Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Blurry view from Chandra’s space telescope


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:

More articles from Physics and Astronomy:

nachricht 'Frequency combs' ID chemicals within the mid-infrared spectral region
16.03.2018 | American Institute of Physics

nachricht Fraunhofer HHI have developed a novel single-polarization Kramers-Kronig receiver scheme
16.03.2018 | Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut, HHI

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: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>