on ground -> Tb field Array –Optimal Y-configuration: 3 sticks; N elements –Each element is one I/Q receiver, 3.5 wide (2.1 cm @ 50 GHz; 6 mm @ 183 GHz!) –Example: N = 100  Pixel = 0.09°  50 km at nadir (nominal) –One “Y” per band, interleaved Other subsystems –A/D converter; Radiometric power measurements –Cross-correlator - massively parallel multipliers –On-board phase calibration –Controller: accumulator -> low D/L bandwidth Bonus: No moving parts! Receiver array & resulting uv samples Example: AMSU-A ch. 1

11. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 11 GeoSTAR proof-of-concept prototype

12. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 12 First-ever images at 50 GHz by aperture synthesis The proof is in the pudding November 2005

13. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 13 Test range & calibration facility Retrieved vs. measured temperatures Red: Large pad (4’x4’ controlled) Green: Small pad (2’x2’ controlled) Black: Main target (ambient) Solid: GeoSTAR retrieval Dotted: Thermistor average GeoSTAR “Near Field range”, JPL Target Temperature controlled pads Beacon @ center

14. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 14 Next stop: Space! Array arms folded for launchStowed in Delta fairingDeployed on-orbit

15. LambrigtsenNASA/AGU - San Francisco, December 16, 2008 15 COMING SOON: SEE THIS IN MICROWAVE! This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration. The PATH SWG Bjorn Lambrigtsen (JPL) Chris Kummerow (CSU) Bob Atlas (NOAA) T.N. Krishnamurti (FSU) Ralf Bennartz (U. Wisc.) Chris Ruf (U. Mich.) Al Gasiewski (U. Colo.) Chris Velden (U. Wisc.) Jeff Hawkins (NRL) Duane Waliser (JPL) Eugenia Kalnay (U. Md.) Fuzhong Weng (NOAA) Ramesh Kakar (NASA HQ) The GeoSTAR team: Todd Gaier, Pekka Kangaslahti, Alan Tanner - JPL Chris Ruf - U. Michigan Jeff Piepmeier - NASA/GSFC