Technology for large space systems: A special bibliography with indexes (supplement 04)

This bibliography lists 259 reports, articles, and other documents introduced into the NASA scientific and technical information system between July 1, 1980 and December 31, 1980. Its purpose is to provide information to the researcher, manager, and designer in technology development and mission design in the area of the Large Space Systems Technology Program. Subject matter is grouped according to systems, interactive analysis and design. Structural concepts, control systems, electronics, advanced materials, assembly concepts, propulsion, solar power satellite systems, and flight experiments

Analytical determination of eclipse entry and exit points considering a conical shadow and oblate Earth

This paper presents a new analytical procedure to model the umbra generated during an eclipse considering an oblate ellipsoid of rotation as occulting body and a conical shadow. The method is based on purely geometrical considerations and results in the analytical definition of the entry and exit points from the conical shadow starting from the knowledge of the Sun position vector, the occulting body position vector and the orbital elements of the spacecraft orbiting the occulting body. The conical shadow also permits analytical definition of the entry and exit points of the penumbra region, which cannot be defined by using the classic cylindrical approach. Some numerical applications are proposed to test the effectiveness of the analytical formulations and to check the error in the prediction of the time spent in the shadow by the satellite. Finally, a discussion between the new conical shadow model and the classic cylindrical eclipse is carried out to see the improvements introduced by the refined geometry and the effects on space missions focusing on the cumulative error when multiple revolutions are considered

Software design for a Cubesat's Orbit Simulator

El proyecto se basa en realizar un software en MATLAB, u otra plataforma a determinar, que integre un simulador de órbitas, que ya se ha desarrollado en un proyecto anterior, en una plataforma de cubesats en el laboratorio, que se van a enviar datos entre ellos. La plataforma consta de un conjunto de nanosatélites en forma de cubo de 1x1x1 dm de dimensión (cubesat). Además de los datos entre cubesats, cada uno enviará, mediante bluetooth, información on-line del consumo de baterías, ángulo de inclinación y estado de la comunicación con otro cubesat. El simulador presentará en pantalla la posición de los cubesats en función de los datos de lanzamiento (simulados) y el tiempo transcurrido desde el mismo. También girará los cubesats según el ángulo real que tenga, en coordenadas terrestres, cada cubesat de la plataforma del laboratorio. Este ángulo se obtiene mediante subsistemas ya desarrollados con anterioridad a este proyecto. También mostrará datos de carga de batería y de consumo en el acto de comunicación de datos, que se obtendrán del subsistema de potencia que se diseña en otro proyecto

A shadow function model based on perspective projection and atmospheric effect for satellites in eclipse

Accurate Solar Radiation Pressure (SRP) modelling is critical for correctly describing the dynamics of satellites. A shadow function is a unitless quantity varying between 0 and 1 to scale the solar radiation flux at a satellite’s location during eclipses. Errors in modelling shadow function lead to inaccuracy in SRP that degrades the orbit quality. Shadow function modelling requires solutions to a geometrical problem (Earth’s oblateness) and a physical problem (atmospheric effects). This study presents a new shadow function model (PPM_atm) which uses a perspective projection based approach to solve the geometrical problem rigorously and a linear function to describe the reduction of solar radiation flux due to atmospheric effects. GRACE (Gravity Recovery And Climate Experiment) satellites carry accelerometers that record variations of non-conservative forces, which reveal the variations of shadow function during eclipses. In this study, the PPM_atm is validated using accelerometer observations of the GRACE-A satellite. Test results show that the PPM_atm is closer to the variations in accelerometer observations than the widely used SECM (Spherical Earth Conical Model). Taking the accelerometer observations derived shadow function as the “truth”, the relative error in PPM_atm is −0.79% while the SECM 11.07%. The influence of the PPM_atm is also shown in orbit prediction for Galileo satellites. Compared with the SECM, the PPM_atm can reduce the radial orbit error RMS by 5.6 cm over a 7-day prediction. The impacts of the errors in shadow function modelling on the orbit remain to be systematic and should be mitigated in long-term orbit prediction

Techniques for monitoring and controlling yaw attitude of a GPS satellite

Techniques for monitoring and controlling yawing of a GPS satellite in an orbit that has an eclipsing portion out of the sunlight based on the orbital conditions of the GPS satellite. In one embodiment, a constant yaw bias is generated in the attitude control system of the GPS satellite to control the yawing of the GPS satellite when it is in the shadow of the earth

Präzise Orbitbestimmung des globalen Navigationssatellitensystems der 2. Generation

GNSS-2 (Global Navigation Satellite System of Second Generation) is a new generation of satellite-based navigation system. The primary goal is to improve the existing satellite systems such as GPS and GLONASS. Europes contribution to a new navigation satellite system of GNSS-2 is called Galileo. The typical space segment of a GNSS-2 system is composed of inclined geosynchronous (IGSO), geostationary (GEO) and Medium Earth Orbit (MEO) satellites. The space segment of the Galileo system is now only composed of MEO satellites. With this new satellite navigation system precise navigation and positioning with accuracy of at least 10 meters without differential techniques may be achieved. Therefore high precision orbit determination is required for successful applications of GNSS-2/Galileo systems with this accuracy level. The precise orbit determinations of IGSO, GEO and MEO satellites are discussed using dynamic and kinematic methods in this dissertation. The effort is focused, however, on IGSO and GEO satellites on ground tracking stations. In Chapter 1, GNSS-2/Galileo development plan and phase are presented. In Chapter 2, the basic observations of orbit determination are discussed, in Chapter 3 current systems used for various orbit determination applications are evaluated, in Chapter 4 major sources of observation errors are analyzed, in Chapter 5 perturbations on IGSO, GEO and MEO are modeled and estimated, in Chapter 6 major algorithms of orbit determination of IGSO, GEO and MEO, for examples, dynamic, reduced dynamic and kinematic methods are developed and discussed, in Chapter 7 high accuracy of IGSO and GEO orbit determination using carrier phase observation are discussed, in Chapter 8 a serious problem of GEO orbit determination during satellite maneuvers is presented and solved, and finally in Chapter 9 the simulation results of a possible satellite tracking system of GNSS-2/Galileo are presented

Development of Innovative GNC Algorithms for Aerospace Applications

The main context of the present dissertation is the SAPERE STRONG (Space Advanced Project for Excellence in Research and Enterprise – Sistemi, Tecnologie e Ricerche per l’Operatività Nazionale Globale) project, founded by Italian Ministry of University and Research (MIUR) with the goal to improve Italian access to Space and Space Exploration. For this purpose, extension of the launch capability of the Vega launcher is included in the project, realized with a Space-Tug which is used to deploy in the nominal orbit a payload spacecraft. This thesis has the objective to develop an advanced orbital simulator as a tool which makes the designer able to develop and test the Guidance, Navigation and Control (GNC) software for the Space-Tug spacecraft. The GNC software is developed in collaboration with the leader industrial company of the project, Thales Alenia Space. Thales Alenia Space (TAS) is in charge of developing the Navigation and Control Function and the main structure of flight software, while Politecnico di Torino collaborates with the development of the Guidance function and the orbital simulator. During the whole project has been planned an internship of 1500 hours inside the offices of TAS in Torino. The project includes also a visiting period of international institution. In the specific frame of this Ph. D. thesis, has been spent three months at the University of Sevilla, with the purpose of study and design of a Galileo receiver as an additional input for determination of position in advanced navigation systems, since the Galileo constellation is near to be fully operative in the next future. Details related to all the activities executed during this internship will be presented in Appendix B. The main objective of this dissertation is the development of innovative GNC algorithms, focusing mainly on the Guidance problem, for aerospace application. An extensive literature review of existing guidance law, control techniques, actuators for attitude and trajectory control, sensors and docking mechanism and techniques has been performed. The Guidance topic has been analyzed focusing on the missile-derived Proportional Navigation Guidance (PNG) algorithm, Zero-Effort-Miss/Zero-Effort-Velocity (ZEM/ZEV) algorithm and Lambert guidance. Feasibility, performance, pros and cons have been extensively studied in this work, especially in an experimental fashion, and new solutions and implementation strategies have been proposed. The literature review has been completed for Control and Navigation issues, as well. Control strategies, actuation systems and algorithm have been investigated, starting from the classical proportional/Integrative/Derivative (PID) controllers, to more recent and innovative control law, such as Linear Quadratic Regulator (LQR). As for the Control function, the Navigation topic, intended as navigation filters and algorithms, has been studied in the last period of this work, while the navigation problem form the hardware side (i.e. sensors) has been deeply analyzed in the present work. In addition to the GNC investigation, the simulation topic has been studied as well, since one of the goals of this dissertation is the realization of an orbital simulator. The orbital simulator is a complete 6 degrees-of-freedom simulator, based on the relative equation of motion (Hill’s equations) for the trajectory computation and based on the classical rigid body equation, including the quaternion notation, for the computation of the attitude dynamics. The orbital environment is well defined, including all common disturbances found in Low Earth Orbits (LEO) and affecting the dynamics of an orbiting body. A complete set of sensors is implemented, including an accurate model of common measurement errors affecting the sensors included in the spacecraft configuration (Inertial Measurement Unit, Star Tracker, GPS, Radio Finder, Lidar and Camera). Actuators are carefully modeled, including a reaction wheels system and a reaction control thrusters system. Errors derived for misalignment of the wheels system and non-nominal inertia and shooting and misalignment errors for the thrusters systems are modeled as well

Goce precise non-gravitational force modeling for POD applications

GOCE was launched in 2009 at 250 km altitude to recover Earth’s static gravity field. As part of the GOCE-Italy project, we carried out the precise modeling for the radiation pressure and the aerodynamic effects on this satellite. This analysis has been performed to reduce the mismodeling of the non-gravitational forces, in order to be able to estimate the ocean tides parameters from the LEO satellites orbital perturbation. A new software ARPA (Aerodynamics and Radiation Pressure Analysis), which takes advantage of the raytracing technique, has been designed and developed to accurately model the non-gravitational perturbations. ARPA can compute the Solar Radiation Pressure (SRP), Earth Radiation Pressure (ERP), the spacecraft Thermal Re-Radiation (TRR) and the aerodynamic forces and torques acting on any satellite with a high level of accuracy. The adopted methodologies and procedure are presented in this thesis, and the results of the tests on GOCE are illustrated and discussed. The NAPEOS (NAvigation Package for Earth Observation Satellites) software, developed and maintained at ESA/ESOC, was upgraded to make use of the new ARPA inputs and adopted to perform the tests on GOCE. The tests were performed on 30 consecutive daily arcs, starting at the beginning of the GOCE science phase on 1st November 2009. The results for the radiation test cases show a significant reduction of the empirical accelerations, especially in the cross-track direction, of about the 20% for the SRP, 12% for the ERP albedo, 13% for the ERP infrared and 20% for the TRR with respect to the standard NAPEOS force modeling (cannon-ball). For the aerodynamics, an important reduction of the post-fit RMS from 7.6 to 7.3 mm has been observed with the new ARPA model, and the a reduction from 4.6 to 4.2 cm of the distance of the orbits computed with ARPA from the official reduced-dynamics GOCE orbits (Precise Science Orbit) has been computed. The obtained results confirm the goodness of the modeling and techniques of ARPA for all the non-gravitational perturbations computed for GOCE. Even though the results are presented for the GOCE satellite, the new technique and software are adaptable to satellite of any shape, whether in Earth-bound orbit, or orbiting another planet, or cruising in interplanetary space