Encyclopedia Astronautica
Dawn



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Dawn
American asteroid probe. One launch, 2007.09.27. Asteroid belt unmanned probe designed to first orbit and survey the asteroid Vesta, and then fly on to the largest asteroid, Ceres. Orbit asteroids Ceres and Vesta.

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

Characteristics

Development Cost $: 281.700 million. Cost Notes: $357.5 total, including $75.8 m mission operations. RCS Coarse No x Thrust: 12 MR-103G x 0.9 N. RCS Propellants: 46 kg (101 lb). Electric System: 10.00 kWh.

Gross mass: 1,218 kg (2,685 lb).
Unfuelled mass: 793 kg (1,748 lb).
Height: 1.64 m (5.38 ft).
Diameter: 1.27 m (4.16 ft).
Span: 20.00 m (65.00 ft).
Thrust: 0.27 N (0.06 lbf).
First Launch: 2007.09.27.
Number: 1 .

More... - Chronology...


Associated Countries
See also
  • Delta The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Development began in 1955 and it continued in service in the 21st Century despite numerous candidate replacements. More...

Associated Launch Vehicles
  • Delta American orbital launch vehicle. The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Delta began as Thor, a crash December 1955 program to produce an intermediate range ballistic missile using existing components, which flew thirteen months after go-ahead. Fifteen months after that, a space launch version flew, using an existing upper stage. The addition of solid rocket boosters allowed the Thor core and Able/Delta upper stages to be stretched. Costs were kept down by using first and second-stage rocket engines surplus to the Apollo program in the 1970's. Continuous introduction of new 'existing' technology over the years resulted in an incredible evolution - the payload into a geosynchronous transfer orbit increasing from 68 kg in 1962 to 3810 kg by 2002. Delta survived innumerable attempts to kill the program and replace it with 'more rationale' alternatives. By 2008 nearly 1,000 boosters had flown over a fifty-year career, and cancellation was again announced. More...
  • Delta 7925H American orbital launch vehicle. Four stage vehicle consisting of 9 x GEM-46 + 1 x EELT Thor/RS-27A + 1 x Delta K + 1 x Star 48B More...

Associated Manufacturers and Agencies
  • JPL American agency;manufacturer of rockets, spacecraft, and rocket engines. Jet Propulsion Laboratory, Pasadena, USA. More...
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • OSC American manufacturer of rockets, spacecraft, and rocket engines. Orbital Sciences Corporation, USA. More...

Associated Propellants
  • Electric/Xenon The many versions of electric engines use electric or magnetic fields to accelerate ionized elements to high velocity, creating thrust. The power source can be a nuclear reactor or thermal-electric generator, or solar panels. Proposed as propellant for some ion motors. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • NASA Report, Dawn Press Package, Web Address when accessed: here.
  • NASA Report, The Ion Propulsion System For Dawn, Web Address when accessed: here.
  • NASA Report, Dawn Newsletters (will open to html page with pdf links), Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Cape Canaveral LC17B Delta launch complex. Part of a dual launch pad complex built for the Thor ballistic missile program in 1956. Upgraded over the decades for use with Thor, Delta, Delta II, and Delta III launch vehicles, it remained in use for over half a century. More...

Dawn Chronology


2007 September 27 - . 11:34 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. Launch Pad: SLC17B. LV Family: Delta. Launch Vehicle: Delta 7925H. LV Configuration: Delta 7925H D327.
  • Dawn - . Mass: 1,218 kg (2,685 lb). Nation: USA. Agency: Martin. Class: Surveillance. Type: Civilian surveillance satellite. Spacecraft: Dawn. USAF Sat Cat: 32249 . COSPAR: 2007-043A. 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.

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