Want to work on something neat in a /sci/ thread?
ITT: METI

So, I've been thinking about good requirements for a broadcast message, intended to be decoded by an unknown intelligent civilization.

We've done it a couple times, but I want a general outline or framework. This outline should dictate the criteria that the most efficient, and overall best possible signal should meet.

So, the examples I can think of off the top of my head right now, are our Arecibo message, and the discs located on the Voyager space craft.

Based on what I know so far, here are some considerations I will start with. Please scrutinize freely.
Once this first general outline is finalized, we'll go in depth into each consideration. (I'll wait for input and we will amend this, when appropriate.) *Also, let's focus on the technical "how" for this signal, not the "what" So I'm not going to dive into what content to include. i.e. Children singing happy birthday in every world language.
I don't care about that. Technical/priority details only.

1. Medium? (Let's just assume this goes through the vacuum of space. I feel that's a benevolent assumption.)
2. Type of signal? Light is always suggested, lasers, or interrupting a constant light source, like blinking a star. This makes sense from the standpoint of arrival speed. (Please don't hang up on semantics for this.)
3. Signal to noise ratio?/distinguishable? (How do we ensure that our signal won't be mistaken for background noise, or a natural fluke?)
4. Tool for decoding? (How do we teach them how to decode the message, from the message itself?)