Presentation #305.02 in the session “The Hill Sphere, Trojans, Horseshoe Orbits, and Resonances”.
Given their small sizes, some defunct artificial satellites undergo rapid YORP-driven spin rate changes. Also, defunct satellite spin states are quite diverse with fast and slow uniform rotators as well as tumblers. These satellites are often bright and easily observed with ground-based telescopes. Taken together, these factors make earth orbit a useful laboratory for studying small body rotational dynamics on short timescales. This is valuable for gaining insights about potential behavior of natural small bodies which evolve more slowly and are much harder to observe. As an example, Benson and Scheeres (2020) previously showed that the angular momentum sun-tracking behavior and tumbling cycles initially studied for defunct satellites may affect meter-sized asteroids as well, with potential implications for Yarkovsky drift rates. For defunct satellites themselves, better understanding and prediction of spin states will aid active debris removal and satellite servicing as well as general space situational awareness. These efforts are necessary to control the growing space debris population. Radar and photometric light curve observations of the defunct geosynchronous (GEO) weather satellite GOES 8 collected in 2018 and 2020 show strong evidence for capture in a tumbling resonance. In such resonances, the satellite’s two fundamental tumbling periods are commensurate and its attitude periodically repeats. Full YORP dynamics simulations for GOES 8 show frequent capture in such resonances. In spite of this, YORP-driven resonance capture mechanisms are not understood. The periodicity of resonant tumbling makes it potentially advantageous for debris removal and servicing operations that must grapple and de-spin these uncontrolled objects. Very little work has been done on resonant tumbling, limited to a brief study for cometary outgassing by Neishtadt et al. (2002). Here, we develop a resonance-averaged model that complements the general tumbling-averaged model presented in Benson and Scheeres (2021). The fast model allows for rapid exploration of YORP-driven dynamics in the vicinity of tumbling resonances. This allows us to determine probabilities of capture into tumbling resonances, estimate capture durations, and investigate the strength of different resonances. While studied here for defunct satellite YORP, this resonance-averaged model can be easily applied to asteroid YORP and comet outgassing. Benson, C. J., Scheeres, D. J., YORP-Driven Spin State Evolution of Meter-Sized Asteroids, AAS Division on Dynamical Astronomy Meeting 51, 2020. Neishtadt, A. I., Scheeres, D. J., Sidorenko, V. V., and Vasiliev, A. A., Evolution of Comet Nucleus Rotation, Icarus, Vol. 157, 2002, pp. 205-218. https://doi.org/10.1006/icar.2002.6829 Benson, C. J., Scheeres, D. J., Averaged Solar Torque Rotational Dynamics for Defunct Satellites, Journal of Guidance, Control, and Dynamics, available online March 4, 2021. https://doi.org/10.2514/1.G005449