If you're going to try to watch a satellite pass, it helps to know when the shiniest spacecraft are going to be zooming overhead. Amateur radio enthusiasts who want to make AMSAT or ARISS contacts need the same information. There's a cool new iPhone app called GoSatWatch (US$9.99, click opens iTunes) that makes looking for earth-orbiting spacecraft a piece of cake.
Once the app is loaded on your iPhone, all you need to do is tap the colorful icon to start the app, then do some initial setup. You should set up your location and allow the iPhone 3G's GPS receiver to determine your local latitude and longitude (iPhone and iPod touch users can enter that information in by hand if desired). More than one observing location can be pre-set in the app.
Next, you can choose which spacecraft or type of spacecraft (Iridium, space junk, visible, etc..) you want to "follow". If you want to watch the International Space Station (ISS) cruising overhead, tap on its button in the Satellite window to toggle its visibility on the map. You can even toggle to see all visible satellites, which is pretty cool because there are often a group of satellites cruising overhead at any time.
There are several different views available to you:
- Map, which shows your earthbound location as an eyeball (gotta like that!) and then shows the current location and ground track of the chosen satellite(s). There's a red oblong shape around the satellite that shows the area of line-of-sight visibility. Left and right arrows let you look at successive orbits, while a clock icon animates the flight of the satellite over time as you drag your finger across the screen.
- Sky shows the overhead sky 360° from horizon to horizon. This is where you can get an idea of where the satellite will be tracking as it flies overhead. The track shows bright yellow during the time that the satellite is in direct sunlight or dim yellow for the time that it's in shadow and won't be visible during the pass.
- Passes, which has a list of the start and end times for visible passes, complete with the peak angular height above the horizon and visible magnitude.
- Satellites is where you choose what to look at. Of particular interest are the Space Shuttle, ISS, and the Hubble Space Telescope, but Iridium communications satellites are fun to watch because they "flare" to extreme brightness.
Now, what's a good reason to purchase this app? There are a couple of them. First, the Space Shuttle isn't going to be flying for very much longer, so it can be fun and instructive to yourself and your family to see it fly overhead as a bright dot in the night sky. You'll have your chance to see it and the Hubble Space Telescope during the upcoming Hubble Servicing Mission.
Second, it's the International Year of Astronomy. Watching the night skies in all of their glory is fun to do whether you're using GoSatWatch to check out man-made objects or another app like SkyWalk to see the natural objects.
As the nights get warmer (for those of us in the northern hemisphere), be sure to get out your iPhone and see what's above you. You might be surprised! Take a look at the gallery to see screenshots of some of the GoSatWatch features.
Late edit: Developer Richard Hein let us know that his company also has an app called GoSkyWatch Planetarium, which is great for using your iPhone or iPod touch to find those non-man-made objects in the night sky.