Propagation and Collision of Orbital Debris in GEO Disposal Orbits

Transcription

1 Propagation and Collision of Orbital Debris in GEO Disposal Orbits Benjamin Polzine Graduate Seminar

2 Presentation Outline Need Approach - Benefit GEO Debris Continuation of Previous Work Propagation Methods Modified Equinoctial Elements Perturbations Collisions Breakup Model Completed Work What s Left

3 Need Need Approach - Benefit GEO is a high-activity, valuable regime Debris remains here for a much longer period of time Debris behavior in the nearby graveyard orbit is not yet fully understood Approach Create a high-accuracy propagator that takes into account major perturbations in this regime Verify propagator for accuracy by propagating real TLE s and comparing outcomes to observed outcomes Simulate collisions within and outside the regime Benefit An understanding of debris behavior and danger to GEO

4 GEO Debris Decommissioned GEO Satellites are generally pushed into a Graveyard Orbit >200 km above GEO Earth gravity perturbations Results in geopotential wells that capture satellites Operational satellites use East-West station keeping to combat this effect Wells have unknown effect on debris population Do they act as sinks?

5 Continuation of Previous Work Continuing the work of Christina Diaz Study of collisional evolution of debris in Geopotential Wells and GEO Disposal Orbits Modeled in Fortran, Visualized in MATLAB Propagation with Cowell s Method Perturbations include: 16x16 Geopotential, Lunar/Solar Gravity, SRP Simulated East/West geopotential wells Could not catch East-West trapped objects Had a suspect upward longitudinal drift

6 Propagation Methods Cowell s Method Summary: Direct integration of position and velocity Pros: Easy to understand, quick to code Cons: Not as accurate as VoP, runs slowly Variation of Parameters (VoP) Summary: Break perturbative force down into changes of each orbital element over time Pros: Accurate Cons: Hard to find errors, non-intuitive, breaks down at zero inclination if using COE element set

7 Modified Equinoctial Elements A VoP element set Seeks to address singularity issues with more common VoP element sets Pros Non-singular for any orbit High accuracy (as a VoP method) Cons Non-intuitive elements Posigrade/Retrograde must be known

8 Earth s Oblateness Perturbations The oblateness of the Earth results in a non-constant gravitational force Earth analyzed as a checkerboard of different gravitational effects Strongest effects for GEO at J 2, J 22 Φ, 1, sin, cos, sin Φ,

9 Earth s Oblateness Perturbations Verified Propagation My J2+J22 Propagation

10 3 rd -Body Gravitation Perturbations Pull of non-earth bodies effect satellite s orbit Strongest sources on an Earth satellite are Sun and Moon Dependent on vector between S/C and body Solar Perturbation Lunar Perturbation

11 Perturbations 3 rd -Body Gravitation (Sun) Verified Propagation My Sun Gravity Propagation

12 Perturbations 3 rd -Body Gravitation (Moon) Verified Propagation My Lunar Gravity Propagation

13 Perturbations Solar Radiation Pressure Photons expelled from the sun exert pressure on S/C Dependent on shape of S/C, orientation, mass distribution, and reflectivity Assumptions made Constant Solar 1367 W/m 2 0 < C R < 2 Spherical spacecraft model A/m ratio P C A m r

14 Perturbations Solar Radiation Pressure Verified Propagation My SRP Propagation

15 Collisions Collisions result in massive fragmentation that can snowball in size Adversely effects safety of satellites in GEO regime Very long time until deorbit is possible Low impact velocity (~1.5 km/s) Typically same orbit, same direction, low orbit speed Use Hanada s experimental scaling of NASA Standard Breakup Model for GEO regime

16 Hanada s Breakup Model NASA Standard Breakup Model describes a highspeed collision model for LEO Hanada gives modification for low-speed GEO breakups Steps Describe size distribution of breakup (L C ) Determine A/m distribution Fragment dv distribution Fragment distribution favors low-mass, low-speed fragmentation

17 Completed Work MATLAB Modified Equinoctial Propagator High accuracy for the following perturbations: Earth s Oblateness (J 2, J 22 ) Sun Gravity Need to be adjusted: Moon Gravity SRP Perturbation Collection of GEO Debris TLE data Breakup model ~75% complete

18 What s Left MATLAB Modified Equinoctial Propagator Address perturbation issues Verification vs. TLEs Completion of Breakup Model Verification against Hanada s output Collision Simulation Collision conditions # of fragments to propagate Verification of orbital well entrapment Behavior analysis

19 Questions?