Connect orbits, ground control and receivers

The 2022 white paper describes the completed BDS-3 configuration in 2020 as 24 medium Earth orbit satellites, three geostationary satellites and three inclined geosynchronous satellites. This is a dated configuration, not a live fleet count. The archive’s Beidou DW 44 is a BDS-3 inclined-geosynchronous spacecraft; Beidou DW 55 is a BDS-3 geostationary spacecraft.

A geostationary orbit stays over nearly the same equatorial longitude. An inclined geosynchronous orbit has Earth’s rotational period but changes apparent latitude during its daily motion. Medium Earth orbit satellites move through a different observing geometry. Use these definitions to explain why “geosynchronous” does not always mean stationary in the sky.

BeiDou’s ground segment includes monitoring, time-synchronization and uplink functions. The space segment broadcasts information, while the user segment includes antennas, receivers and applications. The 2022 system description also includes inter-satellite links. Those links do not turn an ordinary passive receiver into a transmitter.

Build an original fault table with three rows: an incorrect orbit estimate, a blocked user antenna and an incorrectly drawn road. Place them in the relevant part of the service chain. A satellite replacement would not automatically fix the map, and a correct map would not restore a blocked signal. Identify the faulty function before choosing a remedy.

Trace a problem to the relevant part of the service

The International GNSS Service records several identifiers for BeiDou satellites: catalogue numbers, international designators, names and signal codes. It also documents changes in some signal-code assignments. An identifier used to process a measurement needs context; it is not always a permanent nickname for a physical spacecraft.

Consider two observation files from different dates carrying the same signal code. Before joining their histories, consult the relevant code-to-spacecraft assignment for each date. Keep the stable catalogue identity and the observation time in your notes. This is a data-management exercise, not evidence that the two files necessarily came from the same spacecraft.