Frequency Management

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…


But they are few and far between


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

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


• 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


• 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

Frequency Management

Documents

Transcript of Frequency Management