# Distributed Coordination of Space-Ground Multiresources for Remote Sensing Missions
## 2 System Model
### Scenario and Problem Description  
Consider a space-ground coordination network (SGCN) for remote sensing missions which consists of a DRS system and \(N\) RSS systems, as depicted in Figure 1. The RSSs observe the observation objects for the users of their system, and the acquired data are sent back to the ground either by the ground stations belonging to the same RSS system or through the DRS system. The operation control center (OCC) of each RSS system and the operation control center of DRS system are connected through the terrestrial network to exchange data relay requirements and coordinated scheduling information.  
The set of DRSs in the space network is denoted by \(R=\{r_{1},r_{2},...,r_{i},...\}\), where \(r_{i}\) denotes the \(i\)-th DRS. The set of RSS systems is represented as \(\mathcal{N}=\{1,2,...,n,...,N\}\), where symbol \(n\) denotes the \(n\)-th RSS system. The RSS system \(n\) consists of an operation control center, several RSSs, and ground stations. The set of satellites in the \(n\)-th RSS system is denoted by \(S_{n}=\{s_{n,1},s_{n,2},...,s_{n,i},...\}\), where \(s_{n,i}\) denotes the \(i\)-th RSS of \(n\). Similarly, \(G_{n}=\{g_{n,1},g_{n,2},...,g_{n,i},...\}\) denotes the set of ground stations in the \(n\)-th RSS system, where \(g_{n,i}\) represents the \(i\)-th ground station of \(n\). The payload of each RSS includes an imager, a solid-state memory, and two transceivers which are used to communicate with ground stations and the DRSs, respectively.  
The satellite systems adopt the \"prepapplication and offline scheduling\" paradigm [16; 17]. That is, the remote sensing mission requests are submitted to the operation control centers of RSS systems in advance, and then the operation control centers of RSS and DRS systems schedule space-ground resources coordinately for the scheduling horizon offline. Let \(T\) denote the scheduling horizon. There are a number of remote sensing missions requests for each RSS system to complete during \(T\). The mission set of the \(n\)-th RSS system in the scheduling horizon is denoted by \(OM_{n}=\{om_{n,1},om_{n,2},\dots,om_{n,i},\dots\}\). Each mission is described by a 4-tuple. Take the \(i\)-th mission of RSS system \(n\) as an example. \(om_{n,i}=[o_{n,i},b_{n,i},et_{n,i}]\), where \(o_{n,i}\) denote the observation object of mission \(om_{n,i}\), and \(b_{n,i}\) is the amount of data that needs to be acquired and transmitted back to the ground. \([st_{n,i},et_{n,i}]\) is the feasible scheduling window of mission \(om_{n,i}\), i.e., \(st_{n,i}\) and \(et_{n,i}\), respectively, denote the earliest start time and latest end time of \(om_{n,i}\).  
In the mission scheduling stage, the operation control centers of RSS system cooperatively schedule their resources in parallel by interacting with the operation control center of DRS systems for relay requirements and coordinated scheduling information. The outputted resource schedules assign the RSS, DRS (or ground station), and the observation and data transmission window for each mission. The aim of the distributed  
Figure 1: Space–ground coordination network.  
space-ground resource coordinated scheduling strategy is to maximize the number of successfully scheduled missions of the entire SGCN.