Current Status and Milestones Motivation Lunar Flashlight Mission

Lunar Flashlight: Illuminating the Moon’s South Pole

P. O. Hayne1, B. A. Cohen2, B.T. Greenhagen3, D. A. Paige4, J. M. Camacho1, R. G. Sellar1, J. Reiter1 1NASA-Jet Propulsion Laboratory, California Institute of Technology (Paul.O.Hayne@jpl.nasa.gov), 2NASA-Marshall Space Flight Center, 3Applied Physics Laboratory, Johns Hopkins University, 4University of California, Los Angeles Motivation Measurement Approach Recent reflectance data from LRO instruments suggest water ice and other volatiles may be Lunar Flashlight’s four-channel laser projector will illuminate permanently shadowed present on the surface in lunar permanently shadowed regions, though the detection is not yet regions, measuring surface reflectance at wavelengths near 1.4, 1.5, 1.84, and 2.0 µm. Water definitive [1, 2, 3]. Understanding the composition, quantity, distribution, and form of water ice will be distinguished from dry regolith in two ways: 1) spatial variations in albedo, and 2) and other volatiles associated with lunar permanently shadowed regions (PSRs) is identified reflectance ratios between absorption and continuum channels. Water ice band depths will be as a NASA Strategic Knowledge Gap (SKG) for Human Exploration. These polar volatile mapped in order to distinguish the composition of the PSRs from that of the sunlit terrain. deposits are also scientifically interesting, having the potential to reveal important These data will be highly complementary to other lunar datasets, including LRO. information about the delivery of water to the Earth-Moon system. 0.5

Lunar Flashlight Mission 0.45 The Lunar Flashlight (LF) mission is a 6U CubeSat, to be launched as a secondary payload on 0.4

the first test flight (EM-1) of the Space Launch System (SLS), currently scheduled for 2018. The ) goal of LF is to determine the presence or absence of exposed water ice and map its -1 concentration at the 1-2 kilometer scale (Fig. 1). After being ejected in cislunar space by SLS, 0.35

Lunar Flashlight maneuvers into a low-energy transfer to lunar orbit and then an elliptical BRDF (sr 0.3 polar orbit, spiraling down to a perilune of 10-30 km above the south pole (Fig. 2).

H O ice 0.25 2 Highlands Soil (Apollo 14 - 67701) Highlands Soil (Apollo 14 - 66041) 0.2 0.5 1 1.5 2 2.5 Wavelength (µm) Figure 1: View of a permanently shadowed crater near the lunar south pole, probed by Figure 3: Carefully selected spectral bands in the near-infrared can be used to distinguish water frost at Lunar Flashlight’s laser beam. For the first small concentrations (< 1 wt%) from dry regolith. The spectra on the right are examples, derived from time, these shadowed regions will be water ice optical constants [4] and measured reflectance spectra of two Apollo highlands soils [5]. illuminated in four near-infrared spectral bands to determine the abundance of H2O ice Current Status and Milestones and map its distribution in the Moon’s south Currently in Phase B, Lunar Flashlight has completed several important milestones relevant polar region. to science and the mission payload:

• Developed an end-to-end instrument performance model to evaluate uncertainty in [H2O] ice detected under a range of concentrations, particle sizes, and regolith composition (Fig. 3). This model includes radiative transfer [6] for calculating bidirectional reflectance for the given Lunar Flashlight ConOps composition and illumination/viewing geometry, and stray light contributions (Fig. 4).

sp7520192458504 0.5 m/s per day alGtude maintenance Orbit maintenance as needed 102

Idle/Laser Figure 4: Stray light analysis 0 Recharge 10 for Lunar Flashlight, using a ) -1 -2 165 m/s Figure 2: Concept of 3-d ray-tracing model [7] to sr 10 LOI -2 ü Laser test firings ~100 Science Orbits Operations for Lunar calculate background radiance at Earth-based -4 ü System checkout over 2 months. 10 observatories Flashlight Mission. After (left) from modeled fluxes ü Laser power system charge and Radiance (W m discharge tests (right). Model includes direct ü Detumble, panel Extended mission lunar orbit insertion (LOI), 10-6 deployment based on available and indirect solar, infrared, ü Ini?al contact propellant. the spacecraft spirals down and earthshine. -8 to its science orbit, with ~10- 10 Disposal in moon. -500 -400 -300 -200 -100 0 100 200 300 400 500 30 km perilune over the Distance from South Pole (km)

ü Imaging of Jupiter DSN DSN south polar region. • Utilized performance model to select optimal wavelengths for custom fabrication by laser with receiver Pass Pass ü “Day in the life” vendor (DILAS) 10 m/s 15 m/s laser tests to prepare for Moon burn burn • Designed and fabricated laboratory chamber and testbed for detector testing (Fig. 5) Science

L+4 days L+90 days L+194 days Orbit Deploy 1st Flyby and Loiter 2nd Lunar/Earth Flyby and Loiter LOI Science Trims Figure 5: Components of Lunar Flashlight payload testbed (left to right): Cryogenic vacuum chamber for References: detector testing; integrating sphere [1] Gladstone, G. R., et al. (2012) JGR 117, CiteID E00H04. [2] Zuber, M. T., et al. (2012) Nature, 486, 378-381. [3] Hayne, P. O., et al. (2015) Icarus 255, 58-59. [4] Warren, light source; rendering of detector S. G. and Brandt, R. E. (2008), JGR 113, D14. [5] Adams, J. B. and T. B. McCord (1971), Science 171, 567-571, 1971[6] Hapke, B. (1981), JGR 86, B4. [7] Paige, D. A., et al. (2010), Science 330, 479-482. testing setup Acknowledgement: Part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration