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Whiffen, Gregory

Publications and source records attributed to Whiffen, Gregory.

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Dawn's final mission at Ceres: navigation and mission design experience

On Oct. 31st, 2018, the Dawn spacecraft completed its space journey covering more than 11 years including exploration of Vesta and Ceres, two protoplanets in the main asteroid belt. After successfully completing its prime mission at the dwarf planet Ceres, the Dawn mission was extended twice to pursue new scientific objectives. The second extended mission at Ceres, and the final mission for Dawn, presented a series of challenges that were new to the experienced and accomplished Dawn navigation team. This paper discusses mission design and navigational experiences and challenges during Dawn’s final transfer and orbit at Ceres. Topics include reference orbit design of the final science orbit, mission design and planning for the transfer, periapsis targeting over a surface feature, and analysis for planetary protection requirements.

Karimi, Reza↗
NASA NTRS2018

Overview of the Spacecraft Design for the Psyche Mission Concept

In January 2017, Psyche and a second mission concept were selected by NASA for flight as part of the 14th Discovery mission competition. Assigned for an initial launch date in 2023, the Psyche team was given direction shortly after selection to research the possibility for earlier opportunities. Ultimately, the team was able to identify a launch opportunity in 2022 with a reduced flight time to its destination. This was accomplished in large part to crosscutting trades centered on the electrical power subsystem. These trades were facilitated through the Psyche mission's planned use of Solar Electric Propulsion (SEP), which enables substantial flexibility with respect to trajectory design. In combination with low-thrust trajectory analysis tools, the team was able to robustly converge to solutions with a higher fidelity and accuracy of results. These trades also took advantage of the 1300 series product line produced by Space Systems Loral (SSL), which enabled power growth while maintaining strong system-level heritage through its modular design that has been utilized on a large number of geostationary (GEO) communications satellites. This paper presents an overview of the Psyche mission concept, and the unique architecture that enables the use of commercially developed electric propulsion and space power systems from Space Systems Loral to provide flexibility in mission design. This paper then discusses the trades that allowed the Psyche team to meet a 2022 launch date.

Prikl, Zachary↗
NASA NTRS2016

Orbit Transfers for Dawn's Ceres Operations: Navigation and Mission Design Experience at a Dwarf Planet

Dawn, a mission belonging to NASA’s Discovery Program, was launched on September 27, 2007 to explore two objects in the main asteroid belt in order to yield insights into important questions about the formation and evolution of the solar system. Successfully completing all mission objectives at Vesta, Dawn arrived at dwarf planet Ceres in March 2015 and continued its journey to a series of four near circular polar science orbits. Dawn became the first mission to orbit around two extraterrestrial targets; such a mission would have been impossible without the low thrust ion propulsion system (IPS). Maneuvering a spacecraft using only the IPS for the transfers between the mapping orbits posed many technical challenges to Dawn’s flight team at NASA’s Jet Propulsion Laboratory. Failure of the second reaction wheel assembly, shortly before leaving Vesta, added another challenge for Dawn’s flight team. This paper discusses the mission design and navigational experience and challenges during Dawn’s Ceres operations.

Han, Dongsuk↗
NASA NTRS2013

Automating Initial Guess Generation for High Fidelity Trajectory Optimization Tools

Many academic studies in spaceflight dynamics rely on simplified dynamical models, such as restricted three-body models or averaged forms of the equations of motion of an orbiter. In practice, the end result of these preliminary orbit studies needs to be transformed into more realistic models, in particular to generate good initial guesses for high-fidelity trajectory optimization tools like Mystic. This paper reviews and extends some of the approaches used in the literature to perform such a task, and explores the inherent trade-offs of such a transformation with a view toward automating it for the case of ballistic arcs. Sample test cases in the libration point regimes and small body orbiter transfers are presented.

design process↗