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Results for “Attitude and Articulation Control Subsystem (AACS)”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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29 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Cassini Attitude Control Flight Software: from Development to In-Flight Operation

The Cassini Attitude and Articulation Control Subsystem (AACS) Flight Software (FSW) has achieved its intended design goals by successfully guiding and controlling the Cassini-Huygens planetary mission to Saturn and its moons. This paper describes an overview of AACS FSW details from early design, development, implementation, and test to its fruition of operating and maintaining spacecraft control over an eleven year prime mission. Starting from phases of FSW development, topics expand to FSW development methodology, achievements utilizing in-flight autonomy, and summarize lessons learned during flight operations which can be useful to FSW in current and future spacecraft missions.

Architecture↗
NASA NTRS2008

Cassini Attitude Control Fault Protection Design: Launch to End of Prime Mission Performance

The Cassini Attitude and Articulation Control Subsystem (AACS) Fault Protection (FP) has been successfully supporting operations for over 10 years from launch through the end of the prime mission. Cassini's AACS FP is complex, containing hundreds of error monitors and thousands of tunable parameters. Since launch there have been environmental, hardware, personnel and mission event driven changes which have required AACS FP to adapt and be robust to a variety of scenarios. This paper will discuss the process of monitoring, maintaining and updating the AACS FP during Cassini's lengthy prime mission as well as provide some insight into lessons learned during tour operations.

Meakin, Peter C.↗
NASA NTRS1994

Mission Operations Data Analysis Tools for Mars Observer Guidance and Control

The focus of this paper is on the data analysis tools for the Mars Observer Attitude and Articulation Control Subsystem (AACS). Four different categories of analysis tools are presented, with details offered for specific tools. These same tools, and extensions thereof, have been adopted by the Galileo mission operations, and are being designed into Cassini and other future spacecraft mission operations.

mission↗
NASA NTRS1983

Development of the functional simulator for the Galileo attitude and articulation control system

A simulation program for verifying and checking the performance of the Galileo Spacecraft's Attitude and Articulation Control Subsystem's (AACS) flight software is discussed. The program, which is called Functional Simulator (FUNSIM), provides a simple method of interfacing user-supplied mathematical models coded in FORTRAN which describes spacecraft dynamics, sensors, and actuators; this is done with the AACS flight software, coded in HAL/S (High-level Advanced Language/Shuttle). It is thus able to simulate the AACS flight software accurately to the HAL/S statement level in the environment of a mainframe computer system. FUNSIM also has a command and data subsystem (CDS) simulator. It is noted that the input/output data and timing are simulated with the same precision as the flight microprocessor. FUNSIM uses a variable stepsize numerical integration algorithm complete with individual error bound control on the state variable to solve the equations of motion. The program has been designed to provide both line printer and matrix dot plotting of the variables requested in the run section and to provide error diagnostics.

Namiri, M. K.↗
NASA NTRS1993

The Cassini Spacecraft: Object Oriented Flight Control Software

The Cassini AACS object-oriented Flight Software is depicted in increasing levels of detail using a Context Diagram, Architecture Diagrams, an Object Diagram for each object, and a Statechart for each object. The detail contained in the diagrams is enhanced and refined during the Requirements and Design Phases of both Subsystem and Software Development. Examples of all the diagrams as well as the criteria for object selection, the advantages of statecharts, and the ease of modifying the design to accommodate changes in scope are described.

object-oriented↗
NASA NTRS1993

Proposed data compression schemes for the Galileo S-band contingency mission

The Galileo spacecraft is currently on its way to Jupiter and its moons. In April 1991, the high gain antenna (HGA) failed to deploy as commanded. In case the current efforts to deploy the HGA fails, communications during the Jupiter encounters will be through one of two low gain antenna (LGA) on an S-band (2.3 GHz) carrier. A lot of effort has been and will be conducted to attempt to open the HGA. Also various options for improving Galileo's telemetry downlink performance are being evaluated in the event that the HGA will not open at Jupiter arrival. Among all viable options the most promising and powerful one is to perform image and non-image data compression in software onboard the spacecraft. This involves in-flight re-programming of the existing flight software of Galileo's Command and Data Subsystem processors and Attitude and Articulation Control System (AACS) processor, which have very limited computational and memory resources. In this article we describe the proposed data compression algorithms and give their respective compression performance. The planned image compression algorithm is a 4 x 4 or an 8 x 8 multiplication-free integer cosine transform (ICT) scheme, which can be viewed as an integer approximation of the popular discrete cosine transform (DCT) scheme. The implementation complexity of the ICT schemes is much lower than the DCT-based schemes, yet the performances of the two algorithms are indistinguishable. The proposed non-image compression algorith is a Lempel-Ziv-Welch (LZW) variant, which is a lossless universal compression algorithm based on a dynamic dictionary lookup table. We developed a simple and efficient hashing function to perform the string search.

Cheung, Kar-Ming↗
NASA NTRS1990

Mission management, planning, and cost: PULSE Attitude And Control Systems (AACS)

The Pluto unmanned long-range scientific explorer (PULSE) is a probe that will do a flyby of Pluto. It is a low weight, relatively low costing vehicle which utilizes mostly off-the-shelf hardware, but not materials or techniques that will be available after 1999. A design, fabrication, and cost analysis is presented. PULSE will be launched within the first decade of the twenty-first century. The topics include: (1) scientific instrumentation; (2) mission management, planning, and costing; (3) power and propulsion systems; (4) structural subsystem; (5) command, control, and communication; and (6) attitude and articulation control.

Source record↗