Databases (NSDC) of the Natural Planetary Satellites.

Principles and purpose of the project

NSDC: Database of astrometric observations of Natural Planetary Satellites


Why such a database?
The pecularity of the dynamics of the natural satellites is such that for the determination of their orbits and calculation of ephemerides all observations that have been made after their discovery are necessary . Separate researchers are occupied in improving the orbits of different groups of satellites. They are thoroughly looking for observations in different sources, creating their owndatabases which are then mostly inaccessible to other researchers. Creation of such database is a laborious process which includes manual entries of data from publications, contacts with lots of observers, collecting data files, unification of data formats, taking into account different non-standard reductions. That is why there is a necessity for the creation of one unique database of all observations of all planetary satellites.

Requirements for the database.
The database must have the following properties: it should contain all satellite observations ever made in the world, be accessible to any interested person, have standard and yet flexible format, and expand constantly as new observations appear.

Entering and Formating Data.
Data were taken so that all numerical values be transferred from publications or primary sources into the database without any modifications, since all possible subsequent reductions of observations would have been ambiguous because they depend on the current models of celestial coordinates and time scales. On the other hand, it should be clear to the user of the database which standards were applied by the observer when the results were published. Such an approach lead to the fact that each set of observations of planetary satellites that were entered into the database consists of two files. The first file ("content") contains description of the observational results (observed satellites, adopted coordinate system and time scale, observatory name and code, telescope parameters, data format, etc.). The second file ("data") contains numerical values and is intended for reading by calculating programs. The division of data into several sets is determined simply by the data source and by the order in which they went into the database. In the file "content" with explications, the reference is given to the data source as well as the bibliographic reference. This reference is provided with a hyperlink which may be used to call the corresponding reference from the bibliographic database. From there, it is possible to pass this reference to the ADS Abstract Service bibliographic database where the electronic version of the publication is accessible.

Data sources.
Observations are taken from different sources, from both printed publications (scientific journals) and electronic publications. Some files are obtained directly from observers. A search for observations was also made in difficult to access publications, for example in Scientific papers deposited in ALL-RUSSIAN INSTITUTE OF SCIENTIFIC AND TECHNICAL INFORMATION. Data are also taken regularly in electronic form from the Minor Planet Electronic Circulars (MPEC). Some observations are received as mails from the Minor Planet Center (MPC).

Current composition of the database NSDC.
By now our database contains about 90% of all observations of natural planetary satellites available worldwide. These are 95,127 satellite positions divided into 231 sets.

NSDC: Bibliographic database.


Why a specific bibliographic database for Natural satellites?
Since there is enormous amount of publications, the work with the bibliography becomes a very laborious process. So the optimal choice of range of scientific field in which search is made becomes very important. Creation of a well thought-out system of keywords can make search for a pubication considerably easier.

Creation of the bibliographic database.
In 1996, decision has been taken in IMCCE to create the bibliographic database for studies on natural planetary satellites. For this scientific field a special system of keywords has been developed. Since that time, as a result of cooperation between IMCCE and the Sternberg Astronomical Institute (SAI), the bibliography is being constantly enriched. By now more than 3,000 references on theories of motion, astrometry and observations and more than 6,000 references on physics of planetary satellites have been collected.

Access facilities.
To provide easy access to the bibliographic database through Internet, a special program has been elaborated in SAI. Formulation of inquiry is made using a large number of options. Due to user-friendly interface of the program, user rapidly gets necessary information. Output of unnecessary references is minimized.

Sources of the bibliographic data.
The main source of the bibliographic database is the ADS Abstract Service. References from this database were transformed to change their display. In addition, old keywords assigned by the ADS Abstract Service were completely excluded and, according to the new system, new keywords were assigned. When assigning the keywords, information is used from the titles and abstracts of publications. We also have added considerable bibliography of scientific papers published in less accessible journals such as Scientific papers deposited in ALL-RUSSIAN INSTITUTE OF SCIENTIFIC AND TECHNICAL INFORMATION and others.
More detailed information on the sources of the bibliographic data is available (see "Sources").

NSDC: Parameters - Data on the satellites
and their motion.


Usefulness of such information.
For all researches on the dynamics of the natural planetary satellites it is necessary to have a system -- complete, well organized and easy accessible to any user -- which includes numerous parameters describing physical properties and motion of planets and satellites. Of particular importance is to have the newest data close at hand. We provide such data and parameters for orbits, physics of the bodies (masses, albedos, ...) rotation and poles. We provide also the code of algorithms allowing to calculate the ephemerides.

Available information..
More detailed information on the sources is available in "Sources".

The future development of the service
[image] Evolution of satellite orbits.

Origin of satellites.

Review of the most topical problems.

Studies in progress.