Spectrum Management for Science in the 21st Century

Transcription

1 Spectrum Management for Science in the 21st Century Committee on Scientific Uses of the Radio Spectrum Marshall H. Cohen, Co-Chair Albin J. Gasiewski, Co-Chair on behalf of the full committee

2 Committee Membership Radio Astronomy D. Backer UC Berkeley M. Cohen Caltech (co-chair) A. Evans UVA / NRAO J. Moran Harvard L. Mundy U. Md. T. Pearson Caltech Remote Sensing A. Gasiewski U. Colorado, (co-chair) D. Kunkee Aerospace Corp. C. Ruf U. Michigan F. Solheim Radiometrics Corp. D. Staelin MIT Interference and Mitigation S. Ellingson Virginia Tech D. Emerson NRAO P. Kolodzy Kolodzy Consulting A. Tanner JPL J. Johnson Ohio State Policy R. Balstad Columbia U. M. Macauley Resources for the Future Staff: Donald Shapero, BPA Director Brian Dewhurst, Program Officer David Lang, Program Officer 2

3 Origin of the Study The Committee on Radio Frequencies (CORF) and the scientific community were in need of a detailed forward-looking technical study on: Current and future scientific use of the spectrum Trends in active use of the spectrum Potential RFI mitigation technologies and strategies Motivated by the FCC and others considering the use of unused passive frequencies and investigating methods to increase efficient use of spectrum NSF, NASA, and DOC agreed to support the study 3

4 Statement of Task The committee will prepare a report exploring the scientific uses of the radio spectrum emphasizing the passive services which will: 1. Portray the science and applications that are currently being conducted by passive observations using the radio spectrum; 2. Identify the spectrum requirements necessary to conduct such research and facilitate such applications; 3. Identify the anticipated future spectrum requirements for at least the next 10 years; and 4. Advise spectrum policy-makers on the value to the nation of accommodating scientific uses of the spectrum by the passive services, recognizing the need to balance multiple communities. The committee will comment on spectrum use by the relevant scientific communities but will not make recommendations on the allocation of specific frequencies. 4

5 The Passive Services Radio Astronomy Service (RAS) Study all ranges of the heavens, from the Sun to the most distant galaxies and beyond. Study exotic objects, yielding new information about the nature of matter, the origins of the Universe, and man s place in it. Earth Exploration Satellite Service (EESS) Measure terrestrial variables such as surface temperature, soil moisture, atmospheric profiles, and many more. Weather prediction, climate studies. Strong economic value. 5

6 The Importance of EESS Microwave measurements from satellites are vital for weather forecasting (eg: Hurricane Katrina) and long-range climate studies (eg: ice cover) (Left) Image of the wind speed of Hurricane Katrina (in knots), observed by passive microwave radiometers on WindSat, a Naval Research Laboratory satellite, as the hurricane makes landfall near New Orleans on August 28, (Right) Output from a model that combines data from WindSat and other remote sensing instruments. The model provides information on the hurricane s windspeed. The values over land are extrapolations. 6

7 Trends in Radio Astronomy Large new telescope systems with continuous coverage over an extremely wide frequency band, often using instantaneous bandwidth > 1 GHz, with integration time > 1 day. [ex: red-shifted hydrogen from early universe] GBT (Robert C. Byrd Green Bank Telescope) evla (extended VLA) SKA (Proposed Square Kilometer Array) SKA pathfinders in Australia, South Africa Large new high-altitude millimeter telescopes. [ex: astrochemistry in star-forming clouds] ALMA (Atacama Large Millimeter Array) CCAT (Cerro Chajnantor Atacama Telescope) 7

8 U.S. Investments in Passive Observatories Finding: Large investments have been made in satellite sensors and sensor networks, and in major radio observatories. New facilities costing billions of dollars are under construction or are being designed. Finding: Scientific advances have required increasing measurement precision by passive radio and microwave facilities in order to obtain more accurate and thus more useful data sets. This need for precision will continue to increase. 8

9 Extreme Sensitivity & Interference Potential Signals from natural radio emissions are weak, and the equipment used to measure them is necessarily becoming ever-more sophisticated and sensitive. The minimum detected or detectable signal in flux density vs. year of measurement. The sensitivity is proportional to receiver system temperature and inversely proportional to collecting area and the square root of both bandwidth and integration time. For measurements after year 1990 an integration time of 12 hours is assumed. The rapid improvement over time is due to system improvements. The improvement from 1933 to 1983 is about 10 orders of magnitude. 26 W 1Jy 10 2 m Hz 9

10 Protecting Passive Science Observations Spectrum for passive purposes can be likened to parkland preserved for public use: it defies monetization, and as such requires proactive measures for its preservation and shared use. Use of spectrum to make scientific observations is regulated and, in places, protected, but the proliferation of wireless technology challenges engineers abilities to mitigate unwanted radio interference. Most regulations are not aligned with or cognizant of the special needs of passive scientific users. 10

11 Spectrum Usage Radio Frequency Interference (RFI) and its Mitigation 11

12 China Mobile Subscribers (millions) Interference Potential Both the active and the passive services are increasing their use of the spectrum, and so the potential for interference, already strong, is increasing. Satellites cannot hide from ground-based interference, in the way that RAS observatories can The number of Chinese cellular subscribers grew by more than 250 million between Source: China Mobile Ltd Annual Reports

13 Impact of Radio Frequency Interference (RFI) Finding: Important scientific inquiry and applications enabled by EESS and RAS are significantly impeded or precluded by RFI. Such RFI has reduced the societal and scientific return of EESS and RAS observatories, and necessitates costly interference mitigation, which is often insufficient to prevent RFI damage. The effect of RFI on an astronomical image made at the VLA. At left is an image of a faint OH/IR star made in a narrow band at MHz, within the band MHz that is allocated to the RAS on a primary basis. At right is the same field of observation made when an Iridium satellite was 22 degrees from the star. This image is made useless by the RFI. Unpublished images courtesy of G.B. Taylor, NRAO. 13

14 Current RFI Problems Finding: The rules for out-of-band and spurious emissions in the primary allocated RAS bands (e.g., MHz) do not provide adequate interference protection for RAS purposes. Finding: Geographical separation of radio telescopes from transmitters (e.g., radio quiet zones and remote observatories) is currently effective in avoiding much RFI, but proliferation of airborne and satellite transmissions and the widespread deployment of mobile, low power personal devices threaten even the most remote sites. 14

15 An Ominous New Development SMOS, a new remote sensing satellite, sees extensive interference in the internationally protected band MHz. All emissions in the band MHz are prohibited. (ITU International Table, footnote 721) 15

16 SMOS Soil Moisture and Ocean Salinity L-band ( MHz) 69 antennas Dual polarization Field ~ 1000 km Resolution ~ 100 km Image formation time 2.4 sec 16

17 SSMOS S SSSSS SMOS January 2010 Probability of L band RFI

18 SMOS January 2010 Probability of L band RFI Range

19 Unilateral RFI Mitigation Recommendation: Investment in mitigation technology development should be increased to be commensurate with the costs of data denial experienced using systems without mitigation. To this end, NSF and NASA should support research and development for unilateral RFI mitigation technology in both EESS and RAS systems. NASA, NOAA, and DoD should require that appropriate RFI analyses and tests, and practical RFI mitigation techniques, be applied to all future satellite systems carrying passive microwave sensors. Finding: While unilateral RFI mitigation techniques are a potentially valuable means to facilitate spectrum sharing, they are not a substitute for primary allocated passive spectrum and enforcement of regulations. There is no one-sided technological solution to RFI 19

20 Cooperative RFI Mitigation & Spectrum Sharing New methods for cooperative spectral sharing should be explored Recommendation: The NSF, NASA, and NTIA should jointly support research and development for cooperative RFI mitigation techniques and the associated forums and outreach necessary to enable standards development for higher spectral utilization and interference avoidance. Recommendation: As cooperative spectrum sharing techniques come into use the NSF and NASA spectrum managers should work with the regulatory agencies to enable observations that require an extremely wide spectral range. Such observations would provide a useful metric for the effectiveness of spectrum sharing for the passive services. 20

21 U.S. Spectrum Usage Recommendation: The Department of Commerce/NTIA, in collaboration with NSF, NASA, and NOAA, should spearhead the development of a national spectrum assessment system that measures the RF environment with appropriately high resolution in time, space, and frequency for spectrum development and management purposes, based on the spectral and spatial density of emitters. 21

22 Outreach, Community, and Collaboration Recommendation: The EESS and RAS communities should be provided additional support through NSF, NASA, and NOAA to increase their participation in spectrum management forums within the ITU, FCC, NTIA, and other organizations. The goal is to foster outreach, understand interference and regulation issues, and initiate mutual cooperation in interference mitigation. Recommendation: OSTP should create a new permanent representative technology advisory body to identify technical and regulatory opportunities for improving spectrum sharing among all active and passive users, both government and non-government. 22

23 Conclusions (1/2) The radio spectrum is a finite resource, and has been managed as such for the past 75 years by the federal government. The passive services provide both a critical return to society through operations in support of environmental prediction, and scientific intellectual value. Management of the spectrum for passive purposes can be compared to management of other U.S. commons such as public parklands, which defy monetization. 23

24 Conclusions (2/2) Technological innovations continue to increase the scientific utility of the radio spectrum. Unilateral RFI mitigation is not a universally feasible solution to RFI, but cooperative mitigation has significant untapped potential. The next generation of spectrum management policies must enable better sharing of the spectrum as well as contribute to fully understanding the actual use of the RF spectrum. The new initiatives necessary for spectrum management and sharing will neither be easy nor will they make successful management and sharing a certainty. 24

25 Briefings M. Cohen, A. Gasiewski, P. Kolodzy, D. Kunkee, S. Ellingson, and D. Lang briefed the study to these offices: NASA (HQ, 10/28/09) NOAA (NESDIS, 10/28/09) NSF (BPA, 10/29/09) FCC (11/12/09) Senate Office of Sen. Bill Nelson (D-Florida, 11/13/09) White House OSTP (11/13/09) NTIA (12/15/09) DoD (NPOESS IPO,12/15/09) 25

26 Thank You 26