D. TABOADA, R. TABOADA and J. GARCÍA MOLL
The Observation Station for Artificial Satellites located in the city of Puebla, Pue., Mexico, has collaborated for almost five years with the Smithsonian Astrophysical Observatory, Cambridge, Mass., U.S.A in the tracking of artificial satellites by optical means. The creation of the station was begun in August 1957 by Mr. Domingo Taboada, a long time observer of variable stars, at the request of Mr. Leon Campbell Jr., astronomer of the Smithsonian Astrophysical Observatory, in chat of the Moonwatch Program in the United States of America. The collaboration of Mr. Taboada was requested to establish a station in the city of Puebla to observe the Vanguard satellite that would be released during the International Geophysical Year 1957-1958, to form part of the network of the Moonwatch Program, with the assistance of the Smithsonian Astrophysical Observatory in ephemerides and observation equipment.
The stations of that program would scan overlapping areas of the sky along of meridian, each one with a group of observers to maintain a constant watch, at least during the fist orbital stages of the artificial satellites until they wave “acquired”. The basic data of the visual observations would be the “right ascension” and the “declination” of the artificial satellites in the sky as well as the “time” of occupation of that position with reference to a convenient system of coordinates for the calculation of the orbit. Obviously, if such position had to be reported with a minimum precision of 1º of are and 1” of time, it was best to try to observe the satellites while crossing the meridian of the observation station at a great height above the horizon, at down or dusk, when the solar light was reflected on the satellite against a dark sky.
The Moonwatch Program network was composed of station located throughout the wold, making a total of 230 with 70% of them in the United Stated, 10% in Japan and the rest distributed in localities of Australia, South Africa, Europe and Latin American, the station at Puebla being the only one in Mexico. The original group of observers in the station of that city was of 20 persons, all with different occupations and the first reunion took place precisely on October 4, 1957, the day when the first artificial satellite was launched by U.R.R.S.S. This event took the whole world by surprise and originated a great natural curiosity and interest in the observers to see it, although unfortunately it was not visible by naked eye by the group, because of lack of the necessary instruments and of the knowledge if the required observational technique even if the carrier-rocket of this satellite was visible by naked eye and it was never observed.
It must be said that the visual observations of Sputnik 1 were very difficult during the first week in the Western Hemisphere, because it’s crossings did not coincide with the morning or evening twilights. However, on October 10, 1957, a member of the Observation Station for Artificial Satellites of the Moonwatch Program at New Haven, Conn., could catch sight of the carrier-rocket some 1,000 km ahead of Sputnik 1. A 5.5 x wide-field telescope was used to observe the rocket in the northwestern area of the sky at some 40º above the horizon, and its orbit was calculated the following day (October 11) by the Smithsonian Astrophysical Observatory.
With the launching of Sputnik 1 the possibilities of work were enhanced because the necessary ephemerides were available, and finally an observation of Sputnik II was made at 6:05 a.m., on December 14, 1957. This satellite was observed in Puebla during 7 consecutive days by naked eye as a star of 2nd. Magnitud, with a constant variation in brightness possibly due to a rotatory movement around a transverse axis. The measurements then taken were of low quality because of the complete lack of knowledge of the observational techniques, although the satellite was seen in detail and photographed in other places.
As the objective of the Observation Station in Puebla was to cooperate in the visual tracking of the northamerican satellite Vanguard I, its installation was begun on top of the San Juan Hill, located at the west end of the city of Puebla. It was done in accordance with the recommended technique, i.e by placing a cross-like post with its arms oriented from north to south, and 20 6 x elbow reflecting telescopes with 12º of field along the same line scanning a great part of the meridian, approximately 50º on each side of the zenithal point. The installation of the equipment was finished two days before the launching of Explorer I on January 31, 1958, at 10:40 p.m., EST, followed by the launching of Vanguard I and Explorer III, neither of which was within the reach of our instruments due to their small dimensions and to the great height of their orbits, far above calculation.
With the launching of Sputnik III on May 15, 1958, and its carrier-rocket visible by naked eye, a grate practice was obtained during observations which were not made by the cross-like post method, but with a new observations technique which is still in use in Puebla. This technique consists in referring positions of the artificial satellite to the star background which is easily identifiable in a sky chart, and taking the time with chronometer in comparison with the time-signals of WWV Station of the United States of America. The exactitud of the observation was enhanced be measuring the time of the position when the satellite was passing near a bright star or a prominent group of stars (Pl II, Fig. 1).
During the year 1959, due to lack of higher instruments, and because of the small number of artificial satellites released during the favorable epochs, the number of observations until only Mssrs. Taboada (Domingo and Rafael) and García Moll stayed (Pl. II, FIg. 2). In January 1960 the observations of small visual magnitude artificial satellites were begun with 20 x binoculars, and satellites such as Vanguard II and III, Explorer I and even Vanguard I, a small sphere of 15 cm of diameter whose apogee surpassed all calculations and barely had in that position the 11th magnitude were seen. Not only observational techniques were ameliorated, but also data reported by the Puebla Station converted in into one of the best in the world, and brought in August 1960 an investigation ti participate in Project Eco, whose satellite was observed on the very day of its launching, August 25, in 5 consecutive crossing during the whole night (Pl. II, Fig. 3).
In 1951 the Observation Station of the Artificial Satellites in Puebla observed Transit 3B for the fist time in the world was and was one of the three that observed the carrier-rocket of Vostok 1, the firs manned artificial satellite. In 1962 Telstar I was successfully observed during several times, after its launching on July 10 by the NASA an the American Telephone and Telegraph Company Bell Telephone Laboratories for experimental communication repetition. Names, characteristics and number of observations of artificial satellites by optical means in the city of Puebla, Pue., México, between 1957 and 1962 are shown in Table 1.
During the first phases of the Moonwatch Program, and principals during the International Geophysical Year 1957-1958 and the International Geophysical Cooperation 1959, the principal task if the its tracking stations by optical means to follow constantly all launched satellites and to obtain the necessary data to determine the variations of there orbital parameters. When the IGY and the IGC ended stations were requested to continue collaborating in the tracking program with observations of not more than 12 satellites with more or less unstable orbits and of special interest, without stopping observations of recently launched artificial satellites including those entering the denser layers of the terrestrial atmosphere until there disintegration. Of the 230 original stations only 103 continued in the program, and presently there are only 85.
In the las months of 1962 another modification was introduced by transferring 32 of the more important stations, among theme that of Puebla, to the Space Track Group to collaborate in observations of great precision by means of the Baker Nunn photographic cameras. It must be said that some visual observers reached a precision of about 200” of are in the minimum error of position and of less than 1/10 of the error in time, 70% of the observations made in the Puebla Station fall within this range.
It seems that the tracking program has no end and that it continues to be of great importans since its versatility allows observations that can not be made with the photographic cameras. The launching of artificial satellites would be useless without following their trajectory, and their frequent loss requires constant optical observations that may be made in a specially favorable manner in the city of Puebla. Furthermore, it is very important for Mexico and other countries that can thus begin research programs on orbiting satellites and study problems of atmospheric densities, radio frecuency propagation from outside the ionosphere, etc., while not attempting to launch artificial satellites.
D. TABOADA, R. TABOADA and J. GARCÍA MOLL