From the DARPA website: Phoenix Goals
The traditional process of designing, developing, building and deploying space systems is long and expensive. Satellites today cannot follow the terrestrial paradigm of “assemble, repair, upgrade, reuse,” and must be designed to operate without any upgrades or repairs for their entire lifespan—a methodology that drives size, complexity and ultimately cost. These difficulties apply especially to the increasing number of expensive, mission-critical satellites launched every year into geosynchronous Earth orbit (GEO), approximately 22,000 miles above the Earth. Unlike objects in low Earth orbit (LEO), such as the Hubble Space Telescope, satellites in GEO are essentially unreachable with current technology.
Advanced GEO space robotics: DARPA is developing a variety of robotics technologies to address key on-orbit mission needs, including assembly, repair, asset life extension, refueling, etc., in the harsh environment of geosynchronous orbit. Development activities include the maturation of robotic arms and multiple generic and mission-specific tools. …
Satlets: A new low-cost, modular satellite architecture that can scale almost infinitely. Satlets are small independent modules (roughly 15 pounds/7 kg) that incorporate essential satellite functionality (power supplies, movement controls, sensors, etc.). Satlets share data, power and thermal management capabilities. They also physically aggregate (attach together) in different combinations that would provide capabilities to accomplish a range of diverse space missions with any type, size or shape payload. Because they are modular, they can be produced on an assembly line at low cost and integrated very quickly with different payloads. DARPA is presently focused on validating the technical concept of satlets in LEO.
Payload Orbital Delivery (POD) system: The POD is a standardized mechanism designed to safely carry a wide variety of separable mass elements to orbit—including payloads, satlets and electronics—aboard commercial communications satellites.