This is the Windows version, there is also a DOS version available.

It can extract elements from practically any DOS Text file (UNIX files will be detected and a "fix" routine will ask for permission to convert to DOS format). You can drag an element file from the Desktop. You can open your web browser or email program or any text source of elements and cut and paste elements from those sources to the program.

Element Manager can manipulate elements in a number of ways. Selections to limit the number of active satellites based on the age, decay, inclination, eccentricity, mean motion, apogee, perigee, argument of perigee, right ascension of ascending node, International Launch Designation, common name, visual magnitude and radar cross section are possible

The program can make selections or exclusions by NORAD number. You can create multiple select files containing lists of satellites you are either interested in or wish to ignore.

The program offers four different views: 3D-Orthogonal View (the Earth is displayed as a sphere and the satellites orbit it); 2D-Equidistance Mercator View (the complete Earth's surface is displayed and the satellites are shown as icons); WDB-Equidistance Mercator View (it is possible to zoom into it and display just parts of the world's surface with geopolitical details); and Observer's view (useful if you want to know where you have to look to see a satellite). Each of this views offers a bunch of moving around features.

Notice that you can use this program not only for the GPS-satellites but for all other satellites as well, since it uses the standard NORAD two line elements files. We found it rather prone to crashing.

New in version 2.4 is the Weather dialog and the Internet dialog. Check them out. I did also some major internal restructuring on the graphics engine so that you can now use JPEG, GIF, EMF, WMF, TIFF, PCX, and BMP as Textures. The program needs Windows NT/95, the OpenGL DLL's and a color depth of at least 16 bit (65535 colors).

ObsReduce supports all three reporting formats in common use: IOD, UK and RDE (Russell Eberst's abbreviated form of the UK format.) All R.A. and Dec formats and epochs are supported, as are visual magnitude and optical period reporting.

Also supports three observational geometries: satellite in-line with reference stars, satellite forming right-angled triangle with reference stars, and appulses (satellite passing near a single star).

Several star databases, derived from the Tycho 2 catalogue, are available for ObsReduce. The complete set of Tycho 2 stars is also available, consisting of more than 2.5 million stars to about magnitude 13. The program enables the addition of stars missing from the database, as well as coordinates of planets and asteroids.

To aid in finding and confirming reference stars used in observations, ObsReduce has the ability to display predicted satellite tracks computed using the SGP4 and SDP4 orbital models. It also displays the difference between the satellite's predicted and observed time and track, and can compensate for Earth's rotation in the interim, to produce accurate plots of satellite tracks.

- pass prediction results are presented in four modes: text/tabular, two local sky simulation modes, «satellite over an Earth map» mode;

- able to syncronize the PC clock with NTP servers over the Internet;

- able to self-update the TLE files;

- very easy to use and handle (especially for beginners);

- it is principally made for visual observing (namely for the ISS with a magnitude up to -1).