Core technologies and applications
SRI’s experienced teams work together across disciplines to create innovative engineering and operations solutions tough enough to withstand the extreme conditions of space and marine environments.
Compact sensors for uncompromising environments, small satellite payload and mission design, specialized signal processing and exploitation
Advanced technology and systems for remote sensing, geolocation, communications and space situational awareness
Innovative modeling and forecasting for environmental characterization in ocean, nearshore and riverine domains
CMOS, CCD and ROIC design
Device design, simulation and process development for high-performance devices and camera assemblies, ROICs for custom-configured LIDAR and more
SRI International researchers developed Active Pixel CMOS detectors for the U.S. Naval Research Laboratory’s Wide-Field Imager for Solar Probe (WISPR). This is the only imaging instrument aboard the Parker Solar Probe.
We develop an effective medium model of thermal conductivity that accounts for both percolation and interface scattering. This model accurately explains the measured increase and decrease of thermal conductivity with loading in composites dominated by percolation and interface scattering, respectively. Our model further predicts that strong interface scattering leads to a sharp decrease in thermal conductivity, or an insulator transition, at high loadings when conduction through the matrix is restricted and heat is forced to diffuse through particles with large interface resistance. The accuracy of our model and its ability to predict transitions between insulating and conducting states suggest it can be a useful tool for designing materials with low or high thermal conductivity for a variety of applications.
Topside Equatorial Ionospheric Density, Temperature, and Composition under Equinox, Low Solar Flux Conditions
We present observations of the topside ionosphere made at the Jicamarca Radio Observatory in March and September 2013, made using a full-profile analysis approach. Recent updates to the methodology employed at Jicamarca are also described. Measurements of plasma number density, electron and ion temperatures, and hydrogen and helium ion fractions up to 1500 km altitude are presented for 3 days in March and September. The main features of the observations include a sawtooth-like diurnal variation in ht, the transition height where the O+ ion fraction falls to 50%, the appearance of weak He+ layers just below ht, and a dramatic increase in plasma temperature at dawn followed by a sharp temperature depression around local noon. These features are consistent from day to day and between March and September. Coupled Ion Neutral Dynamics Investigation data from the Communication Navigation Outage Forecast System satellite are used to help validate the March Jicamarca data. The SAMI2-PE model was able to recover many of the features of the topside observations, including the morphology of the plasma density profiles and the light-ion composition. The model, forced using convection speeds and meridional thermospheric winds based on climatological averages, did not reproduce the extreme temperature changes in the topside between sunrise and noon. Some possible causes of the discrepancies are discussed.
Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. II. A Study of Three Radars with Different Sensitivity
The sensitivity of radar systems to detect different velocity populations of the incoming micrometeoroid flux is often the first argument considered to explain disagreements between models of the Near-Earth dust environment and observations. Recently, this was argued by Nesvorný et al. to support the main conclusions of a Zodiacal Dust Cloud (ZDC) model which predicts a flux of meteoric material into the Earth’s upper atmosphere mostly composed of small and very slow particles. In this paper, we expand on a new methodology developed by Janches et al. to test the ability of powerful radars to detect the meteoroid populations in question. In our previous work, we focused on Arecibo 430 MHz observations since it is the most sensitive radar that has been used for this type of observation to date. In this paper, we apply our methodology to two other systems, the 440 MHz Poker Flat Incoherent Scatter Radar and the 46.5 Middle and Upper Atmosphere radar. We show that even with the less sensitive radars, the current ZDC model over-predicts radar observations. We discuss our results in light of new measurements by the Planck satellite which suggest that the ZDC particle population may be characterized by smaller sizes than previously believed. We conclude that the solution to finding agreement between the ZDC model and sensitive high power and large aperture meteor observations must be a combination of a re-examination not only of our knowledge of radar detection biases, but also the physical assumptions of the ZDC model itself.