Please join us for a seminar in Remote Sensing

Speaker: Dr. Philip J. Erickson, Assistant director, MIT Haystack Observatory
When: Monday, March 20
Time: 12:20 – 1:10 pm

Title: Sensing Earth's Ionosphere with Really Large Radars: How and Why

Abstract: The human desire to migrate towards an increasingly technological society is placing more and more assets in the space region surrounding our planet. We also wish to send humans through these environments to other worlds, and have an increasing need to communicate across the atmosphere from place to place. These goals require that we understand our near space environment and its many variations, both in space and time. Doing this is quite difficult since nearly all humans still live on the planet's surface, but for more than a century, the space science community has worked with increasingly sophisticated tools toward a better understanding of our natural environment.

Since the early 1960s, physicists and engineers have developed powerful experimental techniques for remotely sensing Earth's ionosphere, comprising the charged part of the tenuous upper atmosphere. In particular, ground-based radars have been built with megawatt class transmitters and large antennas (40 to 50 meter diameter and larger). This class of very large radar system is sensitive enough to use a technique called incoherent scatter, which directly detects weak backscatter from electrons in the upper atmosphere. Furthermore, the physical mechanisms at work in the scattering mechanism also contain information about the ionic species in the upper atmosphere. The result is a technique considered the most powerful ground-based method for remotely sensing ionospheric variations and ultimately for exploring the basic physics of the atmosphere. Density, temperature, velocity, ion composition, and more can be determined, and this information is fundamental to improving our understanding of weather in near-Earth space.

In this seminar, I will provide an overview of the foundations of the incoherent scatter technique, and will give examples from both a radio science and an atmospheric physics perspective on what this experimental technique teaches us about the space and time variations of our planet's atmosphere. Examples will be drawn from nearly 60 years of operation of a large incoherent scatter radar system in operation since 1960 at Millstone Hill in eastern Massachusetts, whose range covers a large portion of the eastern US coast. I will also point out the interdisciplinary connections needed to successfully use the data produced by these systems, involving not only radio physics but signal processing, computer science, and informatics / "big data" approaches. Application of these latter approaches is an emerging science and has the potential to amplify our remote sensing knowledge even further.