Department of Astronomy Center for Radiophysics & Space Research

Sean Marshall

Professor Donald Campbell
Sean Marshall

Research Areas:

Near-Earth asteroids; Saturn's atmosphere

Research Projects:

Arecibo; Cassini


I am currently working on two research projects. For the first project, under the guidance of Don Campbell (Cornell astronomy), Ellen Howell, and Mike Nolan (Arecibo Observatory), I am testing the accuracy of new asteroid thermal modeling software. Many thermal models assume that asteroids are spherical, which is not a good assumption but is often the best that can be done with the limited information that is available for most asteroids. The SHAPE software uses radar-derived shape models to give a more detailed calculation of how an asteroid would appear in visible and near-infrared wavelengths. I am doing a detailed comparison of SHAPE's calculated spectra with actual observations, and with spectra calculated by simpler thermal models. Most of the work for this project involves me sitting at a computer, but I also got to go to Arecibo Observatory to help with some observations!

For the second project, under the guidance of Phil Nicholson and Matt Hedman (Cornell astronomy), I am analyzing stellar occultations by Saturn's atmosphere observed with Cassini's VIMS (IR) instrument. As Cassini watches a star appear to move into the atmosphere of Saturn (an occultation), the star's observed flux does not decrease smoothly. Instead, we see spikes in the light curve, which are believed to be caused by density fluctuations in Saturn's atmosphere. Near the end of an occultation, the spikes appear earlier at long wavelengths than at shorter wavelengths. By analyzing the wavelength-dependent time delays, I hope to be able to determine the dispersion relation for Saturn's atmosphere, and then to compare that to the dispersion relations for helium and molecular hydrogen in order to figure out the helium abundance in Saturn's atmosphere (using only this method).

When not doing research, teaching, taking classes, or answering Curious questions, I enjoy reading, biking, and cheering for Philadelphia's sports teams. I currently hold the department record for the standing long jump: 2.4 meters.


None yet from grad school work, but here are links related to two REU's I did as an undergrad: