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Paper: Relativistic Stellar Aberration Requirements for the Space Interferometry Mission
Volume: 194, Working on the Fringe: Optical and IR Interferometry from Ground and Space
Page: 142
Authors: Turyshev, S. G.
Abstract: We summarize here results of our recent study on the issue of the relativistic stellar aberration requirements for the Space Interferometry Mission (SIM). In particular, we have estimated the astrometric errors introduced by imperfect metrology, inaccurate baseline length estimations, and those due to relativistic orbital motion of the spacecraft. We have shown that motion of the spacecraft in the direction perpendicular to a tile provides the most stringent requirement on the accuracy of knowledge of the barycentric velocity of the spacecraft. Thus the maximum error in the knowledge of velocity's magnitude was justified at the level of sigmav = 3.9 mm/s. What are the main factors that will affect the accuracy of navigation? First, we consider the impact of the solar system's gravity on both dynamics of the spacecraft and future astrometric observations. We have found that the most driving constraint on the spacecraft's navigation is that imposed by the barycentric motion of the observatory and not by the relativistic deflection of light. Second, we have estimated the magnitudes of non-gravitational forces acting on the spacecraft. In particular, we consider five sources of non-gravitational accelerations: (i) solar radiation and (ii) solar wind pressure, (iii) emitted radio power, (iv) anisotropic thermal radiation of the spacecraft, and (v) attitude motions. We evaluated these perturbing forces and show that their contribution, besides the solar radiation pressure, to the measurement error is negligible. We discuss proposals that may minimize the impact of the solar radiation pressure and, therefore, improve the overall navigation accuracy.
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