Drs. Cristina Dalle Ore & Joshua Emery

December 20, 2006

"Outer Solar System Bodies"

NNA05CS63A

This project consists of two main tasks:

One is to collect as much information on the composition of the Solar System bodies for which data is already available or will become available in the near future from both ground and space-based telescopes, as follows, is being conducted by Cristina Dalle Ore:

The other task, conducted by Joshua Emery, is as follows:

This task will investigate the physical structure and composition of several classes of solar system objects. Measurements of thermal fluxes at several wavelengths will provide the means of deriving sizes, albedos, and/or thermal properties of the surfaces of a large number of Kuiper Belt Objects (KBOs), Centaurs, icy satellites of the outer planets, and Pluto. Surface compositions of a moderate number (~30) of asteroids of several dynamical classes (near-Earth, main belt, Trojan, extinct comet candidates), a few of the brightest Centaurs and KBOs, icy satellites of the outer planets, and Pluto will be studied with thermal emission spectroscopy. Reflected fluxes at 3.6, 4.5, 5.8 and 8.0 m m will be obtained for the icy satellites and Pluto as additional constraints on surface composition. The satellites of Saturn will also be studied using near infrared reflectance spectroscopy. This ambitious program is already in progress, and will be carried out using two spacecraft: The Spitzer Space Telescope and the Cassini spacecraft. Spitzer was launched in August 2003 into an Earth-trailing, heliocentric orbit. It is currently functioning well and returning data. The science payload consists of three instruments. The infrared camera (IRAC) collects images in 4 bands centered at 3.6, 4.5, 5.8, and 8.0 m m. For the surface temperatures of most objects in the outer solar system, fluxes measured at these bands will be dominated by reflected sunlight. The infrared spectrograph (IRS) can measure low resolution (R~60–100) spectra over the range 5.3–40µm, and high resolution (R~600) spectra over the range 10–37 m m. Asteroid fluxes in this range are dominated by thermal emission. Small, colder objects in the outer solar system have sufficient emitted flux only at the longer end of this range to be measured by Spitzer. The Multiband Imaging Photometer for Spitzer (MIPS) provides imaging photometry at 24, 70, and 160µm, and very low resolution (R~15–25) spectroscopy over the range 55–96µm. Fluxes of solar system objects are dominated by thermal emission at these long wavelengths. The Cassini spacecraft was launched in 1997, and is due to arrive at Saturn and enter orbit in June 2004. During its mission, Cassini will record images and spectra of the icy satellites of Saturn. The Visual and Infrared Mapping Spectrometer (VIMS) instrument measures spectra over the range 0.3–5.0µm. Radiation from the moons of Saturn is dominated by reflected sunlight over this range.

This work addresses several outstanding problems in planetary science related to each of the specific groups of objects mentioned above, which will, taken together, also provide deeper insights into the origin and evolution of our solar system.