The Dawn mission, part of NASA’s Discovery Program, has as its goal the scientific exploration of the two most massive main-belt objects, Vesta and Ceres. The Dawn spacecraft was launched from the Cape Canaveral Air Force Station on September 27, 2007 on a Delta-II 7925H9.5 (Delta-II Heavy) rocket that placed the 1218-kg spacecraft onto an Earth-escape trajectory. On-board the spacecraft is an ion propulsion system (IPS) developed at the Jet Propulsion Laboratory which will provide a total ΔV of 11 km/s for the heliocentric transfer to Vesta, orbit capture at Vesta, transfer between Vesta science orbits, departure and escape from Vesta, heliocentric transfer to Ceres, orbit capture at Ceres, and transfer between Ceres science orbits. Full-power thrusting from December 2007 through October 2008 was used to successfully target a Mars gravity assist flyby in February 2009 that provided an additional ΔV of 2.6 km/s. Deterministic thrusting for the heliocentric transfer to Vesta resumed in June 2009 and concluded with orbit capture at Vesta on July 16, 2011. From July 2011 through September 2012 the IPS was used to transfer to all the different science orbits at Vesta and to escape from Vesta orbit. Cruise for a rendezvous with Ceres began in September 2012 and concluded with the start of the approach to Ceres phase on December 26, 2015, leading to orbit capture on March 6, 2015. Deterministic thrusting continued during approach to place the spacecraft in its first science orbit, called RC3, which was achieved on April 23, 2015. Following science operations at RC3 ion thrusting was resumed for twenty-five days leading to arrival to the next science orbit, called survey orbit, on June 3, 2015. The IPS will be used for all subsequent orbit transfers and trajectory correction maneuvers until completion of the primary mission in approximately June 2016. To date the IPS has been operated for over 46,774 hours, consumed approximately 393 kg of xenon, and provided a ΔV of over 10.8 km/s to the spacecraft. The IPS performance characteristics are very close to the expected performance based on analysis and testing performed pre-launch. This paper provides an overview of Dawn’s mission objectives and the results of Dawn IPS mission operations through arrival at the second science orbit at Ceres.
[1]
John R. Brophy,et al.
Development and Testing of the Dawn Ion Propulsion System
,
2006
.
[2]
John R. Anderson,et al.
An Overview of the Results from the 30,000 Hr Life Test of Deep Space 1 Flight Spare Ion Engine
,
2004
.
[3]
Marc D. Rayman,et al.
In-Flight Operation of the Dawn Ion Propulsion System Through the Preparations for Escape From Vesta
,
2012
.
[4]
John R. Brophy,et al.
Dawn Ion Propulsion System - Initial Checkout After Launch
,
2008
.
[5]
Hitoshi Kuninaka,et al.
Lessons learned from round trip of Hayabusa asteroid explorer in deep space
,
2011,
2011 Aerospace Conference.
[6]
PSDA,et al.
ARTEMIS ORBIT RAISING IN-FLIGHT EXPERIENCE WITH ION PROPULSION
,
2003
.
[7]
Marc D. Rayman,et al.
The Dawn of Vesta Science
,
2011
.
[8]
John R. Brophy.
Propellant Throughput Capability of the Dawn Ion Thrusters IEPC-2007-279
,
2007
.
[9]
Marc D. Rayman,et al.
In-Flight Operation of the Dawn Ion Propulsion System Through Year Two of Cruise to Ceres
,
2013
.
[10]
M. Rayman.
The successful conclusion of the Deep Space 1 Mission: important results without a flashy title
,
2002
.
[11]
Marc D. Rayman,et al.
Dawn: A mission in development for exploration of main belt asteroids Vesta and Ceres
,
2006
.
[12]
Nicolas Pillet,et al.
Overview of Electric Propulsion Activities in France
,
2007
.