Dawn (spacecraft)

Dawn (English for Dawn ) is a spacecraft of NASA Discovery program, which will orbit the asteroid Vesta and the dwarf planet Ceres in succession and explore. She is the first probe having the visit of objects in the asteroid belt to the main task and serves - as their name resonate - exploring the as yet very initially considered the body shed light on the early history of the solar system.

The mission is managed by the Jet Propulsion Laboratory (JPL ), while the scientific project management at the University of California is located. The total costs are estimated by NASA with 357.5 million U.S. dollars. Of this amount, $ 281.7 million in the development and building the spacecraft and $ 75.8 million to air operations.

• 4.1 Coated instruments

Planning

In November 2005, the preparation of the mission of JPL was stopped. This was due to cost overruns in the manufacture of the probe. In early 2006, it should be decided whether the mission continued with a later start date or is deleted in its entirety. Since the launch window for the probe with more than one year is unusually long, a start of the mission until October 2007 was possible.

On 3 March 2006 it was officially announced that the Dawn mission has been deleted. The mostly finished space probe should be stored. However, the head of NASA, Michael Griffin was briefly known fact that deletion of the mission located for the time being in check. Only three weeks later, NASA announced on 27 March that the Dawn program was resumed.

Mission History

Preparations and start

Built by Orbital Sciences probe should start with a Delta II 7925H - 9.5 - rocket after original plans in July 2007. During the preparations to start a solar wing was damaged by a falling tool on June 11, 2007, but could be repaired without compromising the schedule.

The solar arrays is repaired

Starting on 27 September 2007

The start was delayed for other reasons by three months and removed the already mounted on the probe launcher again and stored. On September 27, 2007 at 11:34 UTC, the back mounted on the rocket NASA's Dawn spacecraft was successfully launched from launch pad 17B of the Cape Canaveral Air Force Station.

Flight through the inner solar system and swing-by at Mars

The first 81 days after the start took the ground control to verify Dawn and the instruments. After that, the probe began on 17 December 2007, to operate one of the ion - cruise engines in continuous operation in order to change the trajectory. On 17 February 2009 Dawn led a swing-by maneuvers on Mars.

Flyby of Mars 17 February, 2009

Scientific Mission to the Asteroid Vesta

From May 2011 gave Dawn the first recordings of Vesta. At this time, the mission served the images of the navigation of the probe and were not optimized in terms of sharpness and resolution. On July 16, 2011 Dawn swung into orbit around Vesta, with a radius of about 16,000 kilometers a. Thereafter, the orbit radius is further reduced gradually. Early August, an orbit was achieved at an altitude of 2700 km, the first images and scientific data are collected in the. From this height, in particular the composition of the surface by means of spectroscopic measurements should be determined. Then the height of the orbit was lowered to nearly 680 kilometers above the surface. In this orbit Vesta's surface and should be mapped by means of stereo images topographic data are collected on the surface. After the flight altitude was again lowered to 200 kilometers. At this height, the composition of the surface should be analyzed in more detail by means of the Gamma Ray / Neutron Spectrometers. When the probe in the spring of 2012 began to move away from Vesta, she remained again in an orbit of 2700 km altitude to collect data. The angle of the sunlight had changed, so that the scientists could observe previously hidden details and different angles of surface structures. The original duration of the Vesta mission was initially extended in April 2012 by NASA forty days until 26 August 2012. Because of the failure of a reaction wheel, the departure of Vesta was then postponed until September. Dawn is equipped with four reaction wheels and really only designed for it to work with at least three. After a first reaction wheel had failed in June 2010, a new software has been installed, the allowed operation with only two reaction wheels with the help of the hydrazine thrusters, so that the failure of this second wheel did not endanger the further mission history.

Vesta from 100,000 kilometers, July 1, 2011

Vesta from 41,000 kilometers, July 9, 2011

First image from orbit 16,000 kilometers in distance 17 July, 2011

Next flight to the dwarf planet Ceres

On September 5, 2012 Dawn Vesta has left and is flown to the dwarf planet Ceres, which it is expected to reach in February 2015. The primary mission is to end in July 2015.

Technology

The Dawn spacecraft has as main body a bus at 1.36 m height and has fully deployed solar panels a span of 19.7 m. The launch mass was 1108 kg, of which 624 kg unladen mass. The probe has three NSTAR ion engines with a specific impulse of 3000 s, whose predecessor was already tested in the Deep Space 1 mission. The thrusters use xenon as support mass and are used for interplanetary transfers as cruise engines. 425 kg xenon leads the probe ( 450 kg were originally planned). For swinging into the orbits of the heavenly bodies on the other hand, conventional hydrazine -burning engines are used. Since the ion drive requires a lot of power, the probe has large solar panels that provide 10 kW of power at startup, when Ceres is expected with even 1 kW. In the original draft four segment solar panels were provided, but in the course of development in fünfsegmentige with 25% more solar panel and thus 25 % more power have been changed.

Dawn span with deployed solar paddles

Dawn xenon tank

Instruments

Dawn on three scientific instruments are integrated:

Coated tools

Two other instruments were removed from the final draft of the probe:

Timing of the mission

• Start: September 27, 2007
• Mars Swing -by at 543 kilometers distance: February 17, 2009
• Vesta arrival: July 16, 2011
• Vesta departure: September 5, 2012
• Ceres arrival: February 2015
• End of the primary mission in July 2015

Others

NASA was interested to November 4, 2006, the opportunity to send their names to a website to let him write on a microchip, the plane carries in the spacecraft. In this Internet campaign "Send your name to the Asteroid Belt" around 365,000 names were registered.

In the mid- 1980s was a space probe to the asteroid Vesta in planning. This Russian-French cooperation was called VESTA and should continue the successful cooperation in the VEGA probes. The launch was scheduled for 1991/92. Due to various factors this mission, however, was set in the late 1980s.