J. L. Remo

• PhD
• Research Associate at Harvard University

We use a thermodynamic framework for silicate-metal partitioning to determine the possible compositions of metallic cores on super-Earths. We compare results using literature values of the partition coefficients of Si and Ni, as well as new partition coefficients calculated using results from laser shock-induced melting of powdered metal-dunite tar...

We applied MBBAY high fluence pulsed radiation intensity driven momentum transfer analysis to calculate X-ray momentum coupling coefficients CM = (Pa - s)/(J/m²) for two simplified comet analog materials: i) water ice, and ii) 70% water ice and 30% distributed olivine grains. The momentum coupling coefficients (CM) max of 50 ×10⁻⁵ s/m, are about an...

Nuclear energy, used in weapons as well as for electricity generation, has the potential to destroy life on Earth. But it also has the potential to save life as we know it. Currently, nuclear explosives are the only technology with the capability to deflect, on relatively short notice, a large asteroid fragment or comet headed for a collision with...

It has been 20 years since planning began for the 1995 United Nations International Conference on Near-Earth Objects. The conference proceedings established the scientific basis for an international organizational framework to support research and collective actions to mitigate a potential near-Earth object (NEO) threat to the planet. Since that ti...

X-ray momentum coupling coefficients, C M, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the Sandia National Laboratories Z-machine. Velocity interferometry (VISAR) diagnostics provided equation-of-state data. Targets were iron and stone meteorites, magnesium-rich olivine (dunite)...

X-ray momentum coupling coefficients, CM , were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the SNL Z-machine. Targets were prepared from iron and stone meteorites, dunite (primarily magnesium rich olivine) in solid and powder forms (~5 - 300 μm grains), and Si, Al, and Fe. All sampl...

High-energy pulsed X-ray momentum coupling is a promising technology for early deflection of NEOs (Near Earth Objects) that might impact Earth. Analytic models for the radiation interactions can often preclude the need for large hydrocode analyses, and offer the advantage of many simple calculations that reveal important features of the nonlinear p...

An electro‐optic laser probe was developed to obtain parameters for high energy density equations of state (EoS), Hugoniot pressures (PH), and strain rates for high energy density laser irradiation intensity, I, experiments at ∼ 170 GW/cm2 (λ = 1064 nm) to ∼ 13 TW/cm2 (λ = 527 nm) on Al, Cu, Ti, Fe, Ni metal targets in a vacuum. At I ∼ 7 TW/cm2 fro...

High energy density (HED) laser, soft X‐ray black body (BB), light, and 20 km∕s mechanical impact interactions in warm dense matter (WDM) regimes are compared at equivalent intensities. Different transport mechanisms induce different equations of state and material responses for HED plasma driven ablation interactions at ∼100’s GPa and ∼ 105 K with...

For Hf-W chronometry of the Earth-Moon system (EMS) there are currently two end member options: (i) the formation of the EMS at ~32 Myr or (ii) formation of 90% of the Earth in the first six Myr followed by a very late (~100 Myr) formation of the Moon.

The response of a range of meteorite and planetary materials of astrophysical and planetary science interest to pulsed high-energy-density soft X-ray irradiation from the Sandia National Laboratories Z-pinch accelerator is described. These materials include selected iron and stony meteorites, magnesium-rich olivine (dunite), and Al and Fe calibrati...

Measurable variations in (182)W/(183)W, (142)Nd/(144)Nd, (129)Xe/(130)Xe and (136)XePu/(130)Xe in the Earth and meteorites provide a record of accretion and formation of the core, early crust and atmosphere. These variations are due to the decay of the now extinct nuclides (182)Hf, (146)Sm, (129)I and (244)Pu. The (l82)Hf-(182)W system is the best...

The chemical composition and structure of super-Earths can be understood from data and models for the chemical evolution of our galaxy, our solar system and models of formation and interiors of planets. Because the relative proportions of most rock-forming elements in stars of our galaxy are rather constant the mineralogy of solid grains that forme...

Sandia National Laboratories NLS (1064 nm) and Z-Beamlet (527 nm) pulsed lasers @ ~ 100 GW/cm 2 and 10 TW/cm 2 were used to attain pressures at 20 – 525 GPa on a variety of metallic and mineral targets. A simple, inexpensive and innovative electro-optical real-time methodology monitored rear surface mechanical deformation and associated particle an...

The concept of high energy density (HED) radiation driven momentum coupling (momentum transfer), CM, to a targets in a vacuum is analytically developed and applied via successive plasma, ablative, and hydrodynamic interfaces undergoing both weak and strong shocks. CM are derived from equations of state (EOS) variables and serve as figures of merit...

The response of meteorite and planetary materials to high- intensity

Our experimental data suggest that the silicate portion of the post-giant-impact terrestrial magma ocean might have been enriched in FeO and capable of very rapid metal-silicate equilibration.

We discuss physical processes taking place in our laser-induced shock experiments of solid and powdered metal-silicate targets and the approach to calculation of shock parameters such as pressures and temperatures and their gradients.

Generation and effects of atmospherically propagated electromagnetic pulses (EMPs) initiated by photoelectrons ejected by the high density and temperature target surface plasmas from multiterawatt laser pulses are analyzed. These laser radiation pulse interactions can significantly increase noise levels, thereby obscuring data (sometimes totally) a...

We describe a new experimental technique involving high energy density lasers that allows measurements of equations of state and momentum coupling coefficients at very high T and P in recovered targets to be made.

Distinct solar system (SS) solid planetary objects are defined in terms of dynamic and solid state characteristics. This includes Keplerian orbits, self gravitation, upper and lower mass limits that effect planet shape, integrity, and equation of state. Criteria are based on parameters that vary with pressure and temperature such as bulk modulus (β...

The metal-silicate fractionation in celestial bodies effectively separates siderophile 182W from lithophile 182Hf into the core and mantle, respectively, making the Hf-W chronometer ideal for dating core-formation in differentiated planetary bodies. It is generally believed that there was equilibration of the Hf-W system during primary metal-silica...

The development of nonlinear dynamics is outlined with emphasis on the concepts leading to the development of a numerical technique known as “fuzzy boundary theory” or FBT. Origins of this methodology are a direct outgrowth of concepts derived from the Hamiltonian formulation, KAM theory, and “Mather regions.” The significance of FBT as a computati...

This paper discusses the momentum coupling coefficient in the relativistic, collisionless realm as contrasted with the collisional, ablation dominated regime. It is shown the total momentum coupling coefficient is a result of the combined ion and photon momenta.

New information about the internal structures of asteroids and comets continues to be obtained. Meanwhile, renewed emphasis on exploration of the Solar System is sharpening the focus on extra-terrestrial raw materials to facilitate the process. The overall energy cost will be reduced significantly by maximizing usage of locally available resources....

The concept of a near-Earth object (NEO) impact projection metric (PM) based on the ratio of the observation time to the impact time, rho(t), for a projected NEO impact is developed. The PM can assist NEO mitigation decision-making that is based on the discontinuously changing cumulative impact probability and help mitigate false alarms of NEO impa...

Effects of natural (meteoroid), manufactured, and missile interception orbital debris (OD) on satellite assets are quantitatively assessed. Enhanced levels of OD generated from either ground- or space-based interceptors are not likely to affect significantly space-based (satellite) assets if the OD generated from ballistic missile warhead intercept...

Energy requirements for near-Earth object (NEO) threat mitigation are addressed. Due to a large NEO mass range and the possibility of limited available time for orbit change, energy requirements can be large (~petajoules). To quantitatively determine energy requirements for a given momentum change use is made of the momentum coupling coefficient, C...

Uncertainties associated with assessing valid near-Earth object (NEO) threats and carrying out interception missions place unique and stringent burdens on designing mission architecture, astrodynamics, and spacecraft propulsion systems. A prime uncertainty is associated with the meaning of NEO orbit predictability regarding Earth impact. Analyses o...

A dynamic metric for near-Earth object (NEO) hazard mitigation quantifies threats from potential NEO impacts with Earth in terms of energy required to perturb threatening NEO orbits to avoid collision. The required energy is based on NEO mass, anticipated velocity change to avoid collision, and the momentum coupling coefficient.

A hazard mitigation scale is presented that quantifies the danger from a potential near-Earth object (NEO) impact with Earth in terms of the energy required to perturb the threatening NEO's orbit to avoid collision in the foreseeable future. The required energy is based on NEO mass, anticipated velocity change to avoid collision, and momentum coupl...

Statistics on near-Earth asteroids (NEAs) discovery and follow-up observations as a function of geographical location are presented. The majority of discoveries and follow up observations are made from the northern hemisphere which has the preponderance of facilities. It is suggested that because of the current dearth of observation programs in the...

Experiments on pure and inhomogeneous materials (meteorite samples) have been performed at the Sandiad National Laboratory (SNL) using a hohlraum source of soft X-rays. It is of interest to deduce the scaling of the ablation pressure with the radiation temperature in this class of experiment. This paper uses similarity relations deduced from a radi...

Experimental results of shock wave effects from high intensity (70 –215 GW) soft X‐ray irradiation on several meteorite targets are presented. From inhomogeneous materials, useful data on particle velocity and in‐situ velocity were obtained and permitted the computation of the yield stress, shock wave velocity, compression, as well as the momentum...

Within observational constraints and analytic orbit determinations, potential NEO hazards and mitigations are characterized in terms of orbit displacements to establish (arbitrary) “safe” closest approach distances and corresponding energies that must be externally applied to achieve appropriate orbit displacements from the Earth. Required orbital...

Scientific and policy developments in the field of Near-Earth Objects (NEOs) since the UN NEO conference in 1995 are briefly outlined. Some areas of research and discovery have exhibited considerable progress while others have languished. In particular, facilities in the southern hemisphere for discovery and tracking of NEOs are inadequate. Suggest...

The effectiveness of various high energy density sources and their coupling coefficients are evaluated in terms of the required payload mass necessary to change the orbit of a Earth-threatening near-Earth object (NEO) by 6 m/s. Included in the analysis are high explosive, high speed projectiles, nuclear explosives and their radiations, high intensi...

When a single-pulse high-power laser irradiates a surface at atmospheric pressure, a laser supported detonation (LSD) wave can form above the target surface. The high-pressure gas behind the LSD wave transfers momentum to the target. The laser target coupling is substantially reduced in vacuum, the coupling coefficient typically being an order of m...

We have developed an innovative method using radiation produced by in flight annihilation of energetic positrons to detect hidden explosives and other illegal substances. The system uses either radioisotope or compact accelerator based methods to generate a high energy positron beam. The high energy positrons annihilate in flight producing a tunabl...

Shock waves generated on eight meteorite and two Al targets by 5.4–5.6 J, 20-ns pulsed Nd:glass laser at 1054 nm generated peak pressures from 0.7 to 11 Gpa. The shock-induced particle velocities in the targets versus time was measured interferometrically. The target momentum coupling and mechanical momentum/energy coupling was highest for th...

Most literature on the effect of near earth object (NEO) impacts on our planet has focused on extinction-level events of the sort that apparently ended the Cretaceous era 65 million years ago, and that are likely to recur on the order of tens of millions ofyears[l]. However, subcritical events will occur with much greater frequency that may cause m...

This paper analyzes laser induced impulse and associated scaling laws appropriate to the intensity range of interest for laser space debris clearing (106 - 1010 W/cm2). A simple radiative fluence model is used augmented by empirical values from some recent experiments.

Critical and Sub-critical cosmic impact (CCI and SCI) hazard mitigation options for near-Earth objects (NEOs) are outlined in terms of the cost effectiveness for long-term surveillance, reconnaissance and mitigation. A simple computation of "Cosmic Insurance" based solely on lost worker productivity is presented, which serves as a starting point to...

Comparative displacement measurements are made using laser diode (LD) and light emitting diode sources, fiber optic collimators, and a dual-photodiode detector (DPD). It is shown that a relative displacement resolution <2 nm is possible with the LD source. This result is interpreted to indicate that the coherent LD sources illuminating the DPD temp...

A measured displacement resolution of <3 nm is demonstrated with a common cathode differential photodetector combined with a laser-diode optical source and a fiber-optic collimator. Resolution, standard deviation, and differences between maxima and minima values for the residuals of the least-squares fit suggest that a coherent laser-diode source t...

A comet model is derived based on the interstellar dust chemical composition in dense molecular and diffuse clouds resulting from their subsequent chemical interactions and UV photoprocessing. The collapsing presolar nebula leads to a porous aggregate model for comet nuclei, from which is derived certain physical properties that include thermal con...

Milestones in the historical development of NEO studies are briefly outlined.

his paper describes experimental approaches to determine how the micro-structure of near-Earth objects (NEOs), responds to high pressure and loading conditions. Meteorites are used as analog materials and are illuminated by high-energy lasers or x-rays to bring them to the required conditions.

: The technologies required to detect, track, categorize, and intercept objects in Earth-impacting orbits can also provide access to their rich storehouse of materials. Mitigation of a clear and present near-Earth object (NEO) threat to the Earth must provide the greatest assurance of success with the least risk to the planet. In some cases, mining...

Mining the potentially vast storehouse of natural resources contained within near-Earth objects (NEOs) could assist mitigation of the danger that a threatening object presents to life on Earth. Properly planned, NEO mining could provide a substantial basis for the exploration and development of space, in addition to providing important tools and op...

Category 0 NEO bodies, such as many comets, appear to be comprised largely of porous ice. Quasi-static and dynamic properties of ice are expected to control the corresponding properties of Category 0 NEO material. These properties depend on temperature, strain rate, and possibly sample history. Corrections must be made of porosity and the presence...

: An analysis identifying opportunities for extending space propulsion capabilities to ranges around 1 AU from the Earth is presented to suggest an effective and practical response to critical interaction missions to Near Earth Objects (NEOs). Consideration is focused on timely interception of NEOs approaching Earth well beyond cislunar range durin...

We considered the coupling of momentum to near-Earth objects (NEO's) for the purposes of collision avoidance or collision damage mitigation through trajectory modification. The momentum sources considered were pulsed lasers, kinetic energy impactors, and nuclear (or conventional) explosives, detonated above or below the surface of the NEO by the no...

The advent of MJ class lasers such a the NIF and the LMJ will provide the scientific community with an important tool to study matter under extreme conditions of pressure and temperature as well as X-ray and neutron irradiation. Specifically, in conjunction with hohlraum targets, it should become possible to study the equations of state, and opacit...

The topics presented in this volume can be thought of as a continuation of those contained within the foundation volume, Hazards Due to Comets and Asteroids, which summarizes most of the preceding work in NEO's and serves as the ideal starting place for those seriously interested in NEO studies.

The topics presented in this volume can be thought of as a continuation of those contained within the foundation volume, Hazards Due to Comets and Asteroids, which summarizes most of the preceding work in NEO's and serves as the ideal starting place for those seriously interested in NEO studies.

An analysis identifying opportunities for extending space propulsion capabilities to ranges around 1 AU from the Earth is presented to suggest an effective and practical response to critical scientific, mitigation, and commercial missions to near-Earth objects (NEOs). The approach developed, which is based on previous studies of flight in field-fre...

Sensitivities, displacement range, and accuracy of two types of optical vibration sensors, one fiber optic with a light- emitting diode source (LED/FO) and the other with a laser diode source and small (approximately 1 mm) optics (LD/SO) were designed, assembled, tested, and compared. For the configurations adopted, sensitivity of the LED/FO with a...

This Viewpoint, arising from a UN conference on the subject, proposes policies to increase awareness of the (small but serious) threat from near-Earth objects (NEOs) and to provide guidelines for cooperative observation, research and — if necessary — mitigation programmes. They include extending the Outer Space Treaty to take in NEOs and creating a...

We describe methods for measuring dynamical properties for two material categories of interest in understanding large-scale extraterrestrial impacts: iron-nickel and underdense materials (e.g. snow). Particular material properties measured by the present methods include Hugoniot, release paths and constitutive properties (stress vs. strain). The ir...

Computational aspects of aperture-integration limits, completeness, normality, biorthogonality, singularities, the Fresnel number, and perturbations are discussed in terms of the non-Hermitian integral operator and its relation to transverse-mode scattering at open (cavity) resonator reflective elements.

This paper investigates one of several possible means of deflection of a large near-Earth object (NEO) on a potential collision course with Earth by means of modest velocity changes (ΔV ≈ 1–200 cm/s) applied to the NEO at perihelion. Given the present uncertainty in the geometry, topography and materials properties of the asteroids and/or comets, a...

Semiconductor laser diode (LD) coherent light source coupling is critical to integrated optic (IO) performance. Direct external coupling of conventional (CD layer) LDs is often inefficient, introduces noise, and is generally counter to the IO micro-concept. Two options are suggested; fiber optic coupling to the IO chip aperture and integration (hyb...

Adaptive and active optics in general, and laser power beaming in particular, requires the construction of large, complex mirror systems. Since these mirrors need to be tested with high accuracy to achieve optimum performance, their unusual shape and size often require the construction of special testing equipment. A full-surface interferometric sc...

Adaptive optics (AO) segmented array systems require los cost nm (piston) and (mu) rad (tilt) range displacement edge sensors to assist in establishing phase continuity between adjacent segments by measuring relative AO edge displacements. Preliminary laboratory experiments using Si based integrated optic (IO) chips coupled to laser diode sources w...

Momentum coupling methods are analyzed for near-Earth object (NEO) orbit modification that can use either conventional explosives (HE) or nuclear explosives (NE) effectively. Enhancing momentum coupling reduces the explosive yield needed to achieve a particular orbital alteration, which, in turn, reduces the number of launch vehicles needed while a...

The need for a number of interferometric sensor systems during fabrication, assembly and operation of large segmented array mirrors, is discussed. Specifically, an interferometric approach is described for calibrating edge sensors and actuators, and aligning the segments during mirror assembly.

An analytical study of laser diode (LD) operation coupled to external cavity scattering elements, which function as variably coupling reflectors (VCRs), is carried out with the purpose of determining the interrelationship between cavity coupling and intracavity optical intensity which determine the current generated at the rear facet PIN detector....

Experimental results are presented from a series of hypervelocity impact tests on simulated comet and asteroid materials for the purpose of characterizing their response to hypervelocity kinetic energy impacts. Nine tests were conducted at the Air Force Arnold Engineering Development Center (AEDC) S1 Range Facility on ice, rock, and iron target sam...

A suite of dynamic propertymeasurements and characterization studies on an iron‐nickel single crystal from the Henbury octahedrite containing Widmanstätten intergrowths of kamacite and taenite (initial density 7.810) has been performed. These measurements include six impact tests(wave profile compression/release) over the stress range 2–20 GPa, met...

Several new applications of excimer lasers in industry and medicine have increased the requirements for control of excimer laser beam parameters. Some applications require precise control of spatial uniformity, pulse-to-pulse amplitude variations and temporal profiles. The spatial and temporal characteristics of excimer laser beams are affected by...

A suite of dynamic property measurements and characterization studies on an iron-nickel single crystal from the Henbury octahedrite containing Widmanstaetten intergrowths of kamacite and taenite (initial density 7.810) has been performed. These measurements include six impact tests (wave profile compression/release) over the stress range 2-20 GPa,...

The objective of the Phase-II research was to design, construct and test a prototype interferometer system (FSIS) for the purpose of testing cylindrical-like mirrors such as those used in grazing incidence X-ray imaging applications. Existing instruments are based on a shearing interferometry, dual laser beam scanning approach, measuring the slope...

Diffraction-scattering calculations for perturbed optical cavity resonators and their relation to optical cavity decay-time measurements are discussed.

A method is described to compute the effect of semiconductor laser facet aberrations and perturbations on threshold current and internal efficiency.

This contract demonstrated the proof-of-principle of the Full Surface Interferometric Scanner (FSIS), an instrument which can rapidly and reliably measure both the full surface figure as well as the macroroughness of grazing incidence optics. The FSIS has the potential to fill the need of SDIO to characterize and qualify the necessary off-axis asph...

© 1986 Optical Society of America