There were two Fleets that did such a thing. One was 500 strong and was preparing to assault Earth at the station Unyielding Hierophant. The second, (name escapes me), was comprise of 15 ships. It was lead by the Prophet of Regret who ordered his fleet to make an immediate slipspace jump to Earth after discovering the location to the gateway portal to the Ark from a Luminary he had captured in 2551. The Luminary did not mention who were the inhabitants of Earth, and as a result, was woefully under prepared.