Most likely, the radio astronomers will be safe.
If you read any trade publications, then you know the FCC has a plan to induce broadcasters to give up some of their frequency spectrum assignments so that more spectrum becomes available for mobile communications. But the FCC plan might also bump the radio astronomy scientists out of off-air TV Channel 37.
The FCC adopted a notice of proposed rulemaking in late September, laying out detailed proposals. The details of this plan are very complicated, but the broad outline is no surprise. In summary, broadcasters can offer their spectrum in return for compensation, which would be derived from an “incentive auction” of the freed-up spectrum. A broadcaster would give up the channel if the compensation were “adequate.”
Just exactly how this will work is pretty fuzzy. The major metropolitan areas have the greatest demand for mobile spectrum, but will any major-market TV broadcasters want to give up their channels? The FCC envisions that a broadcaster that gives up a 6 MHz channel can share capacity on another broadcaster’s 6 MHz channel. How will that work?
The FCC plan would “repack” the UHF spectrum rather than reallocate the individual freed-up channels, moving broadcasters to lower channel numbers so that the higher channel numbers become a block of mobile spectrum. Is that really feasible?
How will the FCC and broadcasters decide what is “adequate” compensation? What will happen to wireless microphones that operate on UHF TV channels? What happens to low-power TV stations and TV translators?
Net proceeds from the incentive auction are to be deposited in the Public Safety Trust Fund to fund a national first responder network and national deficit reduction. Will there be any net proceeds after the broadcasters are paid off?
But I was most surprised by the FCC’s attention to TV Channel 37. Today, Channel 37 (608-614 MHz) is not used for TV broadcasting. It is allocated throughout the world for radio astronomy. The FCC is asking whether to move the radio astronomers to some other frequency (TV Channel 32 at 578-584 MHz is the FCC’s candidate) and put the 608-614 MHz into the mobile communications allocation.
What exactly is radio astronomy, you ask? Recall that astronomy studies celestial objects by analyzing their emissions, traditionally visible light. Radio astronomy detects and analyzes radio emissions rather than visible light.
Radio astronomy is a tool used by scientists to study our universe. Radio astronomers discovered the first planets outside the solar system, circling a distant pulsar. Measurements of radio spectral line emission have identified and characterized the birth sites of stars in our own galaxy and the complex distribution and evolution of galaxies in the universe. Radio astronomy measurements have discovered ripples in the cosmic microwave background that were imposed on the signals by acoustic vibrations of the early universe, which evolved into today’s stars and galaxies.
The emissions that radio astronomers study are extremely weak, and so the receivers they use are vulnerable to interference. They are most vulnerable to transmitters operating on the same frequencies they are receiving, but also from out-of-band emissions from adjacent channels and harmonic emissions and intermodulation products from other channels.
Radio astronomers study some frequencies because they are related to physical phenomena. For example, the 1400-1427 MHz band is used for spectral line observations of the 21 cm hydrogen line. Spectral line observations are performed in the 12-16 GHz band for the study of the formaldehyde line. NASA supports radio astronomy observations in the 22.01-22.5 GHz band for observations of the redshifted H20 line at 22.235 GHz. And the 23.07-23.12 GHz band is used for observations of ammonia lines.
But the Channel 37 band at 608-614 MHz is not used for spectral line observations. It is used for “continuum observations” that take place at numerous frequencies, studying pulsars, distribution of cosmic rays and outbursts of high-energy particles from our Sun. So the FCC suggests that these observations could take place at other frequencies in the UHF range.
The radio astronomers will no doubt respond that the 608-614 MHz band is used for Very Long Baseline Interferometry (VLBI), which is a technique that processes simultaneous observations from radio telescopes across long distances. Scientists use VLBI to study continental drift, rotation of the Earth, earthquakes and space navigation. The National Radio Astronomy Observatory (NRAO) operates the Very Long Baseline Array (VLBA), which consists of 10 telescopes distributed throughout the U.S. and its territories. They would all have to be “retuned” if the FCC moves the radio astronomers to a different part of the UHF band. But, perhaps most significantly, there are radio telescopes in other countries that participate in observations by the VLBA, so the U.S. can’t simply make a frequency change unilaterally.
So the FCC has put Channel 37 “in play” in this new proceeding. I think it’s a bad idea. But I think the FCC’s entire plan to take back spectrum from broadcasters is a bad idea. Undoubtedly, there are some financially weak TV stations that are willing to sell out at the right price. But, in most cases, a broadcaster’s idea of the “right price” and the FCC’s idea of the “right price” are likely to be far apart. So, most likely, the radio astronomers will be safe.