Astronauts_Poem
On this chall, we have a PDF file. When we look at the exif we can see a link to a wiki.
When heading to the bottom of the page, we can see two links to old website available on the waybackmachine. We extract the text of the pdf with a tool like pdftotext. When putting the text on the website we get the message: 
The 10th line is Drove by our curiosity, I found my way: patrolling our spacecraft. You remembered wishes of hope. I am close to.
We create a program to count each word length and replace it with the correct brainfuck character as explained on the wiki.
After that we get the value >]+9[>]+0+0+0<]-[]>] which gives us 270 in decimal.
The NGC 270 is in the constellation of the whale which in French is baleine so the flag is: HACKDAY{baleine}