Geosynchronous orbiting satellites underpin fundamental aspects of modern life—from broadcasting the Super Bowl to early predictions of tornadoes. However, the more than 400 military, scientific, and communications spacecraft that orbit at the same rate as Earth’s rotation are faced with a harsh space environment over their long lives, which can last up to 15 years. There’s no way to service the satellites, and there’s no way to directly dissect what ultimately causes them to fail.
If the high-power amplifier that sends the signals from the satellite down to users on Earth fails, it can disrupt the signal. Satellite designers keep this in mind and build satellites with multiple redundant amplifiers in place to maintain performance. Even though they rigorously test their components during assembly and integration, failures can occur.
Thanks to proprietary data provided by Inmarsat, a leading British telecommunications provider, Lohmeyer et al. were able to perform a detailed statistical analysis on more than half a million hours of satellite telemetry in an attempt to figure out what happened when amplifiers failed. It is nearly impossible to convincingly identify a cause of failure if limited data are available. Thus, the authors also used concurrent space weather data from National Oceanic and Atmospheric Administration satellites to see what was happening in the high-energy electron environment at geosynchronous orbit just before 26 different amplifier anomalies that occurred over 16 years.
The study builds on work the authors published in 2013 showing more failures in times of heightened high-energy electron activity once solar activity begins to wane in the 11-year solar cycle. Those results were surprising, because the anomalies happened at a time often thought to be safe for satellites. Fortunately for Inmarsat, redundant systems allowed uninterrupted signals, and performance was not affected.
In the latest research, the authors identified how increased electron fluence, built up over many days, heightens the likelihood of anomalies. The authors used models to investigate how fluence buildup could lead to internal charging. Experiments showed that the buildup of such charge could not only affect internal satellite components, but could cause current discharges, which could short out circuits.
The authors recommend that satellite manufacturers should consider adding in a shunt resistance, which creates a leakage path and prevents internal charging buildup. (Space Weather, doi:10.1002/2014SW001147, 2015)
—Eric Betz, Freelance Writer
Citation: Betz, E. (2015), Protecting communications satellites from space weather, Eos, 96, doi:10.1029/2015EO037281. Published on 12 October 2015.