Engineering topics
Ely, T.
Publications and source records attributed to Ely, T..
Solar System Ephemerides, Pulsar Timing, Gravitational Waves, & Navigation
In-spiraling supermassive black holes should emit gravitational waves, which would produce characteristic distortions in the pulse time of arrival residuals from millisecond pulsars. There are multiple national and regional consortia that have constructed pulsar timing arrays by precise timing of different sets of millisecond pulsars. An essential aspect of precision timing is the transfer of the pulsar times of arrival to a (quasi-)inertial reference frame, conventionally taken to be the solar system barycenter. The solar system barycenter is determined from the knowledge of the planetary masses and orbits, which has been re ned over the course of the past 50 years by multiple spacecraft missions. Within the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), uncertainties on the solar system barycenter are emerging as an important element of the overall NANOGrav noise budget. We describe what is known about the solar system barycenter, touch upon how uncertainties in it affect gravitational wave studies with pulsar timing arrays, and consider future trends in spacecraft navigation.
Altair Navigation During Trans-Lunar Cruise, Lunar Orbit, Descent and Landing
No abstract available
Navigation and mission analysis software for the next generation of JPL missions
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Mars Network: A Telecommunications and Navigation Network for Future Mars Exploration
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Mars surface asset positioning using in-situ radio tracking
This paper compares positioning performances resulting from DTE only and in-situ orbiter operations through more accurate path reconstruction available from this technique.
Event Detection and Identification During Autonomous Interplanetary Navigation
An autonomous/adaptive interplanetary navigation architecture employing neural networks and genetic algorithms is being developed that will alert navigators when a shift from optimal to suboptimal filtering occurs and assist in modifying the filter parameters to resume optical tracking.
Adaptive Interplanetary Navigation Using Genetic Algorithms
The problem of tuning trajectory determination models for interplanetary navigation is a complex task requiring an intensive search of multiple dynamical and nondynamical models that yield trajectory solutions with minimal errors.
MarsNet: A Mars Orbiting Communications & Navigation Satellite Constellation
Mars has become the focus of an unprecedented series of missions spanning many years, involving numerous nations and evolving from robotic to human exploration.
Constellation Design of the Mars Network: A System for Communication and Navigation at Mars
Mars has become the focus of an unprecedented series of missions spanning many years, involving numerous nations and evolving from robotics to humans.
Constellation Design of the Mars Network
Mars has become the focus of an unprecedented series of missions spanning many years, involving numerous nations and evolving from robotics to humans.
Constellation Design for a Mars-orbiting Satellite Communication
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Impact of Eccentricity on East-West Stationkeeping for the GPS Class of Orbits
The investigation will reveal that the influence of luni-solar perturbations contributes to the growth of eccentricity, thus increasing the probability of encountering chaotic motion during a typical satgellite lifetime.
Impact of Eccentricity on East-West Stationkeeping for the GPS Class of Orbits
A strong relationship exists between eccentricity and the potential for an orbit with a mean motion commensurability to the Earth's rotation rate to be chaotic.
Mars Network Constellation Design Drivers and Strategies
NASA's Jet Propulsion Laboratory has intiated the design of a spacecraft constellation that will provide communication relay and navigation support for a variety of future Mars missions.