Duty Officer Assignment Nodes are located in space sectors. They were added in game as part of the Season 9.5 update patch on 17 July 2014, and replaced Exploration Clusters.
The Afehirr Nebula is a vast area of clouds and gases dominated by highly-charged particles. The danger to ships in this area is significant, which is why it forms a boundary on expansion in this part of the quadrant.
The Arucanis Arm comprises a long curve of star systems spinning off the edge of the border between the Alpha and Beta Quadrants. Much of this arm consists of stellar gasses, nebulae, and matter formed in proto-stars, which gives it a brilliantly colorful display in the dark sky.
The Azlesa Expanse is a dangerous terrritory of charged nebulas, exploding stellar formations, and temporal anomalies. This has presented a challenging battleground for Imperial expansion for many years.
The Betreka Nebula, near Cardassian space, has long been a home for scavengers and smugglers. Though parts of the nebula are home to dangerously corrosive gasses, this simply makes this area an uncharted haven for captains who know the area well - or are willing to take big risks.
The B'Tran Cluster holds a wide range of shrouded systems hidden by spatial anomalies and nebulae. Travel here is extremely hazardous, as the Borg have assimilated some areas, and other areas are filled with navigational dangers.
The Delta Volanis Cluster is a large expanse of space with many uncharted worlds. Most of the systems here are home to small Federation colonies or indigenous populations that have not developed substantial spacefaring capabilities.
The Eridan Belt stretches into vast swaths of unpopulated galactic space. Many of the planets here are found singly orbiting remote stars, so this area of space is a lonely frontier.
The Eridon Nebula is home to many dust-filled systems that formed long ago and left behind large amounts of uncoalesced matter. The region is often credited with mysterious ship disappearances.
The Hromi Cluster is a dense patch of stars and nebulae, not far from the intersection of Federation, Klingon, and Romulan interests. Many of the planets here are rich with useful minerals.
The Khazan Cluster is a mysterious expanse filled with binary and trinary star systems. Many lost, ancient civilizations have left relics and ruins behind on the worlds of this star cluster.
The Rolor Nebula is an area thick with substellar formations and charged gases, similar in many ways to the Badlands. Because of this heavy distortions, long-range scans are less useful than actual survey expeditions.
The T'Ong Nebula has long been a thorn in the side of the Empire, as the shrouded worlds in this system hide the approach of Federation ships from the far side of the Neutral Zone. Young ambitious captains often cut their teeth on patrols in this area.
The Zenas Expanse lies far from the traveled routes of much of the Alpha Quadrant. This cluster houses many bright young stars, and is an area brimming with energy and radiation.