A HISTORY OF CANADIAN IONOSPHERIC WORK
The ionosphere, similar to weather systems, although following general patterns, is in a state of constant and unpredictable change. Changes in the state of the ionosphere over Canada relate to the state of the ionosphere over other countries, however, in addition to this interaction countries outside of Canada make use of the ionosphere over Canada for Radio Communications and space application . Recently consideration is being given to power transmission and weather modification systems adding another dimension to International implication. National borders cannot be considered boundaries for use of the ionosphere as illustrated by Canadian interests locating communication satellites over the coast of Ecuador. In recognition of these facts Canada has agreed to CCIR recommendations to participate in a world wide program of regular ionospheric measurements.
A paper published in the November 1976 issue of 'Radio Science' traces ionospheric measurements to December 1924 and to the NBS (USA) official beginning of a program in 1929. Canada was active in measurements at least by 1932. as revealed by papers by J.T. Henderson , and D.C.Rose which describe results of 1932 measurements using equipment used by Henderson and Rose. Henderson had been pursuing doctoral studies at the University of London where he had continued the findings of Appleton who in 1924 had made the first measurement of the Ionosphere using a CBC broadcast station with frequency modulation . Appleton later developed the pulse technique which gave better resolution of the layers, for which he became well known for measurements at the time of the eclipse of 1927. In the spring of 1932 Henderson brought a sounder from England and established it at VanKleek Hill which was at the point of maximum sun shadow of an eclipse of the sun at ionospheric heights. The first records were obtained in May 1932, and sparked approval from NRC to have an additional sounder made to be located near Cornerbrook Nfld, where tl1e maximum shadow of the sun would be seen at earth level. Henderson used whatever was available to build a sounder and had It set-up the day before the eclipse. In the meantime D.C.Rose had built a sounder which he set up at Kingston Ontario for the same eclipse. He used a converter to feed a TRF broadcast receiver , and, like tl1e British system, used a rotating disk to key (pulse) tl1e transmitter . Rose, had an additional problem since his system of generating tl1e CRT sweep had to be modified at tl1e last minute to obtain a stable and meaningful display.
In the summer of 1938 C.W.McLeish of NRC was provided a $600 grant to develop an ionospheric sounder . This was completed in 1940.
The early World War II years witnessed a rapid expansion of radio communication facilities throughout the world which revealed a need for an understanding of radio wave propagation conditions . The British and the USA had discovered that they could locate German submarines, which were the greatest hazard to shipping, and therefore the War effort, by using radio direction finding techniques at the tinles of the short surface transmissions film the subs. An error in DF bearings (the cats cradle) often aborted efforts to accurately locate the subs, so a meeting was called at Washington attended by Ross Freeman of Canada to consider ways of determining the perturbations involved in the errors. As a result of the meeting, the British Admiralty in 1941 asked the Royal Canadian Navy to provide measurements of the ionosphere from Churchill and shortly after from Arctic Bay. They in turn approached NRC in October 1941 for expertise and equipment that would measure ionospheric layer heights over a range of l .4Hz to 14MHz. Drawing on the work of W.C. MeLeish, equipment was built and operating on land rented near the Old Chelsea school, Chelsea P.Q. by the end of December 1941. Measurements were made regularly on a 24 hour schedule. Interpretation of records became a problem which were referred to F.T. Davies of NRC so often that he was seconded to the RCN to direct that work.
The British Admiralty's request of 1941 was implemented when a second sounder was produced by NRC In June 1943 and shipped to Churchill. Rose Freeman of NRC was placed in charge of the operation. An automatic sounder was also provided by the Admiralty called the BPL249 and after a familiarisation period at Chelsea was operating at Churchill in June 1944. The Carnegie Institute of Boston, who had a station at Barrow Alaska and one in the Antarctic was commissioned by the RCN to meet the requirement for a station at Arctic Bay. The second NRC production model of the manual sounder was shipped to Clyde where the expedition had been forced to stop since the waters to Arctic Bay were impassable. An Admiralty sounder similar to the one at Churchill was also provided and the station went into operation in the fall of 1944. Armour Warwick of DOT was sent there to learn the operation and the station was transferred to DOT in 1945.
In the meantime both British and Canadian military had become alarmed at anomalies in radar measurements over the Irish sea, so a committee called the Canadian Radio Wave Propagation Committee was formed and they set up an experiment at Suffield, Alta., where the land was flat, to investigate the phenomenon. From that committee a working party was formed in 1944 with several members including F.T. Davies and J.C. Meek. This working party was immediately loaded with the task of overseeing the ionospheric endeavour and published a handbook for operators in 1946.
Prince Rupert was selected by the Canadian Army as the sight for an additional ionospheric station which was provided with another NRC sounder which was completed in August 1943. Through F.T. Davies, two manual sounders were obtained from the Carnegie Inst, one was set up at Red Head Cove (St. John's) (or Sloop Cove) in an old radar station by Paul Peters and J.C. Meek in 1944, and the second on the Airforce base at Portage la Prairie, Man.
An expansion of ionospheric investigations under the CRC led to a recommendation that NRC design an automatic ionospheric recorder for Canadian stations. This project was designated AIR (Automatic Ionospheric Recorder). Work was begun in Jan. 1945, and unit completed by June 1945, in time to be shipped to Victoria Beach (Manitoba) for the Solar Eclipse of July 5, 1945. Following the eclipse the sounder was operated from a railway car moving between La Pass and Churchill. When that terminated the sounder was set up it Portage.
The international implications of ionospheric work encouraged a meeting in Washington in 1944 where Canadian, U.K. and U.S.A. representatives of relatively low rank met for the first International meeting on ionospheric measurements.
The close of WW II in Sept 1945 and the cessation of hostilities allowed an increase in the already accelerating interest In the ionosphere. The interest in the mechanism of radio wave propagation demanded much data to form the data base for studies.
A DRB recommendation, based on the conclusions of the Washington meeting presented to the Canadian Cabinet Defence Committee brought approval on Nov. 3, 1947, for an expanded ionosphere measuring program. All the military stations, by this time had been taken over by DOT They, at DRB expense, added Resolute, Baker and Chimo, bringing the full time measuring stations to five. Each station was supplied with HF transmitters so that data could be forwarded to Ottawa daily, who in tum forwarded the data to CRPL in Washington. DRTE provided technical direction and DOT provided operational facilities, including staff.
In January 1949, the National Bureau of Standards in the U.S.A. provided each Canadian station (9) with C2 automatic ionospheric recorders . Another part of the program was the establishment of H.F. transmitter s at Fargo N.D. and at Baker Lake. The signal strengths of these transmitters were recorded continuously at receiving stations including stations established at the Winnipeg Monitoring station, La Pas, Baker and Resolute . Hourly aural readings of WWV and CHU were also determined, and provided very useful propagation information. Baker, Churchill and Resolute also operated fixed frequency sounders for hourly absorption measurements .
The NBS (USA) provide 30K4 Collins two channel transmitters for St. John's, Chimo, Churchill, Baker and Resolute in time for the shipping season of 1950.
A contract was let to Canadian Marconi to produce automatic sounders for the Canadian stations in late 1948 or 1949. A prototype was sent to Ottawa late 1949. (Units were made and paid for jointly by tl1e Canadian Navy, DRTE and Transport; not equally sharing) Units were supplied to St. John's summer 1952, and also to Rupert, and Winnipeg. With the closing of Rupert and St. John's their sounders (LG17's) were shipped to Baker and Resolute respectively probably by ship in 1955.
Returning to 1949, the stations at Resolute and Baker Lake consisted of a living quarter building, a Lab building containing also the diesel generators and a FI (field intensity) building. Chimo consisted of t11e living quarters and lab Only, St. John's had been located in one of tl1e buildings of tl1e then abandoned RCAF airport, Winnipeg had been moved from Portage to an old Broadcast station building on the Headingly Jail property , Ottawa was an adjunct of the DRTE site near tlle Arborartorium (Prescott Highway), the equipment being in a small building near the west bank of tl1e canal, witll film developing facilities being provided by DRTE at tlle building near the highway. Prince Rupert and Churchill were still located in small buildings taken over from the RCN in the townsite of Churchill.
A small power house and two - 25kw generators were installed at Chimo the summer of 1949. That summer Baker had received lOkw transmitters with power plants (2) whict were operating in 1950.
Clyde was closed with the advent of the shipping season in July 1950. A new building was constructed for the Churchill station 9 miles south of the Airport. Resolute was expanded by adding diesel fuel storage tanks and two buildings, one for a garage and another to house 3-75kw diesel generators.
Prince Rupert and La Pas were closed in 1951 and Chimo was also closed in 1953. St. John's was closed in July 1954, but was reopened by the USAF on the Fort Pepperill property that fall. With the closing of the NORAD HQ at Pepperill , the ionosphere station was again taken over by DOT and located in a private house south of the city. After the settlement of the land titles for the Pepperill Air-Base property , DOT rented th( former USAF ionospheric station building from the Province of Newfoundland and the station was again activated at t11at point (where it still is located).  The Ottawa station was moved to a permanent type building called Building 69 purchased from the DND property at Shirley Bay. (1952?).
A fire destroyed the Baker Lake transmitter and power building in 1953. A new power building with two 20kw plants was subsequently built in 1955, at which time the Met. people moved to the same area as the ionospheric station and added 3 houses as married quarters. Due to the many transients at Baker, DOT erected a 20 room building in 1959, and soon thereafter built a larger power house wit11plants with sufficient capacity to provide a sizeable community.
While these activities were under way, an international group met in Saskatoon under the name of the "High Latitude Sounding Committee" (HLSC) to formulate rules for interpretation and standards for presenting ionospheric data. This work was later taken over by another committee called the "World Wide Sounding Committee". This committee worked out standardised procedures for the 1958 International Geophysical Year, and produced the accepted guide document callee "URSI Handbook of lonogram Interpretation . and Reduction" published in 1961. The Canadian Ionospheric measuring program reached its peak at the time of the IGY.
The development of the oblique sounding method by ORTE in 1956 along with IGY preparations brought about an expansion of facilities at Resolute and Baker Lake, where NRC and the Dominion Observatory added buildings along side the original DOT buildings. DOT also added a two building bunk-house and a services building to the Resolute complex.
An intensive oblique measuring program began in 1957 and continued through 1962 with Ottawa being the central station and Resolute and the Hague (Holland) being main satellites, with Winnipeg and Baker making important observations.
In 1959 kw hf transmitters designed for the Department of Transport were installed at Winnipeg, Churchill, Resolute and Ottawa.
Baker Lake was closed as an ionospheric station in the early spring of 1961. The Oblique program was winding down at that time also.
The Winnipeg station was moved from the Headingly Jail property in 1962 to a VHF transmitter building related to the Kenora DOT airport where technicians from the nearby enroute radar station carried out operational and maintenance work.
That year (1962) two new buildings were added to Resolute to accommodate the large number of transients, they consisted of a sizeable mess hall, a recreation building and a modest operations building which were connected to the previous complex of buildings .
DRTE recognised that the Ionospheric program had changed from a research project to a routine operation so negotiations were started for transfer of the whok program to DOT which became effective in 1963. The delay in implementation o: the transfer resulted in the encumbents of the three DRTE position (Bob Stevens, Bill Campbell and the librarian) not being transferred to DOT . The Radio Regulations ionosphere section was closed and the entire program came under the Operations Branch of Transport. The library, frequency prediction section as wel as the administrative responsibilities were transferred from DRTE and DSIS. This assured continuation to Canadian contribution to the world wide ionospheric program . At that time frequency predictions as a service had fallen to a low profile. The oblique and aural monitoring projects were closed during the period of transfer negotiations .
A two man HQ unit controlled the stations which were under DOT Regional operations. In short order the central data reduction centre implemented in the Winnipeg Region in 1959 was moved to Ottawa and the stations were upgraded to the standards of the Operational Branch of DOT. The Radio communications circuit was closed in favour of the DOT air-radio system. Work began immediate! on updating the manual data reduction system to a semi EDP process which was finally operational with the October 1965 data. The newly formed 'computer section' of DOT assigned H.T.Lyon the task of developing the program which became the most advanced in the world. The program took into account the many rules for interpretation as presented by URSI. The Data was tabulated in punched card form using a format recommended by URSI, and data was stored on magnetic tapes to conserve storage space. Also in 1959, Resolute was provided with a new Swedish made 1005W ionospheric sounder.
About 1965, a renewed interest developed in predicting useable frequencies so Garth Roberts of Radio Regulations Branch was assigned to DRTE to complete and update a computerized version of Report 113. This work was finally completed by Judi Campbell in 1974. Out of this work came a method of producing 'maps' of useable frequencies which are entirely computer produced, anc conversational packages for determining radio circuit design criteria.
In 1971 an additional update was made to the ionospheric data reduction process when a digitising technique was developed which relieved data reduction technicians of the chore of recording and plotting thereby allowing the expertise of the technicians to totally control a reduction process. The ionogram was projected onto a 'table' and the operator traced the graph with a 'pen ' which was followed by a mechanism which encoded the graph. The data was written on magnetic tape which was processed by computer, which determined synoptic values, printed monthly charts and produced punched cards for producing daily plots representing penetration frequencies.
After DOC was formed , the ionospheric group was transferred to that Department along with other functions of Radio regulation and spectrum management. The data reduction process was further mechanized by 'Chip' Weis, a consultant, whc developed a computer program that produced the daily graphs of ionopshere penetration frequencies. Canada had, by far, the most advanced data reduction system in the world.
The year 1974 witnessed renewed interest in VI ionospheric work, with Churchill being update by the provision of a new 1005W sounder and the construction of a long wire antenna system for low frequency recording. That year a new station at Kenora was built following recent concepts of long wire antenna for low frequenc) recording and the location of the antenna system in a valley for improved vertical directional characteristics. A new site for the St. John's station was surveyed, and negotiations for new equipment started. During that year agreement was reached with CRC to transfer the ionospheric station building at Shirley Bay to them in return for DOC use of the Ashton ionospheric station as a regular ionospheric station.The Kenora station was closed Dec. 31, 1976.
Why measure the Ionosphere?
Canadian measurements of the ionosphere were at first to support geophysical studies centred about HF propagation for which the Canadian military established at least 6 stations. The International Geophysical Year of 1958 (extending to 1960) provided incentive for a great effort for measurements to provide the data base for intensive scientific studies; at least 20 Canadian stations supported the measunng program.
Measurements of the Ionosphere is a continuing requirement, for example the need for new facilities is stated by the Committee on Solar Terrestrial Research of the Geophysical Research Board (URSI) under date of 1971.
"It is concluded that the capabilities of the radar technique are immense but have not yet been fully exploited because of lack of suitable equipment; a new facility located near the transition between mid-latitude and polar Ionosphere would be able to examine a rich variety of ionospheric processes and would contribute greatly to our understanding of the upper atmosphere and the magnetosphere." or CCIR report 430-1 (1975):
"Considering that the present world-wide network of ground-based ionosondes, operating regularly and participating in the world-wide interchange of data is far from ideal from the viewpoint of ionospheric propagation predictions.":
"Improvements in long and short-term predictions of ionospheric conditions depend upon the availability of new sources of ionospheric observations as well as upon improved methods of ionospheric mapping and predictions. Significant improvement might be possible by supplementing vertical incidence measurements with data obtained from satellites and by other appropriate teclmiques ."
(a) that accurate, quantitative short-term predictions of ionospheric variations a few hours or days in advance would permit more efficient utilisation of radio frequencies and increase the reliability of radio communication services;
(b) that, in addition to the widespread disturbances associated with major geophysical or solar events, there are other hour-to-hour and day to-day ionospheric variation (which may be local in influence) whose effects on operational characteristics, such as MUF and those associated with attenuation fading, multipath interference and atmospheric noise, cannot be predicted by well established techniques;
UNANIMOUSLY DECIDES that the following question should be studied:
"What are the needs and techniques for the short-term prediction
(a few hours or days in advance) of operational parameters for ionospheric radio communications?"
Methods of Measurements
We have considered the Canadian ionospheric measuring network of stations, now let us consider the method of measurement.
Radio waves travel, that is they move about in space, at a known speed slightly s lower than the speed of light. The most convenient means cf measuring the distance of the ionosphere above earth, is to measure the time of travel of a radio wave from earth to the ionosphere and back .
It is necessary that some means be found to inserted on the radio frequency signal, something that will identify the moment that the wave leaves earth so that we can measure time that the wave travelled. The advent of the CRT has made measuring the comparatively short travel time easy. The principle used in RADAR, that is sending a short pulse and measuring the time of the return pulse, has proven to be the most convenient and has been the most popular ; although inserting an appropriate sine wave on a carrier and comparing the sine wave on the return signal, has been used as has the "chirp' technique which measures the difference ir frequency of the echo.
The measuring equipment, therefore, produces radio frequencies in the HF range which are pulsed or otherwise modulated. Some equipment operates on one or more fixed frequencies; however the most common ionosondes sweeps the frequencies from 1 mghz to 15 or more.
The ionosphere, particularly in the high arctic, changes very rapidly, so the sweep time is usually limited to a minute or so. Photographic film is a convenient recording medium , so an ionogram is usually made by impressing a dot on film representing the send pulse an(i another dot representing the return signal which has been moved by the CRT sweep; a distance related to the delay of the return which is directly related to the distance between the dots indicates the time of signal travel, which, since we know the travel speed of a radio wave, is directly translated into layer height. of course an ionogram is made up of many hundreds of dots and therefore appears as a graph of height versus frequency.
Calibration markings indicating frequency and layer height are superimposed upor the film for accurate interpretation.
Output of the Iionospheric Service
Since the data obtained by the Ionospheric program is intended to be used in a wide variety of services ranging from pure research to the planning of specific radio circuits, two basic kinds of information are generated.
While there are many specialised forms of ionospheric data, by far the most used are developed from primary ionospheric data in the form of height versus frequency graphs called 'ionograms'. From the h'f graph the height and frequency values are compiled into tables, one for each ionospheric layer. Graphs are also developed which display the penetration frequencies versus time of day. The two, the tables and the graphs are compiled into booklets monthly, one for each of the main sounding stations, which are distributed to over 50 addresses in many countries .
A second product are monthly booklets presenting graphs of maximum usable frequencies for specific distances. This form of data is used by deep sea shipping and long range aircraft, particularly the Canadian Airforce, and is valued as part of planning long range HF communications backup emergency procedures.
History of data Reduction
Studies of compiled ionospheric data showed that the state of the ionosphere varied in accordance with a general pattern . Based on this understanding systems for determining useable frequencies in advance (predictions) were developed so that H.F. radio communication circuit configurations could be planned . The most noteable early work is "circular 462" published in 1948 by the US Department of Commerce. DRTE of Canada produced "Report 113" in 1954 which overcame errors in calculations for circuits passing through the high latitudes.
The best known systems Developed since 1954, were; the British system dated 1962; an Australian system; the CCIR 'Atlas of Ionospheric Characteristics', 1967; and the USA systems, 'CRPL Ionospheric Predictions' 1962; 'Telecommunications Research and Engineering Report 13' 1972; and the Canadian systems such as developed by DuCharme, Petrie and Roberts 1967. Argentine, Germany and Japan are well known for their systems also.
Each prediction method depends on an "index" determined from current mea surements of the ionosphere and of the sun. Obviously, predicted values at best are for average conditions from which day to day values may depart considerably. Some systems reduce error by also Introducing daily or 6 hour indices determined from hourly measurements of the ionosphere and sun.
The USAF have developed a ionosphere mapping system within the Military Air Weather Service for the purpose of issuing maps of the condition of the ionosphere. Hourly measurements of the ionosphere are an important ingredient for the maps.
In 1973, the service of providing predictions of useable frequencies was transferred frorr DRTE to the DOC ionospheric group. This ceased in March 1976 when commercial Interests claimed that it interfered with the commercial market.
Data has been obtained through using many methods such as measuring signal strength and phase of distant transmissions; oblique sounding systems using separated locked-in sounders; measuring the RF radiation originating from outer space; transmission of the RF generated by lightening flashes; satellite borne sounders; and vertical incidence (Vl), ground based sounders such as are operated under DCTR administration.
The advent of the artificial earth satellite in 1958 opened a new way to obtain ionospheric data. Alouette 1 1965 and II 1971, the International Scientific Ionospheric Satellites (ISIS) and others have made measurements from above the ionosphere where they are clear of man made interference and absorption. The satellite borne sounder showed great promise, however , in addition to the high operating cost (construction cost, launch cost, short life, and sophisticated tracking system), the data reduction process is at least two magnitudes more difficult than VI reduction since the sounder is moving, requiring the location to be calculated, requiring the effects of movement to be inserted, and values must be Interpolated to relate it to specific reference points. None of the Administrations owning ionospheric satellites have been able to circulate what might be considered "routine" data, and none have been able to produce data useful for real time work.
The VI sounder has been proven to be a basic tool, relatively cheap to operate, and the output is considered basic for calibration of more sophisticated systems, and for most studies, particularly for those requiring data on a real time basis.
Bibliography in order of reference in text:
Radio Science, Vol 11, Number 11, pages 847-860 War History of the Radio Branch (NRC) ERAl41 Radio Branch report (NRC) PRA-82
ibid PRA-131 ibid PRA-132
Canadian Journal of Research 8:1-361936 ibid a, 26:137-144 May 1948
The Suffield Experiment 1944 (Met Archives) (2 Vols) Second International Polar Year (1940-1941) (Met Archives) Canadian Second Polar Year Expedition (Met Archives)
Ionospheric Radio Propagation - US Dept of Commerce circular 462, June 25, 1948. Predictions of Optimum Traffic Frequencies for Northern latitudes, Report 113, Defence Research Board, Canada, Nov 1954.
Conclusions of the Interim Meeting of Study Group 6 (CCIR)
Upper Atmosphere Observatory, National Academy of Sciences, 1971.
Information was provided by the following:
G. T. Henderson
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