1. Development, Fabrication, and Testing of 92 GHz Radiometer For Improved Coastal Wet-tropospheric Correction on the SWOT Mission Darrin Albers, Alexander Lee, and Steven C. Reising Microwave Systems Laboratory, Colorado State University, Fort Collins, CO Shannon T. Brown, Pekka Kangaslahti, Douglas E. Dawson, Todd C. Gaier, Oliver Montes, Daniel J. Hoppe, and Behrouz Khayatian Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA

3. SWOT Mission Concept Study Low frequency-only algorithm Low frequency-only algorithm Low and High frequency algorithm Low and High frequency algorithm High-resolution WRF model results show reduced wet path-delay error using both low-frequency (18-37 GHz) and high-frequency (90-170 GHz) radiometer channels.

4. Objectives

5. System Block Diagram Waveguide Components 92-GHz multi-chip module 130-GHz multi-chip module 166-GHz multi-chip module Common radiometer back end, thermal control and data subsystem Tri-Frequency Feed Horn Coupler Coupler Noise Diode Coupler Noise Diode Noise Diode MMIC Components

6. Tri-Frequency Horn Antenna A single, tri-band feed horn and triplexer are required to maintain acceptable antenna performance, since separate feeds for each of the high-frequency channels would need to be moved further off the reflector focus, degrading this critical performance factor. The tri-frequency horn was custom designed and produced at JPL, with an electroform combiner from Custom Microwave, Inc. Measurements show good agreement with simulated results. WR-5 (166 GHz) Feed Horn Rings WR-8 (130 GHz)

7. Tri-Frequency Antenna (Detail) WR-8 Waveguide Port WR-10 Waveguide Port

8. Example of a Ring to Produce Horn Corrugation Largest Horn Ring Pencil Tip For Scale Ring Cross Section Fin for the Ring-Loaded Slot Detail of Feed Horn Rings 17.9 mm

9. Antenna Return Loss Bandwidth measurement with 15-dB return loss or better Center Frequency (GHz) Waveguide Band Bandwidth (GHz) 92 WR-10 11 130 WR-08 18 166 WR-05 26

10. Antenna Pattern 92 GHz 130 GHz 166 GHz Center Frequency (GHz) Waveguide Band Half-power Beamwidth (°) 92 WR-10 22 130 WR-08 24 166 WR-05 32

12. Noise Diode Measurements *Noise diode manufactured for NASA/GSFC

15. Matched Load for Calibration: Modeled and Measured Results 1.45 mm

17. 92-GHz Multi-chip Module (Close-up) Matched Load PIN-Diode Switch Low-Noise Amplifier #1 Band Pass Filter Waveguide to Microstrip Transition Low-Noise Amplifier #2 Detector Attenuator 1 mm

18. 92-GHz Radiometer Prototype Multi-Chip Module Isolator WR-10 Horn Antenna Coupler

19. 92-GHz Radiometer Noise Analysis Measured noise temperature of 2073 K (lossy coupler and isolator) and 964 K (without waveguide components) . Preliminary Noise Temperature Measurement of 1375K Component Gain (dB) Noise Figure (dB) Cumulative Noise Temperature (K) Noise Source - - Directional Coupler -0.75 0.75 55 Waveguide Through Line -0.20 0.20 71 Waveguide to Microstrip transition -0.50 0.50 115 Switch -2.75 2.75 473 LNA 28.00 3.00 1232 BPF -5.50 5.50 1235 Attenuator -4.25 4.25 1235 LNA 28.00 3.00 1254 Attenuator -4.25 4.25 1254 Total Receiver Gain (dB) 37.80 Receiver noise factor 5.32 Receiver noise figure (dB) 7.26 Receiver noise temperature (K) 1253.53

20. 92-GHz Radiometer Performance Analysis

22. Backup Slides

23. ENR Equation Equation 10.6. Pozar. Microwave Engineering 3 rd edition. 0 dB ENR with T g = 580 K and T o = 290K -2 dB ENR with T g = 473 K and T o = 290K