GA CubeSat Simulator Documentation

Program Authors: Andreas Peukert

Gregor Z. Hanuschak Eric Tapio

1.1.1.1 Getting Started In order to run the GA CubeSat simulator you will need a copy of the program as well as MATLAB software. You will also need to “Set Path” on the “Project_GA” folder.

1.1.1.2 Satellites If you want the program to yield meaningful results, you should put satellites in the simulation before you run it. There are two ways to do this.

1.1.1.3 Add a New Satellite (Method 1) One way to add a satellite is to create a new one. To do this, click on the “Add Satellite” button in the main “GUI Environment” screen. This will create a default satellite with an equatorial orbit, a CDH, a payload, and no other subsystems (these defaults can of course be changed). This will also create two windows: a visualization of the satellite’s current attitude and a visualization of the satellite’s current orbit with respect to a 3-dimensional Earth.

Attitude and orbit visualization windows

1.1.1.4 Loading a Saved Satellite (Method 2) The other way to add a satellite is to load a saved satellite. Go to the menu bar at the top of the GUI Environment and choose “Load Satellite” from the “Satellite” pull-down menu. Find the correct directory and select the satellite you want to load.

1.1.1.5 Starting the Simulation The text field displaying the current time will read “1/1/2000 12:00:00”, the default start time. To start the simulation at a time other than the current time, simply edit the text field and enter your desired start time. Remember to keep your new start time in the same format as the default. Note that the current time will increment by the time step. The default time step is 60 seconds, but this can be changed if desired. If you want a very accurate attitude

simulation, it is a good idea to make the time step even smaller, possibly as small as five seconds. It is generally not a good idea to make the time step any bigger, since this will start to make the simulation less accurate. The simulation will begin when the “Start/Stop” button in the GUIEnvironment is clicked once. The simulation will pause (stop) when the “Start/Stop” button is depressed (clicked again).

GUIEnvironment display

As time goes by, you’ll notice changes in the three visualizations: the 3D satellite visualization, the 3D Earth, and the 2D Earth. On the 2D Earth, you’ll notice the tracing of the satellite ground track (or ground tracks if multiple satellite are modeled) as well as the motion of the sun and moon.

A satellite with ground track in a started simulation

1.1.1.6 The “OK”, “Cancel”, and “Apply” Buttons There are three buttons common to nearly all GUIs in the GA CubeSat Simulator:

• “OK” – This button applies any changes you’ve made and exits the current GUI. • “Cancel” – This button exits the current GUI without applying any changes. • “Apply” – This button applies changes you’ve made but does not exit (the GUI

remains open).

1.1.1.7 The “Open Satellite” Button The satellite list box displays all the currently simulated satellites. By clicking the “Open Satellite” button you can obtain more information on any of the satellites, at any time, even when the simulation is running. Clicking the “Open Satellite” button also gives you the opportunity to edit the satellite details and add subsystems to the satellite. In the GUIEnviornment’s satellite list box, click and highlight the name of the satellite of interest and then click “Open Satellite.” The following GUISatellite window will appear:

GUISatellite display

The GUI displays the following information, all of which can be edited:

• Name of the satellite. • Initial satellite position and velocity. If you prefer to edit the Keplerian elements,

click on the “Keplerian elements” button. Clicking on the “Position&Velocity” button returns you to the default view. In order to apply any changes you make to the initial satellite orbit, you must click “Reset” in the environment GUI after clicking “Apply” or “OK” click in the satellite GUI.

• Initial satellite attitude (quaternion and x/y/z angular velocities). In order to apply any changes you make to the initial satellite attitude, you must click “Reset” in the environment GUI after clicking “Apply” or “OK” click in the satellite GUI.

• Satellite inertia matrix. • Cumulative satellite cost. This information comes from the sum of the cost of the

satellite structure plus the cost of the subsystems. It can therefore not be edited directly.

• Satellite drag coefficient. Also displayed, but can not be changed directly:

• Current satellite position and velocity. To see these as Keplerian elements, click on the “Keplerian elements” button. Clicking on the “Position&Velocity” button returns you to the default view.

• Current satellite attitude (quaternion and x/y/z angular velocities). • Total satellite mass. This is computed from the weight of the satellite structure

and its onboard subsystems. • Total satellite cost. This is computed by summing the individual costs of the

subsystems. • Solar radiation pressure. • Magnetic field vector.

1.1.1.8 Introduction to Subsystems: Operational Strategy Many satellite subsystems in the GA CubeSat Simulator include the option for using an “Operational Strategy.” The purpose of an operational strategy is to conserve power. By turning “on” a particular subsystem only when it is absolutely needed we can save battery life. There are three options on how to limit a subsystems use by means of an “Operational Strategy”:

• “Manual” – Default setting, no operational strategy. • “LatitudeBased” – Turn a subsystem “on” only when the satellite is within a

given latitude range. • “DistanceBased” – Turn a subsystem “on” only when it is within a given distance

of a given groundstation (or groundstations if “all” is selected).

1.1.1.9 Viewing Satellite Subsystems In the satellite GUI, note that the subsystem list box contains the subsystems “AttOrbContrSys” (for attitude and orbit control), “ComDataHand” (for command and data handling), “Comm” (for communication), “ElecPowSys” (for electrical power systems), “Structure” (for viewing/changing the structure mass), and “Payload” (for payload). To view a particular subsystem, click and highlight the name of the subsystem and click “Open subsystem.”

1.1.1.9.1 Subsystems: AttOrbContrSys

GUIAttOrbContrSys display

• GPS o “Add GPS” creates a new GPS with default values and adds it to the GPS list

box. o “Delete GPS” deletes the currently highlighted GPS system. o “Open GPS” opens a details window for the currently highlighted GPS

system. Note that you can not directly change the necessary “Power” required by the GPS system. This is indirectly calculated from current and voltage fields and is only updated when the simulation is running. Also note that no power usage calculations will be made for a GPS system unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

GUIGlobPosSys display

• MagnTorq

o “Add MagnTorq” creates a new magnetotorquer subsystem with default values and adds it to the magnetotorquer list box.

o “Delete MagnTorq” deletes the currently highlighted magnetotorquer system. o “Open MagnTorq” opens a details window for the currently highlighted

magnetotorquer system. Note you can not directly change the necessary “Power” required by the magnetotorquer system. This is indirectly calculated from current and voltage fields and is only updated when the simulation is running. Also note that no power usage calculations will be made for a magnetotorquer system unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

GUIMagnTorquer display

Other notes on Magnetotorquers:

• If “Type” is set to “Coil” you can set the windings, area, required current, required voltage, and operational strategy, but not magnetic induction, mass, or density.

• If “Type” is set to “Permanent Magnet” you can set magnetic induction, mass, and density, but not windings, area, required current, required voltage, or operational strategy.

1.1.1.9.2 Subsystems: ComDataHand

GUIComDataHand display

The details window for this subsystem will allow you to set almost all properties for ComDataHand. One notable exception to this rule is the required power. This is calculated from the required voltage and current fields and only updated while the simulation is running. No power calculations will be made while the “Status” field is set to “Off.” Mass calculations however are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

1.1.1.9.3 Subsystems: Comm

GUIComm display

• Modems o “Add Modem” creates a new modem with default values and adds it to the

modem list box. o “Delete Modem” deletes the currently highlighted modem system. o “Open Modem” opens a details window for the currently highlighted modem

system. Note that you can not directly change the necessary “Power” required by the modem system. This is indirectly calculated from current and voltage fields and is only updated when the simulation is running. Also note that no power usage calculations will be made for a modem system unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

GUIModem display

• Receivers o “Add Receiver” creates a new receiver subsystem with default values and

adds it to the receiver list box. o “Delete Receiver” deletes the currently highlighted receiver system. o “Open Receiver” opens a details window for the currently highlighted receiver

system. Note that you can not directly change the necessary “Power” required by the receiver system. This is indirectly calculated from current and voltage fields and is only updated when the simulation is running. Also note that no power usage calculations will be made for a receiver system unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

GUIReceiver display

• Transmitters o “Add Transmitter” creates a new transmitter with default values and adds it to

the transmitter list box. o “Delete Transmitter” deletes the currently highlighted transmitter system. o “Open Transmitter” opens a details window for the currently highlighted

transmitter system. Note that you can not directly change the necessary “Power” required by the transmitter system. This is indirectly calculated from current and voltage fields and is only updated when the simulation is running. Also note that no power usage calculations will be made for a transmitter system unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

GUITransmitter display

1.1.1.9.4 Subsystems: ElecPowSys

GUIElecPowSys display

The electrical power subsystem is divided into three more specific subsystems: PowGen (power generation/solar panels), PowStor (power storage/batteries), and PowDistr (power distribution). Click and highlight the specific subsystem of interest and the click “Open subsystem” for more details.

1.1.1.9.4.1 Subsystems: ElecPowSys: PowGen

GUIPowGen display

• The solar array plot updates in real-time while the simulation is running. It

displays the total power generation vs. time by summing the contribution of all the solar arrays in the neighboring list box.

• “Add SA” creates a new solar array with default values and adds it to the solar array list box.

• “Delete SA” deletes the currently highlighted solar array. • “Open SA” opens a details window for the currently highlighted GPS system.

Note that you can not directly change the “Current” or “Power” produced by the solar array. Current is indirectly calculated from the incoming sunlight and power is indirectly calculated from this and what’s in the voltage field. Both are only updated when the simulation is running. Note that no power supply calculations will be made for a solar array unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

GUISolarArray display

1.1.1.9.4.2 Subsystems: ElecPowSys: PowStor

GUIPowStor display

• The battery plot updates in real-time while the simulation is running. It displays

power storage vs. time by summing the power stored in all the batteries in the neighboring list box.

• “Add Battery” creates a new battery with default values and adds it to the battery list box.

• “Delete Battery” deletes the currently highlighted battery. • “Open Battery” opens a details window for the currently highlighted battery.

Note that you can not directly change “Current” stored in the battery (since this wouldn’t make sense anyway). Note that no power calculations will be made for a battery unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the subsystem physically resides on the satellite even if it’s turned off.

GUIBattery display

1.1.1.9.4.3 Subsystems: ElecPowSys: PowDistr

GUIPowDistr display

The job of this interface is to provide information on the power status of the satellite as a whole. The three plots update in real-time while the simulation is running.

• Power Income Plot: Displays cumulative power generation for all solar arrays vs. time.

• Subsystem Power Need Plot: Displays cumulative power need vs. time for all subsystems in the neighboring list box.

• Battery Power Income Plot: Displays cumulative power storage for all batteries vs. time.

1.1.1.9.5 Subsystems: Structure

GUIStructure display

Any satellite mass or cost not previously accounted for can be entered here. The structure subsystem also lets you edit the type of the satellite structure.

1.1.1.9.6 Subsystems: Payload

GUIPayload display

The payload GUI is concerned only with power details and operational strategy. Note that you can not directly change the necessary “Power” required by the payload. This is indirectly calculated from current and voltage fields and is only updated when the simulation is running. Also note that no power usage calculations will be made for a payload unless its “Status” field is set to “On.” Mass calculations are performed regardless of “Status,” since the payload physically resides on the satellite even if it’s turned off.

1.1.1.10 Saving a Satellite Once you have a satellite with the specific details for a satellite, you probably want to save it to avoid repeating the set up process. Go to the menu bar at the top of the GUI Environment and choose “Save Satellite” from the “Satellite” pull-down menu. Find the correct directory and select the satellite you want to load.

1.1.1.11 Central Body To change properties for the Central Body, go to the menu bar at the top of the GUI Environment and choose “Central Body” and then “Properties.” The following window will appear:

GUICentrBody display

Most of this GUI is just for information purposes, but the following can be changed:

• Magnetic Field Model • Atmosphere Model (although there is currently only one choice). • Groundstations

1.1.1.11.1 Central Body:Groundstations Groundstations have a name and position. The position can be edited or viewed using geodetic or ECI coordinate systems by simply clicking the corresponding button. Groundstations will appear on the two-dimensional Earth as blue circles.

GUIGroundStation display

1.1.1.12 Third Bodies To view the properties of the third bodies, go to the menu bar at the top of the GUI Environment and choose “Third Bodies” and then “Properties.” The following window will appear:

GUIThirdBody display

Currently the Sun and the Moon are the only third bodies. Click on the corresponding name in the list in order to see its properties.