Issues of geologically-focused situational awareness in robotic planetary missions: Lessons from an analogue mission at Mistastin Lake impact structure,Labrador, Canada

Remote robotic data provides different information than that obtained from immersion in the field. This significantly affects the geological situational awareness experienced by members of a mission control science team. In order to optimize science return from planetary robotic missions, these limitations must be understood and their effects mitigated to fully leverage the field experience of scientists at mission control.     

Highlights of a Brushless Direct-Drive Solar Array Control System Design

This paper summarizes a drive system design for controlling the position and rate of solar power arrays on orbiting spacecraft. There are no gears or sliding contact elements used anywhere in the system and only low-speed bearings are needed. Such mechanization is particularly well suited to solid lubrication techniques, and wear rates are very low, so that the drive system can operate directly in the space environment for long periods of time. Three major components were developed for implementation of this design concept. They are: 1) a brushless dc torque motor; 2) a rotary power transformer; and 3) an offset-tooth shaft position and rate sensor. These components are combined in a hybrid system configuration in which the signal processing and logic functions are performed by digital and linear integrated circuits. A root contour and describing function analysis, confirmed by experimentation, shows that several modes of limit cycle generation can occur in the vicinity of null. Compensation circuits are given that inhibit or suppress limit cycling and provide controlled electronic damping of the system. The system offers relatively high stiffness and can be operated at indefinitely low angular rates with minimum power consumption.