C2MS11 — Replace Unsolicited Echo with a Separate Message

According to the Command Echo Request:

“This message is nominally sent after a Command Request is processed by the final destination (e.g., antenna or spacecraft). The Command Echo Message can also be generated without a prior Command Request Message being sent; this is known as an 'unsolicited echo' and can be generated by ground station equipment as a result of the antenna receiving noise or interference.”

The concept of an unsolicited echo seems very strange, because it raises the question of what is being echoed, if it is not the command.

The Command Echo Message Additional Information table has a CMD-ECHO-RESULT value of UNEX "Unexpected echo received" which I suspect is tied to the "unsolicited echo".

If an unsolicited echo is meant to convey that the ground equipment is receiving noise or interference from the antenna, I believe a better approach would be to define a message to capture the noise or interference as an occurrence in the ground string and to send that, rather than to overload the Command Echo Message.

Move to a later release

We may need a new message type, or simply stop saying that there is an unsolicited echo, but either way, it's not urgent enough for 1.1's short timeline.