Dawn

Asteroid belt unmanned probe designed to first orbit and survey the asteroid Vesta, and then fly on to the largest asteroid, Ceres. The ninth NASA Discovery mission, and a follow-on to the Deep Space 1 technology mission, it was equipped with three NSTAR xenon ion engines. The spacecraft used the Orbital/Dulles Star-2-derived bus. The three main instruments were a Framing Cameras, a VIR visible/IR mapping spectrometer, and the GRaND gamma ray and neutron spectrometer. Using its ion engines and a Mars flyby in February 2009, Dawn was scheduled to reach Vesta in 2011 and Ceres in 2015.

Mission profile:

• Mars flyby and gravity assist: 4 February 4, 2009. Dawn will fly within 500 kilometers of Mars and have completed slightly under one orbit of the sun. During the flyby, Dawn may use its science instruments to make observations of the planet. Main purpose of the flyby is to use Mars' gravity to torque Dawn's orbit out of the ecliptic plane, towards Vesta. The flyby will give Dawn a heliocentric delta-V of 1.12 km/sec.
• Vesta arrival: 14 August 2011. Dawn's ion propulsion system will be used to spiral out towards Vesta, and then match its flight path to that of the asteroid. The slow approach ensures there are no time-critical thruster firings. As it approaches, Dawn will conduct a survey of the region around the asteroid for any possible natural satellites, dust and debris. It will then use ion propulsion to brake itself into a polar mapping orbit around Vesta. By the time it reaches the asteroid, Dawn will have accumulated about 1,000 days of ion engine operation. During nine months of Vesta orbit operations, the ion engine will be used to ensure a changing series of circular near-polar orbits, allowing Dawn to study the entire surface of the asteroid. The highest orbit will be roughly 2,500 kilometers altitude, the lowest under 200 kilometers.
• Ceres arrival: 1 February 2015. After leaving Vesta, the spacecraft will spend nearly three years en route to Ceres, making about three-fourths of one orbit around the sun as it spirals outward toward the dwarf planet. Dawn will use its ion propulsion to make a slow approach to and drop into orbit around Ceres. As at Vesta, Dawn will enter a series of circular near-polar orbits that will provide vantage points for studying nearly the entire surface of the dwarf planet.
• End of mission: July 2015. At the planned end of Dawn's primary mission, the spacecraft was to be in a quarantine orbit around Ceres at an altitude of 700 kilometers. This orbit ensured that the decommissioned spacecraft would not impact Ceres for 50 years, supposedly allowing time for action in case some kind of life was detected. Total days of ion engine thrusting during the entire mission were to be 2,000

Development Cost $: 281.700 million. Cost Notes: $357.5 total, including $75.8 m mission operations. Length: 1.64 m (5.38 ft). Basic Diameter: 1.27 m (4.16 ft). Span: 20.00 m (65.00 ft). Mass: 1,218 kg (2,685 lb). RCS Coarse No x Thrust: 12 MR-103G x 0.9 N. Main Engine: NSTAR. Main Engine: 27 kg (59 lb). Main Engine Thrust: 0.27 N (0.06 lbf). Main Engine Propellants: Xenon. Main Engine Propellants: 425 kg (936 lb). Electrical System: 2 x 8.3 m x 2.3 m solar panels. Electric System: 10.00 kWh.

• 2007 September 27 - Dawn - Launch Site: Cape Canaveral. Launch Vehicle: Delta.

  Asteroid belt unmanned probe designed to first orbit and survey the asteroid Vesta, and then fly on to the largest asteroid, Ceres. The Delta upper stage boosted the spacecraft and PAM-D solid third stage to 9.01 km/sec and a 185 km x 6835 km orbit. The PAM-D fired at 12:29 GMT and released Dawn after accelerating it to 11.50 km/sec and sending it into a 1.00 AU x 1.62 AU x 0.5 deg solar orbit. The ion engines were ignited on 6 October. Using its ion engines and a Mars flyby in February 2009, Dawn was scheduled to reach Vesta in 2011 and Ceres in 2015.