Numerical simulation of the LAGEOS thermal behavior and thermal accelerations

Abstract

[1] The temperature distribution throughout the LAGEOS satellites is simulated numerically with the objective to determine the resulting thermal force. The different elements and materials comprising the spacecraft, with their energy transfer, have been modeled with unprecedented detail. The radiation inputs on the satellites are direct solar (eclipse modulated), Earth albedo, and Earth infrared radiations. For each satellite the lifetime temperature (behavior) of 2133 nodes is computed. On the basis of this distribution, individual forces and the net instantaneous accelerations are obtained. Simulations yield typical temperature variations ranging between 30 and 100 K for different elements and materials, whereas the net instantaneous accelerations are on the order of 70 pm s À2 , in good agreement with previous results. Simulations also show the importance of the consideration of a proper orientation of the satellite: LOSSAM yields acceleration differences of up to three times the acceleration obtained with a constant spin axis orientation. The temperature of the four germanium retroreflectors deviates up to 70 and 100 K with respect to their silica counterparts for LAGEOS I and II, respectively. This generates thermal acceleration differences of several pm s À2 , up to 25% of the postulated difference in reflectivity between hemispheres. Two factors play a major role: the spin rate and the Sun aspect angle with respect to the spin axis. On the basis of the latter, two characteristic periods can be distinguished: a rapid spin, slow drift period (until 13 and 8 years after launch for LAGEOS I and II, respectively) and a slow spin, rapid wobbling afterward. The acceleration results will be used in a refined orbit computation in a subsequent investigation.

The LAGEOS satellites orbital residuals determination and the way to extract gravitational and non-gravitational unmodeled perturbing effects

“…However, in Lucchesi (2002), was estimated an amplitude of about 100 pm/s 2 for the effect if the fit is performed taking into account other perturbations with a similar signature. Such result is in agreement with the theoretical study of Slabinski (1997) and with the more recent study of Andrés et al (2006)). Indeed, it is enough a 1% mismodeling of the satellite radiation coefficient, i.e., of the SRP, to drop the amplitude of the Yarkovsky-Schach effect from 193 to %100 pm/s 2 .…”

History of the attempts to measure orbital frame-dragging with artificial satellites

“…(1)), while the even zonal perigee perturbations are identical [54] and cancel out. [68,69,72,[78][79][80][81][82][83][84][85][86][87][88][89][90][91][92]. Iorio and Lucchesi [76] used the covariance matrix of the EGM96 gravity model [93] up to = 20 and a pair of hypothetical satellites S1/S2 with = 12000 km, S1 = 63 4…”

NEUTRINO ASTROPHYSICS AND GALACTIC COSMIC RAY ANISOTROPY IN IceCube

“…to the energy of the physics events. Due to the antarctic glaciological history, the optical properties depend on depth and they have been measured in the past using AMANDA in-situ calibration lasers [8], in the depth range between 1,400 m and 2,000 m. The optical properties down to 2,450 m, the depth of IceCube instrumentation, are extrapolated from ice core observations in other location of the antarctic continent, and a new campaign of extended in-situ measurements is currently being carried out.…”