Excalibur by Jack McDevitt

This one was so believable I actually looked up the fictional NASA mission the story was about.

What if Voyager 2 saw something unexpected when it passed Neptune?

A reporter stumbles across a mission called Arkon 1, but when he starts asking questions about it he is met with some resistance. 

I was rather disappointed the story only ran for 11 pages.  I wish it could have gone longer. 

Well done indeed. 

Jack McDevitt's website - https://www.jackmcdevitt.com/