Longitude

About: Longitude is a research topic. Over the lifetime, 2260 publications have been published within this topic receiving 54988 citations. The topic is also known as: angle of longitude.

Luni-solar effects of geosynchronous orbits at the critical inclination

Abstract: The luni-solar effects of a geosynchronous artificial satellite orbiting near the critical inclination is investigated. To tackle this four-degrees-of-freedom problem, a preliminary exploration separately analyzing each harmonic formed by a combination of the satellite longitude of the node and the Moon longitude of the node is opportune. This study demonstrates that the dynamics induced by these harmonics does not show resonance phenomena. In a second approach, the number of degrees of freedom is halved by averaging the total Hamiltonian over the two non-resonant angular variables. A semi-numerical method can now be applied as was done when considering solely the inhomogeneity of the geopotential (see Delhaise et Henrard, 1992). Approximate surfaces of section are constructed in the plane of the inclination and argument of perigee. The main effects of the Sun and Moon attractions compared to the terrestrial attraction alone are a strong increase in the amplitude of libration in inclination (from 0.6° to 3.2°) and a decrease of the corresponding libration period (from the order of 200 years to the order of 20 years).

Longitudinal structures in Mars’ upper atmosphere as observed by MAVEN/NGIMS

Abstract: Here we report the first comprehensive study of longitudinal structures in Mars' neutral upper atmosphere associated with atmospheric tides in composition, density and temperature using the Mars Atmosphere and Volatile Evolution Mission/Neutral Gas Ion Mass Spectrometer observations during 2015. These are in situ measurements of number densities of atmospheric species (including CO2, Ar, N2, and CO) in the altitude range from 120 to 200 km above the areoid (corresponding to a total density range from ~108–1011 cm−3), providing a data set that is larger than all previous measurements of these waves combined. These observations span from ±70° latitude and cover a wide range of local times and solar longitudes (Ls), allowing for the study of longitudinal structures under various conditions. Furthermore, the data in May and November 2015 are at similar latitudes and local times but different Ls (~340° in May, close to northern spring equinox, and 70° in November, close to northern summer solstice and aphelion), ideal for studying the seasonal effects of tides. Our analysis shows that in each month the Ar density varies with longitude having a large wave structure. It is dominated by wave 2 and 3, accounting for 8–16% of the change of the mean density. Comparison shows that the longitudinal structures at a constant CO2 density level have different amplitudes at different seasons, although their patterns are similar. The temperature structure has a phase difference from the density variation, indicating the dissipation of tides in this altitude region. The longitudinal structure is seen in all species, including major and minor species, consistent with the tidal signatures.

Development of new solar exergy maps

Abstract: In this paper, we develop a solar exergy map concept and conduct a comprehensive case study to show how it is utilized and how it is significant for practical solar applications. Based on the exergy content of the solar radiation, the performance of a photovoltaic thermal (PV/T) system is evaluated for different Indian cities, namely Bangalore (latitude 12°58′N, longitude 77°38′E), Jodhpur (latitude 26°18′N, longitude 73°04′E), Mumbai (latitude 18°55′N, longitude 72°54′E), New Delhi (latitude 28°35′N, longitude 77°12′E) and Srinagar (latitude 34°08′N, longitude 74°51′E) for a year and for different cities of U.S.A., namely Chicago (latitude 41°50′N, longitude 87°37′W), Las Vegas (latitude 36°10′N, longitude 115°12′W), Miami (latitude 25°46′N, longitude 80°12′W), New York (latitude 40°47′N, longitude 73°58′E), Portland (latitude 43°40′N, longitude 70°15′W), San Antonio (latitude 29°23′N, longitude 98°33′W), San Francisco (latitude 37°47′N, longitude 122°26′W), Tucson (latitude 32°7′N, longitude 110°56′W) and Tulsa (latitude 36°09′N, longitude 95°59′W) for different months of January, April, June and October. For the first time, the development of exergy maps for the exergy of solar radiation as well as the exergy efficiency of PV/T system is done for the above-mentioned Indian and American climatic conditions. It is found that the predicted exergy efficiency is in good agreement with the experimental results for the climatic conditions of New Delhi, India. It is observed that the average exergy efficiency is highest in Bangalore from January (28%) to April (32.6%) and from September (32.5%) to December (32.4%) and it is highest in Srinagar from May (29.5%) to August (26.8%) for Indian climatic conditions and for American climatic conditions, the PV/T system gives the best performance in terms of exergy efficiency in Las Vegas (32%) and Tucson (32.5–31.5%) in April and June. Copyright © 2009 John Wiley & Sons, Ltd.

Comet 81P/Wild 2 size, shape, and orientation

Abstract: [1] Spectacular images, taken during the flyby of 81P/Wild 2 by the NASA Stardust spacecraft, were used to determine that the shape of the comet 81P/Wild 2 nucleus can be reasonably modeled as a triaxial ellipse having radii 1.65 × 2.00 × 2.75 km ± 0.05 km (1σ). The shortest axis, considered the rotational axis, has a right ascension of 110° and a declination of −13°. The longest axis, used to define zero longitude, has an argument of prime meridian angle of 155°. All angles use the IAU definitions, are relative to the Earth Mean Equator and Vernal Equinox of J2000 and have uncertainties of ±3° (1σ). The rotational axis was pointed 65° from the sun during the Stardust encounter of 81P/Wild 2, making an area within 25° of the spin axis in continual sunlight and the apparent source of a few major jets.