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Currently, there is considerable interest in developing technologies that will allow the use of high-energy photon
measurements from celestial X-ray sources for deep space relative navigation. The impetus for this is to reduce
operational costs in the number of envisioned space missions that will require spacecraft to have autonomous, or semiautonomous,
navigation capabilities. For missions close to Earth, Global Navigation Satellite Systems (GNSS), such as
the U.S. Global Positioning System (GPS), are readily available for use and provide high accuracy navigation solutions
that can be used for autonomous vehicle operation. However, for missions far from Earth, currently only a few
navigation options exist and most do not allow autonomous operation. While the radio telemetry based solutions with
proven high performance such as NASA’s Deep Space Network (DSN) can be used for these class of missions, latencies
associated with servicing a fleet of vehicles, such as a constellation of communication or science observation spacecraft,
may not be compatible with autonomous operations which require timely updates of navigation solutions. Thus, new
alternative solutions are sought with DSN-like accuracy. Because of their highly predictable pulsations, pulsars emitting
X-radiation are ideal candidates for this task. These stars are ubiquitous celestial sources that can be used to provide
time, attitude, range, and range-rate measurements — key parameters for navigation. Laboratory modeling of pulsar
signals and operational aspects such as identifying pulsar-spacecraft geometry and performing cooperative observations
with data communication are addressed in this paper. Algorithms and simulation tools that will enable designing and
analyzing X-ray navigation concepts for a cis-lunar operational scenario are presented. In this situation, a space vehicle
with a large-sized X-ray detector will work cooperatively with a number of smaller vehicles with smaller-sized detectors
to generate a relative navigation solution between a reference and partner vehicle. The development of a compact X-ray
detector system is pivotal to the eventual deployment of such navigation systems. Therefore, efforts to design a smallpackaged
X-ray detector system along with the hardware, software and algorithm infrastructure required for testing and
validating the system’s performance are described in this paper.
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