Launched in February 1997, the international VLBI Space Observatory Project (VSOP) is the first to link radio telescopes on Earth with one in space. Working together, they create a "virtual" mega-telescope dish that is over 25,000 km wide and by far the most powerful imaging device ever created for space astronomy.
"This was a golden opportunity for the Canadian Space Agency," said Dr. Terry Hughes, a Program Scientist within the CSA's Space Science Program. "Astronomers around the world now have a much sharper view of space thanks to Canadian-made technology and expertise developed as part of this historic program."
The Canadian Space Agency's (CSA) prime contribution to VSOP was to develop new hi-tech instrumentation that could precisely match the data downloaded from the VSOP satellite with that from the terrestrial telescopes. In return for providing the hi-tech synchronization system, Canada's VSOP astronomy team now receives access to all project data.
The Canadian VSOP science team is head by Dr. Peter Dewdney of the National Research Council's Dominion Radio Astrophysical Observatory (DRAO) in Penticton B.C. His co-investigators are Dr. Russ Taylor of the University of Calgary and Dr. Wayne Cannon of York University and Institute for Space and Terrestrial Science (ISAS) near Toronto.
The first Canadian images from VSOP emerged from a process that began on May 25 when telescopes from Australia, South Africa, and Japan simultaneously pointed at a remote quasar 9 billion light years away. Recordings of the quasar's weak signal were sent to the Canadian VSOP science team in Penticton and the University of Calgary, where they were digitally processed by a specially designed supercomputer. After a number of trials, the team was finally able to obtain the information needed to put together their first image.
Dr. Russ Taylor made the first Canadian image in a grueling all night session in his laboratory. The subject of the observations is the distant quasar PKS 1055+018, a galaxy containing a mysterious central object believed to be a super-massive black hole. The object is typical of those that will be studied at resolutions up to 100 times that of the Hubble Space Telescope. Hundreds of quasars, radio galaxies and pulsars will be imaged with this mega-telescope over the satellite's lifetime.
The VSOP satellite, named Halca, was launched on Feb. 12 by Japan's Institute of Space and Astronautical Science (ISAS) and is the first of its kind. Tracking stations (operated by NASA, NRAO, and ISAS) on four continents receive a continuous stream of data from the Halca satellite. The tracking stations and the network of ground telescopes are equipped with the CSA's high-tech tape recorders, which were built by ISTS. The recorded signals are sent to one of three locations in Japan, Canada and the U.S., where a custom computer called a "correlator" is used to combine the signals.
ISAS leads the international collaboration backed by Japan's National Astronomical Observatory, NASA's Jet Propulsion Laboratory, the US National Radio Astronomy Observatory (NRAO), the Canadian Space Agency, the Australia Telescope National Facility, and the European Joint Institute for Very Long Baseline Interferometry.
(1) The VSOP dish is a radio telescope, and not an optical telescope like Hubble, so data is initially received in the form of radio waves, not visual images. Data must first be converted into computer bytes and from there they are used to create scientifically useful images. (2) Creating a telescope dish larger than Earth by placing one antenna in space is possible because the resolution of a radio telescope is dependent solely upon the distance between the farthest points that make up the dish of the telescope. In fact, it was in Canada in 1967 that two entirely different telescope facilities (Algonquin Radio Observatory in Ontario and Dominion Radio Astrophysical Observatory in B.C.) were first combined in order to put this theory into practice. Canadian scientists received an international award in recognition of this accomplishment.
National Radio Astronomy Observatory
July 18, 1997
"This success means that our ability to make detailed radio images of objects in the universe is no longer limited by the size of the Earth," said NRAO Director Paul Vanden Bout. "Astronomy's vision has just become much sharper."
HALCA, launched on Feb. 11 by Japan's Institute of Space and Astronautical Science (ISAS), is the first satellite designed for radio astronomy imaging. It is part of an international collaboration led by ISAS and backed by NRAO; Japan's National Astronomical Observatory; NASA's Jet Propulsion Laboratory (JPL); the Canadian Space Agency; the Australia Telescope National Facility; the European VLBI Network and the Joint Institute for Very Long Baseline Interferometry in Europe.
On May 22, HALCA observed a distant active galaxy called PKS 1519-273, while the VLBA and VLA also observed it. Data from the satellite was received by a tracking station at the NRAO facility in Green Bank, West Virginia. Tape-recorded data from the satellite and from the radio telescopes on the ground were sent to NRAO's Array Operations Center (AOC) in Socorro, NM.
In Socorro, astronomers and computer scientists used a special-purpose computer to digitally combine the signals from the satellite and the ground telescopes to make them all work together as a single, giant radio telescope. This dedicated machine, the VLBA Correlator, built as part of the VLBA instrument, was modified over the past four years to allow it to incorporate data from the satellite. Correlation of the observational data was completed successfully on June 12, after the exact timing of the satellite recording was established. Further computer processing produced an image of PKS 1519-273 -- the first image ever produced using a radio telescope in space.
For Jim Ulvestad, the NRAO astronomer who made the first image, the success ended a long quest for this new capability. Ulvestad was involved in an experiment more than a decade ago in which a NASA communications satellite, TDRSS, was used to test the idea of doing radio astronomical imaging by combining data from space and ground radio telescopes. That experiment showed that an orbiting antenna could, in fact, work in conjunction with ground-based radio observatories, and paved the way for HALCA and a planned Russian radio astronomy satellite called RadioAstron.
"This first image is an important technical milestone, and demonstrates the feasibility of a much more advanced mission, ARISE, currently being considered by NASA," Ulvestad said.
The first image showed no structure in the object, even at the extremely fine level of detail achievable with HALCA; it is what astronomers call a "point source." This object also appears as a point source in all-ground-based observations. In addition, the 1986 TDRSS experiment observed the object, and, while this experiment did not produce an image, it indicated that PKS 1519-273 should be a point source.
"This simple point image may not appear very impressive, but its beauty to us is that it shows our entire, complex system is functioning correctly. The system includes not only the orbiting and ground-based antennas, but also the orbit determination, tracking stations, the correlator, and the image-processing software," said Jonathan Romney, the NRAO astronomer who led the development of the VLBA correlator, and its enhancement to process data from orbiting radio telescopes. "We would be skeptical of a complex image if we had not been able to obtain a good point image first," Romney added.
A second observing target, the quasar 1156+295, observed on June 5, made a more interesting picture. Seen by ground-based radio observatories, this object, at a distance of 6.5 billion light years, has been known to show an elongation in its structure to the northeast of the core. However, seen with the space-ground system, it is clearly shown to have both a core and a complex "jet" emerging from the core. Such jets, consisting of subatomic particles moving near the speed of light, are seen in many quasars and active galaxies throughout the universe. In fact, 1156+295 is one of a class of objects recently found by NASA's Compton Gamma-Ray Observatory to exhibit powerful gamma-ray emission; such objects are among the most compact and energetic known in the universe.
"By showing that this object actually is a core-jet system, HALCA has produced its first new scientific information, and demonstrates its imaging capabilities for a variety of astrophysical investigations," Romney said. "This image shows that the jet extends much closer to the core, or 'central engine' of the quasar than is shown by ground-only imaging," Romney added.
"This is an exciting and historical achievement for radio astronomy," said Miller Goss, NRAO's VLA/VLBA Director. "At NRAO, we have seen our colleagues -- scientists, electrical engineers, computer programmers and technicians in Socorro and Green Bank -- work for years on this project. Now, they can take pride in their success."
Radio astronomers, like astronomers using visible light, usually seek to make images of the objects at which they aim their telescopes. Because radio waves are much longer than light waves, a radio telescope must be much larger than an optical instrument in order to see the same amount of detail. Greater ability to see detail, called resolving power, has been a quest of radio astronomers for more than half a century.
To see a level of detail equal to that revealed by optical telescopes would require a radio-telescope dish miles across. In the 1950s, British and Australian scientists developed a technique that used smaller, widely-separated antennas, and combined their signals to produce resolving power equal to that of a single dish as large as the distance between the smaller dishes. This technique, called interferometry, is used by the VLA, with 27 antennas and a maximum separation of 20 miles, and the VLBA, with 10 antennas and a maximum separation of 5,000 miles. Systems such as the VLBA, in which the antennas are so widely separated that data must be individually tape-recorded at each site and combined after the observation, are called Very Long Baseline Interferometry (VLBI) systems. VLBI was developed by American and Canadian astronomers and was first successfully demonstrated in 1967.
The VLBA, working with radio telescopes in Europe, represents the largest radio telescope that can be accommodated on the surface of the Earth. With an orbit that carries it more than 13,000 miles above the Earth, HALCA, working with the ground-based telescopes, extends the "sharp vision" of radio astronomy farther than ever before. Using HALCA, radio astronomers expect to routinely produce images with more than 100 times the detail seen by the Hubble Space Telescope.
Astronomers around the world are waiting to use the satellite to seek answers to questions about some of the most distant and intriging objects in the universe. As much as one-third of the VLBA's observing time will be devoted to observations in conjunction with HALCA. Over the expected five-year lifetime of HALCA, scientists hope to observe hundreds of quasars, pulsars, galaxies, and other objects.
Launched from Japan's Kagoshima Space Center, HALCA orbits the Earth every six hours, ranging from 350 to 13,200 miles high. The 1,830-pound satellite has a dish antenna 26 feet in diameter. The antenna, folded like an umbrella for the launch, was unfolded under radio control from the ground on Feb. 26. The antenna was pointed toward PKS 1519-273 after a three- month checkout of the spacecraft's electronics, computers and guidance systems.
HALCA observations represent a true international scientific collaboration. In addition to the HALCA spacecraft, built, launched, and operated by Japan's ISAS, the participation of a large number of ground-based radio telescopes is also essential. NRAO's VLBA and VLA instruments, including the VLBA correlator, will be a vital component of this collaboration. Other radio telescopes in the U.S., Japan, Europe, and Australia, also will participate.
NRAO's facility at Green Bank, WV, is one of five tracking stations where the data collected on the spacecraft are received and recorded. Another is at an ISAS facility in Japan, and JPL operates three additional tracking stations, in California, Australia, and Spain. JPL also collects information from all tracking stations to determine the very accurate spacecraft orbit necessary to reduce these observations.
The NRAO Space VLBI efforts in Socorro and Green Bank were supported by funding from the National Aeronautics and Space Administration. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
IMAGE CAPTIONS: [NOTE -- The images can be found at the NRAO's anonymous ftp site, at: ftp.aoc.nrao.edu They are in the pub/press directory.] 1519-273.gif -- Active galaxy (PKS 1519-273) as imaged with HALCA satellite, along with the National Science Foundation's VLBA and VLA ground-based radio telescopes. This is the first VLBI image ever made using an orbiting radio-astronomy satellite. ---------------------------------------------------------------------------- 1519_ground.gif -- The same active galaxy as seen with ground-only radio telescopes. This image is to the same scale as the space-ground image. ---------------------------------------------------------------------------- 1156+295.gif -- The quasar 1156+295 as seen using the HALCA satellite in conjunction with the VLBA. This image shows the quasar's core, bottom right, and a jet of subatomic particles emerging from the core toward the top left. ---------------------------------------------------------------------------- 1156_ground.gif -- Ground-only radio image of 1156+295, showing much less detail. This image is not to the same scale as the space-ground image; if at the same scale it would be larger. ----------------------------------------------------------------------------
SKY & TELESCOPE NEWS BULLETIN
FEBRUARY 14, 1997
Op 12 februari werd vanaf Kagoshima Space Center (Japan) VSOP gelanceerd: VLBI Space Observation Programme. VLBI staat voor Very Long Baseline Interferometry: interferometrie door middel van een grote onderlinge afstand tussen twee of meer samenwerkende telescopen. De VSOP-schotel heeft maar een middellijn van 8 meter. Klein in vergelijking met aardse radiotelescopen. Maar doordat hij vanuit zijn langgerekte, elliptische baan wordt gekoppeld met radiotelescopen op aarde, neemt zijn werkzame diameter toe tot 20.000 km.
JIVE (Joint Institute for VLBI in Europe
NASA Headquarters, Washington, DC
Jet Propulsion Laboratory, Pasadena, CA
National Radio Astronomy Observatory, Socorro, NM
February 7, 1997
The launch of the Very Long Baseline Interferometry (VLBI) Space Observatory Program (VSOP) satellite by Japan's Institute of Space and Astronautical Science (ISAS) is scheduled for Feb. 10 at 11:50 p.m. EST (1:50 p.m. Feb. 11, Japan time.)
The satellite is part of an international collaboration led by ISAS and backed by Japan's National Astronomical Observatory; NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA; the National Science Foundation's National Radio Astronomy Observatory (NRAO), Socorro, NM; the Canadian Space Agency; the Australia Telescope National Facility; the European VLBI Network and the Joint Institute for Very Long Baseline Interferometry in Europe.
Very long baseline interferometry is a technique used by radio astronomers to electronically link widely separated radio telescopes together so they work as if they were a single instrument with extraordinarily sharp "vision," or resolving power. The wider the distance between telescopes, the greater the resolving power. By taking this technique into space for the first time, astronomers will approximately triple the resolving power previously available with only ground-based telescopes. The satellite system will have resolving power almost 1,000 times greater than the Hubble Space Telescope at optical wavelengths. The satellite's resolving power is equivalent to being able to see a grain of rice in Tokyo from Los Angeles.
"Using space VLBI, we can probe the cores of quasars and active galaxies, believed to be powered by super massive black holes," said Dr. Robert Preston, project scientist for the U.S. Space Very Long Baseline Interferometry project at JPL. "Observations of cosmic masers -- naturally-occurring microwave radio amplifiers -- will tell us new things about the process of star formation and activity in the heart of other galaxies."
"By the 1980s, radio astronomers were observing the universe with assemblages of radio telescopes whose resolving power was limited only by the size of the Earth. Now, through a magnificent international effort, we will be able to break this barrier and see fine details of celestial objects that are beyond the reach of a purely ground-based telescope array. We anticipate a rich harvest of new scientific knowledge from VSOP," said Dr. Paul Vanden Bout, Director of NRAO.
In the first weeks after launch, scientists and engineers will "test the deployment of the reflecting mesh telescope in orbit, the wide-band data link from the satellite to the ground, the performance of the low noise amplifiers in orbit, and the high-precision orbit determination and attitude control necessary for VLBI observations with an orbiting telescope," according to Dr. Joel Smith, manager of the U.S. Space VLBI project at JPL. Scientific observations are expected to begin in May.
The 26-foot diameter orbiting radio telescope will observe celestial radio sources in concert with a number of the world's ground-based radio telescopes. The 1,830-pound satellite will be launched from ISAS' Kagoshima Space Center, at the southern tip of Kyushu, one of Japan's main islands, and will be the first launch with ISAS' new M-5 series rocket.
The satellite will go into an elliptical orbit, varying between 620 to 12,400 miles above the Earth's surface. This orbit provides a wide range of distances between the satellite and ground-based telescopes, which is important for producing a high- quality image of the radio source being observed. One orbit of the Earth will take about six hours.
The satellite's observations will concentrate on some of the most distant and intriguing objects in the universe, where the extremely sharp radio "vision" of the new system can provide much-needed information about a number of astronomical mysteries.
For years, astronomers have known that powerful "engines" in the hearts of quasars and many galaxies are pouring out tremendous amounts of energy. They suspect that supermassive black holes, with gravitational fields so strong that not even light can escape them, lie in the centers of these "engines." The mechanism at work in the centers of quasars and active galaxies, however, remains a mystery. Ground- based radio telescopes, notably NRAO's Very Long Baseline Array (VLBA), have revealed fascinating new details in recent years, and VSOP is expected to add a wealth of new information on these objects, millions or billions of light-years distant from Earth.
Many of these same objects act as super-powerful particle accelerators to eject "jets" of subatomic particles at nearly the speed of light. Scientists plan to use VSOP to monitor the changes and motions in these jets to learn more about how they originate and interact with their surroundings.
The satellite also will aim at regions in the sky where giant collections of water and other molecules act as natural amplifiers of radio emission much as lasers amplify light. These regions, called cosmic masers, are found in areas where new stars are forming and near the centers of galaxies. Observations can provide the detail needed to measure motions of individual maser "spots" within these regions, and provide exciting new information about the star-forming regions and the galaxies where the masers reside. In addition, high-resolution studies of cosmic masers can allow astronomers to calculate distances to them with unprecedented accuracy, and thus help resolve continuing questions about the size and age of the universe.
The project is a major international undertaking, with about 40 radio telescopes from more than 15 countries having committed time to co-observe with the satellite. This includes the National Science Foundation's Very Long Baseline Array (VLBA), an array of 10 telescopes spanning the United States from Hawaii to Saint Croix; NASA's Deep Space Network (DSN) sites in California, Spain, and Australia; the European VLBI Network, more than a dozen telescopes ranging from the United Kingdom to China; a Southern Hemisphere array of telescopes stretching from eastern Australia to South Africa; and Japan's network of domestic radio telescopes.
In the United States, NASA is funding critical roles in the VSOP mission at both JPL and NRAO. JPL has built an array of three new tracking stations at its DSN sites in Goldstone, CA; Madrid, Spain; and near Canberra, Australia. A large existing tracking station at each of these sites has also been converted to an extremely sensitive radio telescope for simultaneous observations with the satellite. JPL also is providing precision orbit determination, scientific and operational planning support to the Japanese, and advice to U.S. astronomers who wish to observe with the satellite. NRAO is building a new tracking station at Green Bank, WV; contributing observing time on the VLBA array of telescopes; modifying existing data analysis hardware and software, and aiding astronomers with the analysis of the VSOP data. Much of the observational data will be processed at NRAO's facility in Socorro, NM, using the VLBA Correlator, a special purpose high-performance computer designed to process VLBI data.
VSOP is the culmination of many years of planning and work by scientists and engineers around the world. Tests using NASA's Tracking and Data Relay Satellite System (TDRSS) proved the feasibility of space VLBI in 1986. Just last year, those old data were used again to test successfully the data- reduction facilities for VSOP.
JPL manages the U.S. Space Very Long Baseline Interferometry project for NASA's Office of Space Science, Washington, DC. The VLBA, headquartered in Socorro, NM, is part of the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.