Aka why you can detect any astronomical signals at all Dr Karen ONeil Green Bank Site Director Frequency Management Does it really matter Frequency Management Does it really matter GBT observations with ID: 582524
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Slide1
Frequency Management
Aka why you can detect any astronomical signals at all
Dr. Karen O’Neil
Green Bank Site DirectorSlide2
Frequency Management
Does it really matter?Slide3
Frequency Management
Does it really matter?
GBT observations with
p
ocket digital camera
ON and OFFSlide4
U.S. Frequency Allocation chart
The United States has set aside some frequencies for astronomy…Slide5
U.S. Frequency Allocation chart
The United States has set aside some frequencies for astronomy…
But they are few and far betweenSlide6
U.S. Frequency Allocation chart
The United States has set aside some frequencies for astronomy…
But they are few and far between
Astronomy is not limited to pre-designated frequencies.
Redshift spreads even the allocated astronomy frequencies,
such as 1420 MHz, across more than 1000 MHz in band
Allocation process cannot allow for new discoveries,
exploration of frequency space
Many of the astronomy allocations are shared with other spectrum users
What do we do???Slide7
Frequency ManagementThere are three ways to handle interference:
Spectrum allocationRegional protectionPost-observation excisionSlide8
Frequency ManagementThere are three ways to handle interference:
Spectrum allocationRegional protectionPost-observation excision
The art of
Spectrum Management
Algorithm development
Pattern recognitionSlide9
Spectrum AllocationThree Regions (International Telecommunications Union)Slide10
Spectrum AllocationThree Regions (International Telecommunications Union)
All
countries are sovereign inside their
border (Radio waves always know where to stop, eh
?)No country can operate a satellite transmitter without ITU-R permission (Border
issues are often important)Most general set of rules (Radio Regulations) is an international (every
4-5 years through the UN)http://www.itu.int/ITU-R/12 Slide11
Spectrum AllocationIUCAF:
International Scientific Committee on Frequency Allocations for Radio Astronomy and Space ScienceSponsored by:International Astronomical Union (IAU)
The International Union of Radio Science (URSI)The Committee on Space Research (CoSPAR)
Represents astronomical interests at international spectrum meetingsU.S. astronomy is represented through the National Science FoundationSlide12
Spectrum AllocationSpectrum bands are allocated to
’services’:Service = purpose or applicationMost services are ‘active’ –they transmitRadio astronomy and Earth-sensing are ‘
passive’ (only listen)Radar astronomy and EE-SS (active) also transmit but are distinct Concept of “use” elusive for passive services Examples of “services”:Radiolocation = radar
Radionavigation/Radio Navigation Satellite Service = GPSFixed service (terrestrial point to point)Fixed-satellite service (space-earth, earth-space)Mobile-satellite service (satellite phones)Broadcasting (TV) Slide13
Spectrum AllocationSpectrum allocation is extremely important to protect radio band
It works very slowly, and new laws/protections can take many yearsIn the U.S. the spectrum is typically sold by the FCCRadio astronomy is at a distinct disadvantageSharing of even radio astronomy spectrum is likely coming soonSlide14
Regional ProtectionRegional protection comes in two ways:
Natural or man made protectionLegislationSlide15
Regional ProtectionRegional protection comes in two ways:
Natural or man made protectionLegislationSlide16
Green Bank:
Location
Location
Location
A high mountain valley
with natural terrain shielding
A
great
place for a Radio Astronomy Observatory!Slide17
National Forests around Green Bank
Green Bank
State and National Forests foster low population growth.Slide18
Regional ProtectionRegional protection comes in two ways:
Natural or man made protectionLegislationSlide19
Regional ProtectionRegional protection comes in two ways:
Natural or man made protectionLegislationGreen Bank has two radio
quiet zones:National Radio Quiet ZoneWest Virginia Radio Astronomy ZoneSlide20
National Radio Quiet Zone
Established by FCC and NTIA on Nov 19, 1958.Established in law before radio telescopes were built and before any frequency allocations to Radio Astronomy.
+13,000 mi2 of WV, VA and MDAs part of the normal coordination process, the NRQZ office comments on new or modified, permanent, fixed radio transmitters.Work with applicants in finding a mutually acceptable solution to
their coverage needs and our protection criteria.Slide21
NRQZ
Only bounded area in the US requiring coordination of new or modified, permanent, fixed transmitters.
The NRQZ is a unique and valuable resource in an ideal location.
Centered between Green Bank and Sugar Grove.Slide22
WV Radio Astronomy Zoning Act
August 9, 1956: Protection from interference
by any electrical equipment within 10 milesSlide23
Regional Protection
Natural + legislative protection provide the best environment
Legislation provide protection within designated regionNatural barriers protect from transmissions inside and outside the protected zones
Power Transmitted
in the direction
of the GBT (depends on the antenna and what direction it is pointing as well as the power into the antenna)
Frequency and Bandwidth
over which the power is distributed (depends on the technology being used)
Path Length
Natural
Obstacles
(mountains) in the path (if the attenuation manmade obstacles is known, this too can be considered)Slide24
Regional ProtectionRegional protection comes in two ways:
Natural or man made protectionLegislationGreen Bank has two radio
quiet zones:National Radio Quiet ZoneWest Virginia Radio Astronomy
ZoneCombined protection of two quiet zones is very powerfulTwo new quiet zones now exist
in the world:South
Africa (protection for MeerKAT, Kat64, SKA)Australia (protection for SKA in Western Australia)Slide25
Community AgreementEven
with legal protection community agreement is vitalContinuous challenge with outreach, education, and helpTeach the community who you are and why you needs the protectionShow the community the value of radio astronomy locally and scientifically
Help the community to mitigate the effects of the Quiet Zone(s) as possibleThis is the most difficult
challenge, and one which must be continuously consideredSlide26
Spectrum Management is a challenging issue which must be tackled for radio astronomy to flourish
Crowding of the spectrum will increase, and the space for radio astronomy will shrinkYou can help!
Report RFI whenever you see it in your dataBe conscious of your use of electronic devices near radio telescopesWork with the IAU, URSI, other organizations to protect the radio spectrum