Jet Propulsion Laboratory

About: Jet Propulsion Laboratory is a facility organization based out in La Cañada Flintridge, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Telescope. The organization has 8801 authors who have published 14333 publications receiving 548163 citations. The organization is also known as: JPL & NASA JPL.

Development of the Global Assimilative Ionospheric Model

Abstract: [1] This paper provides an overview of the development of the Global Assimilative Ionospheric Model (GAIM) by a team of investigators from the University of Southern California (USC) and the Jet Propulsion Laboratory (JPL) The USC/JPL GAIM utilizes data assimilation techniques, which are widely used in meteorological applications, for the purpose of monitoring and forecasting Earth's ionosphere We discuss the general structure of GAIM, which includes a first-principles model of the ionosphere, a series of auxiliary models for the driving forces, a data processing subsystem, and an optimization subsystem Two techniques for the estimation of electron density and driving forces in the ionosphere are presented: The four-dimensional variational method and the Kalman filter Some validation methods and results are also presented These results demonstrate the potential of GAIM in providing accurate specification of the ionosphere

Extension of square-root filtering to include process noise

Abstract: Two different square-root filters, one obtained by Potter and the other employing Householder transformations, are extended to include process noise. The relative numerical accuracy of various sequential filters is explored with several examples.

A Candidate Substellar Companion to CoD -33 7795 (TWA 5)

Abstract: We present the discovery of a candidate substellar object in a survey of young stars in the solar vicinity using the sensitivity and spatial resolution afforded by the NICMOS coronagraph on the Hubble Space Telescope. The H=12.1 mag object was discovered approximately 2 arcsec from the TW Hydrae Association member CoD -33 7795 (TWA 5), and the photometry implies a spectral type M8-M8.5, with a temperature of approximately 2600K. We estimate that the probability of a chance alignment with a background objectof this nature is < 2 X 10^(-5), and therefore postulate the object (TWA 5B) is physically associated at a projected separation of 100 AU. Given the likely youth of the primary (~ 10 Myr), current brown dwarf cooling models predict a mass of approximately 20 Jupiter masses for TWA 5B.

High-Redshift Extremely Red Objects in the Hubble Space Telescope Ultra Deep Field Revealed by the GOODS Infrared Array Camera Observations

Abstract: Using early data from the Infrared Array Camera (IRAC) on the Spitzer Space Telescope, taken for the Great Observatories Origins Deep Survey (GOODS), we identify and study objects that are well detected at 3.6 μm but are very faint (and in some cases, invisible) in the Hubble Ultra Deep Field (HUDF) ACS and NICMOS images and in very deep VLT Ks-band imaging. We select a sample of 17 objects with fν(3.6 μm)/fν(z850) > 20. The analysis of their spectral energy distributions (SEDs) from 0.4 to 8.0 μm shows that the majority of these objects cannot be satisfactorily explained without a well-evolved stellar population. We find that most of them can be well fitted by a simple two-component model, where the primary component represents a massive, old population that dominates the strong IR emission, while the secondary component represents a low-amplitude, on-going star formation process that accounts for the weak optical fluxes. Their estimated photometric redshifts (zp) range from 1.6 to 2.9 with the median at zp = 2.4. For the simple star formation histories considered here, their corresponding stellar masses range from (0.1-1.6)×1011 M☉ for a Chabrier initial mass function (IMF). Their median rest-frame Ks-band absolute magnitude is -22.9 mag in the AB system, or 1.5 × L*(K) for present-day elliptical galaxies. In the scenario of pure luminosity evolution, such objects may be direct progenitors for at least 14%-51% of the local population of early type galaxies. Because of the small cosmic volume of the HUDF, however, this simple estimate could be affected by other effects, such as cosmic variance and the strong clustering of massive galaxies. A full analysis of the entire GOODS area is now under way to assess such effects.

Kepler-7b: A Transiting Planet with Unusually Low Density

Abstract: We report the discovery and confirmation of Kepler-7b, a transiting planet with unusually low density. The mass is less than half that of Jupiter, Mp = 0.43 Mj, but the radius is fifty percent larger, Rp = 1.48 Rj. The resulting density, 0.17 g/cc, is the second lowest reported so far for an extrasolar planet. The orbital period is fairly long, P = 4.886 days, and the host star is not much hotter than the Sun, Teff = 6000 K. However, it is more massive and considerably larger than the sun, Mstar = 1.35 Msun and Rstar = 1.84 Rsun, and must be near the end of its life on the Main Sequence.