Description of Satellite Prediction Output

The first header line gives the date, AM or PM, and the time zone.

   1997 Jan   3  Fri evening  *** Times are PM CET

A second header line gives the titles for each data line.

    H  M  S Name            El  Mag Dir Motion Range
   17:32:54 Cosmos 2313     49  2.4  N    ->RU   559
   17:33:37                 68  1.8  NE   ->R    464
   17:34:19                 50  2.2 ESE   ->RD   553

The H:M:S value is the time of the prediction.

The Name is the name of the object.

The El value is the elevation of the predicted point. The horizon is 0 degrees elevation, the zenith is 90 degrees elevation.

The Mag value is the predicted maximum magnitude. This does not mean that the satellite cannot be brighter or fainter than this magnitude. The satellite can be brighter if it reflects the sun better than expected at this phase angle (possibly because a large flat area like a solar panel is reflecting sunlight). Many satellites are often fainter than this maximum magnitude because they are cylindrical and they often do not have the most favorable possible orientation to reflect the maximum amount of sunlight.

The Dir is the direction to look. The directions are N, NNE, NE, ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW, NW, and NNW. Although these are "compass" directions, they refer to "true north", not "magnetic north".

The Motion value is the direction that the satellite is traveling. The possible values are Up, RU (right and up), R (right), RD (right and down), Down, LD (left and down), L (left), and LU (left and up).

The Range value is the distance from the observer to the object (in kilometers).

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Nominally there will be three predictions for each object. The middle prediction will be the "culmination" prediction and the other two will be equally spaced predictions before and after culmination.

    H  M  S Name            El  Mag Dir Motion Range
   17:32:54 Cosmos 2313     49  2.4  N    ->RU   559
   17:33:37                 68  1.8  NE   ->R    464
   17:34:19                 50  2.2 ESE   ->RD   553

The culmination prediction is 68 degrees up in the northeast, moving left to right. The prediction before culmination is 49 degrees up in the north moving up and to the right. The prediction after culmination is 50 degrees up in the east- southeast moving down and to the right.

There are sometimes objects with only one or two predictions:

   19:15:53 Cosmos 1980 Rk  53  2.8 NNW    Up   1042
   19:17:20                 87  2.1 ENE   ->R    859

In this case, the object will go into the Earth's shadow and become invisible before the third prediction point.

There also may be only one or two predictions if the predicted magnitude for another prediction is too faint (due to range and/or poor phase angle).

Links: to the VSO Home Page, the observing guide, shuttle details, the satellite predictions themselves.

Contact: webmaster@satobs.org