This document describes a B.Sc. graduation project (2014). The main objective of this third iteration of the Cairo University Cube Satellite is the design, manufacturing, building and testing selected subsystems of Cube Satellite. The mission of the Cube satellite is Earth imaging and the whole process uses COTS.
This document is organized the introduction and six chapters each describes one of the selected subsystems. The mission analysis and orbital determination chapter selects the best orbit matched to the mission requirements. The electrical power subsystem generates energy via the sun, distributes and manages the power among the other subsystems. The attitude determination and control is responsible for the orientation of the Cube Satellite in orbit, and controls the orientation of the Cube Satellite.
The communications subsystem is responsible for the data transmission from/to the Cube satellite and the ground station. The command and data-handling center (On Board Computer) handles all the data and commands on the Cube satellite and controls the Cube satellite modes and states. Finally, the structure subsystem chapter includes design the cube satellite structure, stress and weight analysis, inertia and natural frequencies determination. All collected and auxiliary data, code snippets, specification sheets… etc. are presented in eight appendices at the end of the document. A secondary objective is enrich the documentation of the current level of the knowhow achieved by the participants of the project.
Table of Contents
Chapter (1) Introduction
1.1 Objectives
1.2 Document road map
1.3 Project layout
Chapter (2) Mission Analysis and Orbital Determination
2.1 Introduction
2.2 Problem Definition
2.3 Survey’s Results
2.4 Statistical analysis of the existing Cube Satellites
2.4.1 Summary of cube satellite parameters
2.5 Types of Orbits and Orbital Parameters Definition
2.5.1 Classical Orbital Parameters
2.6 Orbital Design
2.6.1 Design Attempt
2.6.2 Equations Used
2.7 Orbit Propagator Survey
2.8 Orbit Propagator
2.8.1 Introduction
2.8.2 SGP4 Model
2.8.3 Perturbations considered in the model
2.8.4 Two Line Elements
2.8.5 Model characteristics
2.8.6 Model Verification
2.8.7 Disadvantages of SPG4 Model
2.8.8 Cowell’s Method
2.8.9 Acceleration Components
2.8.10 Implemented Propagator
2.8.11 References
Chapter (3) Electric Power
3.1 Introduction
3.1.1 Abstract
3.1.2 EPS Requirements and Objectives
3.1.3 EPS Constraints
3.1.4 Mission Modes related to EPS
3.2 Definitions
3.3 Progress of the 2nd iteration
3.4 Problems of the last year
3.5 What to be done in 3rd iteration of EPS
3.6 Survey on EPS Main Components
3.6.1 Objective of survey
3.6.2 Solar Panels
3.6.3 Battery
3.7 Main components of EPS
3.7.1 DC_DC Converters
3.7.2 Charging Circuit (Step-up converters)
3.7.3 Adjustable
3.7.4 Low-Dropout Linear regulator (LDO)
3.7.5 Discharging circuit (Step-down converter)
3.7.6 Solar cells
3.7.7 Batteries
3.7.9 Step-Up DC-DC Converters Circuit
3.8 Charging Circuits
3.8.1 LM 317T
3.9 Charging Process
3.9.1 Charging with MAX1555
3.9.2 Charging with MCP73831
3.9.3 Charge with Max1555
3.10 Interfacing with the other subsystems
3.10.1 Individual interfacing tests
3.10.2 Interfacing with the whole subsystems
3.11 Switching Operation
3.12 The final power budget
3.13 Load Cycle representation
3.14 Simulation
3.14.1 Solar cells simulation
3.14.2 Battery discharge simulation
3.15 Recommendations
3.15.1 Solar panels
3.15.2 Step-up regulators
3.15.3 PCB’S
3.15.4 Simulink
3.15.5 Switching Controllers
3.16 References
Chapter (4) Attitude Determination and Control
4.1 Introduction
4.2 Mission Modes
4.3 Pointing Accuracy
4.4 Progress of 2nd Iteration
4.5 Objectives of 3rd Iteration
4.6 Attitude Determination Subsystem
4.6.1 Reference Sensors
4.6.2 Inertial Sensors
4.7 Attitude Determination Methods
4.8 Attitude Control Subsystem
4.8.1 Passive Attitude Control Methods
4.8.2 Active Attitude Control Methods
4.8.3 Conclusion
4.9 ADCs Configuration
4.10 ADCs Requirements
4.10.1 ADCs Hardware
4.10.2 ADCs Software
4.11 ADC Subsystem Deliverables
4.12 Hardware Implementation
4.12.1 Magnetometer Sensor
4.12.2 Testing Equipment
4.12.3 Testing Procedure
4.12.4 Magnetic Field Disturbance
4.12.5 Calibration Algorithm
4.12.6 Sun Sensor
Problems
4.13 Simple Onboard Orbit Model
4.13.1 Two Line Elements
4.13.2 Model Characteristics
4.14 Earth Magnetic Field
4.14.1 MATHEMATICAL FORMULATION OF THE IGRF MODEL
4.14.2 Model Characteristics
4.15 On Board Sun Model
4.15.1 Model Characteristics
4.16 Attitude Determination Algorithm
4.16.1 Triad Algorithm
4.17 Satellite Attitude Control Subsystem (ACS):
4.17.1 Coordinate Systems
4.17.2 Transformation between Frames
4.17.3 Magnetorquer Design
4.17.4 Non-Linear Model of Satellite
4.17.5 Linearization of Mathematical Model
4.17.6 Linear Control Techniques
4.18 References
Chapter (5) Communications
5.1 Abstract
5.2 Acronyms
5.3 Introduction
5.4 Introduction to Communication Science
5.5 The Cube satellite Communication system
5.5.1 The communication system of the cube satellite
5.5.2 COTS
5.5.3 Modified COTS
5.5.4 Custom build
5.5.5 Radio systems for twenty four Cube Satellite
5.5.6 Search about Radio Systems in Table 1
5.5.7 Summary of Cube Sat Launches 2009 to 2012 (49 cube sat)
5.6 Cube Satellite Communication System and Implementation of AX.25 Protocol
5.6.1 Atmega Microcontroller
5.6.2 First configuration
5.6.3 Second Configuration
5.6.4 Cube Satellites Ground Station
5.7 Cube Satellite Antenna Design
5.7.1 Introduction
5.7.2 Review of Literature
5.7.3 Proposed System
5.7.4 System Design
5.7.5 Implementation and Testing
5.7.6 Conclusion and Future Work
5.8 References
Chapter (6) Command and Data Handling
6.1 Introduction
6.2 OBC Survey
6.2.1 OBC Requirements
6.2.2 Collected Data
6.2.3 Data Statistics
6.2.4 OBCs Comparison
6.2.5 Microcomputers Comparison
6.2.6 Conclusion
6.3 Previous Iteration’s Work
6.3.1 What was done in the previous iteration?
6.3.2 Problems of the previous iteration
6.3.3 Techniques planned to be used for solving these problems
6.4 Hardware
6.4.1 Hardware Interfaces
6.4.2 Hardware System Description
6.4.3 Hardware Architecture
6.4.4 Subsystem Hardware Design
6.4.5 Interfacing Pins
6.5 Software
6.5.1 Main Scenario
6.5.2 Operation Modes
6.5.3 Software System Description
6.5.4 Software Architecture
6.6 Implementation and Integration
6.7 References
Chapter (7) Structure
7.1 Introduction
7.1.1 Objectives of Structure Subsystem
7.1.2 Outcomes of the previous iteration
7.1.3 Targets of this iteration
7.2 Main Parameters
7.2.1 Margin of the actual weight values
7.2.2 Available Material
7.2.3 Permitted Size
7.2.4 Design Concepts
7.2.5 Mass budget
7.2.6 Volume Budget
7.2.7 Conclusion of Survey
7.3 Design of 3rd Iteration
7.3.1 Mass Budget
7.3.2 Center of Gravity and Inertia Tensor
7.3.3 Iterations of Configuration of CubeSat’s Structure
7.3.4 Disadvantage of this iteration
7.3.5 Components of Structure
7.3.6 Disadvantages of this Iteration
7.3.7 Strength Analysis
7.3.8 Finite Element Analysis
7.3.9 Failure Analysis
7.3.10 Vibration Testing
7.3.11 Manufacture Phase
7.3.12 Final iteration
7.4 Recommendations
7.4.1 Human Resources
7.4.2 Design Concepts
7.4.3 Finite Element Model
7.4.4 Thermal Control
7.4.5 Vibration testing
7.4.6 Manufacture Phase
7.5 Integration Concepts
7.5.1 Adhesive Material
7.5.2 Mechanical Fasteners
7.6 References
Chapter (8) Integration
8.1 Introduction
8.2 Integration Phases
8.3 Subsystems Hardware
8.4 Cube satellite Assembly
Appendices
3.1 Appendix A: Survey on EPS
3.2 Appendix B: The final PCB’s
4.1 Appendix A: Collected Data about Cubesats used in survey.
4.2 Appendix B: Simulink Model
4.3 Appendix C: Simulation Results
7.1 Appendix A: The drafting figures
Appendix A: Time plans
Project Objectives and Focus
The primary objective of this project is to design, manufacture, assemble, and test specific subsystems for the third iteration of the Cairo University Cube Satellite. The ultimate mission is to achieve Earth imaging functionality using low-cost, off-the-shelf (COTS) components and to document the technical know-how developed during this process.
- Design and implementation of an Electrical Power Subsystem (EPS) based on COTS components.
- Development of an Attitude Determination and Control Subsystem (ADCS) for satellite orientation.
- Implementation of a communication system using AX.25 protocols and amateur radio hardware.
- Development of an On-Board Computer (OBC) system using the Beagle Bone Black platform.
- Structural design and stress/vibration analysis of the 1U cube frame.
Excerpt from the Book
2.8.1 Introduction
Space propagation models use current state information of a satellite to predict a future state of the satellite. As a simplistic example, imagine a car driving down a highway. If we know the location and the speed of the car now, we can make an accurate prediction of where the car will be in an hour. Similarly for satellites, if we know the position and the velocity now, we can make a reasonable guess where the satellite will be in the future. The satellite however, encounters disturbances, or perturbations, along its path that complicates its motion. These perturbations are caused by the Earth’s shape (spherical harmonics), drag, radiation, and effects from other bodies (the sun and moon generally).
Orbit Propagator is a Mathematical model acquires initial state “position and velocity” as input, to calculate the state of the body after certain time period relative to the Earth-centered inertial coordinate system, taking into consideration the perturbing effects on this motion.
Summary of Chapters
Chapter (1) Introduction: An overview of the project objectives for the Cairo University Cube Satellite and a roadmap of the document.
Chapter (2) Mission Analysis and Orbital Determination: Selection of the optimal orbit based on mission requirements, covering orbital parameters and propagation models like SGP4 and Cowell’s method.
Chapter (3) Electric Power: Details on the power generation, distribution, and protection, including solar panel selection, battery management, and DC-DC converter testing.
Chapter (4) Attitude Determination and Control: Description of the ADCS, including sensor and actuator selection, and the implementation of attitude control algorithms.
Chapter (5) Communications: Overview of the communication system architecture, AX.25 protocol implementation, and ground station setup.
Chapter (6) Command and Data Handling: Selection and implementation of the On-Board Computer (OBC), including hardware interfaces and software scenarios.
Chapter (7) Structure: Design and manufacturing of the Cube Satellite structure, including mass budget and static/vibration analysis.
Chapter (8) Integration: The final steps of integrating the standalone subsystems into the full Cube Satellite assembly.
Keywords
Cube Satellite, COTS, Orbital Mechanics, SGP4, Electric Power Subsystem, Attitude Determination and Control, Communication Systems, AX.25, Beagle Bone Black, Structural Analysis, Finite Element Analysis, Satellite Integration, Space Mission, Telemetry, Ground Station.
Frequently Asked Questions
What is the primary goal of this project?
The primary goal is the design, manufacturing, assembly, and testing of selected subsystems for the third iteration of the Cairo University Cube Satellite, specifically focusing on a low-cost, Earth-imaging mission.
Which subsystems are covered in this research?
The research covers the mission analysis, electric power, attitude determination and control, communications, command and data handling, structure, and final integration.
What is the core mission of the Cube Satellite?
The core mission is to perform Earth imaging and transmit data to a ground station using low-cost, off-the-shelf (COTS) components.
What scientific methods are used for orbital propagation?
The project utilizes SGP4 (Simplified General Perturbations) and Cowell's Method to predict satellite motion and position in orbit.
What is the role of the Beagle Bone Black in this project?
The Beagle Bone Black serves as the On-Board Computer (OBC), providing the necessary processing power to handle subsystem tasks, image processing, and task management via a Linux-based operating system.
What are the key technical challenges identified in the structure design?
Key challenges include ensuring sufficient mechanical integrity to withstand launch vibrations while maintaining mass, volume, and size constraints within a 1U form factor.
How does the project handle communication?
Communication is handled via amateur radio equipment, implementing the AX.25 protocol for data transfer, and using AFSK modulation or FSK depending on the configuration.
What is the significance of the "Frozen Orbit" concept mentioned?
The frozen orbit is used to minimize natural orbital drifts caused by Earth's shape, ensuring the altitude remains consistent over time, which is beneficial for power capture stability.
- Quote paper
- Ahmed Ibrahim (Author), 2014, Design, Manufacturing, Building and Testing Subsystems of Cube Satellite, Munich, GRIN Verlag, https://www.grin.com/document/1130870
