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Global observations with information content on water vapor content, ice water content and ice particle size distribution are needed to enhance knowledge of the impact of ice clouds on Earth’s weather and climate. These observations may also help to reduce the uncertainty of global climate models. The Tropospheric Water and Cloud Ice (TWICE) microwave radiometer instrument has been designed to perform temperature and humidity sounding of the atmosphere near the 118.75, 183.31 and 380.20 GHz atmospheric absorption lines, as well as to retrieve ice cloud particle size information from radiometric measurements at 240, 310, 670 and 850 GHz. To acquire high-quality data, the TWICE instrument performs end-to-end, on-orbit calibration of all radiometer channels during each scan. The TWICE instrument is designed to fit within the mass, volume and power constraints of the 6U CubeSat platform.

A new ultra-wide P/L-band radiometer instrument has been developed at the Jet Propulsion Laboratory for polar ocean salinity and seasonal sea-ice thickness measurements. The Arctic field campaign performed with the instrument deployed on the US Coast Guard Cutter Healy from September 13, 2018 to October 20, 2018. A new calibration strategy is developed for the ultra-wide band instrument to minimize the mismatch related effects. A noise-wave model is built to analyze and validate the instrument behavior for the calibration. The calibration strategy is analyzed using the results from the cruise campaign. Sea-ice thickness and sea surface salinity are presented in two other companion papers.

The Tropospheric Water and Cloud ICE (TWICE) millimeter and sub-millimeter radiometer instrument is being developed to enable global observations of upper tropospheric/lower-stratospheric water vapor and ice particle size distribution in clouds. Global observations using the TWICE instrument are critically needed to reduce uncertainties in weather and climate models. A low-noise, power-efficient command and data handling (C&DH) subsystem has been designed and tested to control TWICE data acquisition and other subsystems. Considering the limited power resources available on such platforms, a highly-efficient power regulation board has been designed to minimize power losses and reduce system noise. Furthermore, heavy-ion radiation testing has been performed for some critical commercial-off-the-shelf components to analyze radiation tolerance in low-Earth orbit. The C&DH prototype board meets the functional, noise and size, weight and power (SWaP) requirements for deployment on a 6U -Class satellite.

Radiation effects analysis is essential to improve reliability for space missions. The number of small satellite and CubeSat missions has increased significantly in recent years. Compared to traditional larger satellite missions, CubeSats are designed at lower cost and with shorter development cycles. The reliability of CubeSats and small satellites in on-orbit radiation environments needs to be ensured for mission success. In this study, single event effect analysis has been performed for a 6U-Class satellite instrument in low Earth orbit to improve its on-orbit reliability. Critical commercial off-the-shelf parts of the Command and Data Handling Subsystem of a 6U-Class satellite instrument have been tested under heavy-ion radiation at the Texas A&M University Cyclotron Institute Radiation Effects Facility. SEE characteristics have been tested and analyzed for analog-to-digital data converters, voltage regulators, and current sensing and voltage monitoring devices. Device- and system-level risk analyses have been performed for the Command and Data Handling electronics based on the results of heavy-ion radiation testing. System-level mitigation techniques have been studied to minimize the effects of SEEs on electronic systems for deployment on 6U-Class satellites in low Earth orbit.

Global measurements of upper tropospheric/lower-stratospheric water vapor and ice particle size distribution in clouds are critically needed to reduce uncertainties in global weather and climate models. To address this need, the conically scanning Tropospheric Water and Cloud ICE (TWICE) millimeter and submillimeter radiometer instrument is being developed. A low-noise, power-efficient command and data handling (C&DH) subsystem has been designed to control TWICE data acquisition and other subsystems. The C&DH prototype board meets functional, noise and size, weight and power (SWaP) requirements for deployment in a 6U-class satellite. Considering the limited power resources available on such platforms, a highly-efficient power regulation board has been designed to minimize power losses and reduce system noise. Furthermore, all of the components have been tested for radiation tolerance in low-Earth orbit.

Global measurements of cloud ice particle size, total ice water content and water vapor content in the upper troposphere are critically needed to improve knowledge of the role of ice clouds in Earth's climate, precipitation and cloud processes. Such observations will enable improvement in cloud and moisture simulations in global climate models as well as precipitation forecasts on a global basis. Measurements at a range of frequencies in the millimeter- and submillimeter-wave frequency range provide sensitivity to ice particle size distribution in the range of tens to hundreds of micrometers. To perform this measurement on a global basis, a new millimeter- and submillimeter-wave instrument is currently under development with suitable mass, power and volume to be deployed on 6U-Class nanosatellites. To achieve miniaturized receivers in this frequency range, InP MMIC technology has been scaled to 25-nm gate length transistors, enabling demonstration of low-noise amplifiers with sufficient gain at frequencies up to 1 THz. This technology is being applied to develop direct-detection submillimeter-wave receivers at 240 GHz, 310 GHz and 670 GHz. InP MMIC technology has also enabled multipliers for local oscillators and subharmonic mixers for temperature and humidity sounding channels near atmospheric absorption lines at 118.75, 183.31 and 380.20 GHz.

Global measurements of ice in clouds, both the amount and particle size distribution, are critically needed to reduce uncertainties in global climate models. The retrieval of this information is best achieved with a range of receiver channels across the submillimeter wave range. Advancement of low noise Indium Phosphide (InP) MMIC amplifier technology enabled us to develop miniature submillimeter-wave receivers for a CubeSat scale instrument that achieves 6 km spatial resolution. The heritage of InP MMICs includes continuous operation for four years in the PLANCK Low Frequency Instrument and providing world-record sensitivity with high reliability in several airborne instruments. We have developed a set of InP MMICs for receivers at 240, 310, 380 and 670 GHz with significantly lower noise than previously reported. The noise temperature is NT=450 K at 240 GHz, NT=550K at 310 GHz and NT=650 K at 380 GHz. The 670 GHz LNAs provide a NT of 2400 K. These channels are complemented by the previously-developed and airborne-proven 183 and 118 GHz MMIC receivers that were tested to TRL 6.

The effect of cobs on radar backscatter from a mature corn canopy is considered. In the past, a number of papers have modeled the backscattering properties of corn plants when the cobs are not present. It has been shown by O'Neill et al. [1] that the cob can constitute as much as one third of the total biomass of a mature corn plant. The position of the cob close to the stalk and the lack of knowledge of its dielectric properties make it difficult to model. These difficulties have been overcome with the aid of advanced numerical analysis tools and new biophysical measurements of the corn.

Summary form only given. This paper presents the design, construction and results of measurements of a dual polarized L- band antenna for the NASA Combined Radiometer and Radar System. The radiometer band covers 1.400 -1.427 GHz. and the radar band 1.250 to 1.350 GHz. The focus of this paper is on the radiometer band. The antenna is designed to replace the 48 inch diameter truck-mounted paraboloidal dish used in NASA remote sensing applications because of its excessive loss. It was found that changes of the ambient temperature produced fluctuations in the antenna noise temperature which reduced the accuracy of the radiometer calibration. These fluctuations are caused by the temperature dependent Ohmic loss in the antenna structure, the externally mounted cable connecting the Newtonian feed to the radiometer and in the patch used for the feed. Therefore the principal design goal for the new antenna was to eliminate the need for the cable and the patch and to reduce any additional loss without a degradation of its electrical performance and without increasing its size and weight. A configuration that obviates the need for an external feed-to-radiometer cable connection is a Cassegrain antenna. Its additional advantage is that the feed structure can be designed to have a lower loss than the patch used in the Newtonian feed of the old antenna. Since classic Cassegrain antennas generally require reflectors with diameters of at least 30 wavelengths designing an antenna in a Cassegrain configuration incorporating a reflector with a diameter of only 5 to 6 wavelength represented a real challenge. This challenge was met with the design that employs a novel low loss dielectric (Rexolite) conical support structure for the subreflector. The cone diameter decreases linearly from its base at the apex to the subreflector. The novel feature in this design is that in addition to supporting the subreflector the cone also serves as a dielectric waveguide that illuminates the subreflector. The mechanism for this is the wave within the cone that travels from the apex of the paraboloid toward the subreflector and illuminates it by a partial leakage into the surrounding space. The resulting efficiency is appropriate for a truckmounted antenna system. The input at the apex of the paraboloid employs a circular waveguide that supports two orthogonal TE11 modes thus providing the necessary dual polarization. As confirmed by simulations and measurements the gain and side lobe levels of the new low loss antenna are comparable to those of the old antenna.

The objective of this paper is to discuss the performance of a new L-Band, truck-mounted radiometer antenna. This new low loss antenna has been designed to increase the calibration stability of the ComRAD radiometer system. ComRAD is a dual polarized combined radar radiometer system operating as a radar at 1.3 GHz and as a radiometer at 1.413 GHz. It utilizes the same antenna for both frequencies. ComRAD is used to develop algorithms for the sensing of soil moisture in the presence of vegetation. The system is presently being employed to monitor agricultural crops over the growing cycle in preparation for the upcoming SMAP (Soil Moisture Active Passive) satellite mission.