Engineering topics
Li, Fuk
Publications and source records attributed to Li, Fuk.
New Millenium Program Serving Earth and Space Sciences
A cross-Enterprise program is to identify and validate flight breakthrough technologies that will significantly benefit future space science and earth science missions. The breakthrough technologies are: enable new capabilities to meet earth and space science needs and reducing costs of future missions. The flight validation are: mitigates risks to first users and enables rapid technology infusion into future missions.
The Joint Analyses of Single- and Dual-Frequency/Experimental Dual-Polarization SIR-C and X-SAR Measurements in Precipitation
Progress, future plans and publications regarding the following objectives are presented: (1) Determine the vertical and horizontal spatial distribution of hydrometeors in precipitating clouds; (2) Measure the spatial distribution of liquid water and ice in the clouds; and (3) Measure and determine the limits of measurement of the polarization characteristics related to the shapes and orientations of hydrometeors in precipitating clouds.
The relationship between the microwave radar cross section and both wind speed and stress: Model function studies using Frontal Air-Sea Interaction Experiment data
The Frontal Air-Sea Interaction Experiment (FASINEX) provided a unique data set with coincident airborne scatterometer measurements of the ocean surface radar cross section (RCS)(at Ku band) and near-surface wind and wind stress. These data have been analyzed to study new model functions which relate wind speed and surface friction velocity (square root of the kinematic wind stress) to the radar cross section and to better understand the processes in the boundary layer that have a strong influence on the radar backscatter. Studies of data from FASINEX indicate that the RCS has a different relation to the friction velocity than to the wind speed. The difference between the RCS models using these two variables depends on the polarization and the incidence angle. The radar data have been acquired from the Jet Propulsion Laboratory airborne scatterometer. These data span 10 different flight days. Stress measurements were inferred from shipboard instruments and from aircraft flying at low altitudes, closely following the scatterometer. Wide ranges of radar incidence angles and environmental conditions needed to fully develop algorithms are available from this experiment.
Tropical rain mapping radar on the Space Station
The conceptual design for a tropical rain mapping radar for flight on the manned Space Station is discussed. In this design the radar utilizes a narrow, dual-frequency (9.7 GHz and 24.1 GHz) beam, electronically scanned antenna to achieve high spatial (4 km) and vertical (250 m) resolutions and a relatively large (800 km) cross-track swath. An adaptive scan strategy will be used for better utilization of radar energy and dwell time. Such a system can detect precipitation at rates of up to 100 mm/hr with accuracies of roughly 15 percent. With the proposed space-time sampling strategy, the monthly averaged rainfall rate can be estimated to within 8 percent, which is essential for many climatological studies.
Studies of the dependence of the microwave radar cross section on ocean surface variables during the FASINEX experiment
The ability of theoretical radar cross section (RCS) models to predict the absolute magnitude of the ocean radar cross section under a wide variety of sea and atmospheric conditions was studied using experimental data from the FASINEX Experiment. This consists of RCS data from a Ku-band scatterometer mounted on an aircraft (10 separate flights were conducted), a wide variety of atmospheric measurements (including stress) and sea conditions. Theoretical models are tested. Where discrepancies are observed, revisions are hypothesized and evaluated.
Studies of the radar cross section variations near the frontal boundary during Fasinex
The relationship between Amscat scatterometer measurements during Fasinex (the Frontal Air-Sea Interaction Experiment) and surface winds, waves, and surface stress is studied. Fasinex, which took place during the winter/spring of 1985-1986, focused on an oceanic front in the subtropical convergence zone southwest of Bermuda. Particular attention is given to data collected on February 18 when the Ku-band scatterometer measured the radar cross sections along two 80-km flight paths that ran north-south, approximately perpendicular to the front boundary.