SCP Foundation

1) So the idea here is a china plate - if we drop it, the world ends. Okay, but I feel like there are big chunks of information missing. What is SCP-XXXX-D / G-012? A rock, a living organism, a cloud of gas? (it's a star, right?) That is absolutely critical for both the threat level of the SCP, and for investing the reader in the story.

2) Also, how far away is SCP-XXXX-D? I can't work out how worried to be. And the mechanics of the movement events elude me - is it 3.2 lightyears for every one instance of either kinetic or electromagnetic disturbance? If so, wouldn't the counter-intuitive solution be to establish a single, continuous, disturbance of SCP-XXXX, so that -D only ever moves a total of 3.2 light years?

3) How "directly" by human activity does a disturbance have to be to trigger the antenna? Heavy walking outside the containment box which vibrates the item seems quite indirect to me. And how could a human ever "directly" expose the antenna to electromagnetic disturbance, other than body heat and the human electromagnetic field? Seems to me that the best defence against this SCP is to bury it deep underground, with no human access ever.

4) Containment procedures:

• Why keep it in the original ammunition box? If there is some reason for not burying it underground, why not in a sealed lead container, suspended on a gyroscopic stability plate or some form of gel to minimise vibrations?
• You don't need to designate the box and the secondary container, as neither of these are part of the anomaly. That would make the deep space object SCP-XXXX-B, but only if you refer to the antenna as SCP-XXXX-A.
• Why is temperature control needed?
• You say "the following actions must be taken to avoid SCP-XXXX's signal from reaching its [note spelling] intended target". But you don't tell us what the actions are.
• I would stick to 3 light years as the "rough" average. Anything else seems far too accurate, considering the scale we're measuring on.
• Everything from "If SCP-XXXX-D receives signal…" onwards is description, not containment procedures, and should be moved down accordingly.

5) Description

• The second paragraph is where your description starts. The first paragraph can be cut down to avoid repetition, and the loss of the aircraft can be added to the description of how the SCP was recovered.
• I would delete the sentence "Knowledge of this object has been kept particularly secret…" - the Foundation keeps everything on a need to know basis, and if testing is forbidden, we should expect researchers to abide by that, even if they know about the object.
• I don't think that the paragraph starting "The pilot…" adds anything much to the story, and suggest deleting it.
• My suspension of disbelief suffers in the recovery description. In 1959, the US air force lost a relatively valuable piece of military hardware, and refused to retrieve it on the grounds of cost, despite having radio reports of a technological fault that might have affected all aircraft of this type, but did nothing at all when some aviation enthusiasts (which found out about this how?) hiked up there, presumably at relatively low cost, and took that military equipment away for personal use, and posted videos of that fact online? And then one particular astronomer (who is also an aviation enthusiast?) happened to watch the video, and made the intuitive leap that the antenna shown in the video caused an astronomical event based only on the timestamp? And how did that astronomer know about the P-80 crash, and why did they have access to the military radio reports to know the time of the instrument failure? I think a simpler and less coincidental explanation would help a lot.

6) General comments

There is no need to bold "movement event". You could capitalise it, if you want it to have a defined meaning, but it's a sufficiently obvious phrase to remain uncapitalised, in my opinion.

Almost all of your redactions and blackboxing should be removed. They don't add mystery or allow the reader's imagination to run wild, as it is generally either completely obvious or completely impossible to guess what is behind them. For example:

disturbance of SCP-XXXX may result in its activation and ███ ███████

If staff aren't told the result of its activation, how can they properly contain it? But of course they do know the result of activation, because the article goes on to describe it, making the black box redundant.

Some of suggested destroying the object, but [REDACTED]

This reads as though you couldn't think of a good reason not to destroy the antenna.

it was discovered that [REDACTED] movement event

Is there anything behind that [REDACTED]? I can't work out what would fit there syntactically, other than "there was a".

Alarmed by this finding, the astronomer contacted [REDACTED]

The Foundation? NASA? His estranged daughter?

"this object may bring about the ███████████ of earth."

If it's "the end", then no need to blackbox it, as we can guess that. If not, what does it bring about?