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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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At least 19 records

All sources NASA NTRS DOE OSTI

NASA NTRS1980

SPS antenna pointing control

The pointing control of a microwave antenna of the Satellite Power System was investigated emphasizing: (1) the SPS antenna pointing error sensing method; (2) a rigid body pointing control design; and (3) approaches for modeling the flexible body characteristics of the solar collector. Accuracy requirements for the antenna pointing control consist of a mechanical pointing control accuracy of three arc-minutes and an electronic phased array pointing accuracy of three arc-seconds. Results based on the factors considered in current analysis, show that the three arc-minute overall pointing control accuracy can be achieved in practice.

Hung, J. C.↗

NASA NTRS1981

Onboard utilization of ground control points for image correction. Volume 3: Ground control point simulation software design

The software developed to simulate the ground control point navigation system is described. The Ground Control Point Simulation Program (GCPSIM) is designed as an analysis tool to predict the performance of the navigation system. The system consists of two star trackers, a global positioning system receiver, a gyro package, and a landmark tracker.

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NASA NTRS1988

Space telescope pointing control

The Space Telescope pointing control system is designed to meet the fine pointing performance of 0.007 arc-sec stability, maneuver the telescope 90 deg in 18 min, or less, and provide the capability for deployment from, and retrieval by, the space shuttle. The pointing control system objectives are met using fine guidance sensors for attitude information, reaction wheel assemblies sized to provide both the torque required for pointing, and magnetometers and magnetic torquers for momentum management. A digital computer is used to calculate the control law, attitude reference, momentum management law, and command generator. The command generator shapes the acceleration and incremental angle commands to the control system to limit structural mode excitation. The control techniques are briefly discussed.

Dougherty, Hugh↗

NASA NTRS1985

Configuration trade-offs for the Space Infrared Telescope Facility pointing control system

Conceptual pointing control system designs for the Space Infrared Telescope Facility (SIRTF) are examined in terms of fine guidance pointing and large-angle slewing accuracies. In particular, basic trade-offs between body pointing only and body pointing plus image motion compensation (IMC) are considered using a steady-state linear covariance analysis to compute rms pointing errors. It is shown that body pointing can provide good performance during nominal fine pointing but limits the telescope capability to rapidly slew and acquire targets. Overall, body pointing plus IMC would offer superior performance but must be judged against the difficulties posed by the attitude sensor noise and the higher cost and complexity of IMC. It is recommended that improved sensor designs be pursued while slewing performance be enhanced by a combination of an appropriate command profile and control compensation.

Pue, A. J.↗

NASA NTRS1978

Digital pointing control

The digital pointing control system developed for the Space Shuttle Data Bus is discussed. The device, which interfaces with NASA standard sensor units, contains a front panel controller, a development system to load, inspect, print, and store the program and data, and a 'test jig' to provide closed-loop controller operation. The system is described with particular reference to the tracker-gyro interfaces, the control algorithms and compensation procedures, Kalman-estimation filtering, the proportional power output, and the discrete output capability. The results of simulation studies are presented and the development status is noted.

Studer, P. A.↗

NASA NTRS1992

Algebraic grid generation with control points

The control-point form (CPF) formulation is an algebraically defined class of coordinate transformations by means of which the interior form of the coordinates can be manipulated in the local fashion, and any boundary can be either specified or manipulated in a similar manner. Currently, the most intense activity involving CPF is with such graphic interactive codes as TurboI and TurboT, for which detailed illustrative examples are given; these have furnished experience on whose basis future interactive strategies can be developed.

Eiseman, Peter R.↗

NASA NTRS1991

Implementation of control point form of algebraic grid-generation technique

The control point form (CPF) provides explicit control of physical grid shape and grid spacing through the movement of the control points. The control point array, called a control net, is a space grid type arrangement of locations in physical space with an index for each direction. As an algebraic method CPF is efficient and works well with interactive computer graphics. A family of menu-driven, interactive grid-generation computer codes (TURBO) is being developed by using CPF. Key features of TurboI (a TURBO member) are discussed and typical results are presented. TurboI runs on any IRIS 4D series workstation.

Choo, Yung K.↗

NASA NTRS1991

Implementation of control point form of algebraic grid-generation technique

Choo, Yung K.↗

NASA NTRS1983

Space Telescope pointing control

The Space Telescope Pointing Control System is used to slew the optical axis of the telescope from one target star region of the celestial sphere to the next, and to maintain precision pointing on the target star. A digital computer is employed in the processing of attitude and rate sensor data, in order to generate torque commands for the reaction wheels. The System comprises four major elements: a command generator, the electronic control system, attitude update processing, and momentum management. Emphasis is given to control-related flexibility effects of the Space Telescope's solar cell array and vehicle, and the acquisition methodology and development testing employed, in addition to Pointing Control System design features.

Dougherty, H.↗

NASA NTRS1980

Pointing control for the International Comet Mission

The design of the pointing control system for the proposed International Comet Mission, intended to fly by Comet Halley and rendezvous with Comet Tempel-2 is presented. Following a review of mission objectives and the spacecraft configuration, design constraints on the pointing control system controlling the two-axis gimballed scan platform supporting the science instruments are discussed in relation to the scientific requirements of the mission. The primary design options considered for the pointing control system design for the baseline spacecraft are summarized, and the design selected, which employs a target-referenced, inertially stabilized control system, is described in detail. The four basic modes of operation of the pointing control subsystem (target acquisition, inertial hold, target track and slew) are discussed as they relate to operations at Halley and Tempel-2. It is pointed that the pointing control system design represents a significant advance in the state of the art of pointing controls for planetary missions.

Leblanc, D. R.↗

NASA NTRS2003

An overview of the pointing control system for NASA's Space Infra-red Telescope Facility (SIRTF)

This paper discusses the pointing control system for NASA's Space Infra-Red Telescope Facility (SIRTF). After an introduction to the SIRTF mission and telescope, an overview is given of the pointing control hardware, pointing control architecture, pointing requirements and capability, attitude constraints and commanding, attitude observers and required calibrations.

pointing control attitude estimation calibration↗

NASA NTRS2022

Deep-space Optical Communications Pointing Control Design

This paper provides an overview of pointing control design for NASA’s Deep Space Optical Communications (DSOC) system. DSOC is NASA’s first deep-space laser communications system and includes both a ground system and a space terminal. This paper focus on the pointing control system design and related issues for the Flight Laser Transceiver (FLT), including its key subsystems and components that support the space terminal pointing and control, its operational concept and sequence design, and its control systems design and related analyses. The paper also provides an overview of the achievable system pointing performance that meets the DSOC pointing control design requirements.

Zhu, David↗

NASA NTRS1980

Satellite Power System (SPS) antenna pointing control

Accuracy requirements for the SPS antenna pointing control consists of a mechanical pointing accuracy of three arc minutes and an electronic phased array pointing accuracy of three arc seconds. Results of this study, based on the factors considered in current analysis, show that the three arc minute overall pointing control accuracy can be achieved for the SPS in practice.

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NASA NTRS1975

Flight performance of Skylab attitude and pointing control system

The Skylab attitude and pointing control system (APCS) requirements are briefly reviewed and the way in which they became altered during the prelaunch phase of development is noted. The actual flight mission (including mission alterations during flight) is described. The serious hardware failures that occurred, beginning during ascent through the atmosphere, also are described. The APCS's ability to overcome these failures and meet mission changes are presented. The large around-the-clock support effort on the ground is discussed. Salient design points and software flexibility that should afford pertinent experience for future spacecraft attitude and pointing control system designs are included.

Chubb, W. B.↗

NASA NTRS1990

Anatomy of an experimental two-link flexible manipulator under end-point control

The design and experimental implementation of an end-point controller for two-link flexible manipulators are presented. The end-point controller is based on linear quadratic Gaussian (LQG) theory and is shown to exhibit significant improvements in trajectory tracking over a conventional controller design. To understand the behavior of the manipulator structure under end-point control, a strobe sequence illustrating the link deflections during a typical slew maneuver is included.

Oakley, Celia M.↗

NASA NTRS1982

The Use of Principal Components for Creating Improved Imagery for Geometric Control Point Selection

A directed principal component (PC) analysis and its transformation was applied to 7-channel thematic mapper simulator (TMS) data and 4-channel LANDSAT multispectral scanner system (MSS) data collected over the city of Lancaster, Pennsylvania, to create improved imagery for geometric control point selection for image to image registration. Nineteen temporally stable geometric control points, such as road interactions and bridges, were selected for a 236 sq km area. The control points were visible on both the TMS and MSS imagery. On the first attempt the corresponding image control points were selected on both data sets without using the principal components transformation. Many of the road intersection locations were visible but the actual road crossings could not be distinguished. As a result, mensuration errors using raw data exceeded the equivalent of two (79 x 79 m) pixels. The application of a guided principal components transformation yielded TMS and MSS single band images showing improved detail in the scene's urban and residential infrastructure. The PC transformed data sets were then utilized for the reselection of geometric control points. By shown greater detail, control points on both the TMS and MSS imagery could be located with greater precision using the PC transformed data.

Imhoff, M. L.↗

NASA NTRS1984

The influence of the number of ground control points on the scene-to-map registration accuracy

The optimum number of ground control points required to rectify a full scene or a portion of a LANDSAT MSS scene was investigated using data from southeastern Louisiana/southwestern Mississippi and eastern Kansas. The ground control points utilized were randomly distributed across the partial or full scene. This work suggest that 24 round control points are more than adequate to rectify a partial or full scene of LANDSAT MSS data. The error incurred in choosing ground control points representing artificial versus natural features was also studied.

Dow, D. D.↗

NASA NTRS2006

Instrument Pointing Control System for the Stellar Interferometry Mission - Planet Quest

This paper describes the high precision Instrument Pointing Control System (PCS) for the Stellar Interferometry Mission (SIM) - Planet Quest. The PCS system provides front-end pointing, compensation for spacecraft motion, and feedforward stabilization, which are needed for proper interference. Optical interferometric measurements require very precise pointing (0.03 as, 1-(sigma) radial) for maximizing the interference pattern visibility. This requirement is achieved by fine pointing control of articulating pointing mirrors with feedback from angle tracking cameras. The overall pointing system design concept is presentcd. Functional requirements and an acquisition concept are given. Guide and Science pointing control loops are discussed. Simulation analyses demonstrate the feasibility of the design.

control↗