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The information reveals a miscalculation of only 9 minutes, as the country's Defense Command predicted that the Phobos would fall to 17h51. The Russian military did not report how detected as the spacecraft re-entry, since there was no communication between the control center and the Phobos mission.
Importantly, this is not a failure of Satview, but a normal feature of any program of tracking satellites. Any monitoring system uses so-called "orbital elements" to calculate the position of objects in space. These elements are a series of numbers published several times a day to inform the orbital dynamics of thousands of satellites and debris in space. Through these values the program calculates the position of the object with high accuracy. It is not necessary to use a GPS to know where a satellite is. The orbital elements is enough. However, when a satellite reenters the atmosphere the things change and the softwares do not know that he fell. So continue plotting the sat position on the map. The satellite only ceases to be plotted when the institutions suspend the release of their orbital elements, which can take up to 24 hours. This is done so by Satview, ESA, NASA, Roscosmos, INPE, etc.. As the uncontrolled re-entry is very difficult to predict, the visual accompaniment of a sat near the point of reentry is fundamental. With reports of observers in various parts of the globe is possible to know whether or not the satellite passed over a certain point, increasing or eliminating the chances of re-entry. |
 To track a satellite it is necessary to choose one. That is made by clicking directly on the satellite available on the "Great Visibility" column or after clicking on some of the categories. Once chosen, after a few seconds the program will begin the track the satellite.
On the main screen we can see the World map, where the satellite in movement stands out by two outlined lines. These lines are called "GroundTrack". The red line shows the first 90 minutes of the current orbit and the blue line, the 90 following minutes. Each point represents the position of the satellite at each minute and gets the name of the sub-satellite Point. On the blue screen, right the map, we have the parameters panel, updated every second, which is divided in three main areas, as shown below. Visibility conditions
For a satellite can be observed directly, it is necessary that the sunshine reaches its structure and is reflected into our eyes. For that to take place, it is necessary that the following factors are present at the same time:
When these four conditions are achieved, we say that the satellite will be potentially visible during its passage over our station. Meaning that technically, it can be seen, nevertheless other factors can influence its observation, among them the satellite's altitude and size, its coating material and the atmospheric conditions of the local observation. As a general rule, the closer the satellite passes over our station, the better the observation will be. That closer approach is directly related to the height of the satellite above the horizon line. The angle formed between the satellite and this line is called the elevation angle and the bigger this angle is, the closer to us the satellite will be. The apex of that approach takes place when the satellite is exactly over the zenith, in other words, 90 degrees above the horizon, but not all the passages effectively reach that position.
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