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

Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, Scientific Motivation Current satellite ocean altimeters include a nadir-viewing, co-located 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.

Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 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 ( GHz) radiometer channels.

Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, Objectives Develop low-power, low-mass and small-volume direct-detection high-frequency microwave radiometers with integrated calibration sources at the center frequencies of 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 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 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 Waveguide Through Line Waveguide to Microstrip transition Switch LNA BPF Attenuator LNA Attenuator Total Receiver Gain (dB)37.80 Receiver noise factor5.32 Receiver noise figure (dB)7.26 Receiver noise temperature (K) Preliminary Noise Temperature Measurement of 1375K

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

Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, Conventional altimeters include a nadir-viewing 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

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

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

Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 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 GHz (H 2 O) GHz (O 2 ) 118 GHz (O 2 ) GHz (H 2 O)

Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, GHz Radiometer with Two LNAs Current MMIC detector from HRL has sensitivity of 15,000 V/W One LNA –System Gain of dB and cumulative noise temperature of 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 dB and cumulative noise temperature of 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