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Orbit Design and Analysis

Scope and Description

This topic covers detailed orbit design and analysis for smallsat missions. Orbit design is fundamental to a satellite mission because it determines the relative position dynamics of the spacecraft and locations on Earth and in space. This relative motion drives - among other things - power generation, radiation exposure, orbit lifetime, thermal performance, and the value of instrument data. Smallsats lend themselves to constellations and distributed architectures, both of which open up the orbit design trade space and make analysis significantly more complicated. Even for single-spacecraft missions, orbit design and analysis is a complex task because it is closely connected to so many elements of the spacecraft design. In many cases however, smallsats are constrained by launch opportunities to just a few options for their orbit. In these cases, orbit modeling and analysis is still required to inform detailed design of the spacecraft.

Resources under this topic area are primarily books and book chapters on astrodynamics and satellite orbit design and software tools for orbit simulation and analysis.

Best Practices and Lessons Learned

  • Orbit modeling involves a large number coordinate transformations, time conversions, numerical methods, and force models. Data entry errors and other small flaws can be very difficult to identify but have significant impacts on accuracy. Expert review and thorough visualization and analysis is necessary to verify your models and settings in orbit simulation programs.
  • Carefully consider what level of accuracy is required for a given task, and configure your models appropriately. For the majority of design tasks, high-precision force modeling and small time-steps are not required. If your model is very slow to simulate, consider doing a sensitivity analysis to determine the driving factors and, wherever possible, separate out the tasks that require significant compute time. This will allow you to efficiently iterate on the factors that can be solved quickly and run the most computationally intensive simulations less frequently.
  • Custom scripts that are not following a simple, standard workflow in an established software tool should go through a thorough verification and validation process.
  • Orbit design should start with subject matter expert reasoning, hand calculations, scripts, and spreadsheets to trim down the trade space. Time domain orbit simulations are computationally intensive and are generally not a practical tool for rapid design iteration.

Resources

Software Tool
James R Wertz et al.

This web page contains links and downloads for figures and tables from the new edition of the Space Mission ... Analysis and Design (SMAD) book that the website is associated with. Spreadsheet models for a wide range of space mission modeling tasks are available for download. These spreadsheet models for payload performance, communications, orbit, and several other elements of a space mission can be incorporated directly or adapted for integration into smallsat mission modeling workflows.

Software Tool
a.i. solutions

FreeFlyer is a commercial software tool for space mission design, analysis, and operations. Different ... versions are available for mission design and mission operations. The interfaces emphasize a robust scripting language. In general, this emphasis on scripting-based model development allows experts more control and visibility into the modeling but can make the tool more challenging for non-experts to learn and utilize.

Software Tool
Analytical Graphics Incorporated

STK is a powerful tool for simulation and analysis of complex systems. This software tool can be used ... to effectively model several elements for a small satellite mission in a single simulation. The dynamics of ground vehicles, spacecraft, aircraft, and other objects can be integrated in these mission models. To build upon the capabilities of the baseline tool, various add-on modules are available from AGI. Many third party tools also exist for integration with STK.

This paper presents a "methodology to integrate the deployment of constellations of smallsats into the ... wider design process for these systems." An optimization scheme based on a genetic algorithm is presented in detail and applied to three case studies. Two of these case studies are based on already launched systems, and the third is a notional smallsat mission. This paper is valuable both for its conceptual design optimization techniques and its focus on including deployment scheme in the design-space.

Book
Howard D. Curtis

This book is a good applied astrodynamics text for engineers. There are examples, figures, and computational ... procedures accompanied by MATLAB code. This is not as comprehensive as other similar options, but is more approachable for non-experts.

Software Tool
NASA

GMAT is an open source software system for space mission design, optimization, and navigation. This tool ... can be used to model and simulate the operation of spacecraft subsystems and orbit and attitude dynamics. As a free and open source product, the ease of use, documentation, and support are somewhat limited relative to commercial solutions.

Software Tool
Juan Luis Cano Rodriguez et al.

Poliastro is an open-source Python library used for modeling orbital mechanics and astrodynamics. The ... project website provides Installation instructions, training documents, and other resources to support users.

Software Tool
CS Group et al.

Orekit is an open-source Java library used for low-level space flight dynamics applications. This Java ... library (with a Python wrapper) can be used to propagate spacecraft orbit and attitude dynamics. The project website provides technical documentation, training videos, and community support.

Software Tool
NASA

According to the JPL/NAIF website, this toolkit is intended "to assist NASA scientists in planning and ... interpreting scientific observations from space-borne instruments, and to assist NASA engineers involved in modeling, planning and executing activities needed to conduct planetary exploration missions." This toolkit provides high-precision utilities for coordinate transformations, time conversions, and other tasks involved in modeling the positions and orientations of spacecraft and planets. SPICE can be used with different languages, including C, FORTRAN, MATLAB, and Java.

Book
James R Wertz et al.

SMAD is a practical handbook for space mission engineering covering all aspects of a space system - from ... orbit and constellation design to operations. This reference is valuable as both an introductory text and a reference. This chapter, titled "Orbit and Constellation Design", covers orbit design from a systems engineering perspective, which is a useful supplement to the more modeling and simulation oriented astrodynamics texts also referenced in this knowledge base.

Book
David A. Vallado

This book covers a broad range of topics regarding computational fundamentals of astrodynamics. It is ... a foundational textbook for astrodynamics modeling and simulation. Make sure to check the errata that is available on the publishers website when implementing methods from the text, especially for when using older editions of this book.

Article
Andrew E. Turner

This article details smallsat constellations from design to implementation and operation. Satellite constellations ... can be implemented in various orbits, missions, altitudes, and coverages. This resource focuses on the orbit design and analysis of Earth-orbiting smallsat constellations.

Software Tool
Caltech

Monte is a NASA JPL Python library with modules for trajectory design, navigation, and control. It was ... designed for interplanetary missions, but is suitable for most Earth orbiting and lunar missions as well. In you are developing a small spacecraft mission under a NASA contract, you could be eligible to license this powerful tool for free. This tool is generally more appropriate for more demanding orbit and trajectory design efforts.

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