177,339 research outputs found
NICMOS Photometry of the Unusual Dwarf Planet Haumea and its Satellites
We present here Hubble Space Telescope NICMOS F110W and F160W observations of Haumea, and its two satellites Hi'iaka and Namaka. From the measured (F110W-F160W) colors of –1.208 ± 0.004, –1.48 ± 0.06, and –1.4 ± 0.2 mag for each object, respectively, we infer that the 1.6 μm water-ice absorption feature depths on Hi'iaka and Namaka are at least as deep as that of Haumea. The light curve of Haumea is detected in both filters, and we find that the infrared color is bluer by ~2%-3% at the phase of the red spot. These observations suggest that the satellites of Haumea were formed from the collision that produced the Haumea collisional family
The Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System: The Compositional Classes of the Kuiper Belt
We present the first results of the Hubble Wide Field Camera 3 Test of
Surfaces in the Outer Solar System (H/WTSOSS). The purpose of this survey was
to measure the surface properties of a large number of Kuiper belt objects and
attempt to infer compositional and dynamical correlations. We find that the
Centaurs and the low-perihelion scattered disk and resonant objects exhibit
virtually identical bifurcated optical colour distributions and make up two
well defined groups of object. Both groups have highly correlated optical and
NIR colours which are well described by a pair of two component mixture models
that have different red components, but share a common neutral component. The
small, high-perihelion excited objects are entirely
consistent with being drawn from the two branches of the mixing model
suggesting that the colour bifurcation of the Centaurs is apparent in all small
excited objects. On the other hand, objects larger than are
not consistent with the mixing model, suggesting some evolutionary process
avoided by the smaller objects. The existence of a bifurcation amongst all
excited populations argues that the two separate classes of object existed in
the primordial disk before the excited Kuiper belt was populated. The cold
classical objects exhibit a different type of surface which has colours that
are consistent with being drawn from the red branch of the mixing model, but
with much higher albedos.Comment: Accepted to the Astrophysical Journal. 49 Pages, 15 Figure
Computer program for analysis of split-Stirling-cycle cryogenic coolers
A computer program for predicting the detailed thermodynamic performance of split-Stirling-cycle refrigerators has been developed. The mathematical model includes the refrigerator cold head, free-displacer/regenerator, gas transfer line, and provision for modeling a mechanical or thermal compressor. To allow for dynamic processes (such as aerodynamic friction and heat transfer) temperature, pressure, and mass flow rate are varied by sub-dividing the refrigerator into an appropriate number of fluid and structural control volumes. Of special importance to modeling of cryogenic coolers is the inclusion of real gas properties, and allowance for variation of thermo-physical properties such as thermal conductivities, specific heats and viscosities, with temperature and/or pressure. The resulting model, therefore, comprehensively simulates the split-cycle cooler both spatially and temporally by reflecting the effects of dynamic processes and real material properties
Flight investigation to evaluate the roll-rate stabilization system of the Naval Ordnance Test Station Sidewinder missile at Mach numbers from 0.9 to 2.3
Four-dimensional worldwide atmospheric models: ANYPT and ANYRG
Computer programs read magnetic-tape data bases and computer meteorological profiles for any position, time, and height (from zero to 25 km). System assists in analyses of distortion of information obtained from aircraft-mounted or spacecraft-mounted electromagnetic sensors
Simulation of an automatically-controlled STOL aircraft in a microwave landing system multipath environment
The simulated response is described of a STOL aircraft to Microwave Landing System (MLS) multipath errors during final approach and touchdown. The MLS azimuth, elevation, and DME multipath errors were computed for a relatively severe multipath environment at Crissy Field California, utilizing an MLS multipath simulation at MIT Lincoln Laboratory. A NASA/Ames six-degree-of-freedom simulation of an automatically-controlled deHavilland C-8A STOL aircraft was used to determine the response to these errors. The results show that the aircraft response to all of the Crissy Field MLS multipath errors was small. The small MLS azimuth and elevation multipath errors did not result in any discernible aircraft motion, and the aircraft response to the relatively large (200-ft (61-m) peak) DME multipath was noticeable but small
Nonlinear phononic crystals based on chains of disks alternating with toroidal structures
We study experimentally the acoustic response of a load-bearing, phononic crystal composed of alternating steel disks, and polytetrafluoroethylene o-rings under precompression. The crystal allows for axial, rocking, and shear-polarized wavemodes when excited by a broad-band signal applied off-axis. Finite element analysis is employed to determine the system’s wave modes. The nonlinear interaction between disks and o-rings supports a dynamic response that is tunable with variations in static precompression, leading to controllable frequency shifts in a large band gap. A modal analysis reveals that four of the six principal wave modes are susceptible to external precompression while two modes are not
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