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10-22-2007, Brian Lynch DAWN Space Probe Set for First Light |
Mainz (Germany) / Los Angeles (USA), October 19, 2007—It will be dark when the protective lid that covers the camera eye of the space probe DAWN opens for the first to set its sight on two almost pixel-sized light dots: the asteroids Vesta and Ceres. During the mission to the two planetoids in the asteroid belt of our solar system, the cameras on board will be used for the navigation of the scientific probe for the five billion-kilometer long journey through space in addition to the scientific exploration of the celestial bodies.
It is the first time that the NASA relies on foreign technology for such a critical part of its mission. “This German participation is a great demonstration of trust for us,” explains Dr. Holger Sierks of the Max Planck Institute of Solar System Research (MPS) located in Katlenburg-Lindau, Lower Saxony, Germany. “Our two cameras on board are the eyes of the space probe. They are not only for the scientific exploration of Vesta and Ceres, but also for the optical navigation of the probe with the help of star fields.”
The cameras will take approximately 50,000 photos of the asteroids Vesta and the dwarf planet Ceres. With a median diameter of 516 km, Vesta is the third-largest, while Ceres with its 950-km diameter is the largest asteroid in the main belt. The probe will reach Vesta during October, 2011 and observe the asteroid for six months from orbits at different heights. Afterwards, DAWN will fly on to Ceres to carry out experiments and measurements from February until July, 2015, when the mission will end.
Sierks and his research team worked for three years at the MPS together with the Berlin Institute of Planet Research of the German Aerospace Center (DLR) and the Institute of Data Technology and Communication Nets of Brunswick Technical College (IDA) in the development of the so-called “framing cameras.” They should be sending razor-sharp photographs to the Earth every 1.6 seconds during the mission.
Limitation Calls for Optimal Optics Design
The cameras’ construction is extremely stable, able to withstand the multiple gravity acceleration when the rocket lifted off from Cape Canaveral, FL on September 27, 2007. In order to ensure the success of the DAWN mission, two identical units are being deployed, should one camera system unexpectedly fail.
“Every objective of the 5.5-kg camera had to weigh 750 grams at most,” according to Dr. Herbert Mosebach of Kayser-Threde in Munich, the company commissioned by the Max Planck Institute for developing the camera optics. “For this reason, we had to limit ourselves to four lenses for the optics. Each lens therefore had to have optimal transmission, thermal stability and resistance to cosmic radiation in order to keep sending perfect photos even after nine years in space. Another challenge was the effective suppression of scattered light that allowed the successful measurement of asteroid surfaces in spite of their low brightness.”
Specialty Glass for a Clear View in Space
The lenses with a maximum diameter of 30 millimeters were processed for the telecentric camera objective in such a way that light hits the high-resolution 1024 x 1024 pixel-sized CCD image chip without distortion, precisely at a 90°angle. The synthetic fused silica “Lithosil” and the “BK7G18” boron crown glass as well as the “SFL6” heavy flint glass from SCHOTT were used. To prevent cosmic radiation—which consists mostly of protons, electrons, atom nuclei and X-rays— causing color centers and turbidity inside the glass, SCHOTT adds the chemical element cerium to its optical glasses for space travel applications. Only with “Lithosil” this is not needed. The material is made of pure silicon oxide and therefore does not interact with radiation.
“In space, normal optical glass would become as brown as a latte in a few days,” explains Dr. Thorsten Doehring, who is in charge of optical applications in astronomy at SCHOTT in Mainz. “For the specialty glass types SCHOTT provided for this unique application, radiation stability is particularly high, thus ensuring a permanent high transmission so that we can still get photos from Ceres in the year 2015.”
Further information:
http://www.mps.mpg.de/de/aktuelles/pressenotizen/pressenotiz_20070919.html
http://www.kayser-threde.de/de/press/news_detail.php?id=169
http://www.nasa.gov/mission_pages/dawn/main/
www.us.schott.com/advanced_optics
http://de.wikipedia.org/wiki/Dawn_(Raumsonde)
Information about SCHOTT
SCHOTT is an international technology group that sees its core purpose as the lasting improvement of living and working conditions. For this purpose, special materials, components and systems are developed. The main areas of focus are the household appliances industry, optics and opto-electronics, pharmaceuticals and solar energy. The SCHOTT Group has a presence in proximity to its customers through its production and sales companies in all its major markets. It has approximately 16,800 employees producing worldwide sales of approximately 2.2 billion euros. The company's technological and economic expertise is closely linked with its social and ecological responsibility.
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| Further information: | | Brian Lynch | | E-mail
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| | Advanced Optics
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