Target lock: Sentrobe
Sentrobes are flying robotic enemies that can be encountered within Skyward Sword. They are armed with a cannon that fires projectiles. Their hull has two large parts on each side of its cannon, presumably making them invulnerable by horizontal sword slashes. Deflecting their attacks with a simple shield bash will result in them attacking Link with Sentrobe Bombs. The Sentrobe itself will not come within reach of Link's sword. Once destroyed, the Sentrobe will drop a large crop of Rupees. It can be assumed that they were made by the same civilization that built the Lanayru Mining Facility as a defense mechanism.
The Sentrobe Bombs are small sphere shaped objects with spinning propellers on top. Two are sent out at a time by the Sentrobe, one with a blue vertical line and one with a horizontal line across their bodies. Link must slash the bombs in their respective directions using his sword. If he waits too long, the bombs will explode in his face, dealing damage. The Sentrobe Bombs are quite small and will float in front of Link's face until destroyed.