Development of an Orbital Trajectory Analysis Tool

Since Thailand successfully launched the first earth observation satellite (Thaichote) in 2008, the Geo-Informatics and Space Technology Development Agency (GISTDA) has started developing an orbit analysis tool called “EMERALD†to be used for the current and future mission planned by GISTDA. In this paper, we present the development of a satellite orbit control maneuver, which is one of the analysis tools, by providing essential parameters for an orbital trajectory analysis and design. The algorithms are developed and programmed in a convenient graphical user interface (GUI). The results can guarantee a mission and design a desired orbital mission by calculating suitable maneuver parameters to correct the ground track (GT) and local solar time (LST) under control window including the transfer orbit for the good quality of the mission data. The validation results are in good agreement with Quartz++, which is a flight dynamic software developed by EADS ASTRIUM.Since Thailand successfully launched the first earth observation satellite (Thaichote) in 2008, the Geo-Informatics and Space Technology Development Agency (GISTDA) has started developing an orbit analysis tool called “EMERALD” to be used for the current and future mission planned by GISTDA. In this paper, we present the development of a satellite orbit control maneuver, which is one of the analysis tools, by providing essential parameters for an orbital trajectory analysis and design. The algorithms are developed and programmed in a convenient graphical user interface (GUI). The results can guarantee a mission and design a desired orbital mission by calculating suitable maneuver parameters to correct the ground track (GT) and local solar time (LST) under control window including the transfer orbit for the good quality of the mission data. The validation results are in good agreement with Quartz++, which is a flight dynamics software developed by EADS ASTRIUM

Phase Acquisition and Formationkeeping of a New Power Consumption Monitoring Satellite Constellation

A new satellite constellation proposed for global monitoring of electrical power consumption is described in the paper. The optimal small satellite constellation structure as well as its control accuracy required for serving the mission objective throughout the designed life span is examined. The orbital dynamics is analysed for the purposes of optimal phase acquisition and formationkeeping strategy design. A low-cost strategy for spreading all satellites onto their prescribed positions under both time and fuel consumption constraints is explained. The separation errors due to control system uncertainties are analysed, and the system requirements for the constellation phase acquisition are specified. A control strategy is investigated for keeping of the relative pattern of the constellation in spite of the perturbation effects from atmospheric drag and the potential harmonics of the non-spherical Earth, and fuel expenditure is minimised. The system feasibility is demonstrated via simulation results. The control system relies upon low-cost, practical flight-proven sensing and actuating systems for small satellite missions

Design and validation of flight dynamics system

This paper presents the architecture design of flight dynamics system (FDS) known as “EMERALD” developed by Geo-Informatics and Space Technology Development Agency (GISTDA) and Mahanakorn University of Technology (MUT). The capability of the system enables to provide the state vector of a satellite, mission analysis, orbit events and mission monitoring. The methodologies of orbit determination and event prediction modules implemented for mission management are presented and the validations of both are done by comparing with the previous FDS (Quartz) developed by EADS ASTRIUM. As a result of the implementation, the reduction of the operation time is significant and the prediction performance is high accurate and reliable when comparing with Quartz

Low-thrust orbit control of LEO small satellites.

In this thesis, we investigate the orbit control strategies of small satellites in Low Earth Orbits (LEO) where the disturbance effects are significant, in particular the nonspherical Earth and atmospheric drag effects. These orbits are not suitable to be controlled by using traditional ground-based control strategies which generally require high-thrust propulsion systems and other expensive resources, both onboard and in the ground segment. In order to react to those disturbances spontaneously and keep a small satellite at a pre-defined station using its limited resources, autonomous orbit control technology needs to be enabled. With the current advances in navigation and propulsion technology, as well as onboard computation systems, the only key issue that needs further investigations for practical implementation of an autonomous orbit operation system is the control algorithm. The orbit control strategies we investigate here are treated separately for each of the orbital control phases, i.e. orbit deployment and acquisition, orbit transfer and orbit maintenance. We present various forms of the solutions of the epicycle motion which allow us to treat each control problem according to the control requirements, nature of perturbations, control time scales and available resources. Although applied in different manners, the optimal low-thrust control scheme is a common aim for all control problems investigated here, as we mainly focus upon applications for low cost small satellites in LEO. The verifications of the strategies proposed in this thesis have been demonstrated not only via computer simulations, but also successfully demonstrated on in-orbit small satellite platforms thanks to an active small satellite programme at Surrey Space Centre. The success of this study is hoped to provide a valuable basis for satellite orbit operations which will involve larger number of satellites with more complex configurations in the future

Development of Precise Ephemeris Generation Module for Thaichote Satellite Operations

In this paper, the development of the ephemeris generation module used for the Thaichote satellite operations is presented. It is a vital part of the flight dynamics system, which comprises, the orbit determination, orbit propagation, event prediction and station-keeping maneuver modules. In the generation of the spacecraft ephemeris data, the estimated orbital state vector from the orbit determination module is used as an initial condition. The equations of motion are then integrated forward in time to predict the satellite states. The higher geopotential harmonics, as well as other disturbing forces, are taken into account to resemble the environment in low-earth orbit. Using a highly accurate numerical integrator based on the Burlish-Stoer algorithm the ephemeris data can be generated for long-term predictions, by using a relatively small computation burden and short calculation time. Some events occurring during the prediction course that are related to the mission operations, such as the satellite's rise/set viewed from the ground station, Earth and Moon eclipses, the drift in ground track as well as the drift in the local solar time of the orbital plane are all detected and reported. When combined with other modules to form a flight dynamics system, this application is aimed to be applied for the Thaichote satellite and successive Thailand's Earth-observation missions

Autonomous Control System for Precise Orbit Maintenance

In this paper, we describe a closed-loop autonomous control system that enables orbit operations to be performed without the need of any ground segment. The growing availability of GPS receivers on satellites provides an excellent means for autonomous orbit determination and our work builds upon previous work on orbit determination algorithms developed here at Surrey. The orbit is described using a set of epicycle parameters which provide an analytic model of LEO orbits. The parameters in this model are estimated onboard the satellite using a Kalman filter. We describe an enhancement to this software which provides both control as well as estimation of the orbit parameters and a discussion of how atmospheric drag has been included in the model. The goal of the control part of the software is to ensure that the orbital altitude of the satellite never falls outside of a prescribed window due to drag. We present results of the orbit maintenance software which has been successfully running on Surrey\u27s minisatellite UoSat-12. This satellite is in a 650 km altitude orbit at inclination 64.57o . The satellite has been manoeuvred into a repeat ground track orbit so that the satellite repeats its ground track every 7 days. The orbit maintenance software then attempts to maintain the satellite in its resonant orbit, and also to slowly manoeuvre the satellite into a frozen orbit so that the altitude at each pass does not vary