The observational data are taken from various sources:
- first from printed publications (scientific journals) and electronic publications.
- second from internal publications or notes, more difficult to obtain, for example in Scientific papers deposited in ALL RUSSIAN INSTITUTE OF SCIENTIFIC AND TECHNICAL INFORMATION. Data are regularly taken in electronic form from the Minor Planet Electronic Circulars (MPEC). Some portions of observations come as messages from the Minor Planet Center (MPC).
- third, directly from the observers who send their data to NSDC. In that case, they are asked to provide all the necessary information on their observations, which will be put in the file of description of the data.

Private published databases of observations.
Our database contains data from several databases of observations of some groups of satellites, which were composed by researchers who used the observations to improve satellite orbits using their own theories. These data either did not have bibliographic references to the sources where the observations had been published or these references were incomplete. When we have found complete bibliographic references to all published observations, we included them into the files of description of observations (Content). Formats of such observational data were taken as close as possible to the initial data formats.
We have used the following private databases of observations:

• The catalogue of observations of the Martian satellites published by Morley T.A. A catalogue of ground-based astrometric observations of the Martian satellites, 1877-1982, Astronomy and Astrophysics Supplement Series. 1989. vol. 77. n. 2. p. 209-226.
  This database contains observations made from 1877 to 1982 in 23 observatories located worldwide. T.A. Morley's database has 2212 positions of Phobos and 2600 positions of Deimos relative to Mars as well as 100 mutual positions of the satellites. We managed to find only 3 sets of observations with a total number of satellite positions of 34, which were made from 1877 to 1982 and were not in the catalogue of T.A. Morley.
• A catalogue of observations of Phobos and Deimos provided to us by V.A. Shor. This catalogue had been collected to improve the orbits of the satellites. The results of this work were published in the paper: Shor V.A. Refinement of the orbits of Phobos and Deimos using ground- and space-based observations. Pis'ma v Astronomicheskii Zhurnal. Vol. 14. S. 1123-1130.
  Almost all observations from the catalogue of V.A. Shor made prior to 1983 were in the catalogue of T.A. Morley. We have compared other observations from V.A. Shor's catalogue with the publications of these observations and included them into our database as independent sets of data.
• A catalogue of observations of the Galilean satelites of Jupiter made up by J.-E. Arlot. These observations have been pubished in his Ph. D.: Arlot Jean-Eudes (1982) Amelioration des ephemerides des satellites galileens de Jupiter par l'analyse des observations. These de Doctorat d'etat, Obs. de Paris.
  This set of data contains 3916 positions of the four satellites. The observations have been carried out from 1891 to 1978 in 17 observatories all over the world.
• A catalogue of observations of the eight outer Jovian satellites made up by P. Rocher. Part of these observations was taken from the paper:
  Bordovitsyna T. V. and Bykova L. E. Teorii dvizheniia i efemeridy VI i VII sputnikov Iupitera na 1979-2000 gody. Tomsk : Izd-vo Tom. un-ta. 1978.
• Observations of four out of eight satellites from the catalogue of P. Rocher were used during the construction of numerical model of motion of the satellites. This work is described in the following paper:Rocher P., Chapront J. Observations and ephemerides of the faint satellites of Jupiter. Astronomy and Astrophysics. 1996. v.311. p. 710-714.
  The catalogue of P. Rocher has 1433 observations of the eight satellites made from 1894 to 1993 at 24 observatories located all over the world. We have found 84 bibliographic references of publications of these observations.
• A catalogue of observations of the major Saturnian satellites made up and described in the following paper: Strugnell P. R., Taylor D. B. A catalogue of ground-based observations of the eight major satellites of Saturn, 1874-1989. Astronomy and Astrophysics Supplement Series. 1990. v. 83. n. 2. p. 289-300.
  This catalogue has 26393 observations of the eight major satellites of Saturn made from 1874 to 1989 at 28 observatories located all over the world.

• International Astronomical Union Circular (IAUC)
• Minor Planet Electronic Circulars (MPEC)
• Electronic data at CDS associated to papers published in scientific journals

1. Results of observations.
2. Osculating Keplerian elements of satellite orbits.
3. Satellite ephemerides calculated using formulae of Keplerian motion on the basis of determined orbital parameters.

Observational data available on-line at the Web sites of observers.
In some cases observers publish description of their observations in scientific journals and put their data in their Internet Web site, for example there is a Web site ftp://ftp.nofs.navy.mil/pub/outgoing/plansats. The corresponding paper is: Stone R.C., Harris F.H. (2000) CCD Positions Determined in the International Celestial Reference Frame for the Outer Planets and Many of Their Satellites in 1995-1999. The Astronomical Journal. 2000. v. 119. p. 1985.

Observational data from scientific journals.
Some scientific journals (e.g., Astronomy and Astrophysics) publish papers whose text is in the journal itself while large tables are placed at the journal's Web site. The article has corresponding Web links. In this way results of observations of planetary satellites are also published. An example: Fienga A., Arlot J.-E., Baron N., Bec-Borsenberger A., Crochot A., Emelyanov N., Thuillot W. CCD observations of Phoebe, 9th satellite of Saturn. Astronomy and Astrophysics. 2002. v. 391. p. 767-773.
The table with coresponding observations (plain text file) is available on-line at http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/767.

Observational data entered manually from publications.
A significant number of sets of observations were added to the database manually. From recently, we made scanning and automatic text recognition to convert printed data into digital form. The numerical data are carefully verified after the conversion.

Observational data from observers.
Some observational data are obtained directly from observers as plain text files. A file describing the data is then necessary for use.