Before 1957, nothing made by human hands existed above our atmosphere. But in that year, the Soviet Union launched the world’s first artificial satellite, Sputnik. Since then, thousands of satellites have been launched into Earth orbit.
TheSkyX downloads orbital elements or two line elements (TLEs) from the web to keep track of up to thousands of satellites and other orbital debris. Using these numbers, TheSkyX can calculate where satellites will appear in the sky for any location on Earth.
To manage which satellites are shown, click the Satellites command in the Input menu.
Figure 36: The Satellites dialog (Satellites command from the Input menu).
Satellite TLE data can be imported from the web or from a text file that contains the properly formatted data. TheSkyX uses orbital element information from Space Command Center's two-line element files (TLEs) to predict and display satellites’ positions. Two-line element data must be updated frequently and is available for most satellites on the web.
Gravitational forces, among other things, constantly perturb the orbit of a satellite around earth, so its position is not precisely predictable over long periods of time.
Current satellite TLE data is retrieved from Dr. T.S. Kelso’s Celestrak web site:
Clicking the Import from Web button shows the Import Satellites from Celestrak dialog.
Figure 37: The Import Satellites from Celestrak dialog.
Turn on the desired categories, then click the Download button to retrieve them from the web. Importing all the satellites will most likely sap your computer’s processor, so choose wisely.
TLE data residing in a text file, rather on the web, can be imported and displayed by clicking the Import From File button. The text file must contain TLE data only. For example, the TLE data for the GOES 2 satellite looks like this:
GOES 2
10061U 77048A 98127.50441330 .00000045 00000-0 10000-3 0 97472 10061 13.1659 29.4732 0005723 183.8196 16.8163 1.00281760 21356
The Status section shows the total number of satellites that were successfully loaded, the average age of the TLE data (the “newer” the better) and the number of TLEs that have been rejected because they are older than 45 days.
Use the Advanced tab on the Find window to locate a particular satellite.
When this option is turned on, satellite positions are computed and displayed on the Sky Chart.
Turn on this option if you want to see where the satellite will be in “near” the future. A line will be drawn on the Sky Chart that represents the path that the satellite will travel.
Enter the length of time, in minutes, of the satellites’ path.
Watching the International Space Station fly overhead is a truly exciting event. TheSkyX can be used to predict when the ISS will travel overhead, and show you its path.
To find the best passes for the ISS, do the following.
Click the Satellites command on the Input menu.
Click the Import From The Web button.
Turn on the International Space Station radio button.
Click the Download button.
Click the Satellites From Above Earth button on the Satellites dialog (lower left corner of the window).
Select ISS (ZARYA) from the list of satellites, then click the Find Best Passes button.
A list of the times when this satellite is visible above the horizon is displayed. Double-click the items in the list to show the pass from an above-Earth perspective. Turn on the Update Chart radio button to show the path on the Sky Chart.
Beginning in 1998, a network of sixty-six communication satellites called Iridium was launched into orbit. At any given time, at least one of them is above the horizon for any location on Earth (not counting the territory around the north and south poles). Sometimes, as an Iridium satellite moves across the sky, sunlight bounces off its antennas and solar panels, creating a brief but brilliant Iridium flare. TheSkyX can calculate when the next flare will be visible from your location (they only happen in early evening or shortly before dawn). Click the Tools > Iridium Flares command to find the next flare that you can observe from your backyard.
Choose the Iridium Flares command from the Tools menu.
Figure 38: The Iridium Flares tab on the Satellites dialog (Tools > Satellites command).
Flares can be located based on what time of day they occur.
Daytime Flares occur between sunrise and sunset
Nighttime Flares occur between sunset and sunrise
Dawn/Dusk Flares occur during the morning and evening hours
Choose the All Flares item to search for flares that occur any time, day or night.
Enter the number of days from now to search for flare events. Flare prediction involves some heavy duty computing, so you may want to limit the length of the search to less than a week so on slower computers.
Mountains, trees or nearby buildings can hide flares that occur at lower altitudes. Enter the lowest altitude that a flare can be seen from where you will be observing.
Enter the magnitude of the faintest flare you want to find. Faint nighttime flares are easy to spot; but if you’re looking for a daytime or evening flare, make sure to enter magnitude minus 2 or brighter (the lower the magnitude, the brighter the flare).
Turn on this option to show a line on the Sky Chart that shows where the flare occurs and how long the flare lasts.
This button resets TheSkyX’s date and time to the computer’s clock.
Click this button to begin the search for flares. Even a very fast computer requires a minute or more to locate all the flares for the next month.
The right side of the window shows a report containing the following information for each flare.
Local time when the flare begins.
Coordinated Universal Time when the flare begins.
Maximum magnitude of the flare.
The altitude and azimuth position at maximum magnitude.
The angle, in radians, between observer's line of sight and Sun, subtended at the satellite.
The name of the Iridium satellite.
The mirror number on the satellite that is causing the flare and its angle.
The Julian date of the flare.
Click a column header to sort the column’s contents from smallest to biggest (an ascending sort). Clicking a particular header more than once will invert the sort. For example, clicking the Magnitude header once sorts the flares from brightest to faintest. Clicking it twice sorts from faintest to brightest (a descending sort).
Now the fun begins. Clicking the Watch Flare button orients the Sky Chart so that the selected flare is visible near the center of the window. If no flare is selected, the first flare in the report will be simulated. A green laser pointer momentarily appears, showing you exactly where to look to view the start of flare. They’re really easy to miss in the actual sky.
The excitement builds as the satellite’s mirror begins to reflect the sun’s light and grow brighter for the next few seconds.
Now that you’ve seen a simulated flare, your goal is to go outside and actually observe the real thing. Take your friends or family along; after viewing the flare, they’ll think you are an astronomy wizard.
Often people who have not studied or practiced astronomy are amazed that many satellites are visible to the naked eye. Most times, satellites are observed by chance when someone looks up and catches a glimpse of something moving among the stars. TheSkyX has a useful tool that aids with satellite observation and can tell you not only when and where to look, but also the name and purpose of many satellites in the sky.
Figure 39: The Satellites Above Earth tab (Tools > Satellites From Above Earth).
To observe satellites, select the Satellites from Above Earth command from the Input menu. If this is your first time using the satellites tool, there will not be any satellites listed, and you will have to download some satellite Two-Line Elements (TLE’s) before any satellite data can be shown. You can think of a TLE as a big set of numbers that describes a satellite’s orbit.
To obtain TLE data, click the Satellites button, or select Satellites from the Input menu. The Satellites window appears. From here, you can choose to import satellite data from the web or an existing file. Later, you can also choose to clear all satellite data by clicking Remove All.
Note: Ensure that TheSkyX’s date is set to within 45 days of the current date to avoid date rejection when downloading satellite for import.
Let’s start by downloading some satellite TLEs from the web. To do this, simply click Import From Web... on the Satellites window. You can then choose the satellite category or categories you wish to download from the internet database, Celestrak. After you have selected the desired satellite categories, click Download.
Return to the Satellites From Above Earth window, and you will see the satellites plotted as points around the Earth globe. Also, note that the satellites are also viewable in the Sky Chart.
On the Satellites From Above Earth window, a list featuring your newly downloaded satellites appears on the left. By selecting a satellite(s) from this list and by clicking Show Selected Orbits. The satellite orbits will appear in the viewer. Sliding the Viewing Distance slider will change the view from a distance of 1 Earth radius up to 50 Earth radii. If your mouse is equipped with a scroll wheel, you can use it to adjust the viewing distance, too. If need be, the lower right corner of the window can be dragged to resize it.
By clicking Update Chart, the Sky Chart is updated to show the recent satellite data from a ground-based perspective. Now you will be able to amaze your friends and neighbors with your uncanny ability to “predict” satellite appearances in the heavens!