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Fitting the pieces together: satellites, systems and operations
Published in Jonathan Higgins, Satellite Newsgathering, 2012
What has this to do with the commercial issues of selling space segment? Capacity that is completely station-kept (i.e. stable) commands a higher premium than capacity deemed to be in inclined orbit. The disadvantage of inclined orbit capacity is that both the uplink and the downlink have constantly to track the path of inclination. At the downlink, this is commonly performed by auto-tracking equipment, which not only gradually moves the antenna to keep the satellite on-beam but also ‘learns’ the daily cycle so that it is able to predict the direction to move the antenna. In terms of SNG uplink, this tracking usually has to be performed manually, and although this cycle can also be learnt by the uplink operator, it is often beneficial to make use of daily computer predictions to aid the uplink operator.
Case Study: Performance Observation of NavIC Ionodelay and Positioning Accuracy
Published in IETE Technical Review, 2021
Mehul V. Desai, Shweta N. Shah
The Indian Regional Navigation Satellite System (IRNSS) or the operational name Navigation with Indian Constellation (NavIC) evolved by the Indian Space Research Organization (ISRO) imparts Standard Positioning Service (SPS) and Restriction Service (RS) with a positioning accuracy of 10 and 0.1 m respectively [1–5]. The NavIC system is a territorial navigation system consisting of L5 (1176.45 MHz) and S-band (2492.08 MHz) signal information, providing navigation services to users in the Indian region and extending from its border to 1500 km [6]. The NavIC system contains three Geostationary Orbits (GEO) satellites with longitudes of 32.5° E (IRNSS-1F, 5° inclined orbit), 83° E (IRNSS-1C, 5° inclined orbit), and 131.5° E (IRNSS-1G, 5.1° inclined orbit), and four satellites are in inclined Geosynchronous Orbits (GSO). Two GSO satellites crossed the equator at 55° E (IRNSS-1I & IRNSS-1B, 29° inclined orbit), and two crossed the equator at 111.75° E (IRNSS-1D 31° inclined orbit & IRNSS-1E 29° inclined orbit) [5,6].
A mutual authentication and key update protocol in satellite communication network
Published in Automatika, 2020
Congyu Huang, Zijian Zhang, Meng Li, Liehuang Zhu, Zhengjia Zhu, Xiaoxian Yang
The essential method to guarantee the security of satellite communication networks is to authenticate each new satellite when it launches into the network and exchange a key among the satellites and the on-ground base stations. Several authentication and key agreement schemes have been proposed to provide security assurance in satellite communication networks. For instances, Wullems et al. [15] proposed a public key cryptosystem-based authentication protocol to improve the security of satellite systems. However, the protocol was unidirectional, so it cannot meet the requirement of mutual authentication. Cruickshank et al. [16] designed a mutual authentication protocol between endpoints and satellites. But the designed protocol had a high maintenance cost and a high failure risk. Sasaki et al. [17] put forward a double-layered inclined orbit constellation to improve the robustness of satellite communication network. But they did not consider the security for the network. Zhang et al. [18] proposed a low-earth orbit satellite and group key agreement protocol based 3GPP authentication and key agreement protocol. But they did not consider key update cases. Zhu et al. [19] proposed an entity authentication and access control scheme in satellite communication networks, but the protocol is not suitable for authentication among satellites.