Satellites Are Getting Smaller: Hubble Size to Starlink and Smaller.

On 4 October 1957, the Soviet Union launched the world’s first artificial satellite, Sputnik 1.  It was 83.6 kg, roughly 58 cm in diameter and used 1 watt of power.  Over time, satellites grew in size and complexity, but the recent trend is seeing them shrink.    Hubble was 11,110 kg and 13.2m x 4.2 m and originally estimated at a cost of $400 million US dollars. For Reference, the Hubble Space Telescope is about the size of a city bus or the trailer of a tractor-trailer.

With large complex systems cost overruns, design optimization and other challenges raised the approximate costs of the Hubble Space telescope to over $4.7 billion dollars by the time it launched on April 24, 1990.  Costs to repair and maintain the space telescope increased the cost at least another $5 billion dollars by 2010.  Which such huge costs, the space community needed to find an alternative to large satellites when possible.  The miniaturization of satellites is changing the way we approach space.

Lower Limit(kg)	Upper Limit(kg)	Classification	Examples
1000	1000+	Large satellites	Hubble Space Telescope / Inmarsat-4A F4
500	1000	Medium satellites	O3b
0	500	Small satellites	SpaceX StarLink

This trend of reduced sizes has manifested in the commercial satellite market. Inmarsat-4A F4 (Built by Thales Alenia Space) is a large 6,649 kilograms communications operated by the UK based Inmarsat in partnership with the European Space Agency.   It was launched by an Ariane 5 is a European heavy-lift launch vehicle in 2013. The Inmarsat-4A F4 was placed into a 35,786 km geostationary orbit order to provide mobile communications to Africa and parts of Europe and Asia.   By having the satellite be stationary with respect to the ground, the ground equipment always knew where to point (making it easier on the customer).  These satellites could also cover a wide area based on their distance from the planet.

Disadvantages of Larger GEO satellites

So aside from cost, what was the downside?  Some challenges with larger geostationary satellites are that they are limited options to launch due to the mass.  The more the mass and higher the orbit, the more powerful the rocket.   As a result, these large geostationary satellites are typically lifted by heavy or super-heavy launch vehicles.   The distance signals take to reach the satellite and for the satellite to respond results in latency, which can be greater than half a second of delay.  Since the satellite was a major investment, long life and extensive testing were done to help mitigate the loss of a valuable asset.  Unfortunately, there have been a number of instances where satellites have failed, either during launch or while operational.  Satellites, once done with their operational life were then needed to be de-orbited or placed into a graveyard orbit, with the desire to minimize collision and creation of orbital debris.

Getting closer to the customer

As an effort to make improvements O3b (now SES Networks) chose a different strategy. In 2013 the start of a network of smaller 700kg medium satellites placed in an 8063 km Medium Earth Orbit sought to optimize the operations of satellite communications.  By lowering the mass of the satellite by a factor of ten, the same launch vehicle could lift ten times the number of satellites.  By reducing the altitude of the orbit, the requirements for the launch vehicle were also reduced.  A final benefit was the satellites also reduced latency and with a network of satellites, they the network could increase coverage. 

SpaceX has joined this trend with the Starlink.  60 Starlink satellites are stacked together for launch into Low Earth Orbit.  The combination of lower mass and closer orbit is a game-changer.  Previously, communication satellites like Starlink utilizing Ku and Ka-band are placed in a higher orbit and larger satellite.  A downside of closer orbits is that less of the Earth can be “seen” or covered by the individual satellite.  However, a large constellation orbiting in LEO can work together to provide better coverage with lower latency.  

Some advantages of Smaller satellites in lower orbits:

Starlink offers high-throughput satellite (HTS) communication that can provide low-latency broadband internet service to global coverage.   End of life disposal of smallsats like Starlink is less of a concern since the satellite can be safely deorbited over the ocean.  Two mounting concerns with large constellations of smallsats like Starlink are the increased potential for collision in orbit resulting in debris fields that could potentially put at risk other satellites. The final major concern is from astronomers which are now frequently observing Starlink satellites while they prefer to view celestial bodies.

SpaceX was able to launch 60 Starlink satellites at a time into Low Earth Orbit rather than one Satellite like the Inmarsat-4A F4. One Falcon 9 has a lift capability of roughly 15,600kg and 60 satellites neatly fit into the launch capability of one Falcon 9. SpaceX does need more satellites launched in order to provide continuous coverage, so that is a temporary drawback to Starlink.

Launching multiple satellites concurrently as SpaceX did with the Starlink satellites, SpaceX has started to advertise the Smallsat Satellite rideshare program. $1M for 200kg to SSO with additional mass at $5k/kg. SpaceX is offering access to mid-inclination LEO, GTO, and TLI. Smaller satellites can also be managed by smaller launch vehicles that can provide dedicated launch services or small co-manifested rideshares. Some companies that are offering or developing services include RocketLab, Firefly Aerospace, and Virgin Orbit.

In part two of our review of Satellite sizes, we will delve into even smaller satellites. We will review the CubeSat revolution and further reduction in size to PocketQubes that can fit in your pocket like those developed by Alba Orbital.

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