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5.2.2 Between SOM and Earth after Landing

On Europa's surface, the HGA gimbals so that it can follow the Earth across the sky. Because it can gimbal 80 \ensuremath{^\circ} from the longitudinal axis (the vertical axis as Asterius sits on Europa), the HGA can track the Earth as long as it is more than 10 degrees above the horizon. The high gimbaling angle maximizes the time that Asterius can be in contact with the Earth and DSN.

Currently, we think it may be possible to use axes of rotation similar to an Earth-based telescope. In this system, one of the axes is set parallel to the rotation axis of Europa. Then, the HGA can track the Earth across the sky using only one motor. We do not know if this would add significant mass.