Answer: Jingle Bells

On December 16, 1965, the crew of Gemini 6A added a bit of holiday cheer and a historic space exploration milestone to the NASA archives. Mission specialists back on Earth were monitoring the flight when astronauts Wally Schirra and Thomas Stafford lit up the comlink with a report of an object sighting:

Gemini VII, this is Gemini VI. We have an object, looks like a satellite going from north to south, probably in a polar orbit. He’s in a very low trajectory traveling from north to south and has a very high climbing ratio. It looks like it might even be a … Very low. Looks like he might be going to reenter soon. Stand by one … You might just let me try to pick up that thing.

We’re sure there was a tense moment down below as their terrestrial handlers looked at each other whispering, “Object sighting? The comlink lit up again and the folks down at mission control were treated to the space-based musical performance. Schirra and Stafford had smuggled a harmonica and string of sleigh bells onto the flight and, with the kind of zero-gravity flair that only the first astronaut performers could muster, they whipped up a quick rendition of the holiday classic “Jingle Bells”.

Thanks to the efforts of curious space enthusiasts, the original recording was unearthed and is available for your listening pleasure here.