Earth's Flux Research Articles

Frontier of Understanding Earth's Dynamics

Frontier of Understanding Earth's Dynamics

External thermal modeling satellite platform «Synergy»

In order to conduct thermal research of the satellite platform «Synergy», a mathematical model has been developed for calculating external thermal loads for spacecraft of the CubeSat form factor, operating in various orientation modes in near-Earth circular orbits. When modeling thermal conditions, heat fluxes from the Sun, the earth's flux and atmospheric effects are taken into account. A feature of the model is the transition to a moving geocentric coordinate system for determining the density of heat fluxes of direct and reflected solar radiation. The study of thermal conditions in the process of orbital motion is carried out and the parameters of the position of the orbital plane and the parameters of the Sun are determined at which the maximum and minimum average integral thermal loads are achieved during the orbital period. In these orbits, the motion of the satellite platform was simulated in three typical orientation modes and the density values of the absorbed heat fluxes by its external elements were determined. Four options for the design of the housing are being investigated. The data obtained during the simulation were used for the initial stationary calculation of the temperature field of the satellite platform in the ANSYS software package. The most interesting cases from the point of view of the thermal regime for further thermal research have been identified.

HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: DEPENDENCE ON PLANETARY MASS

The ongoing discoveries of extrasolar planets are unveiling a wide range of terrestrial mass (size) planets around their host stars. In this letter, we present estimates of habitable zones (HZs) around stars with stellar effective temperatures in the range 2600 K - 7200 K, for planetary masses between 0.1 ME and 5 ME. Assuming H2O (inner HZ) and CO2 (outer HZ) dominated atmospheres, and scaling the background N2 atmospheric pressure with the radius of the planet, our results indicate that larger planets have wider HZs than do smaller ones. Specifically, with the assumption that smaller planets will have less dense atmospheres, the inner edge of the HZ (runaway greenhouse limit) moves outward (~10% lower than Earth flux) for low mass planets due to larger greenhouse effect arising from the increased H2O column depth. For larger planets, the H2O column depth is smaller, and higher temperatures are needed before water vapor completely dominates the outgoing longwave radiation. Hence the inner edge moves inward (7% higher than Earth's flux). The outer HZ changes little due to the competing effects of the greenhouse effect and an increase in albedo. New, 3-D climate model results from other groups are also summarized, and we argue that further, independent studies are needed to verify their predictions. Combined with our previous work, the results presented here provide refined estimates of HZs around main-sequence stars and provide a step towards a more comprehensive analysis of HZs.

Proposed lunar heat flow measurement from a polar orbiting satellite

Measurements of lunar heat flow are of scientific value in the determination of the thermal history of the moon and as a boundary condition on theories of its origin and internal structure [NASA, 1965, p. 164]. Unfortunately, because of the geographic limitations of the manned lunar landings and the engineering problems both of drilling holes in the lunar crust and of performing the thermal measurements, the accepted terrestrial method for determining internal heat flow would be difficult to use on the moon. Infrared detectors in orbiting space vehicles can provide regional geographic coverage of the lunar surface emission, but the high ratio of the solar flux to the probable internal flux (greater than 104) makes it improbable that the internal flux can be accurately measured. Even during the lunar night the surface emission flux is greater than 102 times the probable internal flux and is much more sensitive to slight variations in emissivity and thermal conductivity. In areas of permanent shade (near the poles, hidden from the sun's and the earth's flux), however, there is no perturbing external flux, and the internal heat flow could be measured. The surface flux in these areas is due to the moon's internal heat flow and lateral conduction from adjacent areas. At the center of an area of permanent shade, the percentage of surface flux contributed by lateral conduction will decrease as the effective radius of the area increases. Infrared mapping of the polar regions should provide enough information to determine the thermal emission at the center of a permanently shaded area as a function of radius, and hence provide an extrapolation to a limiting radius at which the central surface emission is almost independent of radius. This central surface emission will be independent of lateral conduction and thus will represent the internal lunar heat flow. Thermal mapping of a large permanently shaded area may show a region near the center where the horizontal gradient in flux at the surface is negligible. If this condition exists, no extrapolation would be necessary since the surface flux at the center would be due solely to the internal heat flow.