frequency management
DESCRIPTION
Frequency Management. Aka why you can detect any astronomical signals at all. Dr. Karen O’Neil. Green Bank Site Director. Frequency Management. Does it really matter?. Frequency Management. Does it really matter?. GBT observations with p ocket digital camera ON and OFF. - PowerPoint PPT PresentationTRANSCRIPT
Frequency ManagementAka why you can detect any astronomical signals at all
Dr. Karen O’NeilGreen Bank Site Director
Frequency ManagementDoes it really matter?
Frequency ManagementDoes it really matter?
GBT observations with pocket digital camera
ON and OFF
U.S. Frequency Allocation chartThe United States has set aside some frequencies for astronomy…
U.S. Frequency Allocation chartThe United States has set aside some frequencies for astronomy…
But they are few and far between
U.S. Frequency Allocation chartThe 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???
Frequency ManagementThere are three ways to handle interference:
– Spectrum allocation– Regional protection– Post-observation excision
Frequency ManagementThere are three ways to handle interference:
– Spectrum allocation– Regional protection– Post-observation excision The art of
Spectrum Management
Algorithm developmentPattern recognition
Spectrum AllocationThree Regions (International Telecommunications Union)
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
Spectrum AllocationIUCAF: International Scientific Committee on Frequency Allocations for Radio Astronomy and Space Science
Sponsored 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 Foundation
Spectrum Allocation• Spectrum bands are allocated to ’services’:
– Service = purpose or application– Most services are ‘active’ –they transmit
• Radio 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 =
GPS– Fixed service (terrestrial point to point)– Fixed-satellite service (space-earth, earth-space)– Mobile-satellite service (satellite phones)– Broadcasting (TV)
Spectrum Allocation
• Spectrum allocation is extremely important to protect radio band
• It works very slowly, and new laws/protections can take many years
• In the U.S. the spectrum is typically sold by the FCC– Radio astronomy is at a distinct disadvantage– Sharing of even radio astronomy spectrum is likely
coming soon
Regional Protection
• Regional protection comes in two ways:– Natural or man made protection– Legislation
Regional Protection
• Regional protection comes in two ways:– Natural or man made protection– Legislation
Green Bank:Location
LocationLocation
A high mountain valley with natural terrain
shielding
A great place for a Radio Astronomy
Observatory!
National Forests around Green Bank
Green Bank
State and National Forests foster low population growth.
Regional Protection
• Regional protection comes in two ways:– Natural or man made protection– Legislation
Regional Protection
• Regional protection comes in two ways:– Natural or man made protection– Legislation
• Green Bank has two radio quiet zones:– National Radio Quiet Zone– West Virginia Radio Astronomy Zone
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 MD• As 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.
1. Only bounded area in the US requiring coordination of new or modified, permanent, fixed transmitters.
2. The NRQZ is a unique and valuable resource in an ideal location.
3. Centered between Green Bank and Sugar Grove.
WV Radio Astronomy Zoning Act
August 9, 1956: Protection from interference
by any electrical equipment within 10 miles
Regional ProtectionNatural + legislative protection provide the best environment
– Legislation provide protection within designated region
– Natural 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)
Regional Protection
• Regional protection comes in two ways:– Natural or man made protection– Legislation
• Green Bank has two radio quiet zones:– National Radio Quiet Zone– West Virginia Radio Astronomy Zone– Combined protection of two quiet zones is very
powerful
• Two new quiet zones now exist in the world:– South Africa (protection for MeerKAT, Kat64,
SKA)– Australia (protection for SKA in Western
Australia)
Community Agreement
Even with legal protection community agreement is vital
– Continuous challenge with outreach, education, and helpTeach the community who you are and why you needs the protection
– Show the community the value of radio astronomy locally and scientifically
– Help the community to mitigate the effects of the Quiet Zone(s) as possible
This is the most difficult challenge, and one which must be continuously considered
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 shrink
You can help!Report RFI whenever you see it in your data
Be conscious of your use of electronic devices near radio telescopes
Work with the IAU, URSI, other organizations to protect the radio spectrum