In-orbit satellite sensor alignment determination

Abstract

A sensor alignment system and method is provided that facilitates the precise alignment determination of satellite sensors. The system and method utilizes an Inertial Measurement Unit (IMU) to facilitate alignment determination of multiples sensors on a satellite. The system and method performs a roll of the satellite around a preliminary sensor active axis, using the IMU to measure the rotation rate in both magnitude and direction. The sensor input is monitored by the IMU during the roll around the preliminary sensor axis. The data from sensor output obtained during the roll can be processed to calculate the difference between the preliminary sensor axis and the actual sensor axis. From this calculation the actual alignment of the sensor axis can be determined. Furthermore, by performing this alignment determination operation for multiple sensors the relative alignment between sensors can be determined.

Description

FIELD OF THE INVENTION [0001] This invention generally relates to sensor systems, and more specifically relates to satellite sensor systems. BACKGROUND OF THE INVENTION [0002] Satellites are being in increasingly diverse range of important applications. Today, satellites provide a host of communication, weather, military and scientific services. The increasing use of satellites makes their operational accuracy of increased concern. [0003] For example, many satellites provide a mission sensor that provides important data about some physical quantity. For example, weather satellites may provide radar system that tracks changes in weather. A communication satellite may provide an antenna that receives and transmits remote communication transmissions. An intelligence satellite may provide images of a selected location on the earth's surface. In each of these cases, the mission sensor provides an important service for the operation of the satellite. [0004] One important issue in the cali...

AI Technical Summary

Benefits of technology

[0006] The present invention provides a sensor alignment system and method that provides for precise alignment determination of satellite sensors. The system and method utilizes an Inertial Measurement Unit (IMU) to facilitate alignment determination of multiple sensors on a satellite. The system and method performs a roll of the satellite around a preliminary sensor active axis, using the IMU to measure the rotation rate in both magnitude and direction. The sensor input is monitored by the IMU during the roll around the preliminary sensor axis. The data from sensor output obtained during the roll can be processed to calculate the difference between the preliminary sensor axis and the actual sensor axis. From this calculation the actual alignment of the sensor axis with respect to the IMU can be determined. Furthermore, by performing this alignment determination operation for multiple sensors the relative alignment between sensors can be determined using the IMU as the common reference. For example, the relative alignment between a mission sensor and one or more utility sensors can be determined. Determining the relative alignment between the mission sensor and the utility sensor provides for accurate alignment determination between sensors. The system and method thus allows alignment determination to be performed in-orbit, reducing the impact of gravity on the alignment calibration process. Additionally, this process reduces the need for time consuming and expensive on-the-ground alignment determination.

Problems solved by technology

One important issue in the calibration of these satellites is the determination of mission sensor alignment.

Typically, past methods of determining the alignment of the mission sensor have relied upon a complicated procedure on the ground.

Unfortunately, this type of alignment procedure is time consuming and expensive.

Additionally, this on-the-ground alignment suffers from inherent limitations.

As another example, the effects of Earth's gravity on the satellite may distort the alignment when compared to its eventual operational environment.

Additionally, aligning the mission sensor to optical reference surfaces suffers from inherent inaccuracies.

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