Satellite AR: Satellite tracking with augmented reality on Android

Satellite AR

Point your Android phone at the sky and see actual satellites flying overhead.

About this app

Ever wondered what satellites are flying above your head when you look up? This app will show them to you using augmented reality. Point your phone's camera to the sky, and small icons track the locations of various satellites. For many, a line indicates their projected path across the sky. Those flying in sunlight are labeled in yellow, and those in the shadow of the Earth or Moon, in blue.

This yellow and blue coloring is useful to casual observers who go out looking at the night sky for satellites. Typically, those in shadow (blue) are not visible at all, while satellites in Sun (yellow) may be visible even to the naked eye, depending on size, altitude, and other factors. The best time to spot satellites is often just after dusk or just before dawn, when the Earth's shadow is at a steep enough angle from the observer's point of view that the satellites above are still lit by direct sunlight.

The app also contains a simple star map. The brightest 2000 stars are shown as white dots on the screen, to help the user align the app's display with the sky above.

Compass calibration

The compass (or magnetometer) in most mobile devices can be automatically calibrated by waving the device around in all three dimensions, usually in a figure-eight pattern, while the compass is active. This is a difficult motion to describe, but there are various YouTube videos and other online resources to demonstrate it.

In the case of the Satellite AR app, this motion must be done while the app is in the "view satellites" mode, where you see the sky or a star map that rotates itself in accordance with the compass. A small message at the bottom of the display warns if your compass calibration is poor. This message disappears once the compass reports good calibration.

Usage tips

  • Satellites - There are thousands of active satellites in Earth orbit, and tens of thousands of pieces of debris, so the main screen of this app provides choices to narrow down what you're looking for. In version 2.0 and above, a new button offers to view "all active" satellites currently visible from your location, which is typically only a few hundred, not thousands. If you're not too close to the North or South pole, you should see a solid band of satellites in the sky; these are the geostationary satellites. Additionally there will be some individual, fast-moving satellites that can cross your view of the sky in less than 5 minutes; these are LEO (Low-Earth Orbit) satellites, of which only a handful are visible from your location at one time.
  • Performance - If the app is too slow, click Menu on the main screen, and change the preferences to use a blue or black background instead of the camera preview.
  • Touch for info - Touch a satellite icon when it is in view on the screen for more information about the selected satellite.
  • Manual steering - Enable this in preferences, and you may drag a finger across the display to manually control the camera view angles. In version 2.0 and above, you can pinch-zoom to get a closer view of a crowded sky.
  • Sky watching - If you want to see satellites with your own eyes, pick a warm, clear night away from city lights, and from the app's main menu pick "International Space Station" or "Potentially Visible Objects". Those two categories are the only ones you'll see without fancy optics. Look for satellites shown in yellow, not blue, because only the yellow ones have sunlight shining on the actual spacecraft. If they're all blue, it's the middle of the night, so try looking at a better time, such as the end of dusk or the beginning of dawn, when more sunlight is crossing the LEO space above you. And finally, give your eyes time to adjust to the dark, you need to be able to see lots of stars before you'll spot a typical satellite. The bright screen on your phone or tablet may be working against you here, turn down the brightness and look away as often as possible. A satellite will look like a very faint star, except it moves across the sky in a matter of minutes, and it may "wink out" if it crosses into the Earth's shadow.

How it works

This program demonstrates a tiny sample of the kind of tool that you can create using software technology from Analytical Graphics, Inc. (AGI). In this case, the mobile app contacts a server running AGI Components to determine the satellites currently flying overhead.

NOTE: For export control reasons, the satellite overflight computations are handled on a server, not on the mobile device itself. So this app must transmit its latitude/longitude location to the server for the calculations to run. Military users should use appropriate caution when transmitting their location over an unsecured network.

Contact AGI for more information about building a version of this app on a secure network, or building one that performs the computations directly on the mobile device.

The app asks you to choose a category of satellites and uses your mobile GPS or wireless network to determine your position. This location is then sent to the server, which computes overhead satellite visibility for your location. The server combines satellite data from CelesTrak.com with analysis from AGI Components, and returns azimuth and elevation data back to the mobile device for display.

Legend

  • Satellite icon - Indicates the current position of a satellite.
  • Yellow satellite label - The name of a satellite flying in direct sunlight.
  • Dark blue satellite label - The name of a satellite flying in the shadow of the Earth or Moon.
  • Yellow line - Projected path of a satellite across the sky, flying in direct sunlight.
  • Dark blue line - Projected path of a satellite across the sky, flying in the shadow of the Earth or Moon.
  • Gray line - Previous path of a satellite. When too long, click Menu, Refresh.
  • Green horizon line - Artificial horizon, with compass headings.
  • Yellow arrow in a circle - Points toward satellites that are off-screen.
  • White grid lines - Right Ascension and Declination lines, used to indicate star positions.
  • White dots - A collection of 2000 bright stars, to help align the phone's view with your own.

Required permissions

This app needs certain permissions from Android to run correctly:

  • Your location - The satellites you can see depends on where you're standing.
  • Internet access - The computations are done on a server, so network access is required. No third-party advertisements are downloaded or displayed by this app.
  • Take pictures - The augmented reality effect involves placing the satellite icons in front of a camera preview window, so access to the camera hardware is required.
  • Prevent phone from sleeping - We found it annoying when the screen went black while holding the phone to the sky. So, we don't allow the device to auto-sleep when viewing satellites. Remember to exit the "Satellites view" before putting the phone down. Sleeping is enabled as usual for the other menu screens and other apps.

Change history

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  • Version 2.4 - 2011-Sep-22
    • Added a yellow arrow when satellites are off-screen
    • Added a new setting to disable calibration warnings
  • Version 2.3 - 2011-May-25
    • More helpful error messages for network problems
    • Fixed some problems found by new error reporting system
  • Version 2.2 - 2011-May-24
    • Fixed camera problems for certain types of hardware
    • Added complete error reporting to the camera system
  • Version 2.1 - 2011-May-23
    • Fixed main menu reload when switching portrait/landscape mode
    • Fixed more clock problems for certain types of hardware
  • Version 2.0b - 2011-May-02
    • Fixed a bug where gray lines appear too soon on some devices
  • Version 2.0 - 2011-Apr-27
    • Major redesign of user interface
    • Searchable satellite database
    • Manual location setting for extra privacy
    • Many enhancements and performance tuning
  • Version 1.2 - 2010-Dec-17
    • Added compass calibration instructions
    • Fixed some camera FCs on certain devices
    • Updated app requirements for Android Market
  • Version 1.1 - 2010-Nov-30
    • Added an option to touch a satellite for more information
    • Added a filter to smooth out the screen jitter
  • Version 1.0 - 2010-Nov-09
    • First release

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