Optical Characterization of Deep-Space Object Rotation States
Abstract
Analysis of time-series data can yield remarkably accurate estimates of the frequency of a satellite s brightness modulations. These apparent or synodic frequencies can vary in time, differing from the actual rotation rate of the object by an amount that depends on the relative angular motion between the satellite, illuminator, and observer for reflected light measurements (or between the satellite and observer for thermal emission measurements). When detected with sufficient accuracy, such synodic frequency variations can be exploited to characterize an object s rotation state, using an analysis that does not require any a priori knowledge of the object s shape. For instance, this shape-independent analysis method can be used to derive spin axis orientations and sidereal rotation rates for spinning objects. Remotely determining such rotation parameters can be useful in many circumstances, such as when performing anomaly resolution for satellites that have lost stabilization. Unfortunately, synodic variations cannot be detected by ground-based observers for many objects due to low rates of relative angular motion. This is especially true for non-specular objects in deep-space and geosynchronous orbits. In these cases, deriving spin axis orientations can be accomplished using a shape-dependent method that employs a model of the shape and reflectance characteristics of the object. Our analysis indicates that a simple cylinder shape model can suffice to characterize rotation states for upper-stage rocket bodies, although even this relatively simple model requires significantly more computation than the shape-independent approach.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2014
- Accession Number
- ADA616781
Entities
People
- Doyle Hall
- Paul Kervin
Organizations
- Air Force Research Laboratory