In astronomy, size matters. And for decades radio astronomers have been able to boast that they had the largest telescopes on the planet.
They still do, with some now virtually the size of continents. But until recently the technology used to run them was getting pretty clunky and outdated.
An international effort is now underway to upgrade the world's giant radio telescopes with 21st century technology. The improvements will increase their sensitivity up to 10 times, opening up whole new heavenly realms. At the same time, new and more specialized radio telescope arrays are being built to peer into the universe's earliest star-forming era.
21st Century Radio
"We're leapfrogging several generations of technological progress," said Fred K.Y. Lo, director of the National Radio Astronomy Observatory (NRAO).
The flagship of NRAO is the almost 30-year-old Very Large Array (VLA) near Socorro, N.M., which combines the waves of 28 radio telescopes, each 25 feet in diameter, that are spread out over the desert to create a virtual telescopic dish the size of a small city.
VLA is undergoing a total upgrade, starting with the key element in radio telescope arrays -- the computer correlator that blends all the radio data from all the dishes.
Arrays of radio telescopes combine the radio waves they collect to vastly enhance the resolution of their cosmic images. This has been possible -- and necessary -- for decades because radio waves from space can be more in the range of tens of meters long. That makes them both easier to line up and combine than visible light waves, which are only millionths of a meter long. But combining radio waves also makes for less sharp, lower resolution images.
"Radio waves are very long and so you need very large telescopes," said Rick Perley, who is working on the 21st century Expanded VLA, or EVLA.
To illustrate: A meter-wide visible light telescope is a couple of million times wider than the wavelength of light it gathers. It's analogous to having a computer monitor with lots of very high-density pixels -- that makes for a sharper image. Visible light telescopes can resolve a piece of sky just a few arc seconds across -- at least 60 times a smaller patch of sky than can be resolved with the human eye.
Because radio waves are millions of times longer than visible light, a collecting dish of a 10-meter radio telescope might only resolve an area of sky the size of the moon. The only way to counteract this is by aiming lots of widespread radio telescopes at the same thing and combining their light -- gather a lot more pixels, in other words -- to sharpen the image.
For this reason one of the most important upgrades for the VLA and other radio telescopes is the correlator, which synchronizes all the light from all the radio dishes to create a single high-resolution radio image. The EVLA correlator is being built by Canadian researchers and engineers. Like most new computers, it will be able to handle more data much faster.
Another key hardware upgrade is replacing the 1970s-era radio receivers with far more sensitive modern receivers that can also read more radio wavelengths. Fiber optics are also replacing the old wiring that tied the whole array together.
Faster Scopes, Missing Bands & Radio Lunacy
Fiber optics are central to another big upgrade of radio telescopes in Europe. In April, the 100-meter Radio Telescope Effelsberg in Germany was tied in via fiber optics to radio telescopes at Jodrell Bank in the U.K., Medicina in Italy, Onsala in Sweden and Torun in Poland
The new giant array is being called the fastest radio telescope in the world with a virtual dish that spans Western Europe. The supercomputer correlator that brings it all together is in The Netherlands and can swallow a gigabyte of data per second. That's 500 times what a household DSL line can handle. The resulting resolution is 100 times better than the Hubble Space Telescope.
On another cutting edge of radio astronomy is a brand new international observatory that's under construction in Chile's Atacama Desert. The Atacama Large Millimeter/submillimeter Array (ALMA) will look just at the under-studied shortest radio waves of the universe by combining signals from a field of 66 separate dish antennae.
"Most of the photons in the universe are in the wavelengths range that ALMA will receive," said Anneila Sargent of the California Institute of Technology. "This will be a tremendous advancement for astronomy and open one of our science's last frontiers."
ALMA is expected to see into what's called the Dark Ages of the universe -- a time when the universe's very first stars were forming. Visible light from that time has now been so stretched out that its waves are in the millimeter/submillimeter range.
"We know that every time in the past a new wavelength has been opened up…we have been surprised by entirely unexpected discoveries," said Sargent. "We expect the unexpected from ALMA."
Finally, there are plans to take radio astronomy to the only place near Earth where the radio waves created by Earth itself, and those created by humans, can't interfere with the cosmic signal -- the far side of the moon.
The Lunar Array for Radio Cosmology (LARC) would involve hundreds of small radio telescopes covering two square kilometers on the side of the moon that never faces Earth. The entire observatory would be put in place by robotic vehicles.
Like ALMA and another array now under development in a particularly radio-quiet part of Western Australia, LARC would step even deeper into the Dark Ages with unprecedented resolution and interference.
But, whereas ALMA is under construction, and EVLA is taking shape before our eyes, LARC is a dream that won't break lunar ground until at least 2025, according to LARC's lead scientist Jacqueline Hewitt of MIT.
Discovery News : Discovery Channel : Radio Telescopes Get Makeovers
