The 45-foot portable radio telescope at the NRAO in Green Bank was a 1973 replacement for the retired 42-foot radio telescope that had been hauled around Pocahontas County in West Virginia since 1967 as the outlying fourth member of the Green Bank Interferometer.
Over its 15-year tour of duty in the GBI, the 45-foot was disassembled, packed, hauled to and reassembled in a few nearby locations in the county, most notably in Huntersville. It was critical in helping to prove that the proposed Very Large Array project would be feasible and an extremely valuable tool for astronomy.
Antenna of All Trades
At the conclusion of its successful nomadic phase, the 45-foot settled on piers at Green Bank in 1988 where NASA converted it into a tracking station for orbiting satellites.
GEOTAIL, a joint NASA-Institute of Space and Astronautical Science (ISAS, in Japan) satellite sent up to study the magnetic stream off of the Earth, was the first orbiting craft to benefit from the 45-foot’s space communications. The second was a Very Long Baseline Interferometry (VLBI) test satellite called SURFSAT-1, built by undergraduates and NASA’s Jet Propulsion Laboratory in California.
In 1995 the 45-foot began to send NASA mission controllers the timing signals for orbital corrections, and also it received their scientific data.
In 1996, Comet Hyakutake C/1996 B2 raced across our skies, and the 45-foot was used to examine the molecular-rich ice ball for interesting chemistry.
In 1997, after the launch of Japan’s VLBI Space Observatory Program (VSOP, aka MUSES-B, aka HALCA) carrying an 8m radio telescope, space VLBI became a brief reality. The 45-foot and NRAO’s VLBA participated in creating the largest telescope ever used – over 60,000 miles across! Coordination with the VSOP mission ended in 2001.
In between its late 20th-century tracking duties, the 45-foot telescope conducted the Galactic Plane A survey, mapping the entire Milky Way galaxy in the microwave wavelengths of 8.35 GHz and 14.35 GHz frequencies.
The versatile 45-foot was once again adapted for a new purpose: solar observing. Retrofitted, the 45-foot began taking daily spectral observations of the Sun from decimeter to decameter wavelengths in 2004. As the Green Bank Solar Radio Burst Spectrometer, this little telescope can function as a state-of-the-art instrument for discovering and monitoring solar radio bursts. It works with a smaller partner antenna as the prototype for FASR, the Frequency Agile Solar Radiotelescope, a next-generation instrument for observing solar phenomenon.
FASR will image radio emissions in three dimensions once every second, providing unique measurements of the Sun’s magnetic fields, solar flares, and other drivers of space weather. In other words, FASR astronomers will have the earliest warnings of solar events that might spell trouble for our communications satellites, manned space stations, and ground-based power supplies.