Progress Log

A log concerning my current projects at MSU's 2010 Solar and Space Physics REU program.

7th Week - 5th Week - 3rd Week

7th Week

This week is starting out well. I have talked to Keith Mashburn, who works with David Klumpar, about my project. After I completed the reconstruction of my lost files, I now feel like I can continue with the program. My original goals for the summer are somewhat different than before, but should still be very useful to the SSEL FIREBIRD project.

As of now, I have a program that can simulate the orbits of a satellite using a geoid gravitational model of the Earth, as well as having upper, average, and lower bounds of an atmospheric density model. This means that I treat the Earth as an ellipse while implementing gravitational equations through the use of zonal spherical harmonics, and that I have an atmospheric density model that contains low, average, and high values for the density at a given altitude. In this way, I can perform worst-case and best case scenarios for my simulations. This will give me effective "bounds" on the accuracy of the results.

Now, I wish to continue the development of the program by incorporating an accurate magnetospheric model. I plan to use the International Geomagnetic Reference Field model used in a modified version of the original Cubesim program. I have the opportunity to talk to some graduate students in our partner universities about this magnetic model and its implementation. Hopefully, I can use this model so that it does not significantly slow down the operations of my current program. I will use the model to help predict the orientation of the FIREBIRD satellites given their position in space. This is useful because knowing the attitude (orientation) of each satellite in space lets us know about the cross-sectional area that is affected by atmospheric drag. As of now, my atmospheric drag model assumes that the cross-sectional area is constant with respect to each satellite's direction of motion. Using an accurate magnetic model can show me how the attitude, and subsequently the cross-sectional area, of each satellite changes during its orbit; a different cross-sectional area means a different drag force exerted on the satellite, which will ultimately change its orbital trajectory.

This magnetic model will also have worst and best case scenarios. As suggested by Keith, I will use the best case model of the satellites attitude by assuming perfect attitude control with no oscillations around in orientation perfectly aligned with the magnetic field. In a worst-case scenario, I will assume a full, non-decaying oscillation around an ideal orientation aligned with the field. In a real-life situation, the oscillations of the attitude of the satellite will slowly decay due to magnetic hysteresis. However, the physics behind hysteresis is still rather poorly understood, and our partner universities are still having trouble modeling accurate magnetic hysteresis within their modification of the original Cubesim program. However, I believe these issues will soon be resolved, and I intend to provide a program that will easily accommodate these more accurate hysteresis models. In the meantime, using best and worst-case attitude oscillations in my simulation will give reasonable results within these bounds. This alone will provide a decent framework of a good program that will not only be useful to MSU, but to the rest of the space community as well. I intend to complete this final part of the program in order to let MSU collaborate with other universities towards the creation of the very strong orbital simulator that utilizes a strong atmospheric and magnetospheric model that makes use of magnetic hysteresis modeling for the simulation of the stabilization of the attitude of satellites.