Written by Raiana Kelly
In late April, Scientists at the NIST (National Institute of Standards and Technology) published results for a new atomic clock, the NIST-F4. If the NIST-F4 started ticking 100 million years ago, it would only be off by less than a single second today. The NIST-F4 joins an elite group of clocks that will help us determine and synchronize the universal time standard to a higher degree of accuracy. While that makes little noticeable difference in our everyday lives, it’s good news for the GNSS industry.
The global network of satellites used for satellite navigation technologies like GPS and GNSS are each equipped with an atomic clock that relies on precise timing to provide accurate signals to GNSS receivers on the ground. Even minor errors in time can create significant inaccuracies in position. It’s up to ground control stations on earth to regularly transmit correct time data to the satellites, and that data is based on the universal standard set by atomic clocks like the NIST-F4. The more accurate the atomic clock on the satellite is, the more reliable our positioning results are.
If, like me, you may have been a physicist in a past life and find this technology endlessly fascinating, you can learn more about the NIST-F4 and atomic clocks by visiting the NIST website. If you’d like to learn more about how GPS and GNSS works, and what role atomic clocks and time play in determining our position on earth, take a look at our blog post from last month: “How it Works: GPS, GNSS, RTK, and PPP [2025 Guide].”
The SWPC (Space Weather Prediction Center) expects that our current solar cycle, Solar Cycle 25, will reach its maximum in July of 2025. Solar maximums are characterized by increased sunspots and solar flares, and while the visual effects of these peaks can be enjoyed in the form of more frequent aurora borealis in lower latitudes, the increased solar activity also brings potential disruptions to satellite communications and power grids.
The SWPC predicts that the sunspot activity of Solar Cycle 25 will be below the recorded average, but it’s important to understand that solar disturbances are inherently unpredictable and severe scintillation can lead to GNSS receivers being unable to lock onto signals and calculate a position.
While most disruptions from increased solar activity are experienced in low and high latitudes, mid-latitudes can experience scintillation during peak solar cycles. For geospatial professionals who require centimeter accuracy and/or continuous high-accuracy positioning, being prepared for increased solar activity is essential to minimize disruptions and downtime.
Multi-frequency GNSS receivers that can communicate with multiple satellite systems, such as our Asteri X4i and Asteri X3i, are the most reliable when reducing the errors caused by solar disturbances. This frequency independence allows the receiver to eliminate satellites affected by ionospheric disturbances while still communicating with enough satellites to acquire an accurate position.
Modern receivers capable of withstanding severe scintillation are built with complex algorithms designed to detect and filter out unreliable data. Even with ionospheric noise disrupting signals, the most robust receivers not only evaluate individual satellite signals but combine information from multiple GNSS constellations to compensate for and correct errors. These advanced algorithms allow for the receiver to make partial use of the disrupted satellite data to provide a more reliable position.
One of the best ways we can prepare for the effects of increased solar activity is by staying informed about what to expect and when. Luckily for us, there are various resources available to help, including the NOAA (National Oceanic and Atmospheric Administration) website and Spaceweather.com. The SWPC of the NOAA website tracks and provides real-time data for geomagnetic storms and serves as the national and global warning center for space weather disturbances. Spaceweather.com compiles news and information about various space weather, including solar flares, meteor shows, auroras, and more.
To learn more about how to mitigate GNSS disruptions, you can read the GIM International article, “Signals, Scintillation, and the Solar Effect”. If you’d like to learn more about how GPS, GNSS, RTK, and PPP work together and differ from each other, check out our blog post from last month: “How it Works: GPS, GNS, RTK, and PPP [2025 Guide].”
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