Bimodality in reentry latitude predictions for spacecraft in prograde orbits

Area of Science:

• Orbital Mechanics and Astrodynamics
• Spacecraft Reentry Analysis
• Statistical Modeling

Background:

• Predicting the precise latitude of spacecraft atmospheric reentry is crucial for safety and operational planning.
• Previous models often assumed a unimodal distribution for reentry latitudes, potentially oversimplifying the phenomenon.
• Low Earth orbits (LEO) below 300 km exhibit complex dynamics influencing reentry trajectories.

Purpose of the Study:

• To investigate the probability distribution functions (PDFs) of atmospheric reentry latitudes for spacecraft in LEO.
• To determine if these PDFs exhibit bimodality and identify factors contributing to this characteristic.
• To develop and validate methods for quantifying reentry latitude bimodality and estimating probability densities.

Main Methods:

• Utilized two-line element (TLE) data for initial spacecraft orbit conditions.
• Incorporated coarse estimates of spacecraft aerodynamic characteristics into parametric simulations.
• Employed computational measures to test for and quantify bimodality in reentry latitude data sets.
• Introduced a novel method for approximating bandwidth in kernel estimation of reentry latitude probability density.

Main Results:

• Probability distribution functions for atmospheric reentry latitudes were found to be bimodal for spacecraft in prograde LEO below 300 km.
• Simulations indicated a greater likelihood of reentry occurring near the latitudinal maxima of a spacecraft's ground track.
• Statistical analysis confirmed that actual reentry latitudes generally fall within 1-sigma of observed hemisphere means.

Conclusions:

• The bimodal nature of reentry latitude PDFs is a significant finding for LEO spacecraft.
• This bimodality suggests a predictable pattern favoring reentry at specific latitudinal extremes.
• The developed statistical methods provide a more accurate approach to modeling and predicting reentry phenomena.