Lawrence Livermore National Security, LLC

University of California

Donald W Phillion

Scot S Olivier

Willem H De Vries

Alexander Pertica

John R Henderson

Sergei Nikolaev

Vincent Riot

Brian J Bauman

Matthew A Horsley

Ming Jiang

Joanne L Levatin

Harry K Springer

A space object modeling system that models the evolution of space debris is provided. The modeling system simulates interaction of space objects at simulation times throughout a simulation period. The modeling system includes a propagator that calculates the position of each object at each simulation time based on orbital parameters. The modeling system also includes a collision detector that, for each pair of objects at each simulation time, performs a collision analysis. When the distance between objects satisfies a conjunction criterion, the modeling system calculates a local minimum distance between the pair of objects based on a curve fitting to identify a time of closest approach at the simulation times and calculating the position of the objects at the identified time. When the local minimum distance satisfies a collision criterion, the modeling system models the debris created by the collision of the pair of objects.

Modeling the long-term evolution of space debris

An ephemeris refinement system includes satellites with imaging devices in earth orbit to make observations of space-based objects ('target objects') and a ground-based controller that controls the scheduling of the satellites to make the observations of the target objects and refines orbital models of the target objects. The ground-based controller determines when the target objects of interest will be near enough to a satellite for that satellite to collect an image of the target object based on an initial orbital model for the target objects. The ground-based controller directs the schedules to be uploaded to the satellites, and the satellites make observations as scheduled and download the observations to the ground-based controller. The ground-based controller then refines the initial orbital models of the target objects based on the locations of the target objects that are derived from the observations.

Monitoring objects orbiting earth using satellite-based telescopes

Scheduler for monitoring objects orbiting earth using satellite-based telescopes

A constant volume gas cell optical phase-shifter, particularly applicable for phase-shifting interferometry, contains a sealed volume of atmospheric gas at a pressure somewhat different than atmospheric. An optical window is present at each end of the cell, and as the length of the cell is changed, the optical path length of a laser beam traversing the cell changes. The cell comprises movable coaxial tubes with seals and a volume equalizing opening. Because the cell is constant volume, the pressure, temperature, and density of the contained gas do not change as the cell changes length. This produces an exactly linear relationship between the change in the length of the gas cell and the change in optical phase of the laser beam traversing it. Because the refractive index difference between the gas inside and the atmosphere outside is very much the same, a large motion must be made to change the optical phase by the small fraction of a wavelength that is required by phase-shifting interferometry for its phase step. This motion can be made to great fractional accuracy.

Constant volume gas cell optical phase-shifter

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Dublin, CA, United States of America

Donald W Phillion