## 2 Near Real-Time Remote Sensing Architecture  
### Overall Scheme of NRRS  
Nowadays, remote sensing satellites provide an extraordinarily rich amount of information, and instant information becomes more and more demanding. Near real-time remote sensing, which integrates multiple distinctive features, such as near real-time demand collection, near real-time data transmission, processing, and dissemination, is a new mode of meeting the challenges of time-sensitive scenarios. Traditionally, the data transmission capacity of satellites is limited, and the ground stations for TT&C, as well as data receiving stations, are difficult to be arranged globally. Therefore, the users' needs for remote sensing cannot be uploaded to the satellites in real time, and the acquisition process of remote sensing images is prolonged. The conflict of network resources is more apparent when encountering temporary or urgent observation needs [25]. In the NRRS architecture based on satellite Internet, remote sensing satellites are connected to the satellite Internet as nodes of information. The uploading of satellite commands no longer depends on the limited TT&C stations. Remote sensing data will be transmitted in real time, and the data transmission mode of Storage and Playback will be abandoned, so as to maximize the use of satellite resources. Figure 1 shows the NRRS architecture based on satellite Internet, which consists of the LEO broadband communication constellation, remote sensing satellites, TT&C and data receiving stations, TT&C systems, integrated communication and remote sensing (ICRS) application system, remote sensing users, etc. Compared with the traditional satellite remote sensing system, the presented architecture takes the advantage of the ubiquitous nature of the satellite Internet, which can be found in the following aspects:  
* Requests collection: The users' needs for remote sensing can be submitted to the ICRS application system through the terrestrial network, or they can access the satellite Internet through satellite terminals anytime and anywhere to submit their need for remote sensing. * Task planning: The traditional OC&M system makes overall planning for satellites and TT&C stations. Under the presented architecture, the ICRS application system integrates satellite Internet resources as a whole. User management, session management, data forwarding, and network slicing are handled by the communication network management system. Remote sensing satellites access the Internet as information nodes, and communication resources are immediately available upon application. Therefore, the difficulty of task planning is greatly reduced. Task uploading: The remote sensing commands can be uploaded through the TT&C station, as well as through the satellite Internet, i.e., the commands are transmitted to the remote sensing satellite via the gateway station, communication satellite, and inter-satellite link. * Data transmission: Remote sensing data can be downloaded through traditional data receiving stations, or downloaded to the communication terminal through the inter-satellite links. It can also be directly downloaded to the portable remote sensing terminal. * Data processing: The remote sensing data can be processed in the ICRS application system, and then distributed to users via the terrestrial network or satellite Internet, or processed in real time or near real time at the data receiving station. When the onboard processing capacity is sufficient, it can also be processed in orbit to achieve a fast closed-loop from demand collection to data distribution. **Remark 1**. : _It is worth noting that the proposed NRRS architecture is not limited to the application of third-party communication constellations. There are other solutions for remote sensing data offloading except for using satellite Internet. Remote sensing satellites equipped with ISL can also support a near real-time remote sensing service.