Each of the images for Transmission #3 contains a block of hidden data at the end. Fire up a hex editor and search for FF D9. This indicates the end of a JPEG file. Everything after this is extra.

Rocket Picture

We can tell there is a PNG file hidden in the rocket picture because the extra block starts with ".PNG........IHDR" and ends with "IEND.B`." Heres the extracted image:

Turns out its a space suit skin for Minecraft! View it at http://minecraft.novaskin.me/

Telescope Pictures

In each of the telescope pictures, the extra data starts with "Salted__". So this means its encrypted with OpenSSL. After copying the data to it's own file, you can decrypt it with...

openssl enc -d -aes-256-cbc -in 1.bin -out 1.mp3 -pass pass:"Im floating in a most peculiar way"

These are the MP3 files extracted from each image:

• 1.mp3
• 2.mp3
• 3.mp3
• 4.mp3
• 5.mp3

Here is what the mp3's say:

•  1.mp3: Earth, Farad
  
• 2.mp3: Joule, Circuit
• 3.mp3: Amp, Gain
• 4.mp3: Electron, Capacitor
• 5.mp3: Dialectric, Diode

Theres also more data hidden in these recording. The MP3 metadata has the following comments:

1. Transmission received at T-1090800.0222786265106846
   
2. Transmission received at T-1090800.0296872268554892
   
3. No transmission
4. No transmission
5. No transmission

Also, if you have ffmpeg, try...

ffplay 1.mp3

...to get a Real Discrete Fourier Transform