By John Oncea, Editor
Satellite constellations are being planned and launched by various companies to capitalize on the increase in commercial investment in LEO. In addition, the DoD is planning to launch satellite constellations to enhance the resilience of their satellite missions against interference and attacks from adversaries. So, what exactly is a satellite constellation?
The man on the $100 bill, Benjamin Franklin, published a letter in the Journal de Paris in 1784 explaining how Parisians could save candles by adapting their habits to daylight hours.* Sure, Franklin’s proposal was satire, but it could have planted the seed of an idea in the mind of New Zealand entomologist George Hudson who proposed a two-hour time shift every spring to the Wellington Philosophical Society 110 years later. This would allow Hudson more time to collect insects.
Shortly after Hudson’s proposal, British resident William Willett published his proposal of daylight savings time (DST) as a way to save energy but, after some serious consideration, it was not implemented. Let the record show that Willett was an avid golfer who didn’t like having his round cut short by the early arrival of dusk.
The wheels now put into motion, the city of Port Arthur, Ontario, enacted DST on July 1, 1908. Orillia, Ontario jumped on board four years later then – bam! – the German Empire and Austria-Hungary embraced the idea in 1916 to conserve coal during World War I. Britain and most of its allies soon followed, then European neutral countries, then Russia, and in 1918, the United States.
So, whether you love or hate DST you have bugs, golf, and Gavrilo Princip, the assassin of Austrian Archduke Franz Ferdinand to thank or blame.
* Franklin wrote his letter anonymously, knowing 240 years later I’d want to throttle whoever came up with the idea of DST because it sucks not having time in the evening after work to rake the leaves.
Keeping Up With The Times
Now, let’s talk about how your smartphone, Fitbit, Alexa, TV, and computer automatically update the time when you spring ahead, fall back, or change time zones: it’s an illusion. No, not really.
What happens, according to the National Institute of Standards and Technology (NIST), is that digital clocks get their time from atomic clocks and Global Positioning System (GPS). GPS.gov explains, writing “Each GPS satellite contains multiple atomic clocks that contribute very precise time data to the GPS signals. GPS receivers decode these signals, effectively syncronizing each receiver to the atomic clocks. This enables users to determine the time to within 100 billionths of a second.”
These GPS satellites operate as a constellation and the U.S. “is committed to maintaining the availability of at least 24 operational GPS satellites, 95% of the time,” according to GPS.gov. “To ensure this commitment, the U.S. Space Force has been flying 31 operational GPS satellites for well over a decade.”
Each GPS satellite circles the Earth twice a day, flying in mid-Earth orbit (MEO) at an altitude of approximately 12,550 miles.
“The satellites in the GPS constellation are arranged into six equally spaced orbital planes surrounding the Earth. Each plane contains four “slots” occupied by baseline satellites,” writes GPS.gov. “This 24-slot arrangement ensures users can view at least four satellites from virtually any point on the planet.”
The GPS satellite constellation is operated and controlled by Space Delta 8, located at Schriever Air Force Base, CO, according to the United States Space Force. “With the proper equipment, users can receive at least four satellite signals to calculate time, location, and velocity. The signals are so accurate, time can be figured to within a millionth of a second, velocity within a fraction of a mile per hour and location to within 100 feet. Receivers have been developed for use in spacecraft, aircraft, ships, land vehicles, and precision-guided munitions, as well as for hand carrying.”
Space Force’s GPS constellation is but one of many orbiting the skies above. Let’s take a look at the evolution of this technology, as well as at how it is being used.
Look! Up In The Sky! It’s An Existing And Emerging Swarm!
Sometimes referred to as swarms, “A satellite constellation is a number of similar satellites, of a similar type and function, designed to be in similar, complementary, orbits for a shared purpose, under shared control,” according to Space4Water Portal. “Constellations are used for navigation and geodesy (e.g., GPS, Galileo, and GLONASS), satellite telephony (e.g., Iridium), or Earth Observation (e.g., DMC, PlanetLabs).”
Space4Water Portal adds plans are being made by companies for the development of large-scale constellations in low-Earth orbit and MEO to provide global satellite internet, or Internet of Things to connect machines and systems directly. Having thousands of individual units in a constellation positioned at low altitudes can significantly reduce the time it takes for signals to travel from a ground station to a user via satellite, especially in remote areas where there is no developed ground infrastructure.
Currently, around 2,000 active satellites are orbiting the Earth, but the planned satellite constellations could increase this number by tens of thousands over the next few decades, resulting in greater coverage and accessibility for internet users worldwide.
All of this began when Sputnik 1, the first artificial satellite, was launched in 1957. We’ve come a long way since then, to the point where these constellations are revolutionizing communication, navigation, and the observation of Earth.
“The idea of using satellites for communication purposes dates back to the 1940s when science fiction writer Arthur C. Clarke first proposed the concept of geostationary satellites, writes TS2 Space. “However, it was not until the 1960s that the first communication satellites were launched into orbit. These early satellites, such as Telstar 1 and Syncom 2, operated in higher orbits and relied on large ground-based antennas for communication.”
The 1970s ushered in the first LEO satellite constellations with the launching of Molinya by the Soviet Union and of the U.S. Navy Transit systems. These constellations consisted of just a few satellites and provided limited communication and navigation capabilities but demonstrated the potential of LEO satellites for global coverage and lower latency compared to their geostationary counterparts.
“In the 1980s and 1990s, the concept of LEO satellite constellations gained momentum with the development of the Global Positioning System (GPS) by the United States Department of Defense,” TS2 Space writes. “This success inspired the development of other LEO satellite constellations, such as Russia’s GLONASS and Europe’s Galileo systems, which further expanded global navigation capabilities.”
Satellite constellations evolved further with the launch of the first microsatellites, also in the 1990s. “These small, low-cost satellites opened up new possibilities for scientific research, Earth observation, and technology demonstration missions. The miniaturization of satellite components and the development of advanced manufacturing techniques enabled the production of more satellites at a lower cost, paving the way for large-scale LEO satellite constellations.”
In 1998, the Iridium satellite constellation, aimed to provide global voice and data communication services using a network of 66 satellites, became operational and remains a crucial tool for industries such as aviation, maritime, defense, and more.
The satellite constellation landscape has seen a surge of mega-constellations such as SpaceX’s Starlink and OneWeb in recent years. These projects aim to provide global broadband internet coverage by deploying thousands of satellites, bridging the digital divide and offering new avenues for economic development.
The Inevitable Downside
The number of satellites functioning in LEO has rapidly increased in the past few years, mainly due to investments in commercial constellations. If commercial plans continue as intended, some of these constellations will soon consist of thousands of satellites. Additionally, the Space Development Agency of the Department of Defense is working on plans for constellations composed of hundreds of satellites, primarily in LEO, for multiple missions.
The growing number of LEO satellite constellations has raised concerns about the sustainability of the space environment and the potential for space debris. With more satellites in orbit, there is a higher risk of collisions and the creation of debris, which poses a threat to operational satellites and human spaceflight. To ensure the long-term sustainability of LEO satellite constellations, there is a need for the development of space traffic management systems and proper satellite end-of-life disposal strategies.
The International Astronomical Union (IAU) writes it “is concerned about the impact of satellite constellations on astronomical investigations. The organization, in general, embraces the principle of a dark and radio-quiet sky as not only essential to advancing our understanding of the Universe but also as a resource that should be protected for all the Earth’s inhabitants. Although astronomers are making efforts to simulate satellite constellations, it will take time to understand the effect thousands of additional satellites will have on astronomy at optical and radio wavelengths.”
The IAU and other organizations, such as the American Astronomical Society (AAS), are making efforts to address the impact of the growing number of satellites, particularly those from Starlink, on the brightness of the night sky. One approach is to discuss with SpaceX the possibility of testing spacecraft coatings that can bring down the intensity of Starlink satellites.
Another approach is to develop software that helps observatories schedule their observations such that they minimize the impact of passing satellites. This software is particularly important for sensitive wide-field observations where the passage of satellites can cause detector saturation effects. It is worth noting that the visibility of satellite constellations is highest during twilight hours.
Nature adds, “As we grapple with an unprecedented scale and variety of crises in 2020, near-Earth space is being altered — quietly and permanently. What we do next with space, and for space, will reverberate for science and humanity for generations to come. We can choose to move away from a defensive transactional view of an inanimate space — that awaits ownership and extraction — to a more relational view of space as containing our scientific and cultural ancestry, a healthy ecosystem that holds scientific and cultural practices from all perspectives. Our understanding of our origins, as well as our collective future, in space depends on this.”