Precision Miniature Attitude Determination and Control System

Goddard Space Flight Center, Greenbelt, Maryland

The MAI-400SS Space Sextant is a turnkey Attitude Determination And Control System (ADACS) for CubeSats and nanosatellites. It is an enhanced version of the MAI-400, which is a precision CubeSat ADACS incorporating three reaction wheels, three electromagnets, and an ADACS computer in a ½-U module. This Space Sextant version incorporates two star trackers to improve overall pointing knowledge to 0.02° or better. The star trackers feature “Lost In Space” attitude determination requiring no a priori information.

Maryland Aerospace, Inc. currently manufactures wheel and electromagnet systems (such as the MAI-100 and -200), and Star Trackers have previously been available. Prior to the introduction of the MAI-400SS, it was left to the user to integrate the two. In addition to the required development effort, the result of that approach was likely to be complicated and wasteful of size, weight, and power. In the MAI-400SS, the star cameras, wheels, and electromagnets are highly integrated, combining all attitude determination and control functions into a single, compact enclosure. With this advance, spacecraft developers only need a cursory knowledge of attitude control, freeing them to focus their efforts on the payload and science.

The MAI-400SS Space Sextant provides a turnkey ADACS system that facilitates the rapid development of low-cost CubeSat missions. This integrated ADACS module is designed to be compatible with the 10×10-cm CubeSat form factor so that it can be incorporated into any mission with a minimum of development and integration effort. Once on-orbit, the system autonomously assumes control of attitude functions with no intervention required from either the ground or the spacecraft. It is only necessary to provide power and pointing commands; the MAI-400SS Space Sextant determines attitude, commands the actuators, and the spacecraft assumes the desired attitude.

The MAI-400SS provides high-frequency attitude updates (4 Hz), even at high slew rates (up to 5° per second), using a solid-state MEMS gyro and Kalman filter. The system is designed to function with a high degree of autonomy and availability, and is simple to integrate mechanically and electrically into any standard CubeSat bus.

This work was done by Steve Fujikawa of Maryland Aerospace, Inc. for Goddard Space Flight Center. GSC-16724-1