Stanford Radar Interferometry Group

Radar Interferometry Group

Rare Trips for the Adventurous
Got a burning desire to explore the Carribean's exploding volcanos and Greenland's coldest glaciers? Then you've landed at the right place - the Stanford Radar Interferometry Group. We are a research unit affiliated with two departments, Electrical Engineering - STARLab and Geophysics.

Radar interferometry uses synthetic aperture radar mapping satellites to form detailed images of geological surfaces. This powerful technique can reveal centimeter-sized changes in the Earth's crust due to natural phenomena.

Current attractions:

Land subsidence in Las Vegas, Nevada Falk's paper

Glacial movement of the Petermann Glacier, Greenland

Volcano inflation (simulated) of Mt. Kilauea on the big island of Hawaii

Earthquake deformation from the Landers earthquake, California

Atmospheric water content from ERS interferometry

Sjonni's paper on solution for subsurface deformation at Frenandina volcano, Galapagos, from ERS interferometry

Two-dimensional phase unwrapping using network flow techniques

Large and small versions of inverse solutions for slip distribution from the Hector Mine earthquake of 16 October 1999

Latest Stanford Temperature Plot

People:

Alumnae

	Thesis Title	Where are they now?
Arlen Schmidt	Radar Imaging of Satellites at Meter Wavelengths	SRI International
Curtis Chen	Statistical-cost Network-flow Approaches to Two-dimensional Phase Unwrapping for Radar Interferometry	Caltech Jet Propulsion Laboratory (NASA)
Takuya Ishikawa	Design of a New Radar System for Train Tracking and Control	East Japan Railway Company
Weber Hoen	A Correlation-based Approach to Modeling Interferometric Radar Observations of the Greenland Ice Sheet	MIT Lincoln Laboratory
Sigurjon Jonsson	Modeling Volcano and Earthquake Deformation from Satellite Radar Interferometric Observations	Harvard University
Joern Hoffmann	The Application of Satellite Radar Interferometry to the Study of Land Subsidence Over Developed Aquifer Systems	DLR (German Space Agency)

Post-Docs and Visiting Scholars

Our Research:
Most of our work involves Radar Remote Sensing in its various forms, with a major specialization in Radar Interferometry. We address both the development and implementation of radar systems and their application to scientific studies of the Earth and planets. Some of our ongoing areas of research are:

Science applications

Crustal Deformation from Earthquakes
Our emphasis here is on i) detecting inter-seismic and potentially pre-seismic transient strains, which remain elusive and raise a major challenge to our understanding of the earth, and ii) modeling faulting and crustal rheology from vector co- and post-seismic displacement maps, which complement conventional seismological and geodetic measurements. Sjonni Jonsson has analyzed this radar interferogram of the Hector Mine earthquake
Volcanological Studies
Deformation is also important in understanding volcanic processes. Our work here includes i) modeling magma migration from the spatial and temporal extent of deformation, ii) quantifying pressure changes at depth resulting from magma intrusion beneath volcanic edifices, and iii) analyzing the spatial extent of new material deposited during eruptions. Sjonni also has produced and modeled deformation at Sierra Negra in the Galapagos Islands.
Earth's polar regions and the world's climate
Ice sheets and glaciers in the Earth's polar regions both control and reflect changes in the world climate. InSAR allows us to investigate the mass balance, or the accumulation and loss of ice, in these remote areas. Weber Hoen's thesis examines how InSAR correlation measurements help us estimate ice accumulation rates worldwide. Here is a sample accumulation map, and we need to apply this method to the full Antarctic continent to understand global warming or cooling.
Other studies of ground subsidence
Our group is pioneering other new applications for InSAR. We have found these data to be useful for studying many geophysical phenomena of strong scientific value and societal benefit, such as the study and management of groundwater aquifer systems. Joern Hoffmann has concentrated on the use of InSAR to better model the flow of water underground (figure here) . Other fields under investigation include landslides, floods, oil extraction, and coastal erosion.
Mapping the surfaces of planets and moons in our Solar System
Leif Harcke uses the Arecibo Observatory in Puerto Rico, the NASA Deep Space Facility, and the Very Large Array in New Mexico as powerful radar systems to map the surfaces of solar system objects. We have studied Mercury, Mars, and the Galilean satelltes of Jupiter using these instruments. Here is a sample observational plan.

Signal processing, design, and analysis
Phase Unwrapping
Phase unwrapping is a multidimensional signal processing technique that permits unambiguous interpretation of modulo-two pi phase measurements. Curtis Chen has recently developed a method based on maximum likelihood statistics and network flow models -- see his thesis and a sample figure.
Atmospheric propagation and correction
When radar signals travel through the atmosphere, they are delayed by the presence of water vapor. This corrupts the phase measurements in interferograms. Fayaz Onn is studying this phenomenon and how InSAR data may be improved through combination with GPS data. See a corrupted interferogram.
Very high speed networking and data serving using Internet II
One of our latest technical challenges is serving the science community with very large amounts of radar data via an online archive and distribution. We are now designing and implementing a system that catalogs 150 Gbytes of SAR data each day, and presents these to the world over a web-based interface. There are great challenges here in delivering data at gigabit speeds. Our group is using the new Internet II backbone (map) and developing special purpose data transfer codes to facilitate transfer of these data.

Student Opportunities

Research Assistantships
Most of our graduate students are supported by research assistantships, which generally means that initially you spend half of your time on coursework, and half on a research project. As you complete coursework, all of your time will be spent on research. In some cases projects are set by group needs, but in most cases we are able to define projects according to students' interests. We often have opportunities available in the group, so stop by and ask if you think that radar remote sensing and interferometry is an area that you'd like to work on for 5 years.

Skills and disciplines
Our work is broad in scope, and we expect students to be familiar with many technical areas. Since radar is an eclectic subject, as a group our students encompass many skills. Over the past few and next few years we have completed and anticipate theses comprised of original research in many areas, including:

Digital signal processing Modeling crustal deformation

Digital image processing Modeling groundwater flow

Electromagnetic wave propagation and scattering Space geodesy

High-speed computing Inverse modeling

High-speed networking

Open RA's and other opportunities


Digital signal processing	Modeling crustal deformation
Digital image processing	Modeling groundwater flow
Electromagnetic wave propagation and scattering	Space geodesy
High-speed computing	Inverse modeling
High-speed networking

Weekly group meetings:

Wednesday, 12:00 p.m.
Mitchell Buliding
Room 372

All are invited to attend and participate. Our meetings are informal and usually consist of student presentations of current research or interesting scientific papers. Sometimes we just eat pizza.

Software

Downloadable software packages for radar and InSAR processing
--These are free, but please acknowledge their use in your research--
Documentation is included in some packages, but note that we do not support any of these products formally. You are free to use them but you are on your own as regards installation and usage.

Computer resources

Our group barbecue in June 2002 was well attended. Here are view 1 and view 2 from our group dinner in June 2001. We also have a picture from a pizza party in the spring of 2000.

Contact: zebker_group@insar.stanford.edu