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USRA Comments in Docket 12-268 Final W Signature Before the FEDERAL COMMUNICATIONS COMMISSION Washington, D.C. 20554 In the Matter of ) ) Expanding the Economic and Innovative ) Docket No. 12-268 Opportunities of Spectrum Through Incentive ) Auctions COMMENTS OF THE UNIVERSITIES SPACE RESEARCH ASSOCIATION Universities Space Research Association (hereinafter, "USRA"), hereby submits its comments in response to the Commission's October 2, 2012 Notice of Proposed Rulemaking in the above-captioned docket (“NPRM”). In these Comments, USRA discusses certain proposals in the NPRM regarding observations in the Radio Astronomy Service (“RAS”) at 608-614 MHz (i.e., Channel 37). USRA supports retaining the current allocation for RAS at Channel 37, and urges the Commission to maintain protections for RAS observation in that band. I. Introduction. USRA has an interest in this proceeding due to its relationship with the Arecibo Observatory in Arecibo, Puerto Rico. The Arecibo Observatory (AO) is part of the National Astronomy and Ionosphere Center (NAIC), which is operated by SRI International under a cooperative agreement with the National Science Foundation, and in alliance with Ana G. Méndez-Universidad Metropolitana, and the USRA. The 305 meter William E. Gordon radio telescope at the AO is the largest single-dish radio telescope on our planet. The AO has a long history of being the site where very significant accomplishments in astronomy have occurred, including: {00480584-1 }1 - the first discovery of planets outside of our own solar system; and - discovery of the first pulsar in a binary system, leading to important confirmation of Einstein’s theory of gravitational waves and a Nobel Prize for two radio astronomers who performed their research at Arecibo. The radio telescope at the AO is an important tool for identifying new pulsars, for the large-area mapping of neutral atomic hydrogen and continuum emission, for the compiling of huge red-shift surveys of galaxies, for the detection of Hydroxyl mega-masers and other molecules in ultra-luminous infra-red galaxies, and for much more. The study of a large number of molecular species is now possible, the high end of the frequency range having been ”opened up” by the Gregorian telescope upgrade of the mid-1990s. Additionally, appropriate instrumentation has allowed the AO telescope’s participation in wide-band Very Long Baseline Interferometry (VLBI), adding enormously to the sensitivity of this endeavor for the imaging of the smallest scale structure in both line and continuum radio emitters. The AO telescope is a regular contributor to the National Radio Astronomy Observatory’s High Sensitivity Array, the European VLBI Network and to global VLBI Arrays. Yet, as the Commission knows, this important and expensive scientific instrument is extremely vulnerable to interference from unwanted emissions by other users of the spectrum. It was for this very reason that the Puerto Rico Coordination Zone rules were enacted. See, e.g., Radio Astronomy Coordination Zone in Puerto Rico, Report and Order, 12 FCC Rcd 16522 (1997) (“PRCZ Order”). II. USRA Supports Retaining the Current Allocation for RAS at Channel 37, and Maintaining Protections for RAS Observations. The NPRM seeks comments as to whether the current allocation for RAS at Channel 37 should be retained, or whether an RAS allocation should be moved to a different frequency in the {00480584-1 }2 TV band. USRA supports retaining the RAS allocation at the current frequency of 608-614 MHz (Channel 37). The spacing of most RAS bands with frequencies below 5 GHz was arranged to enable the detailed spectrum of continuum radio sources to be characterized adequately, which is often a matter of determining what fraction of their signal is due to synchrotron emission as opposed to thermal emission from hot gas. This is particularly necessary for Galactic sources located in the crowded plane of our Milky Way Galaxy, where thermal emission from their surroundings and along the same line of sight contributes to the signal. A noteworthy Arecibo example was the discovery of the first millisecond pulsar. This has a typical pulsar-type spectrum, after account is taken of its Galactic position and surroundings, but required equipment sensitive to a 1 millisecond pulse repetition rate to be deployed before it could be identified as a pulsar: the 33 millisecond Crab pulsar was, at the time, the fastest pulsar known, so this revolutionary advance was only achieved as a result of the confidence the observers had in their characterization of its radio spectrum. That has since spawned an industry, which has identified more than 100 millisecond pulsars. These collectively provide a stable timing system that tests our best terrestrial clocks, as well as an ongoing cutting-edge program that seeks to directly detect gravitational wave radiation. The 608-614 MHz band is the only RAS band between 406.1-410 MHz and the 1400- 1427 MHz 21cm band. Its precise frequency for spectral characterization is unimportant: anywhere between ~550 MHz and ~850 MHz would serve. Hence any small, tens-of-MHz change is entirely acceptable for RAS purposes. While similar observations could be performed elsewhere in the 550-850 MHz frequency range, consideration must be made of costs to observatories associated with a change in the RAS allocation, if the change in frequency were {00480584-1 }3 more than a few 10’s of MHz. In addition, changing the RAS allocation from Channel 37 could create confusion and a negative impact on RAS observation at 608-614 MHz in other countries.1 The NPRM raises the possibility of adjusting the Channel 37 allocation on a regional basis, to optimize local frequency consolidations. Since the VLBA has a Channel 37 capability, this of itself implies the utilization of a common band at every one of its sites: these sites span the contiguous states, as well as St. Croix and Hawaii. Thus the RAS cannot support any change that does not maintain uniformity across the nation in any substitute for Channel 37. Arecibo is used in conjunction with the VLBA from time to time, so USRA would greatly prefer that the RAS allocations adopted elsewhere in the country are maintained for Puerto Rico too. The VLBA with/out Arecibo generates maps from the emission observed: the continuum maps are often made to characterize the spectra of point sources, as well as the detailed structure and spectral components of high velocity jets. When directed at Galactic targets, such as supernova remnants, star formation regions, and individual situations of interest such as potential pulsars, magnetars, and gamma ray sources, the angular resolution of the VLBA helps to eliminate both the effects of RFI and contributions from the astronomical surroundings. Thus the VLBA promotes our ability to make millisecond-pulsar type discoveries. Adding Arecibo to the VLBA, or any other VLBI array of telescopes, when these are used to observe at frequencies below 10 GHz, provides a demonstrated increase in sensitivity of at least a factor of four. The resulting “VLBI Telescope” is far and away the most sensitive point source telescope on the planet. Moreover, the Observatory is currently commissioning a 12 m telescope to continuously track a phase reference source to increase the sensitivity gain by a further factor of √2, as this obviates the need for frequent movements between the source of 1 In response to the question in paragraph 204 of the NPRM, USRA understands that the Dominion Radio Astrophysical Observatory in Penticton, British Columbia, currently observes at 608-614 MHz. {00480584-1 }4 interest and the reference. This telescope also increases the possible range of target sources that can be profitably observed using Arecibo in VLBI configurations. These upgrades were undertaken as a result of a meeting convened by the Observatory in 2007 to explore future science cases for Arecibo: the most unheralded of these cases extolled the new capacity provided by the sensitivity enhancements of VLBI that enable radio emission to be observed for the first time from a very wide range of ordinary stars. Among other objectives, this capacity will help to tie the radio and optical reference systems together more accurately, with consequences as diverse as improvements to space navigation for NASA missions, and greater precision of measurements of the movement of the Earth’s pole and differential shifts of its tectonic plates. While Arecibo does not currently have a 608 MHz receiver, one can be quickly repurposed for the band when a project requires it. The NPRM raises the possibility of a much larger frequency adjustment being under consideration. There is no merit for RAS in making a jump to a substantially lower frequency, so far as the original case for having a RAS band circa 608 MHz is concerned, though a jump towards 800 MHz would be acceptable, both for the characterization of radio continuum sources, and for refining at every observed epoch the dispersion measure of millisecond pulsars. Time varying electron densities along the line of sight to millisecond pulsars generate temporal changes to their dispersion measure, which adds noise into the accuracy of their timing observations. That in turn impedes their ability to detect gravitational wave radiation. Regardless of whether the RAS allocation remains on Channel 37 or moves to another frequency, RAS facilities will need protection from interference from White Space or TV Band Devices (“TVBDs”). The Commission has previously recognized the need to protect RAS observations at Channel 37 in connection with TVBDs, as Section 15.707(a) of the {00480584-1 }5 Commission’s rules prohibits operation of such devices on Channel 37. In addition, pursuant to Section 15.712(h), operation of such devices on any channel is prohibited within 2.4 kilometers of certain radio astronomy observatories, including the AO, and there are limitations on TVBD operation on the first available channel above and the first channel below TV Channel 37, as set forth in Section 15.707(a).
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