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Spectrum Management for Science
in the 21st Century
Committee on Scientific Uses of the Radio Spectrum
Marshall Cohen, Co-Chair
Albin J. Gasiewski, Co-Chair
on behalf of the full committee
Committee Membership
• Radio Astronomy
– D. Backer
UC Berkeley
– S. Ellingson
Virginia Tech
– M. Cohen
Caltech (co-chair)
– D. Emerson
NRAO
– A. Evans
UVA / NRAO
– P. Kolodzy
Kolodzy Consulting
– J. Moran
Harvard
– A. Tanner
JPL
– L. Mundy
U. Md.
– J. Johnson
Ohio State
– T. Pearson
Caltech
• Remote Sensing
•
• Interference and Mitigation
– A. Gasiewski
U. Colorado, (co-chair)
– D. Kunkee
Aerospace Corp.
– C. Ruf
U. Michigan
– F. Solheim
Radiometrics Corp.
– D. Staelin
MIT
Staff:
Donald Shapero, BPA Director
Brian Dewhurst, Program Officer
David Lang, Program Officer
• Policy
– R. Balstad
Columbia U.
– M. Macauley Resources for the
Future
Origin of the Study
• Both 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
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.”
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.
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.
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.
Technological and Educational Benefits
of Passive Observations
Finding: Passive microwave Earth remote sensing provides a
diverse and valuable set of educational opportunities.
Finding: In addition to the intellectual benefits it provides, passive
microwave remote sensing studies provide many technological
benefits to American society.
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
1
Jy

10
2
m
Hz
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 (Square Kilometer Array, 2020?, strong US participation)
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)
The Importance of EESS
• Microwave measurements from satellites are
vital for weather forecasting (eg: Hurricane Katrina)
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, 2005.
(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.
Spectrum Usage
Radio Frequency Interference (RFI)
and its Mitigation
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.
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China Mobile Subscribers
(millions)
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The number of Chinese cellular subscribers grew
by more than 250 million between 2002-2007.
Source: China Mobile Ltd Annual Reports.
250
200
150
100
50
0
2002
2003
2004
2005
2006
2007
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 1612.22 MHz, within
the band 1610.6 – 1613.8 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.
(LEFT) Electronically-Scanned Thinned Array Radiometer (ESTAR) image at 1413 MHz from the
Southern Great Plains experiment (SGP97). The vertical lines west of Oklahoma City are
distortions due to RFI.
(RIGHT) Example of RFI in the vicinity of Oklahoma City during SGP97. The signal represents
total power and was recorded west of the arrow in part (a). SOURCE: D. Le Vine, “ESTAR
experience with RFI at L-band and implications for future passive microwave remote sensing from
space,” in Proc. Int. Geosci. and Remote Sens. Symp. (IGARSS), Toronto, ON, Canada, 2002, pp.
847 – 849.
Current RFI Problems
Finding: The rules for out-of-band and spurious emissions in the
primary allocated EESS bands (e.g., 1400-1427 MHz) do not provide
adequate interference protection for EESS purposes.
Finding: There is currently inadequate protected spectrum in C-band
and X-band for operational passive microwave observations of sea
surface temperature, soil moisture, and ocean surface wind speed
and direction.
Finding: The rules for out-of-band and spurious emissions in the
primary allocated RAS bands (e.g., 1400-1427 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.
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
Cooperative RFI Mitigation & Spectrum Sharing
Finding: The emergence of practices for the dynamic use of the
spectrum will result in more devices with greater variability in active
spectrum usage, and the EESS and RAS communities could be
impacted with more unintentional radio interfering devices.
Finding: Nascent technologies exist for cooperative spectrum usage
but the standards and protocols do not.
Finding: New cooperative spectrum management techniques that
could be beneficial for enhanced interference management and
increased spectral utilization have been investigated by regulators but
have not been implemented.
New methods for cooperative spectral sharing
should be explored
Cooperative RFI Mitigation & Spectrum Sharing
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
techniques for the passive services.
U.S. Spectrum Usage
Finding: Greater efforts for radio emission data collection and analysis are
needed to support the enforcement of existing allocations and to support the
discussion and planning of spectrum use.
Finding: Better utilization of the spectrum and reduced RFI for scientific as
well as commercial applications is possible with better knowledge of actual
spectrum usage. Progress toward these goals would be made by gathering
more information through improved and continuous spectral monitoring. This
would be beneficial to both the commercial and scientific communities.
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.
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.
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.
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.
The End