Atmospheric Physics

PRA was founded on the development of remote sensing technology to characterize the refraction and turbulence in the troposphere. PRA evolved this capability into remote sensing in the ionosphere to provide a total electron count (TEC) for understanding radar frequency propagation phenomena in the ionosphere. Since these early technology developments, PRA has applied this capability to understand the impact of sensor handoff between radar sensors that are operating over large distances, the ability to use refraction to track over the horizon, and a methodology for quantifying tropospheric and ionospheric correlation effects between EO/IR sensors and radars.

Contact Information: Bonnie Valant-Spaight, Ph.D. Atmospheric Physics

The Enhanced Tropospheric Effects Compensation (ETEC) System

ETEC Antenna EDCS Skyplot The ETEC system consists of multiple GPS receivers and antennas arranged in an array configuration for the purpose of tracking occulting GPS satellites. PRA developed techniques to use the refraction of GPS signals to characterize the refractivity of the troposphere. The technique was implemented on low elevation satellites for the purpose of understanding low elevation refractivity for radar propagation. PRA was teamed with the National Center for Atmospheric Research (NCAR) to integrate measured refractivity profiles into the Weather Research and Forecasting (WRF) model.

The Total Atmospheric Effects Mitigation (TAEM) System

TAEM Working with the Jet Propulsion Laboratory (JPL), PRA extended the ETEC remote sensing capability to include the ionosphere. The TAEM system measures TEC along the propagation path of GPS signals. The TEC measurements were integrated into the JPL Global Assimilative Ionospheric Model (GAIM) in order to determine the effects of the ionosphere on signal propagation. Using the TAEM measurement system, PRA can provide near real-time measurements to characterize the ionospheric propagation environment.

Ballistic Missile Defense Radar Handover

ETEC Radar Track PRA developed spatially and temporally correlated models of the atmosphere and analyzed the impact of atmospheric turbulence on handing over radar targets over long distances. PRA worked with Lockheed Martin to integrate the turbulence model into the large BMD simulation MEDUSA and characterize the impact of turbulence on the performance of handing a target from an AEGIS radar to another radar.

Track Correlation Effects

PRA extended the BMD handover analysis to included handing over from an EO/IR sensor to a radar. Atmospheric turbulence correlation effects were developed and integrated into a simulation that modeled the early boost phase stage of missile trajectories. The objective of this analysis is to develop algorithms that successfully account for these turbulence effects to improve the probability of handover.