SmallSat Constellation Inter-satellite Link System Simulator

Goddard Space Flight Center Distributed Space Mission (DSM) seeks to design and develop the technologies required to achieve the mission goals.  For a constellation of small satellite performing a coordinate mission, there are inter-satellite links within the constellation for the control and mission data transmission.  This proposal is to develop a system simulator to support the design and optimization of the SmallSat constellation inter-satellite links.   The system simulator is a tool to perform modeling and simulation of the constellation geometry, flight communication system and data transmission protocols for the determination of the optimal configuration of the inter-satellite links relative to the constraints of the mission.   In Phase I, the simulator will address the need of Constellation Design Reference Mission (DRM-C) and Precision Formation Flying DRM (DRM-PFF).  In Phase II, the development of the simulator will be extended to address generic constellation scenarios, from Low Earth Orbit (LEO) to deep space (Cis-lunar and beyond)

The objectives of the study are:

• Develop a SmallSat constellation inter-satellite link system simulator to support the design and optimization of the SmallSat constellation inter-satellite links.
• Develop SmallSat Constellation inter-satellite link communication requirements
• Develop the system simulator architecture that consists of:

            - S, X and Ka-band flight system modeling including link quality and time varying behavior of the SmallSat constellation inter-satellite links      with MATLAB Simulink tool

            - SmallSat constellation geometry modeling with STK

            - Switched packet IP network simulation to model the actual activity within the constellation switched packet IP network with QualNet tool

            - Routing implementation

            - Simulation of the desired user data flow pattern that will ultimately ‘load’ the network.

• Identify SmallSat constellation case scenario to perform demonstration/testing of the network efficient (i.e. inter-satellite link performance) using the system simulator
• Investigate the re-use of the software communication protocol for a testbed for prototype system-level testing

    Deliverables will include:

• SmallSat Constellation inter-satellite link communication requirements
• A SmallSat Constellation Inter-satellite link system simulator that consists of:

           - S, X and Ka-band flight system software model

           - Constellation geometry software model

           - Constellation switched packet IP network simulation software model

           - Routing protocol implementation software model

           - Desired user data flow pattern software model

• SmallSat constellation case scenario design including constellation geometry, flight system parameters, constellation routing table, communication protocol parameters.
• SmallSat constellationcase scenario demonstration/testing and report

Research and Development Plan

SmallSat Constellation inter-satellite link communication requirements

In phase I, the SmallSat constellation inter-satellite link simulator requirements will be derived from the DRM-C and DRM-PFF missions. 

System Simulator Modeling Overview

The simulator will model the flight communication system of the constellation inter-satellite links using STK/MATLAB Simulink tool.  The constellation geometry and the trajectory dynamic will be modelled with STK tool.  The small satellite network performance will be modelled with QualNet tool.

The software and communication protocols for control and data transmission management will borrows heavily from wireless IP networking standards. 

System Simulator Architecture

The simulator architecture will consist of six major elements as shown in Table 1. System Simulator Architecture Elements (see project library)

A small Satellite Constellation simulation scenario is shown Figure 1.(see project library)

The simulator inputs and outputs are shown in Table 2.  Simulator Inputs and Outputs (see project library)

The system simulator will be able to simulate the network efficiency (i.e. inter-satellite link performance) of a constellation configurations for a variety of performance cost-based routing. The inputs to the simulator represent different combinations of mission requirements while the outputs represent how well those requirements are met based on the given constellation configuration. The end goal is that the mission designer is able to evaluate different mission configurations and their associated performance.  

For the DRM-C and DRM-EEF missions, an analysis will be performed by the simulator to provide a solution to the inter-satellite link communication system design. 

Software Communication Protocol Reuse

The software communication protocol developed in this task can be re-used for deployment on a testbed for prototype system-level testing and even for an on-orbit DSM mission and others.