Evaluating LEO Constellations for Global Satellite Navigation Service
We examined the OneWeb LEO constellation and variations of that constellation to determine the minimum size of a LEO constellation needed to provide global satellite navigation service. We used two criteria to assess if the constellation provided global satellite navigation service:
• Did the position dilution of precision (PDOP) values meet the GPS constellation requirements?
• Were the average PDOP values of the LEO constellation less than or equal to current GPS constellation average PDOP values?
From our modelling and simulation, we determined the minimum OneWeb LEO constellation sizes needed to satisfy these two criteria. We did not assess how these LEO satellites would be controlled, how their timing would be synchronised, nor other details of how to make the constellation perform as a stand-alone satellite navigation constellation.
LEO constellations typically consist of more satellites than MEO or geosynchronous orbit (GEO) constellations because LEO satellites have smaller footprints compared to MEO or GEO satellites. LEO satellites also have a significantly shorter orbital period, passing over the earth with a mean motion of 0.06°/s compared to MEO satellites mean motion of 0.008°/s. This faster motion can be an advantage over MEO satellites because it leads to greater multipath rejection of satellite signals. LEO satellites usually transmit stronger signals. In a denied or degraded GNSS signal environment, these stronger signals become an important asset.
Read more in Inside GNSS article. https://insidegnss.com/evaluating-leo-constellations-for-global-satellite-navigation-service/