Spectrum Management at the National Radio Astronomy Observatory: Protecting the Spectrum for Radio Frequency Observations

Chris De Pree, NRAO Deputy Spectrum Manager, National Radio Dynamic Zone Project Director

The National Radio Astronomy Observatory (NRAO) was founded in 1956, and the National Radio Quiet Zone (NRQZ) was established just two years later. In the past 70 years, the NRAO has designed, built and dedicated many of the world’s preeminent radio telescopes, including the 140 Foot Telescope (Green Bank; 1965), the Jansky Very Large Array (VLA; 1980), the Very Long Baseline Array (VLBA; 1993), the Green Bank Telescope (GBT; 2000), and the Atacama Large Millimeter Array (ALMA; 2013). These telescopes have been involved in many groundbreaking astronomical discoveries, most recently the imaging of the event horizons around the black holes at the center of M87 and our own Milky Way. All of these telescopes were designed to operate at remote sites, far from sources of radio frequency interference (RFI) that were common at the time that they were dedicated. The modern era has brought with it an explosion in the number of devices that emit radio waves, from kitchen appliances to consumer devices to electronics in the cars that we drive. Even these sources of RFI are potentially manageable at remote sites. Satellite constellations in Low Earth Orbit (LEO) have changed the balance significantly. Satellites like those in the Starlink network mean that even the most remote radio astronomy sites now have a large number of radio transmitters above them at all times. I will describe current NRAO efforts to better understand and alleviate these new challenges to radio astronomy observations.