Correct path for source image in path, take the real one, not the expected one. increase version nb
{
"name": "spitzer",
"verbose_name": "The Spitzer Space Telescope",
"description": "The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory.",
"image": "spitzer_logo.png",
"link_text" :"Cette image sur le site Spitzer",
"link_url" :"{url}"
}