This is the second of four articles to suggest solutions to the problems that would be caused on Earth from the loss of satellite services. I briefly describe the situation in a previous posting at Impending Space Junk Disaster. This article discusses the use of High Frequency (HF) radio to provide connectivity to replace that which is currently provided by space based platforms.
Telecommunications is the only service that can be backfilled upon loss of satellite services. Space based imaging, mapping, and other remote sensing (such as detecting lightning and forest fires) would be almost totally lost in the absence of satellites. Military intelligence would be relegated to methods from the 1960s, such as high altitude aircraft flyovers (with all the associated limitations and risks including being shot down). However, it would be possible to provide telecommunications services from solely terrestrially based equipment.
The description of HF radio is well documented in several places,1 and there’s no need to restate all of the details here. The term shortwave is also used to refer to HF, from an era 100 years ago when its wavelengths really were the shortest in common use. What makes HF (and to a lesser extent Medium Frequency (MF) waves)2 different, besides their wavelength, is signals in these frequency bands are returned to Earth by the Ionosphere.3 This is in contrast to the significantly shorter wavelength frequencies used for line of sight communications including mobile phones and FM broadcast stations, and the even higher frequencies used with dish antennas for satellite and terrestrial microwave connections. Although HF is also capable of line of sight, its differentiating value is in long distance (beyond line of sight capability) without any intervening repeaters or other manufactured infrastructure.
It’s the long distance capability without additional infrastructure that makes HF a player in a world without orbiting satellites or any other space based platforms. However, as an HF radio path utilizes the natural environment, it is necessarily affected by changes in that environment—and that environment changes like the weather, literally. Space weather4 is actually a thing, and understanding how to work around its variations is a critical skill for anyone operating HF communications equipment. Fortunately, there is information available that takes the very technical and math based space weather information and translates5 it so that it’s usable for HF operators who are not trained in this specialty. There also are real time sounding services to report the current status of the ionosphere6 from different locations around the world.7
The informational support infrastructure is there—as long as the Internet is available. In a situation without satellite services, the Internet would likely be significantly degraded. However, (greatly simplified) data in tabular form might be transmittable over HF, should those running these sounding services choose to do so. Another alternative is Automatic Link Establishment (ALE),8 in which HF stations effectively poll each other on different frequencies and then select the frequency offering the best communications path at that particular time. Successive generations of ALE have been in operation since its inception in the 1970s, and the technology is still under active development. In a world without satellite communications, HF ALE could be implemented at scale to provide further long range connection capability over HF. In the absence of sounding or ALE capability, HF operators still could do a version of manual ALE via coordinated voice radio checks on different selected frequencies.
That gets the communication path established—the next issue is determining exactly what you have after you get an HF circuit working. You’re definitely not going to be streaming music or movies, conducting video conferences, or transferring large files—the bandwidth on HF just isn’t there. That’s one reason everything switched to satellites in the first place, but if the space platforms are no longer there that question becomes moot.
One helpful (partial) analogy might be the difference between sailing ships and those that are propelled by power (diesel, nuclear, etc.). Just as there’s a big difference between means of ship propulsion, there’s a difference between what satellites can carry and what nature (in the form of the ionosphere) can support. In that context, the concept of HF supplementing (what would have been) satellite communications would not be that different from current concepts of adding sails back onto commercial ships.9 If you no longer have powered ships available, everything is not lost, as sailing ships arguably made maritime navigation practical long before the steam engine—the same would be true for HF vs. satellite communications. If it turns out to be all you’ve got, then you have the ability to make the best of it.
And HF is quite capable of providing the best nature (in the form of the ionosphere) can provide. The same brilliant minds that perfected satellite communications systems, can do the same with HF—it’s a ready means to prepare now to reduce potential pain later.
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