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.

High Resolution Atmospheric Inversion of Urban CO2 Emissions During the Dormant Season of the Indianapolis Flux Experiment (INFLUX)

Abstract: Based on a uniquely dense network of surface towers measuring continuously the atmospheric concentrations of greenhouse gases (GHGs), we developed the first comprehensive monitoring systems of CO2 emissions at high resolution over the city of Indianapolis. The urban inversion evaluated over the 2012-2013 dormant season showed a statistically significant increase of about 20% (from 4.5 to 5.7 MtC ± 0.23 MtC) compared to the Hestia CO2 emission estimate, a state-of-the-art building-level emission product. Spatial structures in prior emission errors, mostly undetermined, appeared to affect the spatial pattern in the inverse solution and the total carbon budget over the entire area by up to 15%, while the inverse solution remains fairly insensitive to the CO2 boundary inflow and to the different prior emissions (i.e., ODIAC). Preceding the surface emission optimization, we improved the atmospheric simulations using a meteorological data assimilation system also informing our Bayesian inversion system through updated observations error variances. Finally, we estimated the uncertainties associated with undetermined parameters using an ensemble of inversions. The total CO2 emissions based on the ensemble mean and quartiles (5.26-5.91 MtC) were statistically different compared to the prior total emissions (4.1 to 4.5 MtC). Considering the relatively small sensitivity to the different parameters, we conclude that atmospheric inversions are potentially able to constrain the carbon budget of the city, assuming sufficient data to measure the inflow of GHG over the city, but additional information on prior emission error structures are required to determine the spatial structures of urban emissions at high resolution.

VLA observations of a complete sample of core-dominated radio sources

Abstract: Maps with high dynamic range are presented of a well-defined sample of powerful core-dominated radio sources, all of which have 5-GHz core flux densities >1 Jy. The maps were made at a frequency of 1.64 GHz from combined VLA and B configuration data. A novel technique for producing high dynamic range maps of variable sources from data taken at different epochs is described. It is found that, on average, BL Lac objects are not more core-dominated than the quasars in the sample. This provides no support for the view that BL Lacs are those quasars seen at such small angles to the line of sight that their relativistically beamed core emission swamps that from other components. The results are consistent with most BL Lac objects being the beamed cores of low-luminosity (FRI) radio galaxies

A Measurement of Omega from the North American Test Flight of Boomerang.

Abstract: We use the angular power spectrum of the cosmic microwave background, measured during the North American test flight of the Boomerang experiment, to constrain the geometry of the universe. Within the class of cold dark matter models, we find that the overall fractional energy density of the universe Ω is constrained to be 0.85 ≤ Ω ≤ 1.25 at the 68% confidence level. Combined with the COBE measurement, the data on degree scales from the Microwave Anisotropy Telescope in Chile, and the high-redshift supernovae data, we obtain new constraints on the fractional matter density and the cosmological constant.

Microbiology of the dry valleys of antarctica.

Abstract: The dry valleys of South Victoria Land, Antarctica, together with a few other ice-free areas on the perimeter of the Antarctic continent, form what is generally considered to be the most extreme cold-desert region of the earth. During the past S years, we have been interested in the dry valleys as a model environment for investigating questions connected with the biological exploration o£ Mars. The extraordinary aridity of the region, its low temperature, and its geographical isolation give it a quasimartian character, although it is to be understood that the actual martian environment is still more hostile than that of the valleys. With our associates, we have investigated the kinds, numbers, and distribution of soil microorganisms in the valleys in order to gain insight into the practical problems of searching for life in an extreme environment. Detailed results of these studies have been published by Cameron and co-workers (1-5). In this-article, we review the major findings of our own and of other groups of investigators in this region, especially as they apply to martian exploration.