Session
Technical Session X: Mission Enabling Technologies II
Abstract
The precision of astronomy and stellar photometry missions is strongly influenced by the attitude stability of the instrument platform. Recent developments in the miniaturization of star trackers and reaction wheels have opened the possibility of performing precise stellar photometry with nanosatellites. The BRIght Target Explorer (BRITE) mission uses a constellation of six nanosatellites that will photometrically observe the brightest stars in the sky. Each BRITE satellite will use a CCD imager with a 3-cm aperture telescope. The small telescope is capable of making photometric measurements with precision of 0.1%. This photometric precision is in part made possible by reacquiring target stars using the same set of pixels for multiple observations. This reacquisition requirement implies arc-minute attitude stability. To accomplish this requirement the attitude is controlled by an orthogonal set of three reaction wheels, and estimated with a star tracker, developed jointly by Sinclair Interplanetary, Ryerson University’s SAIL facility and the Space Flight Laboratory. This paper focuses on the challenges of and solutions to three-axis arc-minute pointing stability on the nanosatellite scale. Special attention is given to the effect of reaction wheel jitter, the practical limitations associated with miniaturized star trackers, and attitude estimation without the use of rate gyros. The solutions presented apply to small satellites in general, including BRITE constellation. The first satellites in BRITE Constellation are scheduled to launch in late 2011.
Presentation Slides
Arc-Minute Attitude Stability on a Nanosatellite: Enabling Stellar Photometry on the Smallest Scale
The precision of astronomy and stellar photometry missions is strongly influenced by the attitude stability of the instrument platform. Recent developments in the miniaturization of star trackers and reaction wheels have opened the possibility of performing precise stellar photometry with nanosatellites. The BRIght Target Explorer (BRITE) mission uses a constellation of six nanosatellites that will photometrically observe the brightest stars in the sky. Each BRITE satellite will use a CCD imager with a 3-cm aperture telescope. The small telescope is capable of making photometric measurements with precision of 0.1%. This photometric precision is in part made possible by reacquiring target stars using the same set of pixels for multiple observations. This reacquisition requirement implies arc-minute attitude stability. To accomplish this requirement the attitude is controlled by an orthogonal set of three reaction wheels, and estimated with a star tracker, developed jointly by Sinclair Interplanetary, Ryerson University’s SAIL facility and the Space Flight Laboratory. This paper focuses on the challenges of and solutions to three-axis arc-minute pointing stability on the nanosatellite scale. Special attention is given to the effect of reaction wheel jitter, the practical limitations associated with miniaturized star trackers, and attitude estimation without the use of rate gyros. The solutions presented apply to small satellites in general, including BRITE constellation. The first satellites in BRITE Constellation are scheduled to launch in late 2011.
