VICAR (Video Image Communication And Retrieval) is a raster image file format associated with the VICAR Image Processing System software, which is associated with NASA and JPL (Jet Propulsion Laboratory).
Sometimes this format is called VICAR2. Or maybe there are actually two different formats – it's not clear.
VICAR files begin with the ASCII string "LBLSIZE", which begins a "label" section containing space-separated attribute definitions, with no newlines.
There is no standard filename extension. If the filename has an extension, it may reflect the content of the image, rather than the file format.