Associated Universities (AUI) and the National Radio Astronomy Observatory (NRAO) have made a preliminary examination of the report from the National Science Foundation (NSF) Astronomy Portfolio Review Committee (PRC).

Among the recommendations of that report are that the NSF's Green Bank Telescope (GBT) and Very Long Baseline Array (VLBA) be fully divested from the NSF Astronomy Division's portfolio of research facilities in the next five years, with no further funding from the Astronomy Division.

AUI and NRAO recognize and acknowledge the need to retire obsolete facilities to make way for the state-of-the-art. However, both the GBT and the VLBA are the state-of-the-art, and have crucial capabilities that cannot be provided by other facilities.

Separately the two telescopes provide unparalleled scientific access to the universe. When their information is combined, the instruments provide the highest sensitivity and resolution available for any astronomical instrument in the world.

The Green Bank Telescope
The GBT, located in Green Bank, West Virginia, is the largest and most capable fully steerable single-dish radio telescope in the world. It is a cutting-edge research instrument at the height of its powers, and it is continually growing more capable through the introduction of low-cost upgrades to its light detecting and processing electronics. It is the only world-class astronomical telescope in the eastern United States and has been in full scientific operation for less than 10 years.

Weighing sixteen million pounds, and able to precisely point its 2.3 acres of light-collecting surface area anywhere within all but the southernmost 15 percent of the celestial sphere, the $95 million GBT is an engineering and scientific marvel unlikely to be recreated, much less surpassed, by American astronomy for decades to come.

Indeed, astronomers in other parts of the world are at work trying to build their own telescopes of similar concept and design to the GBT, but none of those telescopes will exceed its performance.

The GBT is used by astronomers and students around the world for important research. It is a powerful tool for searching out the molecular building blocks of life in space, for probing the nature of matter at extreme densities, for mapping diffuse clouds of intergalactic gas that are invisible to other telescopes, for finding beacons in space that can serve as mileposts for calibrating our understanding of cosmic distance scales and the characteristics of dark energy, for detecting gravity waves first predicted by Einstein, and for pioneering and experimenting with new observational tools and techniques.

The GBT's annual cost of operation is about 0.7 percent of the annual federal budget for astronomy and astrophysics, but the cost of replacing it, once it's gone, would be enormous. In an era of constrained budgets, leveraging and improving the existing state-of-the-art through low-cost technology upgrades (the development of which often involves students) is a cost-effective way to keep science moving forward.

Today's GBT, because of such improvements, is 10 to 100 times more powerful than the original telescope, which entered full science operations in 2003. With small upgrades, the GBT has substantial potential to continue on this upward arc of increasing scientific power.

The Very Long Baseline Array
Comprising ten radio dish antennas distributed across 5,351 miles from Hawaii to the U.S. Virgin Islands - a span equal to two-thirds Earth's diameter - the VLBA is astronomy's sharpest tool, the world's largest, highest-resolution dedicated telescope (of any kind). It is capable of creating detailed images of portions of the sky so tiny that they are covered by but one pixel of a Hubble Space Telescope camera.

Commissioned in 1993, the VLBA is now up to 5,000 times more powerful than it was originally, thanks to new state-of-the-art receivers and a data processing supercomputer installed in 2010.

The VLBA is a critical tool for all of astronomy, including research conducted by astronomers who may never directly use the telescope, because knowing distances in space accurately is essential for figuring out the mass, makeup, movement, and evolution of cosmic objects. All of astrophysics hangs on this.

With the VLBA, astronomers can directly measure the distances to and rotation rates of galaxies, create the most accurate map ever of our own Milky Way Galaxy, directly measure cosmological distances to distant masers (helping to characterize dark energy), trace the movements of black holes and pulsars to learn their history and future, predict if and when galaxies will collide (including the Andromeda Galaxy with our Milky Way), pinpoint the exact centers of planets in our solar system and the most accurate distances to stars, and develop the celestial reference grid used by other telescopes.

Such direct distance and position measurements do not depend upon the assumptions that underlie other distance measurement techniques in astronomy.

Beyond the many manifestations of its value as astronomy's most accurate distance and position measuring machine, the VLBA investigates many intrinsically fascinating questions in astronomy, including the growth and feeding of supermassive black holes, the ejection of supercharged gas from galactic cores, and the expansion of supernova shock waves.

Closer to home, the VLBA can uniquely track the spin rate of nearby asteroids; how asteroids' spin influences their paths through space (paths that could disastrously intersect with Earth), and cannot be measured by other telescopes.

The VLBA is even used to track the movements of Earth's crust; this is done by observing distant quasars, and it has implications for fields ranging from GPS navigation to climate change.

The VLBA's annual operation budget is miniscule, less than a half of a percent of the 2012 federal astrophysics budget across agencies. To build the VLBA from scratch today would cost hundreds of millions of dollars.

The Portfolio Review Process
AUI and NRAO believe in prudent planning to ensure the ongoing success of the U.S. astronomy and astrophysics program. However, given the multi-agency nature of federal support for this field, it is essential that important national scientific assets be evaluated in the context of the total investments made in optical, radio, and solar astronomy.

In an era of fiscal constraint, it is even more important to leverage already existing world-leading facilities to maximize the benefit to science and taxpayers while enabling future advances. In radio astronomy, which is primarily supported by the NSF, the GBT and VLBA comprise the best telescopes of their kind that the world has to offer.

As ground-based telescopes, they are extremely cost-effective. These facilities have multiple federal users and sponsors as well as critical state stakeholders who rely upon them.

AUI and NRAO believe that optimizing the United States' astronomy portfolio should involve considerations beyond just the question of what can be cut from a particular funding agency's budget to make room for something new in that same agency's budget. We believe that any recommendations ultimately embraced by NSF should seek to:

+ Ensure that students have ready access to training and instrumentation opportunities at world-class, U.S.-based facilities

+ Provide a strong and broadly-based U.S. program that complements and reinforces our shared-access international facilities

+ Preserve unique and irreplaceable national research infrastructure that maintains U.S. leadership in optical, radio, and solar astrophysics.

None of these goals will be advanced by removing the GBT and VLBA from the portfolio of telescopes funded via the NSF; indeed, they will be hindered.

AUI and NRAO encourage the NSF to work with its other federal agency counterparts to consider a more balanced approach with additional funding scenarios for the entire U.S. federal astronomy portfolio.