Navigation Enabler for Single Satellite Vehicle

J. Hsu, R.T. Bow, T. Tam, P.A. Toth

Abstract:	A global navigation satellite system (GNSS) receiver (referred to as just “receiver” hereafter) needs to simultaneously track and measure the RF signals transmitted by several orbiting GNSS satellite vehicles (SVs) in order to compute the receiver’s position, velocity, and time (PVT) solutions. Therefore, all previous pre-launch verification of a GNSS SV involving actual receivers are limited to static, tracking-only tests due to the receiver’s inability to form a PVT solution while the SV is still on the ground. These tests are considered inadequate in revealing any issues that manifest only when PVT solutions can be formed in a dynamic environment. Additionally, with the growing number of new GNSS systems being developed and new ranging signals being introduced into existing systems, it is of great interest to the GNSS community to verify the interoperability between receivers and a full constellation of SVs in space while the SV is in development stage, as it can be cost prohibitive and sometimes impossible to fix any implementation issues post-launch. Navigation Enabler for Single SV(NESS) is a novel process invented to produce a virtual constellation of GNSS signals with which receivers can navigate in real-time, using actual signals(s) transmitted by a single SV (or equivalent engineering model) under laboratory test conditions. By leveraging a commercial-off-the-shelf (COTS) RF recording and playback system, NESS collects multiple RF recording segments from a single stationary SV, introduces the precise signal dynamics into each recording, and then combines the processed recordings into a new recording that appears exactly as if it were a multitude of signals from an entire constellation in space. A PVT solution can then be obtained when this new recording is played back in real time to an ordinary receiver. With this powerful tool, an SV can be validated as an operational signal-in-space while still on the ground and the test results reflect the performance of the same SV in orbit. Besides application to SV verification, NESS can also be used as an alternative with unmatched fidelity to a COTS GNSS constellation simulator. This paper first provides an overview of the NESS process, its potential applications and benefits, and then describes how NESS played a critical role in demonstrating the backward-compatibility of the GPS Block III SV, which implements a new signal combining method called Majority Vote due to the addition of the civil L1C signal. The objective of the demonstration was to show that legacy receivers do not suffer any performance degradation while navigating with signals transmitted by GPS III SVs. The equipment setup and technical challenges for collecting and processing signals from the actual SV hardware will be described, followed by the characterization of the recorded signals and finally a discussion of the preliminary results from an array of receivers under test.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	1897 - 1906
Cite this article:	Hsu, J., Bow, R.T., Tam, T., Toth, P.A., "Navigation Enabler for Single Satellite Vehicle," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 1897-1906.
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