Attitude Control of High Area-to-mass Ratio (HAMR) Spacecrafts Considering the Eclipse by the Earth

High area-to-mass ratio (HAMR) spacecrafts are sensitive to spatial perturbations. For an HAMR spacecraft in geosynchronous orbit (GEO), solar radiation pressure (SRP) torque and gravity gradient torque have a significant effect on the attitude dynamics. During vernal and autumnal equinox, an HAMR spacecraft in GEO will experience the eclipse by the earth and pass umbra and penumbra when it's in the earth shadow. In penumbra, the sunlight intensity varies with position and SRP-gradient torque is produced. In umbra, the sunlight intensity is zero and SRP torque vanishes. Disturbing torques during the eclipse are different from that in full-light area which needs to be considered in the design of attitude control scheme. In this paper, the SRP torque including SRP-gradient torque and uniform SRP torque during eclipse by the earth is derived. The attitude dynamics of an HAMR spacecraft are modeled according to which the attitude control scheme against small disturbances is designed. Numerical simulations are presented to illustrate the effectiveness of the proposed scheme.