The birth of a telescope 30 times larger than Earth

The birth of a telescope 30 times larger than Earth
Artist's impression of Spektr-R, the 10-meter space-borne antenna of the RadioAstron project. Credit: Lavochkin Association

( -- On 15 November 2011, the Effelsberg 100-meter radio telescope, together with three Russian and one Ukrainian telescope, took part in the first interferometric observations with the orbiting 10-meter antenna Spektr-R of the Russian RadioAstron project. The observations were made at a wavelength of 18 centimeters, targeting the distant, bright, and very compact quasar 0212+735. Interferometric signals have been successfully detected by the RadioAstron team between Spektr-R and the ground antennas, setting a new world record for the size of a radio interferometer and opening a new era in interferometric studies of cosmic radio emission.

The technique of very long baseline interferometry, which has already set a number of world records in astronomy, now enters an entirely new era signaled by a successful detection of interferometric signals ("fringes") made in observations performed with the 10-meter space-borne antenna Spektr-R of the RadioAstron project, three 32-meter antennas of the Russian QUASAR Network, the Ukrainian 70-meter antenna in Evpatoria, and the German 100-meter radio telescope in Effelsberg. The detection was made on 15 November 2011, with observations performed at a of 18 centimeters and targeting bright and extremely compact from the distant quasar 0212+735.

The birth of a telescope 30 times larger than Earth
First interferometric signal ("fringe") between Spektr-R and the Effelsberg 100m radio telescope. Credit: Astro Space Center of Lebedev Physical Institute, Russian Academy of Sciences

"These fascinating results confirm our expectations that we will be able to probe with RadioAstron the conditions in the innermost regions of with unprecedented detail", says Anton Zensus, director at the Max-Planck-Institut für Radioastronomie in Bonn and head of the institute's "Very Long Baseline Interferometry" (VLBI) research group. "The weak signals from such systems require the coordinated use of the most sensitive available such as the 100-m dish in Effelsberg."

In order to perform these observations, data from the space antenna of RadioAstron were recorded on-board and sent to the satellite tracking antenna in Puschino, Russia. These data have been subsequently combined with recordings made at ground-based radio telescopes participating in RadioAstron observations. This is done at a special RadioAstron correlator facility in Moscow. The RadioAstron correlator performs searches for correlations (or interferometric fringes) between the signals recorded at two or more antennas. Using these correlations, images of distant cosmic objects can be reconstructed at a resolution that would have been achieved with a telescope as large as the largest distance between the antennas participating in observations.

The satellite was about 100,000 km away from Earth during the observations of the quasar 0212+735. Planned observations with SpectR will extend out to 360,000 kilometers from the Earth, thus creating a telescope which is effectively 30 times larger than the size of our planet. This kind of telescope will achieve a resolution as fine as 1/100,000 of a second of arc. This resolution is sufficient for measuring the size of a one cent coin on the surface of Moon and reaches within a factor of two of the scale of the event horizon in the supermassive black hole in the center of our Galaxy.

"The RadioAstron team is very excited to get the first interferometric signals", says RadioAstron scientist Yuri Kovalev from Astro Space Center in Moscow. "This achievement confirms a successful operation of the extremely complex system and is a milestone that allows us to move forward to an extensive science program involving radio telescopes located throughout the world."

This exciting new capability promises to help tackling some of the most puzzling problems in astrophysics, including the origin of the most energetic particles in the Universe and the nature of supermassive black holes.

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Dec 08, 2011
I'd like to point out that their 'effective' resolution doesn't take into account the limits of their interferometry. While they have figured out how to get around the obstacle of having to perfectly time and calibrate the multiple signals, it means that they can only run an interference pattern on aligned signals based on a guess of the exact points to match up.

More simply: They are matching the images up based on 'visible' points. But they don't know if the most accurate picture is one pixel to the left, or one pixel to the right...This reduces the effective resolution by 50-75%

Whereas with the laser calibrated interferometry systems used in some telescope clusters, you can get a more exact interferometry - you know exactly how to line the images up to get the most accurate picture, regardless of the data from any individual telescope.

Radioastronomy just isn't as sexy as hubble.

Dec 08, 2011
Really need orbiters specifically designed for this type of mission, so you can use laser pointers, radars, or other non-science instruments to help get more accurate and precise calculations of the distances between individual antennae, and of course more precise alignments to deal with the resolution issue.

It's always good to have extra data points from extra antennae.

Although you can probably use a combination of computer algorithms and human intuition to "guess" the most accurate representation more often than chance by observing changes in appearance of reference objects. For example, a foreground, midground, and background reference object.

But thisis the sort of thing I was hoping for in specfic design.

Let's get 8 or 10 of these things up there orbiting on different orbital planes around the Earth and all over the Solar system, then we'll really get good resolution, and much cheaper than the James Webb too I'll bet....

Dec 08, 2011
That's what I'm hearing is the plan, Nanobanano . . . the plan being to put up more radio dishs.

I'm surprised at the choice of radio telescopes to do this radio interferometry. I'm surprised the Aricebo and the New Mexico array are not included at least part time. Well, i'm sure that the news out of this is only going to get better with time.

Dec 08, 2011
It's a good method. But it's not accurate to imply that it's the functional equivalent of a telescope with a diameter equivalent to 30 earths.

Telescopes, including radio telescopes, are all about capturing photons. An actual radio telescope 30 earths in diameter would capture a vastly larger number of photons and achieve much better resolution.

Alas, building telescopes of that size is well beyond our grasp; and even if it was not, the resources required to build a scope of that size would be better deployed placing smaller arrays farther apart. A few thousand-meter arrays orbiting the sun beyond Neptune would be a good place to start, if our technology grows to the point of enabling them.

Dec 09, 2011
the Effelsberg 100-meter radio telescope

Used to live in that area and ride my motorcycle down the valley where it is located. It's just awesome seeing that huge dish turn and align with some radio source with millimeter accuracy.

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