Unified guidance analysis in design of space trajectories.
Dimensionless differential corrections and proper coordinate system for generalized preflight guidance analysis
GUIDANCE AND CONTROL↗
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Command angle torquing of gyros in the Apollo Guidance and Navigation System.
Apollo Guidance and Navigation System positioning by electrically torquing gyros, discussing error sources
NAVIGATION AND GUIDANCE↗
Princeton experiment package for OAO-C.
OAO-C spacecraft optical and electronics Princeton Experiment Package including telescope, spectrometer, guidance sensor and power supply
Gundersen, N. A.↗
Cost estimation for unmanned lunar and planetary programs
A basic model is presented for estimating the cost of unmanned lunar and planetary programs. Cost data were collected and analyzed for eight lunar and planetary programs. Total cost was separated into the following components: labor, overhead, materials, and technical support. The study determined that direct labor cost of unmanned lunar and planetary programs comprises 30 percent of the total program cost. Twelve program categories were defined for modeling: six spacecraft subsystem categories (science, structure, propulsion, electrical power, communications, and guidance and integration, test and quality assurance, launch and flight operations, ground equipment, systems analysis and engineering, and program management). An analysis showed that on a percentage basis, direct labor cost and direct labor manhours compare on a one-to-one ratio. Therefore, direct labor hours is used as the parameter for predicting cost, with the advantage of eliminating the effect of inflation on the analysis.
Dunkin, J. H.↗
Statistical modeling of software reliability
This working paper discusses the statistical simulation part of a controlled software development experiment being conducted under the direction of the System Validation Methods Branch, Information Systems Division, NASA Langley Research Center. The experiment uses guidance and control software (GCS) aboard a fictitious planetary landing spacecraft: real-time control software operating on a transient mission. Software execution is simulated to study the statistical aspects of reliability and other failure characteristics of the software during development, testing, and random usage. Quantification of software reliability is a major goal. Various reliability concepts are discussed. Experiments are described for performing simulations and collecting appropriate simulated software performance and failure data. This data is then used to make statistical inferences about the quality of the software development and verification processes as well as inferences about the reliability of software versions and reliability growth under random testing and debugging.
Miller, Douglas R.↗
Comparing Consider-Covariance Analysis with Sigma-Point Consider Filter and Linear-Theory Consider Filter Formulations
Recent literature in applied estimation theory reflects growing interest in the sigma-point (also called unscented ) formulation for optimal sequential state estimation, often describing performance comparisons with extended Kalman filters as applied to specific dynamical problems [c.f. 1, 2, 3]. Favorable attributes of sigma-point filters are described as including a lower expected error for nonlinear even non-differentiable dynamical systems, and a straightforward formulation not requiring derivation or implementation of any partial derivative Jacobian matrices. These attributes are particularly attractive, e.g. in terms of enabling simplified code architecture and streamlined testing, in the formulation of estimators for nonlinear spaceflight mechanics systems, such as filter software onboard deep-space robotic spacecraft. As presented in [4], the Sigma-Point Consider Filter (SPCF) algorithm extends the sigma-point filter algorithm to the problem of consider covariance analysis. Considering parameters in a dynamical system, while estimating its state, provides an upper bound on the estimated state covariance, which is viewed as a conservative approach to designing estimators for problems of general guidance, navigation and control. This is because, whether a parameter in the system model is observable or not, error in the knowledge of the value of a non-estimated parameter will increase the actual uncertainty of the estimated state of the system beyond the level formally indicated by the covariance of an estimator that neglects errors or uncertainty in that parameter. The equations for SPCF covariance evolution are obtained in a fashion similar to the derivation approach taken with standard (i.e. linearized or extended) consider parameterized Kalman filters (c.f. [5]). While in [4] the SPCF and linear-theory consider filter (LTCF) were applied to an illustrative linear dynamics/linear measurement problem, in the present work examines the SPCF as applied to nonlinear sequential consider covariance analysis, i.e. in the presence of nonlinear dynamics and nonlinear measurements. A simple SPCF for orbit determination, exemplifying an algorithm hosted in the guidance, navigation and control (GN&C) computer processor of a hypothetical robotic spacecraft, was implemented, and compared with an identically-parameterized (standard) extended, consider-parameterized Kalman filter. The onboard filtering scenario examined is a hypothetical spacecraft orbit about a small natural body with imperfectly-known mass. The formulations, relative complexities, and performances of the filters are compared and discussed.
Lisano, Michael E.↗
Variations in Cathodoluminescent Intensity of Spacecraft Materials Exposed to Energetic Electron Bombardment
Many contemporary spacecraft materials exhibit cathodoluminescence when exposed to electron flux from the space plasma environment. A quantitative, physics-based model has been developed to predict the intensity of the glow as a function of incident electron current density and energy, temperature, and intrinsic material properties. We present a comparative study of the absolute spectral radiance for several types of dielectric and composite materials based on this model which spans three orders of magnitude. Variations in intensity are contrasted for different electron environments, different sizes of samples and sample sets, different testing and analysis methods, and data acquired at different test facilities. Together, these results allow us to estimate the accuracy and precision to which laboratory studies may be able to determine the response of spacecraft materials in the actual space environment. It also provides guidance as to the distribution of emissions that may be expected for sets of similar flight hardware under similar environmental conditions.
plasma environment↗
Variations in Cathodoluminescent Intensity of Spacecraft Materials Exposed to Energetic Electron Bombardment
Many contemporary spacecraft materials exhibit cathodoluminescence when exposed to electron flux from the space plasma environment. A quantitative, physics-based model has been developed to predict the intensity of the glow as a function of incident electron current density and energy, temperature, and intrinsic material properties. We present a comparative study of the absolute spectral radiance for several types of dielectric and composite materials based on this model which spans three orders of magnitude. Variations in intensity are contrasted for different electron environments, different sizes of samples and sample sets, different testing and analysis methods, and data acquired at different test facilities. Together, these results allow us to estimate the accuracy and precision to which laboratory studies may be able to determine the response of spacecraft materials in the actual space environment. It also provides guidance as to the distribution of emissions that may be expected for sets of similar flight hardware under similar environmental conditions.
orders of magnitude↗
The Virtual Space Telescope: A New Class of Science Missions
Many science investigations proposed by GSFC require two spacecraft alignment across a long distance to form a virtual space telescope. Forming a Virtual Space telescope requires advances in Guidance, Navigation, and Control (GNC) enabling the distribution of monolithic telescopes across multiple space platforms. The capability to align multiple spacecraft to an intertial target is at a low maturity state and we present a roadmap to advance the system-level capability to be flight ready in preparation of various science applications. An engineering proof of concept, called the CANYVAL-X CubeSat MIssion is presented. CANYVAL-X's advancement will decrease risk for a potential starshade mission that would fly with WFIRST.
CubeSat↗
Spacecraft Autonomy in the New Millenium
NASA's New Millenium Program (NMP) is designed to dramatically reduce mission costs and enable new and more frequent exploration missons.
new↗
Navigation and Guidance for the Mars Surveyor 1998 Mission
In December, 1998 and January 1999 NASA will launch two spacecraft to Mars as part of the overall Mars Exploration Program managed at JPL. One is an orbiter that will arrive at Mars in October of 1999 carrying a science payload for remote sensing.
navigation↗
Guidance and navigation requirements for unmanned flyby and swingby missions to the outer planets. Volume 1: Summary report
Unmanned spacecraft missions to the outer planets are of current interest to planetary scientists, and are being studied for the post 1970 time period. Flyby, entry and orbiter missions are all being considered using both direct and planetary swingby trajectory modes. The navigation and guidance requirements for a variety of missions to the outer planets and comets including both the three and four planet Grand Tours, are summarized.
Source record↗
Revisiting Optimal Guidance Solution for Vertical Landing and Take-Off
The vertical landing and take-off are crucial phases of a rocket-powered spacecraft's powered descent and ascent trajectories, during which its motion is confined to a single (vertical) axis. It is well-known that the minimum-propellant guidance solutions for vertical landing and take-off in a vacuum, consist of only one coast and one full-thrust arc and no singular arc exists in these problems. However, an exact solution for the vertical descent problem is not found in the literature. In the present work, exact guidance solutions for the optimal vertical landing and take-off are presented that are valid for arbitrary boundary conditions. The time-based and switching function-based guidance law implementations are discussed and their performance is compared using lunar descent and ascent simulations.
powered descent↗
Astrodynamics 1989; Proceedings of the AAS/AIAA Astrodynamics Conference, Stowe, VT, Aug. 7-10, 1989. Parts 1 & 2
The conference focuses of analytical and numerical aspects of astrodynamics and celestial mechanics with emphasis on planetary mission design, trajectory analysis and design, orbit determination, attitude determination and control, guidance systems, and dynamics and control of large flexible space structures. Trajectory computation techniques, satellite dynamics, and geocentric satellite orbit analysis are presented, along with earth orbiter mission analysis, trajectory optimization applications, planetary spacecraft orbit determination, and orbiting debris considerations. Neutral upper-atmosphere density is addressed, and guidance analysis, planetary mission design and analysis, trajectory analysis, estimation/identification techniques are discussed in addition to the dynamics and control of space structures or multi-body systems.
Thornton, Catherine L.↗
A Survey of the Spacecraft Line-Of-Sight Jitter Problem
Predicting, managing, controlling, and testing spacecraft Line-of-Sight (LoS) jit- ter due to on-board internal disturbance sources is a challenging multi- disciplinary systems engineering problem, especially for those observatories hosting extremely sensitive optical sensor payloads with stringent requirements on allowable LoS jitter. Some specific spacecraft jitter engineering challenges will be introduced and described in this survey paper. Illustrative examples of missions where dynamic interactions have to be addressed to satisfy demanding payload instrument LoS jitter requirements will be provided. Some lessons learned and a set of recommended rules of thumb are also presented to provide guidance for analysts on where to initiate and how to approach a new spacecraft jitter design problem. These experience-based spacecraft jitter lessons learned and rules of thumb are provided in the hope they can be leveraged on new space system development projects to help overcome unfamiliarity with previously identified jitter technical pitfalls and challenges.
Dennehy, Cornelius J.↗
Constrained low-thrust guidance.
Constrained low thrust guidance algorithms for three axis and spin-stabilized, constant power, solar electric propelled spacecraft on fixed time rendezvous missions are developed. A 'bang-bang' type of minimum-propellant thrust program is used. Control constraints arise from the specification that the thrust vector must remain fixed relative to the solar panels. The guidance law is derived from deterministic linear perturbation theory and is controllable to first order on trajectories containing at least two thrust arcs. The number and timing of guidance updates and the effectiveness of the guidance law in compensating for state and control estimation biases and uncertainties are discussed. Numerical comparisons between the optimal control and the restricted control case are presented on a Encke comet rendezvous.
Ungs, M. J.↗
Space shuttle guidance, navigation and control design equations. Volume 4: Deorbit and atmospheric operations
A baseline set of equations which fulfill the computation requirements for guidance, navigation, and control of the space shuttle orbiter vehicle is presented. All shuttle mission phases are covered from prelaunch through landing/rollout. The spacecraft flight mode and the aircraft flight mode are addressed. The baseline equations may be implemented in a single guidance, navigation, and control computer or may be distributed among several subsystem computers.
Cox, K. J.↗
L2 Earth Atmosphere Observatory: Formation Guidance, Metrology and Control Synthesis
The Earth Observatory Formation at L2, a Lagrange libration point, is a unique large aperture (25 m diameter) space telescope concept that will improve the knowledge and understanding of dynamic, chemical and radiative mechanisms that cause changes in the atmosphere, and can lead to the development of models and techniques to predict short and long-term climate changes. The results of this concept definition study show that the telescope concept is feasible, and can have technology readiness in the 2020 time frame. Further advanced development in several subsystems is needed, such as higher efficiency Xenon ion thrusters with throttling, and optical quality large membrane mirror with active shape control. It presents an analysis and solution of guidance, sensing, control, and propulsion problems for a formation of two spacecraft on the Sun-Earth line in the neighborhood of the Sun-Earth L2 point, that observes Earth s atmosphere during continuous solar occultation by the Earth. A system architecture is described for the observatory, and its components that include unique mission specific metrology. The formation must follow a powered trajectory with strictly limited fuel use to observe solar occultation. A configuration of ion thrusters and reaction wheels for translation and attitude control is designed along with algorithms for orbit following and formation control. Simulation results of the orbital and formation dynamics are presented that verify performance of the control systems.
Earth Atmosphere Observatory Formation↗