FreeFlyer Lab

What is FreeFlyer?

FreeFlyer is a platform that can simulate different orbital scenarios of involving a spacecraft.

Background and Key Concepts to Consider

• Demonstrating the orbit of a spacecraft
• Desired outcomes to analyze
  • Calculating the ground track of a satellite in its orbit
  • Solar irradiance
  • Input surface area of solar panels
  • Solar panels efficiency
  • How to calculate the power generated from results

Materials and Setup

Materials

• Windows or Linux computer
• FreeFlyer

Making an Account

When signing up for a FreeFlyer account, make sure to use your hawaii.edu email address. This will ensure that you will get the year-long license.

Installing FreeFlyer / Getting a License

Follow these instructions for installing and retrieving a license:

https://ai-solutions.com/_freeflyeruniversityguide/installing_freeflyer.htm

Procedures

Main Lab Procedures

While there are many functionalities to FreeFlyer (comprehensive tutorial list at the bottom of this lab procedure), we are going to focus this lab on:

1. Building and plotting the orbit of your mission,
2. Generating power output from your satellite’s solar panels, and
3. Generating an operations timeline of when your satellite is within distance limits to communicate.

For each of the different tutorials, generate plots and save certain data products that will contribute to your spacecraft design.

Satellite Orbit

Although there are six different orbital elements to consider, this tutorial will focus on two. This tutorial will teach you how changing different orbital element values will affect a spacecraft’s orbit.

https://ai-solutions.com/_freeflyeruniversityguide/orbital_elements_tutorial.htm

Save your .MissionPlan file and take a screenshot of your orbital trajectory just like the screenshots above.

Simulating Spacecraft Location and Contact Times:

In order to take a look into FreeFlyer’s orbital capabilities, we will be running an example mission plan provided by FreeFlyer.

1. 1. Locate your FreeFlyer folder by going to “File” then “Open”
   2. Enter the FreeFlyer *version number* (64-Bit) folder
   3. Click on ‘Sample Mission Plans’
   4. Click on ‘Coverage and Contact Analysis’
   5. Open ‘GroundStation.MissionPlan’ with FreeFlyer
   6. Modify GroundStation1 with the GPS coordinate for UH Manoa: 21°17’49.20″ N -157°49’1.20″ W
   7. Click on ‘Run’ (Blue Triangle Button)
   8. Observe the plots and simulation
      1. You may navigate the charts by click and drag
      2. A report of the PassData found in Mission Sequence provides parameters for a set of angle, range, and contact time information. In Output Properties you may export the data as a text file for plot points used to generate the plot

We will now simulate our own spacecraft orbits. We will be focusing on the ‘Right Ascension of the Ascending Node’ tutorial. Although this tutorial’s initial focus is another one of the six elements of orbit, it will also teach you how to simulate spacecraft orbiting around Earth and when it is within range of a specific ground station.

https://ai-solutions.com/_freeflyeruniversityguide/orbit_orientation.htm

Save the .txt file of the ground station contacts with UH Manoa (or a ground station of your choice) and screenshot the orbit trajectory ground track with ground stations in view.

Simulating Power Profiles from Orbit:

Ensuring that the Spacecraft is receiving enough power through simulation, this tutorial teaches you how to create a custom attitude frame (important for pointing) and generate power profiles from your satellite’s solar panels. Make sure to save the panelPower as a function of time in a text or excel file for a later lab.

https://ai-solutions.com/_freeflyeruniversityguide/mission_constraints_on_spacecraft.htm

Lab Review and Deliverables

To review, by the end of this lab which contained three tutorials, you should have:

• Defined the orbital elements of your mission
• Saved the .MissionPlan file of this orbit
• Taken a screenshot of your mission’s orbital trajectory
• Taken a screenshot of orbital trajectory ground track with areas of illumination
• Generated and saved a .txt file of power profile over time
• Taken a screenshot of orbital trajectory ground track with contact times to ground station
• Generated and saved a .txt file of contact times with your ground station over time

Tips

• When adding a spacecraft, always change the Element Type to Keplierian

Comprehensive List of Tutorials

1. Orbits
   1. Orbit Shapes and Sizes – In this section, we will discuss the various aspects of an orbit that make up its shape and size.
   2. Orbit Orientation – In this section, we will discuss and demonstrate the other four Keplerian elements.
2. Attitude
   1. Attitude State Representations – In this section, we will discuss the different ways to represent the attitude of a spacecraft.
   2. Attitude Reference Frames – In this section, we will discuss the coordinate system that the spacecraft’s attitude is referenced to.
   3. Mission Constraints on Spacecraft Attitude – In this section, we will combine the different ways to represent a spacecraft’s attitude and how they can change with a variety of reference frames into one mission problem.
3. Maneuvering
   1. Hohmann Transfer – In this section, we will discuss the most efficient transfer a spacecraft can make to change the size of an orbit.
   2. Bi-Elliptic Transfer – In this section, we will discuss a different transfer that is more efficient in certain scenarios.
   3. Phasing Maneuver – In this section, we will discuss maneuvers that change the size of an orbit in order to meet the original orbit at a different point in time.
   4. Plane Change Maneuver – In this section, we will discuss how to make an inclination change.
4. Interplanetary Topics
   1. Interplanetary Hohmann Transfer – In this section, we will discuss using the Hohmann transfer for interplanetary transfers for earth orbiting spacecrafts.
   2. Patched Conics Transfer – In this section, we will discuss realistically modeling using multiple two-body problems instead of one multi-body as used in the interplanetary Hohmann transfer.
   3. Gravity Assist – In this section, we will discuss a spacecraft flying near a celestial body and having their flight path redirected and continued onto its hyperbolic trajectory.
   4. The B-plane – In this section, we will discuss making planetary flybys or rendezvous where a spacecraft has a specific hyperbolic trajectory past a planet.
5. Targeting
   1. Inclination Change – In this section, we will discuss how to use FreeFlyer to find the Δv components found in the previous plane change tutorial without using equations.
   2. B-Plane Targeting – In this section, we will discuss how the B-Plane can be used by mission planners to fly by a specific location on a planet, or target a capture orbit of a specific inclination.
6. Real World Modeling
   1. Multi-Body Effects – In this section, we will discuss different forces acting upon a spacecraft.
   2. J2 Perturbation – In this section, we will discuss the orbital effect from the earth actually being more oblate than spherical.
   3. Atmospheric Modeling – In this section, we will discuss another force to be considered when modeling LEO spacecraft – atmospheric drag.
   4. Solar Radiation Pressure – In this section, we will discuss another force that can affect bigger, lighter and slower spacecraft due to transfer of momentum from photons.