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.

Orbiting Carbon Observatory: Inverse method and prospective error analysis

Abstract: [1] The objective, design, and implementation of the OCO inverse method are presented The inverse method is the algorithm which finds the profile-weighted mean mixing ratio, XCO2, which best fits the measured spectrum, given a “forward model” which calculates the spectrum for a given atmospheric state, surface, and instrument properties Minimizing bias among comparative values of XCO2 is a critical objective The algorithm uses an “optimal,” maximum a posteriori inverse method, with weak a priori constraint, and employs a state vector containing atmospheric and surface properties expected to vary significantly between soundings An extensive operational characterization and error analysis will be employed, producing quantities designed to aid atmospheric modelers in use of the OCO data In particular, comparison to inverse models of surface CO2 flux will require use of the OCO column averaging kernel and a priori state vector An off-line error analysis has also been developed for more detailed error studies, and its use is illustrated by prospective application to case studies of nadir observations in summer and winter at three sites Uncertainties due to noise, geophysical variability, and spectroscopic parameters are considered in detail At low and midlatitudes, the single-sounding errors due to these sources are expected to be ∼07–08 ppm for high-sun conditions and ∼15–25 ppm for low sun (winter) Errors from the same sources in semimonthly regional averages are predicted to be <1 ppm for all conditions

Eddy dynamics from satellite altimetry

Abstract: Most of the kinetic energy of ocean circulation is contained in ubiquitous mesoscale eddies. Their prominent signatures in sea surface height have rendered satellite altimetry highly effective in observing global ocean eddies. Our knowledge of ocean eddy dynamics has grown by leaps and bounds since the advent of satellite altimetry in the early 1980s. A satellite's fast sampling allows a broad view of the global distribution of eddy variability and its spatial structures. Since the early 1990s, the combination of data available from two simultaneous flying altimeters has resulted in a time-series record of global maps of ocean eddies. Despite the moderate resolution, these maps provide an opportunity to study the temporal and spatial variability of the surface signatures of eddies at a level of detail previously unavailable. A global census of eddies has been constructed to assess their population, polarity, intensity, and nonlinearity. The velocity and pattern of eddy propagation, as well as eddy transports of heat and salt, have been mapped globally. For the first time, the cascade of eddy energy through various scales has been computed from observations, providing evidence for the theory of ocean turbulence. Notwithstanding the tremendous progress made using existing observations, their limited resolution has prevented study of variability at wavelengths shorter than 100 km, where important eddy processes take place, ranging from energy dissipation to mixing and transport of water properties that are critical to understanding the ocean's roles in Earth's climate. The technology of radar interferometry promises to allow wide-swath measurement of sea surface height at a resolution that will resolve eddy structures down to 10 km. This approach holds the potential to meet the challenge of extending the observations to submesoscales and to set a standard for future altimetric measurement of the ocean.

Radii and Effective Temperatures for G, K, and M Giants and Supergiants

Abstract: Interferometrically determined angular diameters obtained at the Palomar Testbed Interferometer (PTI) for 80 giant and supergiant stars are presented in this paper.

On the solution of algebraic equations over finite fields

Abstract: This article gives new fast methods for decoding certain error-correcting codes by solving certain algebraic equations. As described by Peterson (1961) , the locations of a Bose-Chaudhuri Hocquenghem code over a field of characteristic p are associated with the elements of an extension field, GF(pk). The code is designed in such a way that the weighted power-sum symmetric functions of the error locations can be obtained directly by computing appropriately chosen parity checks on the received word. Good methods for computing the elementary symmetric functions from the weighted power-sum symmetric functions have been presented by Berlekamp (1967) . The elementary symmetric functions, σ1, σ2, …, σt are the coefficients of an algebraic equation whose roots are the error locations x t + σ 1 x t − 1 + σ 2 x t − 1 + ⋯ + σ t = 0 Previous methods for finding the roots of this equation have searched all of the elements in GF(pk) ( Chien, 1964 ) or looked up the answer in a large table ( Polkinghorn, 1966 ). We present here improved procedures for extracting the roots of algebraic equations of small degrees.