A New Radio Observatory in Space

Early this morning a slender rocket roared up into the blue sky from the Baikonur launch complex in Kazakhstan, and a worldwide team of radio astronomers collectively roared with excitement as well. Riding atop the booster was Spektr-R, a radio observatory that will soon help them study some of the most universe's most energetic and enigmatic objects.

They've been waiting to celebrate for a very long time. Spektr-R got the green light for development in 1978, at which time the launch was envisioned for 2001. This mission's road to space was full of the usual technical and funding potholes, but the biggest hurdle was the collapse of the Soviet Union and the economic difficulties for Russia that followed. Through it all, Nicholas Kardashev and his development team at Lebedev Physical Institute in Moscow (part of the Russian Academy of Sciences) managed to keep the project inching forward.

With two successful firings of its Fregat upper stage, Spektr-R is now orbiting Earth in a highly elliptical loop that stretches out to roughly 210,000 miles (340,000 km) — most of the way to the Moon. The orbit is so distended that throughout the mission's five-year duration its shape, orientation, and period (currently 9½ days) will shift continuously due to gravitational perturbations from the Moon and Sun.

But the whole point is to get the four-ton spacecraft as far from Earth as possible. It will become part of RadioAstron, a gigantic ground- and space-based radio interferometer of unprecedented scale and, therefore, unprecedented ability to resolve radio-bright features in galactic and extragalactic targets.

(Time out for an explanation: A telescope's angular resolution depends on its aperture. Interferometry combines the radio energy collected by two or more radio telescopes in a way that achieves the resolving power of a single virtual telescope as big as the individual dishes' distances from one another.)

Operating in four frequency bands — 0.3, 1.6, 5.0, and 22 gigahertz (correpsonding wavelengths: 92, 18, 6.2 and 1.4 cm), Spektr-R and large ground-based radio dishes will combine forces to discern details down to 7 micro-arcseconds. If I'm doing the math right, that's effectively good enough to pick out grains of sand on a California beach from a vantage point in New York City!

Ken Kellermann, who co-chairs RadioAstron's international advisory committee, states that Spektr-R will create interferometric baselines 30 times greater than are possible among dishes confined to Earth's surface. "It will give by far the highest angular resolution available in astronomy," he notes.

Five days from now, Spektr-R will unfurl 27 carefully nested panels to form a graceful antenna 33 feet (10 m) across — the largest telescope ever launched. By November, following three months of engineering checks and test observations, the spacecraft should be ready for interferometric trials with some of the world's largest ground-based radio dishes. Those players include facilities in the continental U.S., Puerto Rico, Germany, Italy, and Russia.

To get an idea of the incredible range of cosmic targets that radio astronomers are waiting to study, just scan this long list of presentations from a 2008 symposium titled ""Radio Universe at Ultimate Angular Resolution."

Spektr-R will be especially useful in probing the supermassive black holes and energetic jets found at the centers of neighboring galaxies. One of the best-known examples is in Messier 87, a supergiant elliptical galaxy located some 54 million light-years from Earth. With a little luck, RadioAstron scientists believe they can observe the event horizon of the 7-billion-Sun black hole at its core. ("M87 is a good target," observes Kellermann, but NGC 5128 may be better.

This isn't the first time that radio astronomers have paired big "ears" on the ground with one in space. From its launch in 1997 until 2005, Japanese astronomers operated HALCA (short for Highly Advanced Laboratory for Communications and Astronomy), a 26-foot (8-m) radio dish. HALCA's orbit only extended out to about 13,000 miles (21,000 km), which when operated together with ground-based receivers yielded a resolution of 2 milli-arcseconds.

David Jauncey (Australia Telescope National Facility) has been a principal player in both RadioAstron and VSOP, the corresponding collaboration involving HALCA. "VSOP was an amazing success," he says. "It was an basically an engineering mission, but it achieved amazing results both in terms of the science undertaken and also, in some ways as important, in the international collaboration that was achieved." Given the greatly improved capabilities afforded by Spektr-R, he adds, "I think that the expectations for RadioAstron are rightly very high."

Notably, this isn't the first time that Kardashev has gotten a 10-m radio dish into orbit. Die-hard space aficionados will recall that in June 1979 a ferry craft delivered the KRT-10 radio telescope to the Salyut 6 space station. Cosmonauts Vladimir Lyakhov and Valery Ryumin operated the big dish for several weeks — then had to conduct an emergency spacewalk when its wire-mesh surface became entangled with the station's exterior after they tried to eject it.