meetings - Space Flight Mechanics Committee

Feb 12, 2013
Puna Room C&D
SESSION 16: SPECIAL SESSION: DAWN
Chair: Dr. Shyam Bhaskaran, Jet Propulsion Laboratory
13:30 AAS Ion Propulsion: An Enabling Technology for the Dawn Mission
13-342 Charles Garner, NASA / Caltech JPL; Marc Rayman, NASA / Caltech JPL; John
Brophy, NASA / Caltech JPL; Steve Mikes, NASA / Caltech JPL; Gregory Whiffen,
NASA / Caltech JPL
The Dawn mission, part of NASA's Discovery program, is enabled using an on-board ion
propulsion system (IPS) developed at JPL that will provide 11 km/s of delta-V to the
spacecraft using less than 400 kg of xenon propellant. IPS is used for primary propulsion
for cruise to Vesta and Ceres, and for orbit maneuvers. IPS operations have been almosttrouble-free,
delivering 7 km/s of delta-V while using 260 kg of xenon for cruise to Vesta
and orbit maneuvers.
13:50 AAS Thrust Direction Optimization: Satisfying Dawn's Attitude Agility
13-343 Constraints
Gregory Whiffen, NASA / Caltech JPL
NASA’s Dawn mission is exploring the giant asteroid Vesta and the dwarf planet Ceres.
The Dawn spacecraft has complex, difficult to quantify, and severe limitations on its
attitude agility. The low-thrust transfers between science orbits at Vesta required complex
time varying thrust directions due to Vesta's strong and complex gravity. Thrust design
objectives (like minimum propellant or minimum transfer time) often result in thrust
direction evolutions that cannot be accommodated by the attitude control system. Several
new optimal control objectives, called thrust direction optimization were developed and
used to successfully navigate Dawn through all transfers at Vesta.
14:10 AAS Dawn Maneuver Design Performance at Vesta
13-344 Daniel Parcher, NASA / Caltech JPL; Matthew Abrahamson, NASA / Caltech JPL;
Alessandro Ardito, ARPSOFT s.r.l.; Dongusk Han, NASA / Caltech JPL; Robert
Haw, NASA / Caltech JPL; Brian Kennedy, NASA / Caltech JPL; Nickolaos
Mastrodemos, NASA / Caltech JPL; Sumita Nandi, NASA / Caltech JPL; Ryan Park,
NASA / Caltech JPL; Brian Rush, NASA / Caltech JPL; Brett Smith, NASA / Caltech
JPL; John Smith, NASA / Caltech JPL; Andrew Vaughan, NASA / Caltech JPL;
Gregory Whiffen, NASA / Caltech JPL
The Dawn spacecraft orbited the asteroid Vesta from July 16, 2011 to September 5, 2012,
successfully accomplishing the four planned science orbits and two planned rotational
characterization orbits. The lowest-altitude science orbit lasted four months, with 20
planned orbit maintenance maneuvers. Navigation results from Vesta demonstrate that the
navigation plan was sufficient to achieve orbit delivery accuracy requirements. This paper
23 rd AAS / AIAA Space Flight Mechanics Meeting Page 63