Digital camera on the "China Eye" telescope interference far more than the phone

We always knew that electronic devices such as mobile phones would interfere with the operation of radio telescopes, so the radio telescopes in service would control the electromagnetic equipment around them. Recently visited a radio Telescope in Australia as I carry traverse to the child parks, 64 - meter Telescope (Parkes Telescope), Australia Telescope dense array (ATCA), will be put at the gate of the park "mobile phone to shut down or the flight mode, the camera can be used and popular".

And guizhou 500 m FAST telescope is within a few kilometers around the electromagnetic quiet area, set up the legal prohibition from using mobile phones near the telescope, and is more rigorous than Australian side telescope, even digital cameras also banned. But when FAST was completed last year, a number of eagle-eyed classmates found that in the news pictures, tourists were still taking pictures with their mobile phones and digital cameras.

So we can't help but wonder: is this the mobile phone, the digital camera that is used to take photos, what's the impact on the operation of FAST telescope? Should it be?

A recent article by huang shijie, a student at guizhou university and other people, conducted an experiment on this problem in the analysis of electromagnetic interference of FAST visitors electronic equipment.

This paper where a used to distinguish the interference resulting from the basis: the international telecommunication union once made a proposal "radio astronomical observation protection threshold" (ITU - R RA. 769), the document is given each frequency radio observations on the required "quiet" corresponds to what is electromagnetic radiation power. The spectrum of interference signals measured in the experiment will be compared with this standard.

The authors experimented with three electronic devices: mobile phones, digital cameras and tablets, specifically red rice 2, nikon D7000 and iPad Air. The test first measured the radiation intensity of the three products at a distance of one meter in a microwave darkroom that was insulated from the outside interference. It then estimates the attenuation of signals in different positions around FAST telescope to the telescope. Combining the two, the interference intensity of several products is given to the telescope near FAST.

Mobile phones, cameras and ipads are all decaying enough at high frequencies to get below the threshold. But at low frequencies, all of them are above the threshold, which can interfere with the operation of the telescope. It's important to note that cell phones are almost as disruptive as dial-up interference, and even in standby, a digital camera produces enough radiation to interfere with FAST running at low frequencies. If the experiment without what the nature of the error, this is a very surprising conclusions, which means that the Australian side a variety of telescopes to adopt the policy of "encouraging photography" is wrong, the policies of the FAST to ban mobile phones and digital cameras are necessary.

In neighboring FAST the viewing platform, no obstacles jammer blocker interference sources of radiation, only when the electromagnetic wave propagation in the three-dimensional space free attenuation caused by weakened slightly, so the test a few products can produce serious interference to FAST - more than ten thousand times beyond the threshold. And it's worth noting that the digital camera, with the nikon D7000 as an experimental prototype, is more than 1,000 times stronger than the interference of mobile phones and ipads.
The study, though limited to a limited number of products, represents a significant amount of support for the electromagnetic control policy around FAST telescope. In order to achieve FAST and efficient operation, early scientific output, hope you future visit FAST telescope, can consciously completely shut down their cell phones, cameras, hand ring, smart watches all electronic products.