Test image from Gaia: Slightly shaky to start with, but it’ll get there. (Image: ESA/DPAC/Airbus DS)
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Largest ever space camera is ready to map a billion stars

The European Space Agency's Gaia telescope is so powerful, it see stars with power akin to measuring the width of a human hair at a distance of 500 km.

After its successful launch in December, the European Space Agency’s (ESA) Gaia has now taken up its position in space and is ready to survey the skies. With the help of two onboard telescopes focused onto the largest ever space camera, Gaia is estimated to catalogue nearly one billion stars in its 5-year mission.

Like Hipparcos before it, ESA’s Gaia will map stars in the Milky Way. It will do this by measuring the brightest billion objects and determine their three-dimensional distribution and velocities. It also has the ability to measure the temperature, mass, and chemical composition of these billion objects.

Gaia will be able to discern objects up to 400,000 times dimmer than those visible to the naked eye. The positional accuracy of its measurements are akin to measuring the width of a human hair at a distance of 500 km.

The process will involve scanning each part of the sky an average of 70 times over its five-year mission lifetime, which means scanning the entire sky twice every 63 days, once through each of the two telescopes, making it a powerful tool for spotting time-evolving phenomena such as binary systems, supernovae, and exoplanets. Compared to Hipparcos, Gaia will be able to measure 500 times the number of stars, extending to objects 1000 times dimmer than the dimmest that Hipparcos could catalogue.

The technology that makes this possible is the largest camera ever launched into space – 940 million pixels. That is why a lot of effort before launch was on figuring out exactly how to get the huge amount of data Gaia will produce back down to Earth.

When a picture is taken a number of charged-coupled devices (CCDs) – the stuff most digital camera sensors are made off – are dedicated to spotting objects before they fall onto the main focal plane. This allows the instrument to track the objects as they pass and only retain small regions around the object, reducing the file-size needed to be sent to Earth. In five years it will send only 100 TB of data. Once the data arrives to Earth, there is a system in place to analyse the data and distribute alerts to ground-based observatories if anything quickly evolving and potentially interesting is spotted, such as supernovae.

The catalogue produced by Gaia is expected to contribute to many areas of astrophysics, multiply our database of exotic objects such as exoplanets, white and brown dwarfs, and supernovae many-fold, contribute to more precise measurements of General Relativity, help to constrain the measurements of the presence and location of dark matter, and give us more accurate information about our galactic neighbourhood and its evolution.

Gaia was successfully launched on 19 December. After a month’s transit, it is now in orbit at about 1.5 million km away from Earth. By virtue of its position opposite the Sun from the Earth and its large sunshield, it will be able to see objects as close as 45 degrees from the Sun, allowing it to spot asteroids with orbits that lie between the Earth and the Sun, which are candidates for Earth collision, and very difficult to observe from the ground.

Staff on the ground are conducting in-orbit testing, during which the exact orbital parameters are determined, and all systems are tested for performance. Calibration images have been obtained, and the ground team is working on procedures to resolve a few remaining issues, such as reducing contamination on the CCDs and dealing with sunlight diffracted around the sun-shield.

Beyond the alert system allowing quick ground-based follow up, the first proper Gaia catalogue will take two years to complete and will be made available to the wider scientific community. Following this, new iterations will be issued about once a year, which will add more precisely determined characteristics of these objects. It is expected that Gaia’s database will have many new discoveries waiting to be mined from it, fuelling astronomers for decades to come.

Ben Dryer has received funding from the UK Space Agency to perform Gaia data analysis.

This article was originally published on The Conversation. Read the original article.The Conversation

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Fark.com’s censorship story is a striking insight into Google’s unchecked power

The founder of the community-driven website claims its advertising revenue was cut off for five weeks.

When Microsoft launched its new search engine Bing in 2009, it wasted no time in trying to get the word out. By striking a deal with the producers of the American teen drama Gossip Girl, it made a range of beautiful characters utter the words “Bing it!” in a way that fell clumsily on the audience’s ears. By the early Noughties, “search it” had already been universally replaced by the words “Google it”, a phrase that had become so ubiquitous that anything else sounded odd.

A screenshot from Gossip Girl, via ildarabbit.wordpress.com

Like Hoover and Tupperware before it, Google’s brand name has now become a generic term.

Yet only recently have concerns about Google’s pervasiveness received mainstream attention. Last month, The Observer ran a story about Google’s auto-fill pulling up the suggested question of “Are Jews evil?” and giving hate speech prominence in the first page of search results. Within a day, Google had altered the autocomplete results.

Though the company’s response may seem promising, it is important to remember that Google isn’t just a search engine (Google’s parent company, Alphabet, has too many subdivisions to mention). Google AdSense is an online advertising service that allows many websites to profit from hosting advertisements on its pages, including the New Statesman itself. Yesterday, Drew Curtis, the founder of the internet news aggregator Fark.com, shared a story about his experiences with the service.

Under the headline “Google farked us over”, Curtis wrote:

“This past October we suffered a huge financial hit because Google mistakenly identified an image that was posted in our comments section over half a decade ago as an underage adult image – which is a felony by the way. Our ads were turned off for almost five weeks – completely and totally their mistake – and they refuse to make it right.”

The image was of a fully-clothed actress who was an adult at the time, yet Curtis claims Google flagged it because of “a small pedo bear logo” – a meme used to mock paedophiles online. More troubling than Google’s decision, however, is the difficulty that Curtis had contacting the company and resolving the issue, a process which he claims took five weeks. He wrote:

“During this five week period where our ads were shut off, every single interaction with Google Policy took between one to five days. One example: Google Policy told us they shut our ads off due to an image. Without telling us where it was. When I immediately responded and asked them where it was, the response took three more days.”

Curtis claims that other sites have had these issues but are too afraid of Google to speak out publicly. A Google spokesperson says: "We constantly review publishers for compliance with our AdSense policies and take action in the event of violations. If publishers want to appeal or learn more about actions taken with respect to their account, they can find information at the help centre here.”

Fark.com has lost revenue because of Google’s decision, according to Curtis, who sent out a plea for new subscribers to help it “get back on track”. It is easy to see how a smaller website could have been ruined in a similar scenario.


The offending image, via Fark

Google’s decision was not sinister, and it is obviously important that it tackles things that violate its policies. The lack of transparency around such decisions, and the difficulty getting in touch with Google, are troubling, however, as much of the media relies on the AdSense service to exist.

Even if Google doesn’t actively abuse this power, it is disturbing that it has the means by which to strangle any online publication, and worrying that smaller organisations can have problems getting in contact with it to solve any issues. In light of the recent news about Google's search results, the picture painted becomes more even troubling.

Update, 13/01/17:

Another Google spokesperson got in touch to provide the following statement: “We have an existing set of publisher policies that govern where Google ads may be placed in order to protect users from harmful, misleading or inappropriate content.  We enforce these policies vigorously, and taking action may include suspending ads on their site. Publishers can appeal these actions.”

Amelia Tait is a technology and digital culture writer at the New Statesman.