NIAC Focus: Molecular Composition Analysis of Distant Targets

This drawing illustrates a system concept for investigating the molecular composition of a distant target, such as an asteroid or comet. A spacecraft is sent to the asteroid, and enters into orbit. Solar cells generate electricity that is used to power a laser, which is directed at the asteroid's surface. The laser will heat a spot on the surface, and very quickly material will begin to evaporate from the spot. The glow from the heated spot is visible at the spacecraft through the plume of evaporated material. Sensors in the spacecraft measure the intensity of light across a span of wavelengths; analysis of light intensity patterns provides information about materials in the plume of evaporated material. Credits: Mark Pryor (Vorticity, Inc.) , Gary B. Hughes (Cal Poly SLO)
This drawing illustrates a system concept for investigating the molecular composition of a distant target, such as an asteroid or comet. A spacecraft is sent to the asteroid, and enters into orbit. Solar cells generate electricity that is used to power a laser, which is directed at the asteroid’s surface. The laser will heat a spot on the surface, and very quickly material will begin to evaporate from the spot. The glow from the heated spot is visible at the spacecraft through the plume of evaporated material. Sensors in the spacecraft measure the intensity of light across a span of wavelengths; analysis of light intensity patterns provides information about materials in the plume of evaporated material.
Credits: Mark Pryor (Vorticity, Inc.) , Gary B. Hughes (Cal Poly SLO)

NASA’s Innovative Advanced Concepts (NIAC) program recently selected 13 proposals for Phase I awards. Below is one from Gary Hughes of California Polytechnic State University.

Molecular Composition Analysis of Distant Targets

Gary Hughes
California Polytechnic State University

We propose a system capable of probing the molecular composition of cold solar system targets such as asteroids, comets, planets and moons from a distant vantage. Our concept utilizes a directed energy beam to vaporize or sublimate a spot on a distant target, such as from a spacecraft near the object. With sufficient flux, our published results indicate that the spot temperature rises rapidly, and evaporation of materials on the target surface occurs (Hughes et al., 2015; Lubin and Hughes, 2015; Lubin et al., 2014).

The melted spot serves as a high-temperature blackbody source, and ejected material creates a molecular plume in front of the spot. Molecular and atomic absorption of the blackbody radiation occurs within the ejected plume. Bulk composition of the surface material is investigated by using a spectrometer to view the heated spot through the ejected material.

We envision a spacecraft that could be sent to probe the composition of a target asteroid, comet or other planetary body while orbiting the targeted object. The spacecraft would be equipped with an array of lasers and a spectrometer, powered by photovoltaics.

Spatial composition maps could be created by scanning the directed energy beam across the surface. Applying the laser beam to a single spot continuously produces a borehole, and shallow sub-surface composition profiling is also possible.

Our initial simulations of laser heating, plume opacity, material absorption profiles and spectral detectivity show promise for molecular composition analysis. Such a system has compelling potential benefit for solar system exploration by establishing the capability to directly interrogate the bulk composition of objects from a distant vantage.

We propose to develop models, execute preliminary feasibility analysis, and specify a spacecraft system architecture for a hypothetical mission that seeks to perform surface molecular composition analysis and mapping of a near-earth asteroid (NEA) while the craft orbits the asteroid.

Hughes, G.B., Lubin, P., Meinhold, P., O’Neill, H., Brashears, T., Zhang, Q., Griswold, J., Riley, J., and Motta, C. “Stand-off molecular composition analysis,” Nanophotonics and Macrophotonics for Space Environments IX, edited by Edward W. Taylor, David A. Cardimona, Proc. of SPIE Vol. 9616 (Aug, 2015).

Lubin, P. and Hughes, G.B. “Directed Energy for Planetary Defense.” Chapter in: Allahdadi, Firooz, and Pelton, Joseph N. (Eds.), Handbook of Cosmic Hazards and Planetary Defense, Springer Reference, 1127 p., ISBN 978-3-319-03951-0 (2015).

Lubin, P., Hughes, G.B., Bible, J., Bublitz, J., Arriola, J., Motta, C., Suen, J., Johansson, I., Riley, J., Sarvian, N., Clayton-Warwick, D., Wu, J., Milich, A., Oleson, M., Pryor, M., Krogen, P., Kangas, M., and O’Neill, H. (2014). “Toward Directed Energy Planetary Defense,” Optical Engineering, Vol. 53, No. 2, pp 025103-1 to 025103-18 . doi: 10.1117/1.OE.53.2.025103