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Abstract-Several solar gas rich lunar soils and breccias have trapped 40Ar/36Ar ratios >lo, although solar Ar is expected to yield a ratio of <0.01. Radiogenic 40Ar produced in the lunar crust from 40K decay was outgassed into the lunar atmosphere, ionized, accelerated in the electromagnetic field of the solar wind, and reimplanted into lunar surface material. The 40Ar loss rate depends on the decreasing abundance of 40K. In order to calibrate the time dependence of the 40Ar/36Ar ratio in lunar surface material, the period of reimplantation of lunar atmospheric ions and of solar wind Ar was determined using the 235U-136Xe dating method that relies on secondary cosmic-ray neutron-induced fission of 235U. We identified the trapped, fissiogenic, and cosmogenic noble gases in lunar breccia 14307 and lunar soils 70001-8, 70181, 74261, and 75081. Uranium and Th concentrations were determined in the 74261 soil for which we obtain the 235U-136Xe time of implantation of 3.252::; Ga ago. On the basis of several cosmogenic noble gas signatures we calculate the duration of this near surface exposure of 393 k 45 Ma and an average shielding depth below the lunar surface of 73 k 7 g/cm*.A second, recent exposure to solar and cosmic-ray particles occurred after this soil was excavated from Shorty crater 17.2 2 1.4 Ma ago. Using a compilation of all lunar data with reliable trapped Ar isotopic ratios and pre-exposure times we infer a calibration curve of implantation times, based on the trapped 40ArP6Ar ratio. A possible trend for the increase with time of the solar 3He/4He and 20NeP2Ne ratios of about 12%/Ga and about 2%/Ga, respectively, is also discussed.

We demonstrate coherent combining (phase locking) of seven laser beams emerging from an adaptive fiber-collimator array over a 7 km atmospheric propagation path using a target-in-the-loop (TIL) setting. Adaptive control of the piston and the tip and tilt wavefront phase at each fiber-collimator subaperture resulted in automatic focusing of the combined beam onto an unresolved retroreflector target (corner cube) with precompensation of quasi-static and atmospheric turbulence-induced phase aberrations. Both phase locking (piston) and tip-tilt control were performed by maximizing the target-return optical power using iterative stochastic parallel gradient descent (SPGD) techniques. The performance of TIL coherent beam combining and atmospheric mitigation was significantly increased by using an SPGD control variation that accounts for the round-trip propagation delay (delayed SPGD).

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