Satellites plugin

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Revision as of 08:07, 29 January 2010 by Matthewg42 (Talk | contribs)
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Contents

Introduction

The Satellites plugin simulates satellites in Earth orbit. Satellite orbits are not very precisely predicted using the existing orbital models for the planets, as there are other factor involved - irregularities in the Earth's gravitational field, lunar interactions, atmospheric drag and so on.

This plugin implements the SGP4 and SDP4 models, and takes as it's input data NORAD TLEs (two line elements). TLEs for hundreds of satellites are available online and are regularly updated.

Usage

Enabling the Satellites plugin

This plugin comes bundled with Stellarium version 0.10.3, although it is not enabled by default. To enable the plugin, open the configuration dialog and go to the plugins tab. Click Satellites from the list of available plugins and check the load at startup checkbox. You will need to re-start Stellarium for changes to take effect.

Using the Satellites plugin

To see the position of artificial satellites, you must have the observer location set to Earth. You must also turn on Satellite indicators on the main tool bar as shown in the image below:

sat_howto_02.jpg

Searching for satellites

It should now be possible to search for artificial satellites using the regular search dialog (F3). Note that at any given time, most Satellites will be below the horizon.

sat_howto_03.jpg

Diaplaying satellite data

When you have selected a Satellite, information about it will be shown just as for any other object which is selected. This includes:

  • Normal positional data (RA/Dec, Alt/Azi and so on)
  • Range in kilometers. This is the line-of-sight distance between the observer and the selected satellite
  • Range Rate in kilometers per second. This is the closing/parting speed of the satellite. It is useful when calculating doppler shift necessary for communications (and is also just nice to know)
  • Altitude of the satellite above the ground in kilometers
  • Comms data. Some satellites broadcast on frequencies which can be received by the general public or used by amateur radio operators. Where such data is known about a satellite Stellarium will show it.


sat_howto_04.jpg

Configuration

When the satellites plugin is loaded, the configuration button in the plugins tab of the configuration dialog will be enabled. Clicking this button (or pressing Control+Shift+Z) will open the configuration dialog for the satellites plugin.

Settings tab

In the settings tab you can control how often the Satellites plugin downloads updates for the TLE elements of known satellites. The default is every 72 hours. If an update is due when Stellarium is started, it will commence 30 seconds or so after the plugin is loaded.

sat_howto_05.jpg

Satellites tab

The Satellites tab shows data on known satellites and lets you choose which ones are visible. Note that for each satellite which is visible, Stellarium must do extra work to calculate and show the position of the satellite. If Stellarium is running very slowly with the Satellites plugin enabled, try reducing the number of satellites which are visible.

You can select and go to a satellite by double clicking it in the list.

At time of writing, this dialog is only doe display information about satellites and changing their visibility. In future it will be possible to edit descriptions, comms data and so on, but this is not yet implements.

sat_howto_06.jpg

Sources tab

The Sources tab lets you see (and modify) where Stellarium is getting its TLE data from. The default is a list of sources from celestrak.com.

sat_howto_07.jpg

Adding new Satellites

At time of writing, there is no simple way to add and remove satellites using the GUI. However, you can modify the satellites.json file manually using a text editor.

This this method you can edit the tags for a satellite, modify the description and comms data, and even add new satellites.

TODO: PLEASE SOMEONE WRITE A NICE GUIDE FOR THIS

TODO: Provide download links for alternative satellites.json files which include specialist lists of satellites.

TODO: Find alternative Sources lists.

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