Quick position determination using 1 or 2 LEO satellites

Nadav Levanon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We describe an approach for a medium accuracy position determination of a user terminal (UT) on the Earth surface, using one or two low Earth orbit (LEO) satellites. The positioning approach is intended to meet the requirements of a worldwide personal communications system using LEO satellites. The basic two requirements are: 1) immediate positioning, and 2) horizontal position accuracy of the order of 10 km. Those requirements stem from the need of the system to know the user's approximate location before it connects his call. The approach makes use of the two-way communication with the UT, which can receive, transmit, and make its own measurements. Delay and Doppler measurements are used in order to enable instantaneous positioning with one satellite, and in order to achieve unambiguous positioning with two satellites. A simplified Globalstar satellite constellation and the expected Globalstar delay and frequency measurement accuracy are used to demonstrate the concept and to evaluate its performances.

Original languageEnglish
Pages (from-to)736-754
Number of pages19
JournalIEEE Transactions on Aerospace and Electronic Systems
Issue number3
StatePublished - 1998


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