1. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 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

2. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 2 Scientific Motivation Current satellite ocean altimeters include a nadir-viewing, co-located 18-37 GHz multi-channel microwave radiometer to measure wet- tropospheric path delay. Due to the large diameters of the surface instantaneous fields of view (IFOV) at these frequencies, the accuracy of wet path retrievals begins to degrade at approximately 50 km from the coasts. Conventional altimeter-correcting microwave radiometers do not provide wet path delay over land. LandOcean Advanced technology development of high-frequency microwave radiometer channels to improve retrievals of wet-tropospheric delay in coastal areas, small inland bodies of water, and possibly over land such as for the Surface Water Ocean Topography (SWOT), a Tier-2 Decadal Survey mission.

3. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 3 SWOT Mission Concept Study Low frequency- only 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. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 4 Objectives Develop low-power, low-mass and small-volume direct-detection high-frequency microwave radiometers with integrated calibration sources at the center frequencies of 90-170 GHz Design and fabricate a tri-frequency feed horn with integrated triplexer at the center frequencies of 92, 130, and 166 GHz Develop and test sufficient Excess Noise Ratio (ENR) noise sources at the center frequencies of 90-170 GHz Integrate components into MMIC-based radiometers at 92, 130 and 166 GHz with the tri-frequency feed horn and test at a system level

5. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 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 Noise Diode Coupler Noise Diode MMIC Components

6. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 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. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 7 Tri-Frequency Antenna (Detail) WR-8 Waveguide Port WR-10 Waveguide Port

8. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 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. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 9 Antenna Return Loss Bandwidth measurement with 15-dB return loss or better Center Frequency (GHz) Waveguide Band Bandwidth (GHz) 92WR-1011 130WR-0818 166WR-0526

10. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 10 Antenna Pattern 92 GHz130 GHz Center Frequency (GHz) Waveguide Band Half-power Beamwidth (°) 92WR-1022 130WR-0824 166WR-0532 166 GHz

11. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 11 Noise Diodes for Internal Calibration Nadir-pointing radiometers are flown on altimetry missions with no moving parts, motivating two-point internal radiometric calibration, as on Jason-2. Highly stable noise diodes will be used to achieve one of these two points. Radiometric objectives Provide an electronically-switchable source for calibrating the radiometer over long time scales, i.e. hours to days. RF design objectives from radiometer requirements Noise diode output will be coupled into the radiometer using a commercially-available waveguide-based coupler. Stable excess noise ratio (ENR) of 10-dB or greater, yielding ~300 K of noise deflection after a 10-dB coupler.

12. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 12 Noise Diode Measurements *Noise diode manufactured for NASA/GSFC

13. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 13 92-GHz Radiometer Design This direct-detection Dicke radiometer uses two LNAs and a single bandpass filter for band definition. Direct-detection architecture is the lowest power and mass solution for these high-frequency receivers. Keeping the radiometer power at a minimum is critical to fit within the overall SWOT mission constraints, including the power requirements of the radar interferometer.

14. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 14 92-GHz Bandpass Filter: Modeled and Measured 4.6 mm 5-mil (125-µm) thick polished alumina substrate Measured using a probe station with WR-10 waveguides Modeled and measured in open air Frequency (GHz) 35 mils (0.89mm) wide

15. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 15 Matched Load for Calibration: Modeled and Measured Results 1.45 mm

16. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 16 92-GHz Multi-Chip Module 92-GHz direct- detection radiometer with Dicke switching and integrated matched load 17.9 mm

17. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 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. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 18 92-GHz Radiometer Prototype Multi-Chip Module Isolator WR-10 Horn Antenna Coupler

19. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 19 92-GHz Radiometer Noise Analysis Measured noise temperature of 2073 K (lossy coupler and isolator) and 964 K (without waveguide components). ComponentGain (dB) Noise Figure (dB) Cumulative Noise Temperature (K) Noise Source-- Directional Coupler-0.750.7555 Waveguide Through Line-0.200.2071 Waveguide to Microstrip transition-0.500.50115 Switch-2.752.75473 LNA28.003.001232 BPF-5.505.501235 Attenuator-4.254.251235 LNA28.003.001254 Attenuator-4.254.251254 Total Receiver Gain (dB)37.80 Receiver noise factor5.32 Receiver noise figure (dB)7.26 Receiver noise temperature (K)1253.53 Preliminary Noise Temperature Measurement of 1375K

20. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 20 92-GHz Radiometer Performance Analysis

21. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 21 Conventional altimeters include a nadir-viewing 18-37 GHz microwave radiometer to measure wet-tropospheric path delay. However, they have reduced accuracy within 40 km of land. Addition of high-sensitivity mm-wave channels to Jason-class radiometer will improve wet-path delay retrievals in coastal regions and provide good potential over land. We have developed noise sources at 92 and 130 GHz and a tri-frequency feed horn for wide-band performance at center frequencies of 92, 130, and 166 GHz. To demonstrate these components, we have produced a millimeter-wave MMIC-based low-mass, low-power, small- volume radiometer with internal calibration sources integrated with the tri-frequency feed horn at 92 GHz. Summary

22. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 22 Backup Slides

23. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 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

24. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 24 Move to Higher Frequency Supplement low- frequency, low-spatial resolution channels with high-frequency, high-spatial resolution channels to retrieve PD near coast High-frequency window channels sensitive to water vapor continuum 183 GHz channels sensitive to water vapor at different layers in atmosphere 22.235 GHz (H 2 O) 55-60 GHz (O 2 ) 118 GHz (O 2 ) 183.31 GHz (H 2 O)

25. Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 25 92-GHz Radiometer with Two LNAs Current MMIC detector from HRL has sensitivity of 15,000 V/W One LNA –System Gain of 26.05 dB and cumulative noise temperature of 727.4 K –Antenna Temperature of 600 K results in 550 µV, i.e. 417 nV/K –Antenna Temperature of 77 K results in -46 dBm Two LNAs –System Gain of 54.55. dB and cumulative noise temperature of 727.6 K –Antenna Temperature of 600 K results in 392 mV, i.e. 295 µV/K –Antenna Temperature of 77 K results in -18 dBm TSS (Tangential Sensitivity) of these detectors is typically -44 dBm so might be measuring the noise at 77 K if more loss is in system than expected so two LNAs results in a more robust system