# Toward Integrated Satellite Operations and Network Management: A Review and Novel Framework
## 2 State of the Art
### Satellite Operations and Management Systems
#### 2.2.1 Operations in Sporadic Connectivity Constellations
An overview of distributed planning and scheduling is presented in [57], in which the two main approaches are described: goal achievement and HTN. Their work remarks that satellite onboard decisions still require ground-based higher goal decisions (centralized scheduling). A hybrid approach is proposed in [58] because fully distributed solutions require frequent ISL communications to capture the global state of the constellation. A hybrid model with a centralized layer to allocate tasks based on global information and a distributed layer to coordinate single satellites is proposed. Distributed systems usually rely on multi-agent-based negotiation assignment methods and rely on ML algorithms. Task scheduling can be further classified into two categories: (1) online scheduling and (2) offline scheduling. The latter schedules tasks that are known a priori, while the former schedules dynamic tasks that appear throughout the scheduled plan. In [59], the online scheduling of unpredictable incoming EO tasks is described. Two ways of dealing with such dynamic tasks are online control and online learning. Lyapunov optimization [60] is used for this specific use case to solve the regret minimization problem under time-averaged constraints. An example of operations control for an operative EO mission is described in [61]. The tool used for scheduling the ground segment of NASA's CYGNSS mission for hurricane detection is described. The paper presents the different architectural components of FlexPlan, the general mission planning system from GMV. A detailed description of how Planet manages the operations of its three main constellations (RapidEye, SkySat, and Dove) is presented in [62]. The RapidEye constellation does not require any deconfiction algorithms. Satellites are tasked using the in-house APS software, and human interaction is only present if an alarm is triggered. SkySat constellation tasking is partially automated, with input tasks being operator-defined. Finally, the Dove constellation is always imaging and does not depend on user-based tasks. Therefore, the in-house planning tool deconflicts and optimizes daily activities. All the processes are automated, with only human supervision once a day. The nominal operations of this constellation are automatic, including telemetry monitoring and schedule uploads. More examples of COTS software for satellite operations are also presented in [63]. Epoch Integrated Product Suite (IPS) is an automation tool for satellite nominal operations, namely TC/TM. Braxton ControlPoint (AceCP) is a tool focused on ground segment procedures automation, namely GS antenna scheduling, GS control and status, and TC/TM. Like IPS, the spacecraft-specific scheduling needs to be plugged in by a third party. Major Tom is a cloud-based tool based on the open-source flight software stack Kubos. Major Tom is focused on automating the GSN, TM management and anomaly detection, and file transfer monitoring. Finally, the Hify satellite control system from GMV is a mission and fleet management tool, offering cross-ground synchronization, anomaly detection, automatic execution of nominal passes, and generation of analysis reports. SCOOP is another example of an operations planning and scheduling tool for EO missions [64]. The Microwaves and Radar Institute of DLR has developed the tool. The software has two cores: (1) the simulator, which is a COTS tool called FreeFlyer, and (2) the planner, written in Perl. SCOOP software has a detailed definition of constraint, both temporal and for resources. The scheduler, however, is quite simple: first, it allocates GS passes in FIFO and then data acquisition tasks are ordered in priority again in FIFO. A power-aware toolchain for satellite operations management is presented in [65; 66]. The Hands-Off Operations Platform (HOOP) combines a series of modules to automate the scheduling of satellite operations, including telemetry processing and contact plan design.