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RADICAL RIMU Attitude Determination/Calibration Filter - Software Components PDF Print E-mail
Article Index
RADICAL RIMU Attitude Determination/Calibration Filter
Software Components
Advanced Capabilities
Filter States
Further Reading
All Pages

Software Components

The RADICAL software, which is written in C, comprises core filter functions; a command interpreter; pre-processing; data ingest, synchronization, and buffering functions; and Matlab support software for sensor simulation and for plotting and tabulating results.

Core Filter Functions

The core filter functions include Extended Kalman Filter functions, a command interface, telemetry interface, initialization for cold and warm start, processing of disjoint telemetry streams, default and active parameter tables, advanced measurement error models, parity residual update for full observability of the gyro calibration parameters, fault detection and performance monitoring functions, diagnostic output data, telemetry output in a choice of three different size but customizable packets, and several other features. The covariance matrix in a calibration filter can become ill conditioned during its initial convergence and in other situations. Therefore UD-factorized covariance algorithms are used in RADICAL to ensure numerical stability and accuracy. The covariance matrix is never computed, except that certain elements of the covariance matrix are computed only for output and for convergence threshold tests. RADICAL is suitable for real-time on-board calibration, automated or semi-automated ground-based processing of telemetry, and desktop analysis and design. It has been used to support NASA, military, and commercial spacecraft. The RADICAL filter was instrumental in anomaly resolution, performance verification, and provisional ground-based processing of attitude telemetry for a commercial imaging satellite.

Command Interpreter

For ground-based processing and desktop analysis, the Command Interpreter provides a powerful and flexible command-line user interface. The Command Interpreter reads one or more script files that tell the interpreter how to execute the RADICAL filter. Commands may also be input manually or from another program, which can include commands to read script files. The script files can be nested. The Command Interpreter gives the user considerable flexibility to perform various operations during processing of telemetry data without having to modify code. The scripting commands are fairly simple in function and format. The commands define telemetry, parameter, and output file names and locations; control execution of the filter; and interact with the filter at specified times during processing. Wildcards are defined to simplify the specification of file names.

Matlab Support

Matlab scripts are used to plot the filter states, estimation errors (if truth data is avaialble from a simulator), residuals, standardized residuals (chi variables), covariance information, and measurement update information.