This craft is integrated into the Sentinel Class Starship.
One of the features of the Sentry-class runabout. It was designed in 2377 as an alternative design to the already successful Danube class. Although the runabout performed well in both space and atmospheric environments, Starfleet officials felt that it was a waste of resources to develop a new runabout without good reason. Their opinion changed, however, when the runabout found its niche as a test bed for new sensor technologies.
When the Sentinel-class design specs called for a Runabout-sized auxiliary craft, Starfleet Research and Development offered up the Sentry-class design on the condition that they could modify the Sentinel prototypes long range sensor array to accommodate the powerful sensor data streams sent by the Sentry via subspace.
Essentially, the Sentry-class can be sent out beyond the effective range of the Sentinel's long range sensors and boost its capabilities further. Of course the new sensor range is only limited to the direction of the Sentry-class, but the Sentry's potential as a scout, makes her a perfect design for the Sentinel's arsenal.