Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Blurry view from Chandra’s space telescope

06.11.2003


ONE of NASA’s highest profile space telescopes is losing its sight. The $2 billion Chandra X-Ray Observatory is suffering from a mysterious build-up of grease on an optical filter in front of one of its cameras, blocking almost half the light at some frequencies.



Since being placed in orbit by the space shuttle in 1999, Chandra has been studying X-rays emitted by astronomical objects such as quasars and black holes. It is expected to carry on working for up to 15 years.

Jane Turner, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, was one of the first scientists to spot something strange in her data. She compared data from an instrument on Chandra called the Advanced CCD Imaging Spectrometer (ACIS) with similar data from a European spacecraft called the X-ray Multi-Mirror (XMM) telescope, and found some discrepancies in the low-energy region of the X-ray spectrum.


This low-energy data is useful for determining how much gas there is between the instrument and an X-ray source because it can show how much light is absorbed. If you didn’t know about the contamination, she says, it could look as if there was a gas cloud in front of the object of study.

Scientists soon identified a problem with a filter in front of the instrument, which allowed them to add a correction factor to their data. "It slowed everyone down at first, but these things happen," she says. Astronomers had expected to see a certain amount of contamination on the filter.

Some materials used on spacecraft evaporate in a vacuum and tend to settle on the coldest surfaces nearby. ACIS is at about -100 C. But the level of contamination is much higher than anyone anticipated.

"There is ten times as much contamination as we expected at launch," says Herman Marshall, an astrophysicist with the Center for Space Research at MIT. In the three years since the launch, a layer of grease 0.37 micrometres thick has built up on the filter. That’s thicker than the filter itself, he says.

Scientists are not yet sure what is causing the build-up. Analysis of the contamination shows that it contains carbon and fluorine, which points to a problem with a fluorocarbon lubricant called Braycote used on the spacecraft or with other sources of fluorine such as Teflon-coated screws.

Braycote was chosen because it does not normally evaporate at low temperatures. But Marshall thinks the contamination may have occurred when molecules in the lubricant were broken down by mechanical stresses and then bombarded with radiation.

These breakdown products could then have evaporated and settled on the filter. The contamination only affects a small percentage of the data Chandra is collecting. "The issue is mainly with sources at lower energies and lower temperatures," says Dan Schwartz, a physicist at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts.

But in this region of the spectrum the contamination is absorbing about half of the light, he says. "I would guess about 20 to 25 per cent of people have added uncertainty in their data, but it probably doesn’t affect scientific conclusions." Now engineers are working out how to remove the grease. Next month, they may heat up the instrument in the hope of boiling away the contaminants.

A "bakeout" has its own risks, because too much heat could damage the camera or the filter. Or the contamination could settle somewhere worse, says Chandra programme manager Keith Hefner. So far, the other instruments on board are unaffected. "The vehicle is still performing well," says Hefner.

Claire Bowles | EurekAlert!
Further information:
http://www.rbi.co.uk

More articles from Physics and Astronomy:

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

nachricht Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>