High frequency microwave and millimeter radiometers with low noise amplifier front-ends commonly suffer from gain instability, or so-called “flicker” noise. This noise has a 1/fenergy spectrum and hence is also commonly referred to as 1/fnoise. The effect of this noise on a passive instrument is to degrade its sensitivity and introduce post-processing calibration errors such as ‘striping’. In this paper we present a 1/fnoise mitigation technique using a combination of single frequency tone injection and high spectral resolution digital signal detection. This technique can be used in radiometers with sufficient information redundancy so that a limited portion of the detected signal spectrum can be dedicated to noise mitigation. A key requirement of implementing this technique is application specific integrated circuit (ASIC) or field programmable gate array (FPGA)-based spectral decomposition of the radio frequency energy. A proof-of-concept hardware setup and signal processing steps required to implement such a technique are presented in this paper. Measurements presented here show a reduction up to 87 % in 1/fnoise energy using this technique and are applicable to airborne and ground-based instruments.

The EZIE mission is a first of its kind to measure the temporal and spatial characteristics of Earth’s ionospheric auroral electrojet currents remotely using a mm-wave radiometer called the Microwave Electrojet Magnetogram (MEM). EZIE measures the 118 GHz oxygen emission line that splits in frequency in the presence of a magnetic field. This effect is known as the Zeeman effect. From these measurements of the 50 km spatial resolution magnetic fields at 80 km altitude the ionospheric currents that caused them can be calculated. The EZIE mission consists of three MEM payloads on three spacecrafts, each MEM contains four polarimetric radiometer receivers with a polyphase filter bank spectrometer. MEM can indirectly measure magnetic field strength and direction. In this paper we present the unique calibration design of the MEM payload that does not include any internal or external calibration sources. We discuss the MEM payload and present results from pre-launch testing and calibration of the MEM system.

We present here the on-going design of a hyperspectral radiometer called HyperSounder operating near two Oxygen absorption lines at 60 and 118 GHz, and the water vapor absorption line at 183 GHz for airborne atmospheric sounding. This radiometer is designed to be installed onto a Gulfstream V (G550) aircraft operated by the National Oceanographic and Atmospheric Administration’s (NOAA) Office of Marine and Aviation Operations (OMOA). The key enabling technology used in this instrument is fast sampling ASIC based spectrometer chipsets that allow for wide-band width and high resolution signal detection.

This paper introduces a novel method of experimentally characterizing atmospheric turbulence effects on millimeter wave propagation in a controlled laboratory environment. A large fan array wind tunnel with 36x36 individually programmable dual-fan units is used to create turbulent flows over a controlled temperature gradient. A W-band (95 GHz) radar is used to propagate RF energy through this turbulence while meteorological parameters such as wind speed, temperature and humidity are measured by co-located sensors. The effect of temperature gradients and wind speeds are shown to increase and shift the measured power spectrum of the radar signal. This experimental setup can be used to verify and expand on existing scintillation theory, and generate a statistical channel model to better understand the effects of turbulence on millimeter wave propagation.

We present the development of a hyperspectral microwave radiometer for high-altitude balloon deployment to better observe the Planetary Boundary Layer (PBL) with unprecedented sensitivity. The new hyperspectral radiometer is based on the existing High-frequency Airborne Microwave and Millimeter-wave Radiometer (HAMMR) instrument. Our key innovation from existing microwave sounders is increasing the number of channels around the oxygen and water-vapor absorption lines with high-resolution spectral sampling, thereby reducing profile retrieval errors and providing wide-band coverage over the frequency range of 18-200 GHz. In this paper, we present the overall system design, including the Stratollite subsystem, the full optical subsystem, and on-going RF and IF subsystems testing. We also show preliminary outdoor radiometric test results using a complete 48-72 GHz radiometer system. The hyperspectral HAMMR-HD balloon experiment will acquire up to 30 days of high-resolution PBL data, over a variety of weather conditions, and over land and ocean.

The Smart Ice Cloud Sensing (SMICES) instrument aims at providing onboard smart autonomous observation of upper tropospheric water vapor and ice particle size distribution in clouds at various local times. SMICES is an active/passive combined sensor with sounding channels at 380 GHz, radiometric channels at 250, 310 and 670 GHz, and a radar instrument operating at 239 GHz. A low-noise, low-power radiometer command and data handling (C&DH) subsystem has been designed to acquire the 24 analog radiometer channels and 8 analog thermistor data. A radiometric power regulation system provides the required power supplies for the other radiometric subsystems of the SMICES instrument. An on-board FPGA provides command and control of other instrument subsystems, performs synchronous data acquisition. The radiometer electronics are designed to fit into less than 2U horizontal dimensions of a CubeSat instrument. An AI controller unit directly interfacing with radar and radiometer C&DH subsystems performs on-board artificial intelligence operations for full system autonomy. The AI unit will control the radar instrument depending on the system health conditions, including the battery level, and based on the observed scene through the radiometer instrument.

An endfire synthetic aperture radar (SAR) for use on a cylindrical ice-penetrating cryobot is presented. The SAR facilitates obstacle detection and mapping inside ice for subsurface exploration using such a cryobot vehicle. The SAR is comprised of four azimuthally arranged directional log periodic antenna elements flush-mounted onto the cryobot’s surface. Aperture synthesis is facilitated by the downward trajectory of the cryobot as it slowly melts through ice. The radar front end and back end are designed using commercial-off-the-shelf (COTS) components and a customized field-programmable gate array (FPGA)-based digital design for signal generation, reception, and processing. Theoretical analysis of the SAR geometry is presented for the case of a point target in which the maximum likelihood estimation (MLE) approach is used for position estimator development. The novelty of this system lies in the use of pairs of antennas, with fixed baselines between them, to implement multiple coherent monostatic SARs to estimate target position in three dimensions. Specifically, range estimation is implemented by conventional chirp processing, polar (or elevation) angle estimation is achieved by SAR processing, and azimuth angle estimation is facilitated using pairs of four azimuthally arranged antennas that can be analyzed as multiple fixed baseline interferometric radars. Radar signal coherency tests and experimental validation of point target estimation and spatial resolution performed in a laboratory environment using the endfire SAR are presented in this study.

In this study we report on the current state-of-progress of the Water Sounding Short-range Radar (WASSR) project. The proposed WASSR instrument will facilitate estimation of near-surface water vapor profile on Mars. This project is supported under NASA's Maturation of Instruments for Solar System Exploration (MatISSE) program and is a frequency modulated continuous wave (FMCW) differential absorption radar (DAR) instrument. The scope of the work presented here includes a discussion of (i) the science background and motivation for profiling water vapor near the Martian surface, (ii) the differential absorption radar (DAR) technique implemented at the 557 GHz water vapor absorption line, and (iii) the submillimeter wave radar system implementation and characterization.

This paper presents submillimeter wave (SMMW) propagation and meteorological measurements obtained using the TAIPAS system operated continuously over a period from August 15 to August 30, 2018. The TAIPAS system is a 320-340 GHz, coherent, line-of-sight transmissometer which can be used to measure propagated power and spectral properties of directional electromagnetic (EM) waves at SMMW frequencies at and around the 325.153 GHz water vapor absorption line.The overall goal of the TAIPAS project is to develop a comprehensive predictive model relevant for atmospheric propagation in the range of ~1 MHz - 3000 GHz.

In this paper a forward looking (end fire) synthetic aperture radar (SAR) system is described for the Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice explorer (VALKYRIE) project. Design and analysis of novel conformal log periodic antennas for the radar and the forward looking SAR ambuguity function is presented. Fabrication and laboratory characterization of the antennas system design and in situ testing of the SAR system are discussed in detail.

In this paper a forward-looking synthetic aperture radar (IceSAR) system is described for the `Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice explorer' (VALKYRIE) project. Fabrication and laboratory characterization of novel log periodic antennas for IceSAR and system design and in situ testing of the synthetic aperture radar system are presented.

An inverted-F antenna with meandered line is characterized in this paper in terms of its proximity to the human body. Radiation characteristics are simulated and analyzed in the context of proximity of the antenna to human body tissue. The dependence of radiation characteristics like radiation pattern, resonant frequency, radiation efficiency, gain and front-to-back ratio; on the type & dimensions of body model is reported and discussed. Furthermore an improvement in the antenna design using a High Impedance Structure (HIS) as a ground plane is suggested. The antenna operation with this ground plane is simulated for radiation characteristics in close proximity to the body.