Comments on the commercialization of expendable launch vehicles

The President's national space policy encourages private sector investment and involvement in civil space activities. Last November, the President designated the Department of Transportation as lead agency for the commercialization of expendable launch vehicles. This presents a substantial challenge to the United States Government, since the guidelines and requirements that are set now will have great influence on whether American firms can become a viable competitive industry in the world launch market. There is a dual need to protect public safety and free the private sector launch industry from needless regulatory barriers so that it can grow and prosper

Theoretical Transmission Spectra During Extrasolar Giant Planet Transits

The recent transit observation of HD 209458 b - an extrasolar planet orbiting a sun-like star - confirmed that it is a gas giant and determined that its orbital inclination is 85 degrees. This inclination makes possible investigations of the planet atmosphere. In this paper we discuss the planet transmission spectra during a transit. The basic tenet of the method is that the planet atmosphere absorption features will be superimposed on the stellar flux as the stellar flux passes through the planet atmosphere above the limb. The ratio of the planet's transparent atmosphere area to the star area is small, approximately 10^{-3} to 10^{-4}; for this method to work very strong planet spectral features are necessary. We use our models of close-in extrasolar giant planets to estimate promising absorption signatures: the alkali metal lines, in particular the Na I and K I resonance doublets, and the He I $2^3S$ - $2^3P$ triplet line at 1083.0 nm. If successful, observations will constrain the line-of-sight temperature, pressure, and density. The most important point is that observations will constrain the cloud depth, which in turn will distinguish between different atmosphere models. We also discuss the potential of this method for EGPs at different orbital distances and orbiting non-solar-type stars.Comment: revised to agree with accepted paper, ApJ, in press. 12 page

The Size Distribution of Trans-Neptunian Bodies

[Condensed] We search 0.02 deg^2 for trans-Neptunian objects (TNOs) with m<=29.2 (diameter ~15 km) using the ACS on HST. Three new objects are discovered, roughly 25 times fewer than expected from extrapolation of the differential sky density Sigma(m) of brighter objects. The ACS and other recent TNO surveys show departures from a power law size distribution. Division of the TNO sample into ``classical Kuiper belt'' (CKB) and ``Excited'' samples reveals that Sigma(m) differs for the two populations at 96% confidence. A double power law adequately fits all data. Implications include: The total mass of the CKB is ~0.010 M_Earth, only a few times Pluto's mass, and is predominately in the form of ~100 km bodies. The mass of Excited objects is perhaps a few times larger. The Excited class has a shallower bright-end size distribution; the largest objects, including Pluto, comprise tens of percent of the total mass whereas the largest CKBOs are only ~2% of its mass. The predicted mass of the largest Excited body is close to the Pluto mass; the largest CKBO is ~60 times less massive. The deficit of small TNOs occurs for sizes subject to disruption by present-day collisions, suggesting extensive depletion by collisions. Both accretion and erosion appearing to have proceeded to more advanced stages in the Excited class than the CKB. The absence of distant TNOs implies that any distant (60 AU) population must have less than the CKB mass in the form of objects 40 km or larger. The CKB population is sparser than theoretical estimates of the required precursor population for short period comets, but the Excited population could be a viable precursor population.Comment: Revised version accepted to the Astronomical Journal. Numerical results are very slightly revised. Implications for the origins of short-period comets are substantially revised, and tedious material on statistical tests has been collected into a new Appendi

De-biased Populations of Kuiper Belt Objects from the Deep Ecliptic Survey

The Deep Ecliptic Survey (DES) discovered hundreds of Kuiper Belt objects from 1998-2005. Follow-up observations yielded 304 objects with good dynamical classifications (Classical, Scattered, Centaur, or 16 mean-motion resonances with Neptune). The DES search fields are well documented, enabling us to calculate the probability of detecting objects with particular orbital parameters and absolute magnitudes at a randomized point in each orbit. Grouping objects together by dynamical class leads, we estimate the orbital element distributions (a, e, i) for the largest three classes (Classical, 3:2, and Scattered) using maximum likelihood. Using H-magnitude as a proxy for the object size, we fit a power law to the number of objects for 8 classes with at least 5 detected members (246 objects). The best Classical slope is alpha=1.02+/-0.01 (observed from 5<=H<=7.2). Six dynamical classes (Scattered plus 5 resonances) are consistent in slope with the Classicals, though the absolute number of objects is scaled. The exception to the power law relation are the Centaurs (non-resonant with perihelia closer than Neptune, and thus detectable at smaller sizes), with alpha=0.42+/-0.02 (7.5<H<11). This is consistent with a knee in the H-distribution around H=7.2 as reported elsewhere (Bernstein et al. 2004, Fraser et al. 2014). Based on the Classical-derived magnitude distribution, the total number of objects (H<=7) in each class are: Classical (2100+/-300 objects), Scattered (2800+/-400), 3:2 (570+/-80), 2:1 (400+/-50), 5:2 (270+/-40), 7:4 (69+/-9), 5:3 (60+/-8). The independent estimate for the number of Centaurs in the same H range is 13+/-5. If instead all objects are divided by inclination into "Hot" and "Cold" populations, following Fraser et al. (2014), we find that alphaHot=0.90+/-0.02, while alphaCold=1.32+/-0.02, in good agreement with that work.Comment: 26 pages emulateapj, 6 figures, 5 tables, accepted by A

Do Proto-Jovian Planets Drive Outflows?

We discuss the possibility that gaseous giant planets drive strong outflows during early phases of their formation. We consider the range of parameters appropriate for magneto-centrifugally driven stellar and disk outflow models and find that if the proto-Jovian planet or accretion disk had a magnetic field of >~ 10 Gauss and moderate mass inflow rates through the disk of less than 10^-7 M_J/yr that it is possible to drive an outflow. Estimates based both on scaling from empirical laws observed in proto-stellar outflows and the magneto-centrigugal disk and stellar+disk wind models suggest that winds with mass outflow rates of 10^-8 M_J/yr and velocities of order ~ 20 km/s could be driven from proto-Jovian planets. Prospects for detection and some implications for the formation of the solar system are briefly discussed.Comment: AAS Latex, accepted for Ap

Constraining the Physical Properties of Near-Earth Object 2009 BD

We report on Spitzer Space Telescope IRAC observations of near-Earth object (NEO) 2009 BD that were carried out in support of the NASA Asteroid Robotic Retrieval Mission (ARRM) concept. We did not detect 2009 BD in 25 hrs of integration at 4.5 micron. Based on an upper-limit flux density determination from our data, we present a probabilistic derivation of the physical properties of this object. The analysis is based on the combination of a thermophysical model with an orbital model accounting for the non-gravitational forces acting upon the body. We find two physically possible solutions. The first solution shows 2009 BD as a 2.9+/-0.3 m diameter rocky body (rho = 2.9+/-0.5 g cm-3) with an extremely high albedo of 0.85(+0.20/-0.10) that is covered with regolith-like material, causing it to exhibit a low thermal inertia (Gamma = 30(+20/-10) SI units). The second solution suggests 2009 BD to be a 4+/-1 m diameter asteroid with pV = 0.45(+0.35/-0.15) that consists of a collection of individual bare rock slabs (Gamma = 2000+/-1000 SI units, rho = 1.7(+0.7/-0.4) g cm-3). We are unable to rule out either solution based on physical reasoning. 2009 BD is the smallest asteroid for which physical properties have been constrained, in this case using an indirect method and based on a detection limit, providing unique information on the physical properties of objects in the size range smaller than 10 m.Comment: 28 pages, 8 figures, accepted for publication in Ap

Optical Guidance System /OGS/ for rendezvous and docking Final report

Optical guidance system for Apollo rendezvous and dockin