A5022152022- Soil Moisture and Remote Sensing
- Precipitation Measurement and Analysis
- Meteorological Phenomena and Simulations
- GNSS positioning and interference
- Geophysics and Gravity Measurements
- Ocean Waves and Remote Sensing
- Spacecraft Design and Technology
- Tropical and Extratropical Cyclones Research
- Calibration and Measurement Techniques
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Climate variability and models
- Radio Astronomy Observations and Technology
- Satellite Communication Systems
- Spacecraft Dynamics and Control
- Atmospheric aerosols and clouds
- Inertial Sensor and Navigation
- Oceanographic and Atmospheric Processes
- Cryospheric studies and observations
- Climate change and permafrost
- Planetary Science and Exploration
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Antenna Design and Optimization
- Ionosphere and magnetosphere dynamics
- ICT Impact and Policies
University of Michigan
2015-2025
Michigan United
2017-2020
Goddard Space Flight Center
2018
Stinger Ghaffarian Technologies (United States)
2018
Ann Arbor Center for Independent Living
2011
University of Colorado Boulder
1998-2002
Wayne State University
1995
Measurements of near surface wind speed made by the Cyclone Global Navigation Satellite System (CYGNSS) constellation GNSS-R satellites are evaluated and their uncertainty is assessed in two ways. A bottom-up assessment begins with a model for error engineering measurements propagates that through retrieval algorithm analytically. top-down performs statistical comparison between CYGNSS coincident "ground truth" speed. Results approaches compared. Overall performance, as determined method,...
Abstract The Global Precipitation Measurement (GPM) mission is a constellation-based satellite designed to unify and advance precipitation measurements using both research operational microwave sensors. This requires consistency in the input brightness temperatures (Tb), which accomplished by intercalibrating constellation radiometers GPM Microwave Imager (GMI) as calibration reference. first step sensors involves prescreening sensor Tb identify correct for biases across scan or along orbit...
The calibration algorithm used by the Cyclone Global Navigation Satellite System (CYGNSS) mission to produce version 2.1 of its Level 1 (L1) science data products is described. Changes and improvements have been made algorithm, relative earlier versions, based on first year on-orbit result. L1 consists two parts: first, 1a (L1a) converts raw 0 delay Doppler maps (DDMs) processed counts into received power in units watts. Second, L1a DDMs are then converted 1b bistatic radar cross section...
Abstract The NASA Cyclone Global Navigation Satellite System (CYGNSS) constellation of eight satellites was successfully launched into low Earth orbit on 15 December 2016. Each satellite carries a radar receiver that measures GPS signals scattered from the surface. Wind speed over ocean is determined distortions in signal caused by wind-driven surface roughness. operates at sufficiently frequency to allow for propagation through all precipitation, including extreme rain rates present eyewall...
The Cyclone Global Navigation Satellite System (CYGNSS) uses a bistatic radar configuration with the Positioning (GPS) constellation as active sources and CYGNSS satellites passive receivers. GPS effective isotropic radiated power (EIRP), defined product of transmit antenna gain pattern, is great importance to accurate Level 1B calibration mission. To address uncertainties in EIRP, ground-based monitor (GCPM) system has been built accurately precisely measure direct signals. A PID thermal...
The goals of this study are the evaluation current fast radiative transfer models (RTMs) and line‐by‐line (LBL) models. intercomparison focuses on modeling 11 representative sounding channels routinely used at numerical weather prediction centers: 7 HIRS (High‐resolution Infrared Sounder) 4 AMSU (advanced microwave unit) channels. Interest in topic was evident by participation 24 scientists from 16 institutions. An ensemble 42 diverse atmospheres results compiled for 19 infrared 10 models,...
Multiple independent intercalibration techniques are used to derive calibration adjustments for the development of a fundamental climate data record physically consistent brightness temperature from series six special sensor microwave/imagers (SSM/Is). The include direct polar matchups, double differencing against model simulations reanalysis profile data, matchups with Tropical Rainfall Measuring Mission Microwave Imager, vicarious cold calibration, and an Amazon warm calibration....
With rising demand for smaller, lower mass microwave instruments, internal calibration using noise diodes is becoming increasingly more attractive space-borne radiometer applications. Since can exhibit on-orbit excess temperature drift, internally calibrated systems typically require vicarious recharacterization. The GMI the first instrument of its kind to include both (noise diodes) and external (hot load/cold sky) systems. dual-calibration system provides unprecedented capability directly...
An intercalibrated Fundamental Climate Data Record (FCDR) of brightness temperatures (Tb) has been developed using data from a total 14 research and operational conical-scanning microwave imagers. This dataset provides consistent 30+ year record global observations that is well suited for retrieving estimates precipitation, precipitable water, cloud liquid ocean surface wind speed, sea ice extent concentration, snow cover, soil moisture, land emissivity. initial FCDR was series ten Special...
Global Navigation Satellite System (GNSS) Reflectometry uses reflected GNSS signals for Earth remote sensing applications. Absolute calibration of a Delay Doppler Map (DDM) requires an accurate estimate the effective isotropic radiated power (EIRP) transmitter, e.g., Positioning (GPS). However, variable transmit by numerous Block II Follow-on (IIF) and Replenishment-Modernized (IIR-M) GPS space vehicles has been observed due to their flex mode. Nonuniformity in antenna gain patterns further...
An intercomparison of microwave multiple scattering radiative transfer codes used in generating databases for satellite rainfall retrieval algorithms has been carried out to ensure that differences obtained from techniques do not originate the underlying code employed forward modeling. A set profiles containing liquid water and ice contents cloud rain as well snow, graupel pristine were distributed participants together with a black box routine providing Mie single scattering, atmospheric...
The double difference method of inter-calibration between spaceborne microwave radiometers is combined with the vicarious cold calibration for calibrating an individual radiometer. Vicarious minimizes effects geophysical variability on radiative transfer models (RTMs) brightness temperature (TB) data and it accounts frequency incidence angle dissimilarity radiometers. Double differencing reduces sensitivity to RTM error improper accounting variables in RTM. When together, two methods...
All sensing systems have some inherent error. Often, these errors are systematic, and observations taken within a similar region of space time can correlated error structure. However, the data from frequently assumed to completely independent uncorrelated This work introduces model for GNSS-reflectometry (GNSS-R) using NASA’s Cyclone Global Navigation Satellite System (CYGNSS). We validate our against near-simultaneous between two CYGNSS satellites, double difference results with modeled...
Since its launch in 2016, a number of wind speed retrieval algorithms have been developed for the NASA CYGNSS satellite observations. We assess their accuracy and precision characterize dependence performance on environmental factors. The uncertainty itself is considered. triple colocation method validation used to correct quality reference products with which compared. sea state also considered, particular attention being paid long wave portion surface roughness spectrum that less closely...
An algorithm to detect radio-frequency interference in microwave radiometer brightness temperatures is developed and applied K-band observations from AMSR-E, WindSat SSM/I. This uses the monthly peak difference between co-polar at 22 19 GHz find RFI. Data July 2005, 2008, January 2008 are shown. Less RFI seen SSM/I data than or AMSR-E data, likely due differences center frequency spatial resolution. A significant source of present 2009 that was not 2005. transmissions DirecTV 10 satellite,...
A constellation of disparate radiometers is inherent to the Global Precipitation Measurement (GPM) mission concept. The task Intersatellite Calibration Working group generate adjustments make measurements all these physically consistent. key role GPM Microwave Imager (GMI) on Core satellite serve as a transfer standard among radiometers. TRMM (TMI) has served this during development phase and for interim corrections early in mission. stability GMI appears be very good based calibration been...
GeoSTAR-III, a 180 GHz prototype for the Precipitation and All-weather Temperature Humidity Sounder (PATH), is culmination of decade technology development funding. The interferometric radiometer comprises 144 receivers operating from 165-183 utilizes 192×192 input, ASIC based mixed signal correlator. demonstration this instrument raises readiness subsystem to level 6 (TRL 6) correlator TRL 5. We demonstrate full functionality system with observations Sun Moon as well nearby thermally...
The uniaxial perpendicular and magnetocrystalline anisotropies in strained 〈100〉-oriented Ni-Cu superlattices have been determined by in-plane out-of-plane ferromagnetic resonance magnetization measurements for varying Ni Cu thicknesses. X-ray-diffraction patterns of the superlattice structure these films indicate that lattice contracts while dilates along growth direction. Utilizing measured strain with known elastic magnetostriction constants bulk Ni, calculated strain-induced...
The vicarious warm and cold calibration techniques are combined to provide an end-to-end two point method for spaceborne microwave radiometers. uses stable external sources permit of the complete radiometer, including its primary antenna. Both gain offset corrections radiometer can be computed since reference points at both ends measurement range available. is demonstrated using WindSat radiometer. Calibration errors found which vary with azimuthal scan position in a manner that suggests...
The Equivalent Isotropically Radiated Power (EIRP) by GPS satellites is needed to accurately calibrate the normalized bistatic radar cross section (NBRCS) measured Cyclone Global Navigation Satellite System (CYGNSS). EIRP product of transmit power and antenna gain. To determine EIRP, we first estimate power. A ground-based constellation monitor (GCPM) system has been built calibrated precisely measure signals. received repeatable verified with German Aerospace Center (DLR)'s independent...
We develop methods of using boreal, temperate, and tropical forests as vicarious calibration sites for spaceborne microwave radiometers. The extended improved techniques enable examining warm-scene performances a complement to cold scenes over the ocean, providing information about scan-dependent biases, detecting correcting possible errors, intercalibrating different Specifically, this paper shows results follows. Warm-scene is expanded beyond previously utilized in Amazon rainforest...
This article presents a detailed examination of fluctuating input noise power levels on the analog-to-digital convertor (ADC) sampling hardware NASA Cyclone Global Navigation Satellite System (CYGNSS) instruments and associated impacts level 1 normalized bistatic radar cross section (NBRCS) estimation performance. The impact external variations both CYGNSS science navigation channels is quantified with respect to how received low-level ADC distribution subsequent NBRCS estimation. work...