Friday, May 20, 2016

How to spot a satellite

There are hundreds of satellites orbiting earth and it is possible to see a lot of them with the naked eye. They are however only visible for an hour or so after sunset and and hour before sunrise.

Why are satellites only visible after sunset and before sunrise?

The satellite needs to be in the sunlight so that it can reflect the sunlight in order to be visible. You on the other hand, needs to be in the dark so that you can see the sunlight being reflected of the satellite. See image below.

Click to enlarge

This condition is only possible just before sunrise and after sunset. 

If you look up in the sky just after sunset (or before sunrise if you are brave), it won't be long before you see a satellite. With a satellite tracking program like DESA Satellite Tracker or using a website like Heavens Above, you will be able to predict exactly when and where a satellite will appear.

How to spot a satellite using DESA Satellite Tracker

You can download DESA Satellite Tracker from the TheCoder website (it's free).
After you installed, you will need to update the satellite data (you will be prompted, just select 'Update'). 
You will also need to select the satellites to track. Good ones to choose that is usually clearly visible:
  • ISS (Internation Space Station).
  • HST (Hubble Satellite Telescope)
  • Tiangong (Chinese Space Station)
You can also select some others. The most default satellites that you can choose from in DESA Satellite Tracker is visible with the naked eye. 

You will also need to make sure you have set up your monitoring station correctly (click on Monitoring Station). The monitoring station is your location (longitude, latitude and elevation). You can just click on the link in the setup screen to get your details. These details are needed to correctly calculate the position of the satellite in relation to yours.

Once all that is done (sounds like a lot, but you only need to do it once), then you can just open DESA Satellite Tracker after sunset. When a satellite is in viewing range, an alarm will sound and on the left bottom of the screen a message like the one below will appear.


Click on the satellite that is in range (see below).


The details of the selected satellite will appear on top of the screen. In the Lookup box the following will show:


The elevation is elevation above the horizon, 90 degrees will be straight up, so 23.4 will just be above the horizon. 
The Azimuth is the direction. 0 degrees is North, 90 East, 180 South and 270 West. So 158 will be South-East.
You will also be able to get a good idea of where the satellite is in relation to your position by simply looking at the map.

Then all you need to do is go outside and find it.

Why use DESA Satellite Tracker?

A website like Heavens Above will allow you to get a list of satellites with dates and times and where you will see them (it is a great website by the way). So why wait for an alarm to go off on your computer if you can simply get the dates and times from a website?

Well, ... where is the fun in that?  Picture this:

The whole family sits in front of the TV, then .... suddenly ...  the ALARM!! (be warned, the alarm is a bit intense).
Everyone rushes to the Satellite Control Room (okay, the computer, but it is a pretty cool looking app) to find out what satellite is in range and where it is. Then everyone rushes outside to be the first one to spot the satellite.

Never gets old!

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