Quadros-1 probe

From Memory Alpha, the free Star Trek reference.

The Quadros-1 probe was an unmanned, long-range interstellar probe launched by the Federation during the 22nd century. Its mission was to perform a detailed survey of distant parts of the Milky Way Galaxy. The probe charted parts of the Gamma Quadrant, including the Idran system. (DS9: "Emissary")

It could be speculated that the probe was very large in size, possibly resembling an automated starship, similar to the Friendship 1 space probe.