The MIT-IRTF Joint Campaign For NEO Spectral Reconnaissance

R.P. Binzel (MIT), A.T. Tokunaga (Univ. of Hawaii)

Objectives

• Measure the spectral characteristics of NEOs having propulsion requirements < 7 km/sec so that mission planning can be driven by scientific criteria (basic knowledge of the target properties) rather than by simple dynamical (minimum DV) requirements.

• Characterize the properties of objects in comet-like orbits for understanding asteroid-comet connections-- identification of extinct comet candidates will constrain the comet source fraction for NEOs.

• Characterize the potentially hazardous asteroid subgroup and to specifically compare with the broader NEO population to understand better meteorite sources.

Near-Earth objects (NEOs) are the most accessible objects in the solar system for spacecraft missions, with many having sample return (or human exploration) propulsion requirements substantially lower than the Moon. We are undertaking a joint MIT-UH reconnaissance of specific subsets of the NEO population with immediate dissemination of data open to the entire community. Our specific science goals are:

Obtaining data, dissemination, and some results

Data is obtained remotely from MIT using undergraduate and graduate students. This provides education, training, and research in an effective manner.

Reduced data are archived on the web and are accessible to anyone (http://smass.mit.edu/minus.html). A link to this web site is on the IRTF home page as well.

In the following slides we show some recent results.

MIT Campus

NASA IRTF

Joint Program Operations via Remote Observing:

Spectrum of Earth-approacher 2004 MN4 reveals an S-type to Q-type class, allowing estimates for its albedo and a size ~300 m.

2004 MN4

Potentially Hazardous Asteroids

Low albedo NEOs in the vicinity of 1 AU become warm enough to emit measurable thermal flux shortward of 2.5 m, as seen for 2001 ME1. Thermal modeling by Rivkin et al. 2005 (solid line) fits an albedo of 3%.

Spectral and Albedo Results

Spectrum of Geminid meteor stream parent body 3200 Phaethon and the spectrum of the low activity comet 2004 TU12. The coma density may have been low enough to allow this spectrum to represent the nucleus. The spectral upturn beyond 2 m is likely due to thermal emission, from which the albedo may be constrained (Rivkin et al. 2005).

Comet Candidates

Comparison of 69230 Hermes (points) to L6 chondrite meteorites (red line). The blue line represents a linear mixture of 60% L6 material and 40% neutral material with the same albedo as the meteorite, which lowers the absorption band contrast. Such an effect could also be due to particle size effects rather than mixture with spectrally neutral material.

Meteorite Links