Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View

Small satellite systems enable whole new class of missions for navigation, communications, remote sensing and scientific research for both civilian and military purposes. As individual spacecraft are limited by the size, mass and power constraints, mass-produced small satellites in large constellations or clusters could be useful in many science missions such as gravity mapping, tracking of forest fires, finding water resources, etc. Constellation of satellites provide improved spatial and temporal resolution of the target. Small satellite constellations contribute innovative applications by replacing a single asset with several very capable spacecraft which opens the door to new applications. With increasing levels of autonomy, there will be a need for remote communication networks to enable communication between spacecraft. These space based networks will need to configure and maintain dynamic routes, manage intermediate nodes, and reconfigure themselves to achieve mission objectives. Hence, inter-satellite communication is a key aspect when satellites fly in formation. In this paper, we present the various researches being conducted in the small satellite community for implementing inter-satellite communications based on the Open System Interconnection (OSI) model. This paper also reviews the various design parameters applicable to the first three layers of the OSI model, i.e., physical, data link and network layer. Based on the survey, we also present a comprehensive list of design parameters useful for achieving inter-satellite communications for multiple small satellite missions. Specific topics include proposed solutions for some of the challenges faced by small satellite systems, enabling operations using a network of small satellites, and some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications Surveys and Tutorial

Qualification of Inter-Satellite Link Laser Communication Terminals on CubeSats - CubeISL

Free Space Optical (FSO) communications on the rise to replace classic Radio-Frequency (RF) systems in many sectors of satellite communication. DLR has a long heritage in developing Laser Communication Terminals (LCT’s) for LEO satellites. Major requirement for the design of the terminals is the optical characterization. Beside the verification in the laboratory, the terminals must withstand the harsh conditions of launch and space and fulfil all functionalities. To characterize the LCT’s optical properties, DLR developed and built an Optical Ground Support Equipment (OGSE) which mirrors the functionalities of an Optical Ground Station (OGS), in a small scale, to test and adjust the LCT’s. This paper describes the setup of the OGSE and its capabilities. The success of the New Space move is based on short qualification and development times. Thus, DLR tailors common standards to the needs of the final mission. The paper describes the qualification approach with the example of the world’s smallest LCT OSIRIS4CubeSat (O4C). The next step is to transfer the technology from Direct-To-Earth (DTE) into the Inter-Satellite Link (ISL) domain in the CubeISL project. To reduce time and cost efforts for development and qualification, subsystems and processes were reused from O4C

Optimization of intersatellite routing for real-time data download

The objective of this study is to develop a strategy to maximise the available bandwidth to Earth of a satellite constellation through inter-satellite links. Optimal signal routing is achieved by mimicking the way in which ant colonies locate food sources, where the 'ants' are explorative data packets aiming to find a near-optimal route to Earth. Demonstrating the method on a case-study of a space weather monitoring constellation; we show the real-time downloadable rate to Earth

Proactive TCP mechanism to improve Handover performance in Mobile Satellite and Terrestrial Networks

Emerging standardization of Geo Mobile Radio (GMR-1) for satellite system is having strong resemblance to terrestrial GSM (Global System for Mobile communications) at the upper protocol layers and TCP (Transmission Control Protocol) is one of them. This space segment technology as well as terrestrial technology, is characterized by periodic variations in communication properties and coverage causing the termination of ongoing call as connections of Mobile Nodes (MN) alter stochastically. Although provisions are made to provide efficient communication infrastructure this hybrid space and terrestrial networks must ensure the end-to-end network performance so that MN can move seamlessly among these networks. However from connectivity point of view current TCP performance has not been engineered for mobility events in multi-radio MN. Traditionally, TCP has applied a set of congestion control algorithms (slow-start, congestion avoidance, fast retransmit, fast recovery) to probe the currently available bandwidth on the connection path. These algorithms need several round-trip times to find the correct transmission rate (i.e. congestion window), and adapt to sudden changes connectivity due to handover. While there are protocols to maintain the connection continuity on mobility events, such as Mobile IP (MIP) and Host Identity Protocol (HIP), TCP performance engineering has had less attention. TCP is implemented as a separate component in an operating system, and is therefore often unaware of the mobility events or the nature of multi-radios' communication. This paper aims to improve TCP communication performance in Mobile satellite and terrestrial networks.Comment: 5 pages, 2 figure

The Ionospheric Nanosatellite Formation, Exploring Space Weather

The Ionosphereic Observation Nanosat Formation (ION-F) is a constellation of three satellites being built by Utah State University (USUSat), University of Washington (DawgStar), and Virginia Polytechnic Institute (HokiSat). The program is under NASA Goddard direction but had been started as part of the AFSOR/DARPA University Nanosatellite Program. It has progressed with support from industry, NASA Goddard, the Air Force Research Labs, and the Air Force Space Test Program. The primary scientific objective is to measure the fundamental parameters of ionosphereic density irregularities that effect radio wave propagation including communications, navigation, and the Global Positioning System. This data will also be used in the development and validation of global ionospheric models. Student teams, with direction from faculty and professionals, are designing and building these 15kg three axis stabilized satellites. The satellites will fly as a string of beads, with varying inter-satellite separation, over an approximate one-year mission. Two of the satellites incorporate propulsion systems for controlling the evolution of the string of beads constellation. Navigation will be provided by an onboard GPS system developed by the John Hopkins Applied Physics Lab. ION-F is one of the first tests of a small satellite constellation for making scientific observations of the near Earth space environment

Current optical technologies for wireless access

The objective of this paper is to describe recent activities and investigations on free-space optics (FSO) or optical wireless and the excellent results achieved within SatNEx an EU-framework 6th programme and IC 0802 a COST action. In a first part, the FSO technology is briefly discussed. In a second part, we mention some performance evaluation criterions for the FSO. In third part, we briefly discuss some optical signal propagation experiments through the atmosphere by mentioning network architectures for FSO and then discuss the recent investigations in airborne and satellite application experiments for FSO. In part four, we mention some recent investigation results on modelling the FSO channel under fog conditions and atmospheric turbulence. Additionally, some recent major performance improvement results obtained by employing hybrid systems and using some specific modulation and coding schemes are presented