Effects of atmospheric winds and aerodynamic lift on the inclination of the orbit of the S3-1 satellite

Abstract

Aerodynamic drag and lift effects on the inclination of the orbit of the S3‐1 satellite (1974‐85D) have been used to infer atmospheric zonal wind speeds at an altitude of 175 km and to estimate the satellite surface thermal accommodation coefficient. The unusually high quality of the orbital and attitude data permitted the 7‐month data span to be analyzed in six nonoverlapping subintervals, thereby resulting in finer local time and spatial resolution than is normally obtained in such studies. The aerodynamic lift force was found to be quite sensitive to the assumed value of the thermal accommodation coefficient, a quantity that is neither well known nor well understood. The inclination data were best fit (in a least squares sense) when the accommodation coefficient was greater than 0.95. Best agreement with theoretical models in terms of wind speed and direction was obtained when the accommodation coefficient was taken to be nearly 1.0. In this case the inferred wind was ∼400 m/s eastward at 1900–2100 LT and ∼200 m/s westward at 0700–0900 LT. The study indicates that if accurate zonal wind velocities are to be derived from satellite orbital inclination changes, care must be taken to ensure that the shape and orientation of the satellite are such that the lift forces generated are sufficiently small that the resulting uncertainty due to inadequate knowledge of the accommodation coefficient does not cause significant error.

Earth’s Energy Imbalance Measured From Space

“…However, for a circular orbit and a spherical satellite, the drag force is directed along the satellite's velocity vector or travel direction [54], respectively, hence acts orthogonal to the radial acceleration component. The associated lift effect at 1300 km is negligible [55][56] on spherical or near-spherical space crafts [57] and might not affect the direct measurement of EEI via the radial acceleration component either. Nevertheless, [58] [59] have noted that slight departures from perfect sphericity induce significant changes in drag effects.…”

Aerodynamic Analysis Based on Challenging Minisatellite Payload Satellite Lift-to-Drag Measurements

“…For QS reflection, the reflection velocity is chosen according to Eqs. (14) and (16). The accommodation coefficient is decided by the mass of the molecule, the molecular mass of the surface material, and the incidence angle.…”

“…Pilinski et al [15] provide a comprehensive summary of this work that indicates that satellite accommodation coefficients decrease with increased altitude and decreased solar activity. The first investigation of satellite aerodynamics based on drag-and-lift measurements was performed by Ching et al [16] by analyzing the semimajor axis and inclination changes caused by aerodynamic forces on the S3-1 satellite near 160 km altitudes. Accelerometers on the space shuttle orbiter later enabled studies of aerodynamics by measuring lift and drag between 60 and 190 km altitudes [17][18][19].…”

Gas-Surface Interactions in Low-Earth Orbit

“…Analyses [31,32] for two more paddlewheel satellites soon followed. As attitude control systems improved, paddlewheel satellites fell out of favor, so this source of information dried up; however Ching, et al [33] used the lift and drag of the S3-1 satellite to measure accommodation coefficients at a perigee altitude of 169 km in low-Earth orbit, and confirmed Beletsky's high value of accommodation coefficient below 200 km [32]. Imbro, et al [34] later analyzed more Ariel 2 data, and confirmed the analysis in [31].…”