Latest Threats to Radio Astronomy

Ken Tapping

Over the last few months, some new issues have arisen in the never-ending process of protecting radio astronomy in the face of more and more demands for space in the spectrum for new radio services. Some of these have appeared out of things that have been evolving for some time; others are new.

Ultra-Wideband Technologies

These are systems based upon the assumption that the operating bandwidths are so huge that the spectral power per Hertz will be so small that conventional radio services won't even know UWB signals are falling in their band. We are not convinced this would be the case for radio astronomy bands.

After largely futile attempts to develop viable models to estimate what the interference problems if any might be between UWB systems and other spectrum uses, such as radio astronomy, commercial pressures have overcome caution and have led to these systems entering the market. The USA went ahead before international discussions were completed, and because of the close connections between US and Canadian markets, Canada will probably have to follow suit. Our national spectrum managers are proving supportive and we should be able to get some help if this becomes a significant interference problem. Something new has arisen in Europe, which we hope to keep under control.

There is a footnote in the Radio Regulations, number 5.340, listing all the bands for which radio astronomy or other passive (non-transmitting) radio services are the sole users. A proposal has arisen in Germany to remove two bands from the 5.340 list: 1400-1427 MHz (cosmic neutral hydrogen) and 23.6-24 GHz (ammonia). The argument is that these bands fall within frequency bands to be used by ultra-wideband radars. The 1400-1427 MHz band would be good for wall and ground penetration radars and the 22-26 GHz band for automobile collision avoidance radars. The proponents of these systems argue that they are short-range and their power is distributed over such a wide bandwidth that the power per Hz would be negligible. However, footnote 5.340 is allegedly inhibiting their deployment. The danger is the possibility of gradual demolition of 5.340 by small nibbles. In addition, taking a band out of the 5.340 list opens the door to other transmissions, not just UWB. This is unacceptable. The radio astronomers involved in spectrum protection issues are fighting this, and Industry Canada agrees that proposals like this are rather silly. With a bit of luck and effort we should be able to keep this within the German borders or possibly kill it. This will not stop the radars but it is not yet clear how much of a problem they will be, or will be at all. We want that footnote left alone. We have been assured that the 23 GHz issue is a temporary one, to allow the deployment of collision avoidance radars in the 22-26 GHz band pending the availability of equipment in the intended band, which is up near 70 GHz. However, once a large capital investment has been made, with cars all over the place using these systems, with the concomitant need to maintain stores of spares etc., once established, those vehicle radars might be very difficult to move out of the 23 GHz band.

Industry Canada supports us in our desire to keep the list and protection measures for radio astronomy unchanged. UWB systems lie outside the normal spectrum management process, and keeping UWB outside means these devices are not allowed to interfere with any official spectrum user, such as us. Modifying the Radio Regulations in any way to accommodate or recognize UWB implies official acceptance as UWB being another service, with "rights".

Broadband Internet Over Power Lines

Another system that has defied attempts to make prior estimates of the magnitude of potential  interference problems has been the proposed use of electrical power lines to transmit broadband information (up to maybe 70 MHz). Modelling methods are still being discussed in Geneva. Canada has been evaluating a test system near Sault Ste. Marie. Indications so far are that when the link is in use, communication attempts by nearby radio amateurs have been completely obliterated. The situation for radio astronomy in the VHF bands could be rather difficult, but as yet, we have no data.

However, once again the USA has leaped ahead of the international discussion (and competition) and has started to put these systems into commercial operation. Canada may once again be forced to harmonize with the US . We await results.

We continue to liaise with Industry Canada on this one.

Cross-Border Leakage - Intended and Unintended

In setting up a satellite system that serves users on the ground, one specifies a "service area", where the intended user community is located. Inside this area the power levels are sufficient to meet the needs of the user community. Inevitably, the service area is surrounded by a "coverage" area, where the power levels are lower, and insufficient for users. In order to avoid interfering with systems licensed to operate in the coverage area, the ITU specifies the maximum power levels on the ground outside the service area. However, problems arise when the coverage area spills across a border into a neighbouring country, and when the company operating the satellite system has strategic plans to expand the service across the border at some later date. In principle, there is no need for Country A to inform Country B about "coverage" signals extending across the border. This could be serious. If for example, we do build a Large Adaptive Reflector radio telescope at the HIA's Dominion Radio Astrophysical Observatory, we would like to use this instrument, which would be one of the largest radio telescopes in the world, to access as much spectrum space as possible. One thing we can do is to liaise with our national spectrum managers to have some national protection, perhaps temporary, for bands of interest that are not allocated internationally to radio astronomy. However, un-notified coverage signals coming from satellite services licensed to operate south of the border could make the chosen bands unusable.

It could be worse than that. A spokesman for one company said that in order to save money in hardware modifications, it is one of those "unreported but widely practiced procedures" is to build systems that put service level signals on the ground over the currently licensed and that part of the coverage area planned for future expansion of the service. In that way money is saved later on, when the system is expanded into the new (Canadian) service area. If there is no prior notification of this, things could get even stickier for radio astronomy.

There are some bipartite working arrangements between the USA and Canada , and we need to ensure that to the best extent possible, we know enough about what the other guy is up to in order to identify or problem areas. Ken Tapping is a member of the US Committee on Radioastronomy Frequencies, which provides a valuable additional forum for discussing issues like this. The next meeting is in early April.

Creating Undesired Loopholes

Industry Canada pointed out this one. Those guys continue to be very helpful. The USA is currently discussing a proposal to modify two ITU Resolutions that list potential bands and services that could cause interference problems for radio astronomy, and list the obligations of the concerned parties to work together as required to solve the problem. The changes would do two things: (a) they would create a "Window of Opportunity" extending until the publication of the results of the 2007 World Radio Conference or even beyond that, where new satellite services being registered inside that window will be exempt from the requirements in those resolutions, and (b) stop any future "Band-by-Band Studies".

The ITU has set up a series of studies wherein radio astronomers and other spectrum users identify particular radio service bands that could cause interference to particular radio astronomy bands. The objective of these studies is to find out if the problem can be avoided, and if not, what can be done about it. With new services appearing all the time, and with new radio astronomy bands being allocated and new technologies being deployed, it is obvious that whether we like it or not, this study process will probably have to be kept going for the foreseeable future.

The Canadian national position on this is to oppose the loopholes and promote the ongoing band-by-band study process.

Things Look Grim?

The issues reported here might create the impression that "they" are out to get radio astronomy. This is not the case. The process of competition to get spectrum space has been going on as long as there has been a radio spectrum, and that this process has been very Darwinian. With the incredible rate of growth of new radio communication and other technologies, the competition has become very fierce. At science conferences our objective is to present our ideas/results as clearly and honestly as possible, so that our peers will be honestly convinced, or not. With billions of dollars at stake, the companies in the communications business have to focus on the main objective, which is to get what they want, in the best way they can. With the pressure this high, protecting our science involves jumping into the arena too. Our national spectrum managers do help, but they gauge the importance of issues relevant to us on the basis of how vigorously we participate in dealing with them. People are trying on various proposals all the time, and we have to respond.