Sensitivity of Line-of-Sight Estimation to Measurement Errors in L-Shaped Antenna Arrays for 3D Localization for In-Orbit Servicing +
Footnote †: This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)]([https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/))). [PERSON]  
1 Basis of Electronics Department, Technical University of Cluj-Napoca, 400114 Cluj-Napoca, Romania; [EMAIL_ADDRESS]  
[PERSON]  
2 Control Data Systems SRL, 400267 Cluj-Napoca, Romania; ovidiu. a potential option on refueling), navigation for automatic rendezvous and docking, and ISLs for cooperative rendezvous and docking. At present, the extensive standardization effort of all these components is carried out with the important issue of the interoperability of the several participants in the IOS scenarios. In the docking/birthing scenarios, the ISL must be \"gifted\" with important functionalities: low latency data communication, metrology (to support coarse and fine ranging, angle of arrival (AoA), or line-of-sight (LoS) measurement), and safety functionalities for collision avoidance. The prospect of existing space communications standards brings out several recommendations from the Consultative Committee for Space Data Systems (CCSDS). According to CCSDS recommendation [3], two major standards paths are recommended: the Wi-Fi Alliance certifications (heavily drawn from IEEE 802.11 standards [4]) and the 3 rd Generation Partnership Project (3 GPP)--Long Term Evolution (LTE) and beyond--standards for mobile High Data Rate Wireless Proximity Network Communications architecture, protocols, and communication standards in support of activities associated with space missions. Another relevant and live recommendation from the CCSDS is the Proximity-1 network protocol [5; 6; 7; 8]. The Proximity-1 network protocol has two significant short comings when it comes across IOS: (i) the lack of support for networking: a peer-to-peer communication link between the two spacecraft is a minimum requirement, but the possibility of multiple access networking between a servicer and multiple serviced spacecraft should be foreseen (a servicer could guide multiple serviced vehicles at the same time or a servicer can have several docking stations--like a \"gas-station\" scenario); (ii) the lack of support for navigational assistance: coarse/fine ranging and LoS are necessary features to assist in the spacecraft's guidance and with the navigation controller (GNC) before the optical link is established and as a back-up system after the optical link is established; (iii) the lack of support for collision avoidance: although space debris handling is not necessarily related to IOS, it is a constant headache for current space operators looking for cleaning up the increasingly crowded orbits [9]; (iv) the lack of network time distribution that may be used for timestamping events in the local device. Thus, we see a clear technological advantage in developing an ISL system that also provides ranging information and supports the spacecraft with line-of-sight (LoS) angle and relative tilt measurements [10]. Nowadays, ranging is enabled in ISL communication by the deployment of pseudorandom coded modulation [11] with either Gaussian Minimum Shift Keying (GMSK) or Phase Shift Keying (PSK) [12], but these procedures only offer ranging without the capability for AoA measurement. Traditionally, radio detection and ranging (RADAR) systems are aimed at determining the range--or the distance--and the AoA of a target.