Strange sounds in the sky

Strange sounds in the sky, anyone know anything about this?

Another secret TFT project?

I was given a postcard with the sky on it when I joined AMBER, the same as the one Rachel got from her farther Dr Baxter. Trying to work out what it means. There are numbers on the back:

6,5 24,16 2,4 17,22
24,32 28,3 8,4
15,10 29,5 4,6 18,13
8,13 3,10 1,7 33,3

I'm thinking grid references for something...