Introduction
Professor Gerhard Beutler, the newly elected president of the International Association of Geodesy (IAG) Commission on International Coordination of Space Techniques for Geodesy and Geodynamics (CSTG), requested that I should write the history of the Commission as an introductory article to the reconstituted CSTG Bulletin (last published in 1991), presumably in my capacity as an IAG fossil (a hardened remnant reflecting historical times).
The Road to Moscow
Xith General Assembly, Toronto, Ontario, Canada, September 4 - 13, 1957
Some space geodetic techniques found their origins already in the pre-space era, such as the method of stellar triangulation, developed in the 1940s by Y. Vaisala of Finland, in which flares lifted by stratospheric balloons were photographed in the back ground of stars for the purpose of connecting distant geodetic datums. Somewhat later during the early 1950s, photographic observations utilizing the Moon as a target, either when eclipsing the Sun or when occulted by stars also had been utilized for the same purpose. A system similar to Vaisala's, but with flashing (stroboscopic) light targets carried to great heights by a missile was proposed by R.d 'E.Atkinson of the United Kingdom. It was also suggested that to monitor variations in the rotational vel ocity of the Earth, the Moon also be photographed in the background of the stars by means of a network of special cameras, developed by W. Markowitz of the U.S.Naval Observatory. This proposal became a major international program later on.
In the great anticipation of artificial satellite launches during the IGY (International Geophysical Year, July 1, 1957 û December 31, 1958) one could witness a flurry of activities, e.g., the Smithsonian Astrophysical Observatory (SAO) in Cambridge, Ma ss., was organizing its famed Moonwatch Teams for the early visual detection of satellites and was developing the Baker-Nunn worldwide satellite tracking camera system for photographing satellites against the background of stars. Engineers in NASA were w orking on the Minitrack system for the interferometric tracking of the 15 kg Explorer 1 and the 1.5 kg Vanguard 1 satellites, hoped to be the first artificial satellites (to respectively explore the inner radiation belt of the Earth and to prove that the Earth is pear-shaped!), only to be beaten to this distinction by the 83 kg Sputnik 1 launched by the Soviets on October 4, 1957 and the huge (500 kg) Sputnik 2 on November 3, 1957. Explorer 1 eventually got launched on January 31, 1958 and Vanguard 1 on M arch 17 of the same year. Thus the space age began in earnest, coincidentally just three weeks after J. de Graaff Hunter of the U.K., President of the IAG, brought the XIth General Assembly to a close. At the time of the Assembly, IAG was organized into five Sections (Triangulation, Precise Leveling, Geodetic Astronomy, Gravimetry, and Geoid), six Permanent Commissions (PCs) and 16 Special Study Groups (SSGs). The Commissions and Study Groups were dis tributed among the Sections, depending on their subject. Space and astronomy related matters belonged to Section III (Geodetic Astronomy) under the presidency of Professor Jacques Cox of Belgium, although none of the PCs or SSGs dealt with them. Consequen tly during the General Assembly very few (if any) presentations even mentioned space or artificial satellites.
The Assembly ended with the election of Professor Gino Cassinis of the Politecnico Milano, Italy, as IAG President, and Professor Roelof Roelofs of the Delft Technological University, The Netherlands, as President of Section III. Pierre Tardi, France, wa s reelected as IAG General Secretary. He had been in this office since 1946. The only sign that IAG had anticipated a role at the threshold of the space age was the formation of the new SSG No. 9, Geodetic Applications of Lunar and Future Artificial Satel lite Observations, under the leadership of W. Markowitz. Many Resolutions (16) were adopted (an IAG questionable tradition), most of them related to gravimetry and to refraction, the hot topic and the Cinderella of the times, but none to space geodesy .
XIIth General Assembly, Helsinki, Finland, July 26 - August 5, 1960
After the last Assembly and less than nine months after the launch of Vanguard 1, the first scientific results from the Minitrack tracking network (10 stations) were announced at the Conference on Contemporary Geodesy in Cambridge, Mass., December 1-2, 1 958. Ann Eckels of NASA gave the value of 0.0016232 for the second degree zonal harmonic of the Earth gravity field, corresponding to a flattening of 1/298.3 for the terrestrial ellipsoid, determining that the Earth is less flat than previously believed ( 1/297). J. Allen Hynek of the SAO (later known as the Galileo of UFOlogy) proudly showed-off with the Baker-Nunn photographs of the tenth magnitude Explorer 1. Don Lautman of the SAO complained that the Vanguard Computing Center, using the methods of gene ral perturbations, could handle only the effects of the even degree zonal harmonics and not longitude-dependent terms nor those that changed sign with latitude. This was due to the fact that to include such terms as well would have taken 50 hours of com puting time on the IBM 704, apparently not readily available for such a purpose. Lautman also expressed hope that geodesists would be very pleased to have actual X, Y, Z coordinates on the Earth with respect to the Center. Indeed! Further quotes from va rious participants: We believe that the Doppler method yields in fact about the same accuracy as the interferometry (Minitrack) method, .... but we have not been able to get any equipment to test it out and last but not least, Science, like women's ha ts, tends to go in cycles. Fifteen years ago interest in geodesy was near the vanishing point and I would have said that the possibility of gathering together a group like this today was as probable as finding a live dodo bird.
A year and a half later, at the General Assembly Professor Cassinis, a colorful personality (at one time he was the mayor of Milan) in his presidential opening address took care of space geodetic efforts with a single sentence, although he paid special tribute to V is l (stellar triangulation) and to Markowitz (Moon camera). The hot discussion topic of the time was the intrinsic and three dimensional geodesy la Professor Antonio Marussi of the University of Trieste, Italy, and Brigadier Martin H otine, Director of Overseas Surveys, U.K.
During the sessions of Section III a great deal of discussion (although no formal presentations) took place on the geometric and dynamic applications of artificial satellites, just like during the other two meetings held about a year before the General Assembly: The Symposium on Electronic Distance Measurements (Washington, D.C., May 1959) and on Three Dimensional Geodesy (Venice, July 1959). As evidenced in the future, person to person discussions at such gatherings, rather than formal presentations, proved to be more effective and led to proposals to form a new Permanent Commission related to satellite geodesy and some other groups.
The General Assembly elected Charles A. Whitten of the U.S. Coast and Geodetic Survey as the next IAG President, changed the name of Section III to Geodetic Astronomy and Artificial Satellites and elected W. Markowitz as its President. Jean-Jacques Leval lois, France, was elected as the next IAG General Secretary. He was to nurse IAG along through 1975. The Assembly formed three additional commissions, two of them permanent: PC VII, Recent Crustal Movements to be led by Yuri Mesherikov of the Academy of S ciences, U.S.S.R., and PC VIII, broadly named Artificial Satellites (the subject of this Historical Note) to be led by Alan H. Cook of the National Physical Laboratory, Teddington, U.K. The third Commission (not permanent and included here only for histo rical interest) was on Organization with Professor Cassinis in charge, to review the IAG organization and to prepare a plan for a possible reorganization. After his death in 1964, honoring his memory, the group was renamed to the Cassinis Commission and is re-formed at every other General Assembly to review the IAG organization and keep it from becoming fossilized.
It was already recognized at this time that ICSU's (International Council of Scientific Unions) COSPAR (Committee for Space Research) should also be involved in the work of the IAG PC VIII Commission on Artificial Satellites. COSPAR was established in 19 58 to continue the programs of the International Geophysical Year. For certain political (Cold War) reasons the science managers in Eastern Europe appeared to have greater confidence and influence in the COSPAR family than in the IAG/IUGG (International Union of Geodesy and Geophysics). For this reason a joint IUGG/COSPAR Committee was appointed within PC VIII to foster collaboration between East and West. Members of this Committee were Y. Boulanger, U.S.S.R, William Kaula, U.S., Fred Whipple, U.S., and J. Zhongolovitch, U.S.S.R. The effectiveness of the Committee is difficult to assess, at best.
The number of SSGs were increased to 19, two of them in Section III, but only No. 9, mentioned already, continued with problems related to satellite geodesy. The number of Resolutions adopted also increased to 28 (!) of which two may be of interest here : No. 13, which encouraged that a high altitude satellite equipped with flashing lights and devices for electronic tracking be placed in orbit (was the satellite ANNA in mind?), and No. 22, which further encouraged authorities to launch satellites into orbits that would yield new information of the Newtonian attraction of the Earth.
XIIIth General Assembly, Berkeley, California, U.S., August 19 - 31, 1963
Since the last Assembly there were two symposia reporting further progress in satellite geodesy. The most insignificant detail, which however, stands out in the author's memory, happened at the first meeting, at The Ohio State University, Columbus, Febru ary 6-8, 1961 on Geodesy in the Space Age, where Professor W.A. Heiskanen, the organizer of the symposium and about five feet tall, physically removed the heavy weight, William Kaula of NASA, who just would not stop talking about his pioneering work, fr om the podium. The second symposium in Washington, D.C., co-organized by IAG, COSPAR and the American Geophysical Union, April 26-28, 1962 was the first (of six) of the series Use of Artificial Satellites for Geodesy. This very successful series, convened primarily by George Veis of the Technical University of Athens, continued for some twenty years in the picturesque resorts of Lagonissi and Ermioni, Greece. In 1973 the title, due to the expanding interest of the clientele, was changed to Use of Artifi cial Satellites for Geodesy and Geodynamics. The Washington symposium held at the U.S. Naval Observatory was the first meeting fully devoted to satellite geodesy. During the three days one could learn about new technologies, e.g., the Wild-BC4 and PC-1 000 ballistic cameras or the exotic SECOR developed for four-station simultaneous electronic distance measurements. The Transit (Doppler) navigation system was also described, which as a side-product already returned some new information on the gravity f ield. George Veis, at the time with the SAO, presented the latest set of geocentric station coordinates of the Baker-Nunn network and Hellmut Schmid of the U.S.Coast and Geodetic Survey was seeking opinions on the feasibility of establishing a 36 station Worldwide Satellite Triangulation Network using the BC-4s and balloon satellites specially launched for this purpose, a project successfully completed later. Yoshihide Kozai of Japan, at the time also at the SAO, presented his latest set of zonal harmoni cs up to the ninth order, while the skeptics in the audience were smiling, and discrepancies in the values of the first few tesseral harmonics were subject of heated discussion. In the last minute Navy Cdr. Mark Macomber rushed in announcing ANNA (the fla shing satellite, but also equipped with Doppler, SECOR, and other goodies) and distributed his paper still wet from the censor's ink.
About fifteen months later Charles Whitten opened the XIIIth General Assembly. In his opening address there was clear indication that he has already foreseen the difficulties of the future. The need for IAG (and the funding agencies) to adequately consid er the many proposals expected due to the fast development of satellite geodetic technology, and the need to select ideas which are truly challenging and which merit efforts and international cooperation. The tremendous accumulation of data would require world centers or services for storage and analysis, the need for computer facilities for international projects and for the distribution of the analysis products. He expressed hope that with the goodwill which existed within the community and proper organ ization these challenges can be met.
Section III devoted two sessions to related matters. In the first, on the figure of the Earth and on fundamental constants related to the solar system, Alan Cook led the discussion to recommend revised values for adoption and to represent IAG's position in this matter at the forthcoming International Astronomical Union (IAU) Assembly in Hamburg, 1964. During the second session J.J. Levallois reported on the results of French photographic observations of the Echo 1 balloon (communication) satellite, George Veis discussed the utilization of the BakerBaker-Nunn network, and William Kaula the determination of the geoid. The SSG reports and the private discussions clearly indicated the need for more IAG involvement in satellite geodesy.
Brigadier Guy Bomford of the U.K. was elected IAG President. Section III and PC VIII were to continue under the same leaders (W. Markowitz and A.H. Cook). SSG No. 9 was discontinued and in some sense replaced by two new SSGs: No. 26 Geodetic Connections Through Artificial Satellites lead by S ren Henriksen, U.S., and No. 28 Dynamics of the Artificial Satellites by A.H. Cook. IAG ended up with a total of seven PCs (No. IV was discontinued) and 19 SSGs of which only the above two were to deal with satelli te geodetic matters.
Of the 38 Resolutions adopted only No. 7 was related to satellite geodesy recommending that immediate consideration be given to the problem of establishing a worldwide satellite triangulation network to be used as the basis upon which all terrestrial triangulation is adjusted. It also requested recommendations for the guidance of member nations as to target vehicles and observation systems required and as to measures of cooperation between nations that will be necessary in order that such network may be established.
IAG was having difficulties establishing leadership in satellite geodesy. Maybe for this reason, two additional resolutions were adopted by IUGG: No. 58 invited the American Geophysical Union to undertake the necessary steps by the U.S. Government to e stablish a Central Bureau for the Geodetic Uses of Artificial Satellites at the SAO. The Bureau primarily shall function as the central information collection and distribution agency, i.e., as a clearinghouse for satellite geodesy and advisor upon req uest. No. 59 invited COSPAR to participate (with IUGG) in the formation of a Scientific Council on the Geodetic Uses of Artificial Satellites. The Council together with PC VIII will provide advice to the Central Bureau on subjects such as the establish ment of worldwide programs, the most suitable instrumentation and operational techniques and on the optimum orbital and physical parameters of future satellites. The Council was to consist of seven members, three each from COSPAR and from IUGG, and the Di rector of the Central Bureau. The importance of getting COSPAR involved was explained earlier. Although the Bureau's Charter was approved only at the next General Assembly in Lucerne in 1967, it started its operation (with great expectations) in 1965. IA G/IUGG members of the Council were W. Markowitz, Max Kneissl, F.R.G., and H.M. Dufour, France, while COSPAR appointed Y. Shchegoliev, U.S.S.R., E. Buchar, Czechoslovakia, and Desmond King-Hele, U.K. The seventh member was Fred Whipple, in his capacity as the Director of the Bureau (and of SAO). Later George Veis took over the directorship and the Bureau was moved to Athens. The Bureau functioned with reasonable success for about a decade, when for budgetary and various other reasons could no longer keep u p with the ever increasing amount of observational data and other information. It should be considered as the first attempt to establish an international geodetic satellite information and data center.
XIVth General Assembly, Lucerne, Switzerland, September 25 - October 7, 1967
It was about half way between the General Assemblies, probably in Lagonissi at the 2nd Symposium on the Use of Artificial Satellites for Geodesy, April 26-May 2, 1965, when the honeymoon was over. Satellite geodesy reached its maturity and was no long er considered experimental. It became operational and the foundation of a number of important national and international projects.
By this time Project ANNA was part of history, the satellite although still in orbit already fulfilled its main mission to prove the feasibility of cooperative geodetic ventures, although the SECOR system on board failed early on. Nancy Roman of NASA ann ounced the next and much more ambitious project, the National Geodetic Satellite Program (NGSP), which managed by NASA would consist of five geodetic satellites and would involve every organization who cared and would be able to participate and on an inte rnational basis. The order of zonal harmonics determined reached the fourteenth (so reported David E. Smith of the Radio and Space Research Station, Bucks, England, and later of NASA's fame!), while that of the tesserals reached the seventh (said Richard Anderle of the U.S. Naval Surface Weapons Laboratory, Dahlgren, Virginia). Some tesserals in the 12th-15th order were also available as determined from resonance effects.
Hellmut Schmid presented accuracy aspects of his super Worldwide Satellite Triangulation Network, which became a reality within the framework of the U.S. Coast and Geodetic Survey and the Army Map Service, and whose fill-in portion was already in progr ess between Antigua and the Aleutians. But the handwriting was already on the wall: Dick Anderle claimed that the Transit/NNSS (Navy Navigational Satellite System) Doppler system is becoming a most cost effective and powerful positioning tool and competit ive with the photographic method. His preliminary tests yielded positions of tracking stations in agreement with the first-order triangulation to 10-20 meters over baselines up to 5300 km long (today, using the Global Positioning System (GPS) satellites, a technique which later made NNSS obsolete, this number would be a few cm and in the absolute sense. Thus the accuracy of a triangulation net today must be assessed from comparisons against the GPS results rather than the other way around).
In other results, improved values for geodetic datum positions relative to the center of the Earth, for the Gaussian gravitational constant and for the flattening (1/298.25) and the semi diameter of the terrestrial ellipsoid were presented. On the instru mentation front, the routine operations of the various camera and Doppler systems were reported and an experimental laser tracking device was under development at Air Force Cambridge Research Laboratory (AFCRL), announced O.W. (Obie) Williams. As to cry stal-ball-gazing, it seemed certain that laser developments will continue and that small and inexpensive (!) Doppler positioning devices will be forthcoming. Satellite geodesy was to explode (with or without IAG).
It was during the symposium that IAG's Permanent Commission VIII gave birth to its Western European Sub-Commission (WEST) with the primary mission to satellite triangulate 15 countries in Western Europe (President: Col. J. Kelsey and later Maj. Gen. R.C. A. Edge both of the U.K.). It was only natural that an Eastern European Sub-Commission (EAST) should follow, and it was established on October 30, 1966 in Karl Marx Stadt, G.D.R., to satellite triangulate seven countries in Eastern Europe (President: Ludo slav Cichowicz and later Wenda Dobaczewska, both of Poland). Both subcommissions, in cooperation with each other, were instrumental in establishing a geodetic control network over much of Europe by means of simultaneous photography of satellites such as G eos 1 and the balloons Echo 1& 2 and PAGEOS. As such a cooperative task required, numerous working meetings were held, practically on an annual basis, until both were discontinued in 1972, the WEST in Graz, Austria and the EAST in Ulan Bator, Mongolia, mo st of their tasks accomplished and the remainder taken over by the reorganized PC VIII (see below).
About two years after Lagonissi the General Assembly was opened by Brigadier Bomford, by now retired from Oxford University, who after paying tribute to the three IAG Presidents who passed away between the two Assemblies (G. Cassinis in 1964, F.A. Vening Meinesz in 1966, and J. de Graaff-Hunter in 1967), announced that it is customary that you should listen for some minutes, to a presidential address, to which we must now proceed. He described the amendments to the IUGG statutes and by-laws, which were passed during an extraordinary IUGG General Assembly two days before, and which are no doubt beneficial and of relatively little consequence. He also announced the plan to form a new Cassinis Commission which, as it will be seen at the next IAG General Assembly, will have satellite geodetic consequences. Bomford's sense of humor never left him and he has been greatly admired, and he did not say one word about satellite geodesy.
At the sessions of Section III, President Markowitz informed the audience about the symposium held in Stresa, Italy, in 1964 on Continental Drift and the Motion of the Pole, where among other interesting topics the question of the existence of continenta l drift vs. the secular drift of the pole, as determined from astronomical observations, were heatedly debated. It was also here where the feasibility of lunar laser observations for the above purposes were suggested by C.O. Alley and Peter Bender, U.S. Alan Cook reported on the IAU 1964 set of fundamental constants pointing out that the new system was both simpler in structure and in better accord with observation although, as it has been the case ever since, somewhat already out of date.
A great deal of time was spent by S ren Henriksen and George Veis on the accuracy and the reference frames of star catalogues used in the photographic plate reductions for satellite tracking. The author also got involved, and presented an account on exis ting global satellite tracking networks, the purposes of which were to connect geometrically the major geodetic datums, and to refer all tracking stations to a common framework. NASA data services were described by William Strange, and finally W. Markowit z discussed the techniques for the precise time synchronization of satellite observations, particularly by means of VLF signals and traveling clocks.
The General Assembly elected Antonio Marussi as IAG's next President. A.H. Cook took over Section III and Permanent Commission VIII (renamed Geodetic Use of Artificial Satellites) and continued the presidency of SSG No. 28 as well. His energies appeared to be unbounded. PC VIII's twins EAST and WEST received the appropriate acknowledgements of and sanctions to their existence, and SSG No. 26 was continued under Henriksen. IAG ended up with 23 SSGs and the seven PCs distributed in its five Sections. The Assembly also adopted 33 Resolutions of which five may be considered satellite geodesy related: No. 1 recommended a set of constants defining the Geodetic Reference System 1967, and No. 15 the continuation of the Central Bureau of Satellite Geodesy's invaluable work in furtherance of satellite geodesy along the lines indicated in its charter. No. 16 appreciated and encouraged the work of PC VIII and endorsed the resolutions and recommendations of EAST and WEST adopted at their respective meetings . No. 17 recommended that whenever possible laser ranging systems be collocated with satellite tracking cameras, and be used in simultaneous observing programs, and finally, No. 20 urged that the possibility of using artificial satellites and corner r eflectors on the Moon to measure continental drift and other relative movements with high accuracy be studied. The General Assembly in Lucerne finished its work on a high note!
XVth General Assembly, Moscow, U.S.S.R., August 1 - 14, 1971
In April 1970 the Cassinis Commission met in London and recommended a number of changes in the IAG organization: The five-section structure was retained but in accordance with their functions their names were changed to Control Surveys, Satellite Techniq ues, Gravimetry, Theory and Evaluation and Physical Interpretation. The desi gnation Permanent was removed from the PCs and their number was reduced to six, however, the old numbering system was retained. Thus PC VIII simply became Commission on Satelli te Geodesy under Section II. The system of SSGs was also retained. The term of office for the various presidents was to be limited. The General Assembly on August 2, 1971 approved all the recommendations. In the interim, in June 1971 COSPAR at its 14th Plenary Meeting in Seattle established under its Working Group I, the Panel 1C Satellite Geodesy and Geodynamics. After some negotiations it was agreed that this Panel and the new Commission on Satellite Geodesy will have the same membership and the same president. The initial membership consisted of 17 members nominated by COSPAR and 12 by IAG. The Central Bureau for Satellite Geodesy was placed under the Commission. EAST and WEST were to be dissolved so on and their remaining task would be taken over by the Commission. The charter of the Commission were defined as to study projects implying international cooperation, to propose or sponsor such projects, to follow their organization and advancement in t ime, to help as much as possible in the implementation of the scientific goals. The arrangement was fully endorsed by COSPAR at its 15th Plenary Meeting in Madrid, May 1972.
At the General Assembly Professor Marussi in his presidential opening address paid tribute to those who passed away between the two General Assemblies. Of those mentioned in this paper were Y. Mesherikov, L. Cichovitz, M. Hotine and Y. V is l . W. A. Hei skanen died just after the Assembly in October. Memento mori!
In the sessions of the still Section III, satellite geodetic programs were reported on, such as the ISAGEX, EXGEOS, the Arctic-Antarctic, the Riga-Sofia, the Europe-Africa programs, and the Troms -Catania and Malvern-Graz baselines to provide scale for t he global satellite triangulation. Satellite geodesy was on its way! The Assembly elected Yuri Boulanger of the Soviet Academy of Sciences as the next IAG President, and George Veis as Section II (!) President. The Commission on Satellite Geodesy was to be led by Jean Kovalevsky, France. Included in the Commission, in ad dition to the twins EAST and WEST, were two new Working Groups: Laser Ranging to the Moon led by C.O. Alley, and Laser Ranging to Satellites by G.C. Weiffenbach of the SAO. Section II's SSG Nos. 26 and 28 were continued under their earlier titles and lead ers (S. Henriksen and A.H. Cook) established eight (!) years ago. At this point IAG had six Commissions and 20 SSGs distributed in its five new Sections.
This time the Assembly adopted only (!) 16 Resolutions of which three are of interest here: No. 9 urged all agencies to inform the Central Bureau of Satellite Geodesy of their current and future plans for distribution to all interested parties, No. 10 appointed six members to an IAU/COSPAR Panel to coordinate lunar laser observations, and No. 15 recommended that geodesists should actively participate in the Geodynamics Project, for which terrestrial and satellite data are of great importance for s tudies of the Earth, its interior and various geophysical phenomena. On this note the XVth General Assembly of the reorganized IAG ended in Moscow.
XVIth Assembly, Grenoble, France, August 18 - September 6, 1975
In his opening speech Professor Yuri Boulanger expressed his fear of speaking to such a competent audience, consisting of lions of modern geodesy and that for this reason he completely forgot his English. He compared his situation to the strong young f ellow who applied to a lion-trainer vacancy in a circus. Another applicant was a small girl who was sent into the lion's cage first to show her talents. She performed admirably and the lions obeyed her with apparent pleasure. Then the director of the circ us asked the young man Can you do all this girl has just done? upon which he replied that Yes, of course, provided there are no lions in the cage.
Then Boulanger continuing in Russian, pointed out two important changes taking place in geodesy, both due to the improvements in technology: The possibility of and the need to introducing time as the fourth coordinate in geodesy, since the Earth can no longer be considered rigid. The possibility of replacing the relative methods with the absolute, both in satellite positioning and in gravimetry. He also discussed the potential applications of satellite altimetry for the improved determination of th e geoid, and of Very Long Baseline Interferometry (VLBI), observing extra galactic radio sources for observing continental drift. It was a forward looking speech.
Jean Kovalevsky in his report on the Commission on Satellite Geodesy, in essence reiterating Boulanger's comments, emphasized that it was clear that the main objectives of space geodesy for the years to come will be focused on geodynamical studies: Plate tectonics, refined analysis of Earth rotation, and shorter wavelength gravity field studies. Already during the previous period between the Assemblies a number of experiments were concerned with these aspects of geodynamics, but there was no internation al global project undertaken yet. In fact the first second generation geodetic satellites, Geos 3 and STARLETTE, were only launched respectively in February and April 1975, in the year of the Assembly. The star (in the sense of being most observed) o f geodetic satellites, LAGEOS, was waiting to be launched only the following year, in May 1976. Of the global programs sponsored by or reported to the Commission, only a few are mentioned here. The Worldwide Satellite Triangulation Network was completed and the results, based on 14,500 composite BC-4 directional camera observations on PAGEOS (Passive Geodetic Satellite) from 45 stations and scaled by seven geodimeter traverses, published. The r ms error was 4.5 m. The general adjustment of some 160 globally distributed tracking stations using various types of cameras, with SECOR observations for scale, was also completed at The Ohio State University (OSU WN14). At this point one must mention the fact that by now Doppler observations using small receivers have almost completely taken over camera tracking for station positioning, with an rms error of less than 1 m in the relative sense, in North America (to support the readjustment of the North A merican Datum), in Australia and in Europe, where a first campaign (European Doppler Observation Campaign:, EDOC) was organized in May 1975.
The improvement of the knowledge of the gravity field as represented by new models (GRIM, GEM, etc.) which came from the inclusion of laser satellite tracking stations (six in 1971 and 12 in 1974) and from the improvement in the precision of such systems from 2m in 1969 to 40 cm in 1974. Major efforts to collect data for gravity field improvement included the International Satellite Geodesy Experiment (ISAGEX) with 50 participating stations which produced 1,800 photo plates and SAO's Earth Physics Satel lite Observation Campaign (EPSOC) in which over 90,000 laser observations of the Geos 1, 2 and the BE-C satellites were collected. The harmonic coefficients now included tesserals complete to the order 16-20 with additional zonal and resonance harmonics. The internal accuracies for the orbit, geocentric station coordinates and the geoid were about 4-10, 2-10, and 3 meters, respectively. Geodynamic results included the determination of polar motion with the Doppler technique since 1968. The Dahlgren Polar Motion Service (DPMS) using TRANET observations computed pole positions every other day with an rms error of about 0.02 arcsec. The ne w geodetic satellites mentioned earlier promised further geodynamic experiments: STARLETTE was designed to search for the variable part of the Earth gravity field (tides), and Geos 3 and Seasat (launched in 1975) were to continue the 1973 Spacelab experi ment for sea surface studies using radar altimetry. The first plate tectonic motion determination based on laser satellite tracking was in progress since 1973 in California in the San Andre
as Fault Experiment (SAFE) led by David E. Smith, by now with NASA . Satellite geodynamics was making reasonable progress.
The General Assembly elected into the presidency of the IAG T.J. Kukkam ki of the Finnish Geodetic Institute, of Section II Bernard H. Chovitz of NOAA, and of Commission VIII Yoshihide Kozai of the Tokyo Astronomical Observatory, Japan. Michel Louis, Fra nce, was elected as the next IAG General Secretary. Just like his predecessor, J.J. Levallois, he served IAG in this capacity with distinction for the next sixteen years. The author was appointed to become Editor in Chief of the 50 year old official journ al of the IAG the Bulletin Geodesique. He served until 1987.
The signs of changing times were also reflected in the SSG reorganization. Section II now owned, No. 32 Lunar Laser Ranging (also COSPAR's Panel 1D) led by J.D. Mulholland, U.S., No. 33 Satellite Laser Ranging (also COSPAR's Panel 1A) under G.C. Weif fenbach (later M. Pearlman of SAO and Peter Wilson, F.R.G), and No. 44 Comparison and Reduction of Doppler Satellite Observations for Geodesy chaired by W.E. Strange. SSG No. 26 was renamed Geodetic Satellite Contributions to Terrestrial Geodesy and mov ed to Section I (Control Surveys), and No. 28 was discontinued. Section V (Physical Interpretation) also included a SSG related to space geodesy, No. 48 Realization of Reference Systems for Geodesy and Geodynamics led by E.M. Gaposchkin of the SAO. IAG at this point had 23 SSGs and five Commissions distributed between its five Sections: No. X Continental Networks in Section I, No. VIII Satellite Geodesy in Section II, No. III International Gravimetric Commission in Section III, No. V Earth Tides and No. VII Recent Crustal Movements in Section V), and three Commissions outside the Sections (No. VI International Geodetic Bibliography, No. IX Education in Geodesy, and No. XI Geodesy in Africa. IAG became a complex organization and one which finall y appeared to catch up with changing times!
The General Assembly adopted 28 Resolutions of which a few have relevant historical interest: No. 1 gave new estimates for fundamental geodetic constants without replacing the Geodetic Reference System 1967. No. 9 recommended that detailed investigations into the accuracy of the Doppler methods, especially with regard to scale and orientation, be carried out. No. 10 urged that new radio-frequency satellite systems, proposed for navigation, be made accessible to all users, and encouraged rapid develop ment and implementation (an eye on GPS?). No. 11 recommended that earnest attention be paid to further development of geodetic satellite techniques, lunar laser ranging and VLBI for the study of recent crustal movements and geodynamics. No. 12 consideri ng the planned 1977 EROLD (Earth Rotation by Lunar Distances) experiment suggested simultaneous monitoring of Earth rotation using LAGEOS laser observations and VLBI. No. 13 expressed appreciation for the work of the Central Bureau of Satellite Geodesy an d thanked the Hellenic Committee on Geodesy and Geophysics (the Bureau had been transferred to Athens by this time). Finally, No. 26 recommended that the design principles and practical implications of geodetic data bases, (storage, retrieval, updating) b e discussed and experiences exchanged.
XVIIth General Assembly, Canberra, Australia, December 2 - 14, 1979
The author at this point is running out of time, and finds it impossible and maybe, at least from the point of view of providing more background material to understand the history of the Commission, even unnecessary to continue the review of events and a ctivities as he has done for the previous Assemblies, although they continue to be impressive and interesting. This task hereby is passed on to another amateur note maker, but only after mentioning one more event of profound geodetic consequence: The l aunch of the first demonstration satellite of the NAVSTAR Global Positioning System (GPS) in June 1977 (followed by four others by mid 1979) changing geodesy for the next generation. The GPS era has began and the rest of the story is for someone else to write. For this reason the rest of this paper will be restricted to the organizational aspects of the history of the Commission and maybe to a few selected gems difficult not to mention.
After the Grenoble Assembly it became increasingly clear that ongoing space geodetic and geodynamic activities needed better coordination in both the scientific and the organizational sense. Scientific justification for better coordination included the n eeds for more inter- disciplinary interaction within the geophysical sciences, and for better utilization of techniques such as geodetic satellites, lunar laser ranging and VLBI in a complementary rather than competitive mode, especially for geodynamic applications. Organizational justification for better coordination included the proliferation of groups belonging to various international scientific or engineering associations and to national agencies, duplicating to some extent each other's work and u sing up resources which could be utilized better elsewhere. This proliferation was also reflected in the increasing number of IAG symposia and other meetings on specialized topics: 26 symposia (including 12 related to space geodesy and geodynamics) and t wo summer schools were held since the last Assembly. The time was ripe to reorganize the Commission on Satellite Geodesy. The impetus actually was given by COSPAR which in June 1979 at its 22nd Plenary Meeting in India dissolved all its Working Groups and replaced them with a small number of Interdisciplin ary Scientific Commissions (ISCs), and dissolved all Panels, including No. 1C. The new ISC B The Earth-Moon System, Planets and Small Bodies in the Solar System was willing to offer again joint ownership for the Commission, but this first required an op portunity for IAG to do some soul searching, especially in view of the new needs explained above. Such an opportunity was provided by the General Assembly in Canberra a half a year later.
The General Assembly elected into the Presidency of IAG Helmut Moritz, Austria, of Section II L. Aardom, The Netherlands and of Commission VIII the author. The eight Commissions were continued and 32 SSGs were formed of which eight were related to space geodesy (the numbers before the decimal point indicate section affiliations, the names of the presidents are in parentheses). The continuing SSGs included 1.26 (Juhanni Kakkuri, Finland), 2.32 (Peter Shelus, U.S.), 2.33 (Peter Wilson, F.R.G.), and 5.48. T he new SSGs were 2.51 Radio Interferometric Techniques (William Carter, U.S.), 2.54 Satellite Radio Tracking Techniques (William Strange, U.S.), 2.55 Predictive Models for Space Techniques (Dieter Lelgemann, F.R.G.), 5.64 Determination of Sea Surface To pography (Bruce Douglas, U.S.).
As far as Commission VIII is concerned, its Charter was changed to the following: Develop links between various groups engaged in the field of space geodesy and geodynamics by various techniques, coordinate the work of these groups, elaborate and propos e projects implying international cooperation, follow their progress and report on their advancement and results. To reflect its new role the Commission's name was changed to International Coordination of Space Techniques for Geodesy and Geodynamics (CST G). COSPAR was approached to include CSTG formally in its new organization, and in Budapest, 1980 at its 23rd Plenary Meeting it was incorporated as Interdisciplinary Scientific Subcommission B.2 under ISC B.
In order to establish the links between the various groups engaged in space geodesy and also to promote the use of space technology in the less developed areas of the world the CSTG Bulletin was planned to be published at regular intervals both in Engl ish and Spanish. The Bulletin was to be distributed to all members of the Commission, the main targets being the General Members (see below) who in turn were expected to disseminate the information provided to interested groups in their respective countri es. Originally the Bulletin was to be published twice a year, however, for various reasons in the first twelve years only twelve Bulletins were published and none after. It is the author's hope that with the publication of this issue at least the once per year rate can be maintained from now on.
The new structure of the membership included General Members nominated by the National Committees of the IUGG member countries, a Steering Committee consisting of the chairmen of the relevant IAG SSGs (see the list above), representatives of existing co operative programs (e.g., EDOC, EROLD, Intercosmos), of other IUGG Associations, COSPAR, etc., and International Secretaries, one each from agencies or other organizations which were in charge of major space projects (elected were: Edward A. Flinn, U.S., Jean Kovalevsky, and Alla G. Massevitch, U.S.S.R.). This latter group together with the Commission President formed the Executive Committee.
As originally conceived and reflected in its Charter, it was not CSTG's goal to set up programs on its own or to conduct scientific investigations. The individual contacts necessary to establish scientific cooperation were to be properly maintained throu gh the SSGs, Panels, or Projects. Some of these, where international cooperation/coordination had administrative implications may have become CSTG Subcommissions. In fact, the Projects MERIT and MEDOC have already been established as such in Canberra.
Project MERIT was conceived at the International Astronomical Union (IAU) Symposium No. 82, Time and Earth Rotation in Cadiz, Spain, where it was recommended to set up a Working Group to evaluate the use of space techniques vs. astrometry for Earth rotat ion monitoring. After several meetings the Working Group proposed to the IAU XVIIth General Assembly in Montreal, 1979 to organize the Project Monitoring of Earth Rotation and Intercomparison of the Techniques of Observation and Analysis (MERIT). The Proj ect was officially endorsed and George A. Wilkins of the Greenwich Observatory was put in charge. The objectives of MERIT were to foster the development of new techniques for the measurement of the variations in the rate and axis of rotation of the Eart h, to obtain precise data on Earth rotation in order to increase our understanding of the causes and effects of the variations, and to make recommendations on the observational basis and organizational arrangements for future international services on Ea rth rotation. The objectives were to be accomplished through a set of observational campaigns utilizing all relevant techniques and the evaluation of the results. Project MERIT resulted in the establishment of the International Earth Rotation Service (IE RS) in 1988, replacing the Bureau International de l'Heure (BIH).
Motion of the Earth by Doppler Observing Campaign (MEDOC) under the leadership of F. Nouel, France, had similar objectives. Using permanent Doppler tracking of satellites Earth rotation parameters were provided every other day and through collocations wi th VLBI and laser stations comparisons were made on the terrestrial reference frames defined by each system. Returning to the General Assembly, IUGG adopted a number of Resolutions of interest here:
No. 7 recommended the use of the new Geodetic Reference System 1980, No. 8 invited the IAU to reconstitute Project MERIT and designate it as a joint IAU/IUGG project and urged full technical and financial support to the development and implementation, N o. 11 requested COSPAR to include CSTG formally into its new structure, and No. 12 recognizing the significant contributions of the U.S. Navy Navigation Satellite System and the Defense Mapping Agency to satellite geodesy, urged it to strive for the same high levels in the future both with its current systems and those under development.
IAG Resolution No. 7 recommended that the HIPPARCOS mission be given high priority by the European Space Agency, No. 8 urged the launching of altimeter-carrying satellites, No. 10 invited governments to reobserve regularly geodetic surveys and to monitor crustal deformations using satellite laser ranging and VLBI, No. 13 recommended that a Worldwide Reference Network be established with satellite techniques and VLBI, that such points be well monumented and connected to national networks, that gravity als o be measured at such points and that particular urgency be given to establishing such points in plate tectonic convergence zones and the surrounding known seismic zones. It was on this note that the Canberra Assembly came to a close.
XVIIIth General Assembly, Hamburg, F.R.G., August 15 - 27, 1983
Hamburg has the distinction of being the only city which hosted two IAG General Assemblies. The first in 1912, called the General Conference of the IAG, was the last before World War I and before the first IUGG General Assembly in Brussels, 1919.
The geodetic explosion between the General Assemblies required IAG to organize, the first time in its history, a General Scientific Meeting about half time between the Assemblies in May 1982 in Tokyo, Japan. This was to become a regular event: Edinbur gh, Scotland, in 1989 and Beijing, P.R.C., in 1993. All together 27 specialized symposia took place during the time period, 12 of them space geodesy related. The Cassinis Committee recommended to change the responsibilities and the names of the Sections to fine tune the IAG structure, especially to accommodate the fact that space techniques now cut across the entire spectrum of the IAG organization. The five Sections have become Positioning, Advanced Space Technology, Determination of the Gravity Fie ld, General Theory and Methodology, and Geodynamics.
CSTG has also become a major organization. Its membership completed, its work began in earnest through its project and subcommissions. In addition to MERIT and MEDOC, already in place in Canberra in 1979, the new groups established between the Assemblie s included the African Doppler Survey (ADOS) project, and the Subcommissions on Standards (SCS), Deployment of Transportable Systems (DOTS), International Radio Interferometric Surveying (IRIS), and the IUGG/IAU joint Working Group on the Establishment a nd Maintenance of a Conventional Terrestrial Reference System (COTES). These activities will now be described briefly below.
The need to establish a continental control network for Africa was identified at the 1st U.N. Regional Cartographic Conference in Nairobi, Kenya, 1963. The use of satellites for this purpose was recognized by the 2nd Conference in Tunis, 1966. But it w as only after the 1979 IAG General Assembly, at the request of the Commission on Geodesy in Africa (CGA), that in 1981 an actual campaign was proposed by CSTG to accomplish the above objective. The project with unprecedented international cooperation wa s completed in about five years and resulted in Doppler satellite determined positions of about 1m accuracy for several hundred control points in all African countries but two. The observations were conducted through a sister country arrangement based o n bilateral agreements between the sisters arranged by CSTG and CGA. Four centers were appointed for the computations and inter comparisons: The Regional Center for Services, Mapping and Remote Sensing (RCSSMRS), Nairobi, Kenya, which was also the execut ive body for ADOS under CSTG and CGA, the European Consortium of Belgium, France, F.R.G., and the U.K., DMA, which also provided the precise ephemerides for five NNSS satellites, and the African Consortium of Tunis, Algeria, and the Ivory Coast, under the coordination of the African Association of Cartography. The combination of the results was performed at The Ohio State University. The final report was published by RCSSMRS under the editorship of W.W.L. Chodota, who in many ways was indispensable for A DOS, and presented by him to the General Assembly in 1987.
Technical specifications for ADOS have been established by the SCS created in 1981 under the leadership of Claude Boucher, France. SCS Publication No. 1 and 2 provided respective standards for ADOS field work and data reduction. Subsequent publications, reflecting the work of SCS, included standard exchange format for Doppler (No. 3), and for other related data formats for Doppler and GPS (No. 4). SCS also initiated the description of space geodetic stations participating in international programs (ide ntification, monumentation, local surveys, etc.) in SCS Publication No. 5.
Subcommission DOTS was formed in 1982, after the Tokyo meeting, for the purpose of coordinating the international deployment of mobile laser and VLBI systems which were to come into operation in different countries. DOTS was formally established under th e chairmanship of Peter Wilson and comprised of members of each organization active in developing precise mobile equipment (NASA, NOAA, Delft University of Technology and IfAG, Frankfurt, F.R.G.). Plans were being developed for the deployment of such sys tems in the Eastern Mediterranean and in South America. The former was to support the Working Group of European Geoscientists for the Establishment of Networks for Earthquake Research (WEGENER) project.
Subcommission IRIS was set up in 1983 to review, recommend, initiate, conduct, manage, and coordinate activities deemed beneficial to the development and utilization of Astronomical Radio Interferometry for the practice of geodesy. It's initial primary function was to support multiple technique programs such as MERIT and COTES. The IRIS Steering Committee consisted members from countries in the possession of VLBI, China, F.R.G., Japan, Sweden and the U.S., with William Carter as Chair.
Subcommission MEDOC, now under the coordinator A. Piuzzi, France, was about to start its second experiment, MEDOC 2, after taking into account what was learned from MEDOC 1 (1977 - 1980). This meant to extend the network to about 20 stations distributed around the world tracking two NNSS satellites and reducing the communication delay to one week. The standard exchange format recommended by SCS would be used. MEDOC was to be fully operational and support MERIT until its end, and would be pursued at least for several years after.
Subcommission COTES (establishment of the terrestrial reference frame) established at the meeting in Tokyo, May 1982, under the author's chairmanship, was to do what its name implies. At the time the importance of improving the terrestrial reference fram e, especially for precise orbit computations or for many geodynamic applications requiring absolute positions, was not generally recognized. In fact it was extremely difficult to persuade organizations to spend resources for this effort. They were busy do ing other things and did not want to be bothered with things like collocations. Only much later when inconsistencies in the various types of analyses could not be explained away, were observational efforts redirected to take care of reference frame r equirements. Thus COTES should be considered a pioneer, regardless of its short independent life. At the first MERIT workshop in Grasse, France, May 18 - 21, 1981, it was agreed, maybe because the author was in a hospital, to consider ways in which MERIT could be utilized to assist COTES and support its establishment in Tokyo. However, at the second workshop at the Greenwich Observatory (at the time in Herstmonceux Castle), May 15 -20, 1983, it appeared that to join forces would be more effective to acco mplish the objectives of both groups. The Project MERIT/COTES was formed soon thereafter, with George Wilkins as Chairman and the author as Vice Chairman.
Project MERIT in considering how best to achieve its objectives explained earlier decided that it would be appropriate to organize an international program to obtain and analyze data on Earth rotation by both current (astrometry and Doppler) and new (sat ellite and lunar laser and VLBI) methods. The group organized a preliminary, short campaign that would test and develop both the techniques and the organizational arrangements that will be required during the main campaign planned for 1983/84. The short campaign was conducted during the three-month period August-October, 1980, and the review conducted during the first MERIT workshop mentioned above. The report on the short campaign and on the workshop was published in 1982. The planning for the main cam paign was accomplished during the second workshop in Herstmonceux Castle. It was decided to observe with all techniques on a regular basis between September 1, 1983 and October 31, 1984, with an intensive period of observations between April 1 and June 30 , 1984 to look for short periodic variations in Earth rotation. Mobile lasers and VLBIs were to support the reference frame effort. It was planned to submit MERIT's final recommendations to the IAU in 1985 and to IUGG in 1987, at the subsequent General As semblies of these Unions.
During this time period the CSTG Bulletin was published five times (# 1 May 1980, # 2 November 1980, # 3 July 1981, # 4 June 1982, and # 5 March 1983, with the Spanish editions following about six months later). These Bulletins reported on practically al l space geodetic activities and plans, totalling 884 pages. They were instrumental as vehicles of communication and in forming links for future international cooperative projects.
The General Assembly in Hamburg elected into the Presidency of IAG P.V. Angus-Leppan, of Section II Richard Anderle, U.S., and of CSTG (under Section II) the author through July 1984, when at the next COSPAR Plenary, Christoph Reigber, F.R.G. was to take over. The new CSTG Executive Committe was then to include Surya Tatevian, U.S.S.R., Y. Kozai, Japan, the author and of course Reigber.
The IAG at this point had eight Commissions, unchanged since Moscow, and 36 SSGs. Of the latter relevant to the subject of this note (which is becoming intolerably long for a note) were the following: 1.75 World Vertical Reference System (R.H. Rapp, U. S.), 1.76 Positioning with GPS (C.C. Goad, U.S.), 2.54 Satellite Radio Tracking Techniques (B.E. Schutz, U.S.), 2.80 Lunar Laser Ranging (R.W. King, U.S.), 2.81 Specifications of Methods for Handling Systematic Errors Arising from Satellite Laser Ranging Instrumentation (J. Gaignebet, France), 2.82 Compression and Smoothing of Data Obtained from Space Techniques (D. Lelgemann, F.R.G.), 2.84 Atmospheric Effects on Geodetic Space Measurements (F. Brunner, Switzerland), and 4.94 Theory of Geodetic Refere nce Frames (J. Wahr, U.S.).
As far as resolutions are concerned IUGG Resolution No. 1 considered the success of ADOS, urged all organizations to support follow-up activities, such as training seminars and coordinating the various geodetic networks in Africa. No. 2 noted the forthc oming discontinuation of the NNSS and the development of GPS and GLONASS (the USSR's Global Navigational Satellite System), strongly urged that these systems made available to the scientific community for maximum accuracy positioning. No. 3 recommended t hat all analyses using data obtained during the MERIT campaign adhere to the MERIT Standards document. No. 5 requested the World Meteorological Organization to make every effort to collect the most complete possible set of observations during the MERIT i ntensive campaign for the purpose of studying possible correlation between the observed short periodic variations in Earth rotation and in the atmospheric angular momentum.
IAG Resolutions which shed light on the state of the art at the time included No. 3 which considered the importance of programs such as the MERIT/COTES and the Crustal Dynamics Project of NASA and urged the participating countries to devote utmost care to station selection, monumentation etc., so as to enable unambiguous reoccupation of the sites. No. 5 recommended that particular efforts be made to group radio and laser tracking systems at common sites with emphasis on achieving global coverage f or the collocated systems. No. 7 recommended that national authorities extend their support for the development and operation of precise space-related positioning systems, such as laser ranging and VLBI.
XIXth General Assembly, Vancouver, B.C., Canada, August 10 - 22, 1987
After 30 years (longer than one professional life time), IUGG returned to Canada for another General Assembly. Since the last Assembly IAG sponsored an unusally large number (37) of symposia and other meetings of which 12 were related to space geodesy. I n addition to partaking in these scientific gatherings, CSTG's life continued through its Projects, Subcommissions and Bulletins.
The ADOS project was reviewed at the 3rd Symposium on Geodesy in Africa, April 1986 in Yamoussoukro, Ivory Coast. The 10 remaining countries were urged to cooperate. Final strategies for the analysis and publication were discussed at the 4th Internation al Symposium on Satellite Positioning in Austin, Texas in May 1986. At the end 45 countries carried out ADOS observations and over 275 (monumented and documented) stations were established. The various African geodetic datums could be unified. The final r eport was presented to this General Assembly. The project was followed up by two training seminars, one in English in Nairobi, and one in French in Yamoussoukro.
Project MERIT/COTES also came to the final reporting stage. The data obtained during the main campaign and the overlapping intensive campaign were analyzed by two or more independent centers for each technique and it became clear that satellite laser ran ging and VLBI were able to provide more precise estimates of polar motion, Universal Time, length of day and station coordinates than optical astrometry and Doppler tracking could, which were the primary contributors to the international services (BIH and the International Polar Motion Service, IPMS) before 1980. This conclusion has been officially arrived at the MERIT Workshop and Conference held at The Ohio State University, Columbus, July 29 - August 2, 1985, where a draft recommendation on the technic al and organizational concepts of a new International Earth Rotation Service (IERS) were prepared. The recommendations and the final report were endorsed by the IAU during its XIXth General Assembly, New Delhi, India, November 1985 and now they were prese nted to this General Assembly for endorsement. As mentioned earlier the IERS started its operations on January 1, 1988.
Subcommission MEDOC in view of the above developments was dissolved and CSTG at this point comprised five subcommissions: SCS (Standards) and IRIS (Radio Interferometric Surveying) continued under the leadership of Claude Boucher and W.E. Carter. The l atter started its monthly IRIS Earth Orientation Bulletin with issue No. 1 in March, 1984. It continued through December 1994 (No. 130).
Subcommission DOTS (Deployment of Transportable Systems) became a victim of restructuring (a term coined and the method widely used internationally much later). Firstly, it was considered more effective to transfer the responsibility for the transporta ble VLBI systems from DOTS to IRIS. There was also an urgent requirement for an efficient international coordination of laser tracking activities with both fixed and mobile stations. Thus for this purpose a new Satellite Laser Ranging Subcommission (SLRS) was formed under the chairmanship of B. E. Schutz in 1986. SLRS was considered an extension of such a coordination already performed by him at the University of Texas, Austin during the MERIT/COTES activity. The primary objectives were to coordinate and assist in planning activities of individual stations and networks for the optimal collection of data and to provide a forum for discussion of station operations and the development of standards. SLRS was to play an important role of tracking current and future laser reflector equipped satellites, such as the twins ETALON-I and II (launched in 1989), the twin of STARLETTE STELLA (1993), LAGEOS I (1976) and II (1992), and others such as AJISAI (1986), ERS-1(1991), TOPEX (1992), GFZ-1 (1995), or the GLONASS and certain GPS (PRN-5 (1993) or PRN-6 (1994)) satellites, or METEOR-3 (1994).
The fourth Subcommission International Campaign for Optical Observations of Geosynchronous Satellites (COGEOS), was actually formed before SLRS, in 1985 under the leadership of Anna M. Nobili, Italy, for the purpose of organizing a long term internationa l camera tracking campaign of geosynchronous satellites in order to determine resonant geopotential harmonic coefficients and their time variations. The fifth GPS Subcommission to promote international projects useful to the development and utilization of GPS for geodesy and geodynamics was chartered at the end of the Assembly and chaired by Gerald L. Mader of NOAA.
CSTG Bulletins published during this time period included # 6 December 1983, # 7 December 1984, # 8 November 1985, # 9 March 1987. The Spanish editions were delayed because of difficulties finding resources, but were published eventually in 1987/88. Just as before the four issues of the Bulletin covered the entire spectrum of space geodesy on a total of 974 pages.
Presumably as a punishment for his roles in IAG activities such as ADOS, MERIT/COTES, CSTG and the Bulletin Geodesique, the General Assembly elected the author as the next IAG President, a sure sign of going downhill. Barbara Ko aczek, Poland, became Sec tion II President and Christoph Reigber, F.R.G., continued to lead CSTG with the Executive Committee unchanged from the previous period.
The IAG structure at this point included eight Commissions, those listed earlier (Moscow) and the new International Geoid Commission (XII) chaired by Richard H. Rapp, U.S., under Section III, and 33 SSGs. The new SSG structure again reflected changing g eodetic requirements. Of the relevant SSGs formed at the previous Assembly and listed earlier in this paper, 2.80 - 82, 2.84, and 4.94 were discontinued. SSG 1.75 was re-formed into 1.102 Vertical Reference Systems (D. Zilkoski, U.S.), 1.76 was split i nto two: 1.104 Static and Geodynamic Positioning with GPS (Yehuda Bock, U.S.) and 1.105 GPS Kinematic Positioning Methods and Applications (G. Lachapelle, Canada). The new SSGs included 2.106 Determination of Orbits to Centimeter Accuracy (O.L. Colombo, U.S.), 2.107 Gravity Field Determination by Satellite Gravity Gradiometry (R. Rummel, The Netherlands), 2.108 Evaluation of New Concepts of Satellite Systems for Position Determinations (M. Prilepin, U.S.S.R.), 2.109 Application of Space VLBI in the Fiel d of Astrometry and Geodynamics (I. Fejes, Hungary) and 5.123 Definition and Realization of Terrestrial Reference Systems (C. Boucher, France). As before (and as in the future) some of these SSGs proved to be more effective than others!
Light shedding Resolutions included IUGG No. 1 which based on Project MERIT/COTES conclusions, established in cooperation with IAU the International Earth Rotation Service, within the Federation of Astronomical and Geophysical Data Services (FAGS) as of January 1, 1988, and thanked those operating the IPMS and BIH for their services now discontinued. No. 4 recommended that space agencies should continue to develop a dedicated gravity mission. IAG Resolution No. 1 recommended that all GPS investigators adopt the FICA (Floating point, Integer, Character, ASCII) format and that conversion software to create such formatted records be developed!
XXth General Assembly, Vienna, Austria, August 12 - 23, 1991
Vienna never hosted an IAG General Assembly before, although the predecessor of IAG, the Europaische Gradmessung held its first General Conference there 120 years ago in 1871.
Although a new Cassinis Committee recommended changes in the IAG Statutes and By Laws, the division into Sections and Commissions and their designations were not affected. Thus the basic IAG organization is to continue as before at least through 1999. On the other hand, the SSGs' lifetime are to be limited generally to a single period of four years. The IAG sponsored symposia and other meetings between the General Assemblies this time numbered only 26 of which eight were related to space geodesy, inclu ding those held during the General Scientific Meeting in Edinburgh, Scotland, August 3 - 12, 1989. Were things slowing down?
As during the previous period CSTG's work continued through its Subcommissions, which met regularly, and through its publications. There were no CSTG projects in progress, although both the WEGENER and the Intercosmos IDEAL (Investigation of the Dynamics of the European Asian Lithosphere) projects received great support from the CSTG Subcommissions.
Subcommission IRIS under the Chairman James Campbell, F.R.G., operated four major network programs primarily for regular 24 hour observing sessions at certain intervals (once every 5 - 30 days): IRIS-A (Atlantic) with three VLBI stations in the U.S. (We stford, Richmond, Mojave) and two in Europe (Wettzell, Onsala), IRIS-P (Pacific) with two stations in the U.S. (Fairbanks, Mojave), and one each in Japan (Kashima) and in Tasmania (Hobart). IRIS-S (South) with the three IRIS-A U.S. stations, Wettzell and Hartebeesthoek, South Africa, and IRIS-I (Intensive) for daily one hour sessions on the Wettzell - Westford baseline for high resolution UT1 determination. The IRIS network had also been occasionally extended to include three stations (Medicina, Noto, Ma tera) in Italy. IRIS also continued to cooperate with the five station NAVNET operated by the U.S.Naval Observatory (USNO). A 1985 agreement to make optimal use of the resources of the IRIS-A network and NAVNET resulted in the National Earth Orientation S ervice (NEOS) in the U.S.
Satellite laser ranging performance has steadily improved and new third generation systems have begun operations, some of them performing at the 1 cm (1 mm for a normal point) or better precision. New transportable lasers also began operations includin g those from Japan (HTRLS), from Europe (MTRLS) and the NASA TLRS systems. Two-color laser experiments have been initiated by NASA and the French space agency. These new developments kept the SLR Subcommission busy. Six Subcommittees were formed: Format f acilitated the adoption of formats. Operations fostered laser system characterizations. Collocations developed a Standard Collocation Plan. Normal Points promoted extensive normal point tests and evaluation. Data Collection and Distribution promoted wide and easy access to SLR data. The Subcommission published six issues of its widely distributed SLRS Newsletter for the purpose of disseminating information within the SLR community.
The sixth Site Issues subcommittee evolved into a separate CSTG Subcommission on Space Geodetic Measurement Sites (SGMS) under the chairmanship of John Bosworth of NASA in 1989 because of the broad nature of site issues which required interaction between the VLBI, GPS and SLR systems. The SGMS structure included Committees on Site Cataloging, Site Surveying Standards, Site Occupation Documentation, and Site Selection, Stability and Monumentation. The very active group met twice a year and published four issues of the SGMS Newsletter, distributed to 350 addresses in 32 countries.
The proliferation of GPS activities and the lack of coordination lead the GPS Subcommission to concentrate on issues of standards and formats. The MERIT Standards were selected and promoted for GPS data analysis. An effort was made, together with SSG 1.1 04, to evaluate various software packages in general use by distributing a standard data set. The FICA data format created for easy exchange of data obtained by various types of receivers was found to be impractical and a new Receiver Independent Exchange Format (RINEX) was recommended for this purpose, while the FICA was retained for archiving. The fifteen issues of the GPS Bulletin published by the Subcommission were of great importance in promoting these ideas. The Subcommission played also an import ant role in the creation of the Cooperative International GPS Network (CIGNET), which continuously operated GPS receivers mainly at VLBI and SLR sites (15 stations) for the purposes of defining a GPS terrestrial reference frame and of providing GPS satell ite ephemerides. The CIGNET data were delivered daily to the National Geodetic Survey/NOAA where the computations were performed. The CIGNET experience was used in 1990 - 91, when IAG initiated discussions and issued a Call for Proposals for a MERIT type of test campaign leading to the establishment of the International GPS Service for Geodynamics (IGS) on January 1, 1994.
CSTG Bulletins published during this time period included # 10 June 1988, # 11 June 1989 and # 12 September 1991, the Spanish edition following in about a year later.
The General Assembly elected into the Presidency of IAG Wolfgang Torge, F.R.G., of Section II Christoph Reigber, and of CSTG Bob E. Schutz. The CSTG Executive Committee now included Ch. Reigber, B.E. Schutz, Artur Stolz, Australia and Y. Yatskiv, Ukraine . The IAG structure was reduced to eight Commissions (No. VI was discontinued), 29 SSGs, and four Special Commissions (SCs), basically SSGs of longer missions. The SC category was established the first time in Vienna upon the recommendation from the Cas sinis Committee.
The SSG structure changed considerably since Vancouver. Of those listed in this paper as relevant to the subject matter, SSGs 1.102, 1.104, 2.106, 2.108 and 5.123 were discontinued. Continued under different Chairs were 1.105 (H. Landau F.R.G.), 2.107 (J .O. Schrama, The Netherlands), and 2.109 (J. dßm, Hungary). New SSGs included 1.126 Permanent GPS Arrays (Y. Bock), 1.127 Error Propagation in GPS Networks (L.W. Baran, Poland), 2.130 Non Gravitational Force Modeling Effects on Satellite Orbits (J. Ries , U.S.A.), 2.131 Spaceborne GPS/GLONASS (T. Yunck, U.S.A.), 2.132 Time Varying Gravitational Effects on Satellite Orbits (C. Shum, U.S.A.), 2.151 Altimetry: Optimal Processing for Geodesy, Geophysics and Oceanography (W. Bosch, F.R.G), and 5.143 Rapid Earth Orientation Variations (J.O. Dickey, U.S.A.) joint with IAU. In addition, the SC 6 WEGENER Project (P. Wilson, F.R.G) was created.
Of the Resolutions adopted by the General Assembly and relevant to CSTG were the following: IUGG No. 2 endorsed the definition of the Conventional Terrestrial Reference System (CTRS) as adopted by the XXIst IAU General Assembly, Buenos Aires, 1991, No. 3 recommended the establishment of SSG 5.143 jointly with IAU, No. 5 recommended that the concept of IGS be explored by means of test campaigns during which the global VLBI and SLR systems should also be used for intensive observing campaigns. IAG Resolut ion No. 1 recommended implementation strategies for the establishment and use of the CTRS as defined by the IUGG and IAU, and No. 3 recommended the continuation of observations at existing Lunar laser stations and the establishment of new stations to imp rove global distribution.
XXIth General Assembly, Boulder, Colorado, July 2 - 14, 1995
After 32 years the IUGG reconvened its General Assembly in the U.S. Originally the 1987 Assembly was to be held here, with the idea that at least one of these meetings should be held in one professional lifetime, but the U.S. National Committee for the I UGG yielded to the Canadian request and at the end did not submit a formal invitation.
Since the last Assembly CSTG continued its routine work mostly within its four Subcommissions of which two elected new Chairs: T. Yoshino, Japan, for IRIS and John Degnan of NASA for SLRS. A workshop IRIS '93 was held in Tokyo. A number of new permanent VLBI sites were established and several sites were visited with mobile systems. Although these developments appeared to be promising, paradoxically funds for running the stations and correlating the observations appeared to be drying up! The final IRIS B ulletin was published in December 1994. SLRS and SGMS continued to publish their respective Newsletters. The thick SLRS Newsletter appeared twice in November 1993 and July 1995, while the SGMS Newsletter was published at a frequency of about one or two per year. GPS Subcommission activities seemed to be absorbed by IGS.
In the GPS area, probably the most significant event was the IGS test campaign conducted between June 21 - September 21, 1992 to verify the proposing organizations' ability and willingness to perform. The campaign was highly successful to the point th at in order to avoid interruption it evolved into the IGS Pilot Service and on January 1, 1994 into the permanent IGS. Since then the Service provides GPS precise ephemerides, clock and Earth rotation parameters all available within two weeks. More recent products are weekly coordinates for the IGS Network of more than 75 globally distributed stations. The General Assembly elected Klaus Peter Schwarz, Canada, as the next IAG President, Reiner Rummel, F.R.G., as Section II President, and Gerhard Beutler, Switzerland, as CSTG President continuing also as Chair of the IGS Governing Board.
IAG became meaner and somewhat leaner after it undertook a major reorganization of its Commissions, SCs and SSGs, ending up with six Commissions, seven SCs and 23 all new SSGs. The two out of Section Commissions (IX and XI) and all SSGs were discont inued. SC 6 WEGENER Project continued under S. Zerbini, Italy. Upgraded from SSG 2.107 to SC 7 was Gravity Field Determinations by Satellite Gravity Gradiometry (H. Ilk, F.R.G).
Of the new SSGs relevant to this paper, and reflecting the ever changing trends of space geodesy, were the following: 1.159 Use of GPS Positioning for Atmospheric Monitoring (M. Bevis, U.S.A.), 2.160 SAR Interferometric Technology (R. Klees, The Nether lands), 2.161 Spaceborne Atmospheric Sounding (C. Rocken, U.S.A.), 2.162 Precise Orbits Using Multiple Space Techniques (A. Marshall, U.S.A.),
It was at this Assembly where both the IUGG and the IAG Executive Committees finally and rationally recommended only a minimum number of Resolutions (seven each). Of those indicating the current state of affairs were IUGG No. 1 which requested national a gencies to contribute to the operation of the IERS by providing observations and products in compliance with IERS strategy (a plea for increasing the VLBI effort?), and No. 2 which recommended the implementation of a dedicated gravity mission (a wish al ready recommended as IUGG No. 4 in 1987!).
This note should end with a paragraph on CSTG. After the elections were over and the resolutions passed, CSTG's new President and the Subcommissions got down to work. IRIS voted to change its name to Subcommission on VLBI (Tom Clark of NASA, Chair). SLRS' scope was broadened to include lunar laser ranging and it continued as Subcommission on Satellite Laser Ranging and Lunar Laser Ranging (John Degnan). The GPS Subcommission was replaced by the Subcommission on Precise Satellite Microwave Systems (Pa scal Willis, France) to recognize the fact that although IGS absorbed much of the GPS work other systems such as GLONASS, DORIS, and PRARE should have a home within CSTG. SGSM was also renamed Earth Science Sites Subcommission (John Bosworth) presumably in expectation of multiple geophysical instrumentation at the space geodetic sites. In addition the Project Coordination and Combination of the Analysis in Space Geodesy was established under Tom Herring, U.S.A. to encourage common processing strategies and common observations.
The new CSTG appears to be energetic, restructured and on its way. Its newly conceived role today and in the near future, together with objectives for the next quadrennium are described in another article in this volume by G. Beutler and H. Drewes, CSTG's new President and Secretary, respectively. The author wishes them great success in continuing the great traditions of Commission VIII, and .....We shall see, as blind men say!
Travaux de l'Association Internationale de Geodesie, Tome 23-29, 1968 - 1992
Bulletin Geodesique Nos. 47/48, 58, 70, 86, 87, 102, 118, Vol. 50 No. 1, 54 3, 58 3, 62 3, 66 2, 1958 - 1992 CSTG Bulletins # 1 - 12, 1980 - 1991
World Wide Web home pages:
http://www.gfy.ku.dk/~iag/ - International Association of Geodesy
http://cddis.gsfc.nasa.gov/ Crustal Dynamics Data Information System
http://igscb.jpl.nasa.gov/ - International GPS Service
http://www.dgfi.badw-muenchen.de/cstg.html CSTG
Ivan I. Mueller, Professor and Chairman Emeritus, Department of Geodetic Science and Surveying, The Ohio State University, Columbus, OHá43210; U.S.A.; Fax: 001 - 614 - 292 2957; Tel.: 001 - 614 - 292 2269; e-mail: mueller@mps.ohio state.edu