Russia’s Soyuz 2.1 rocket set another record during a July launch when it delivered 73 satellites in one mission. The largest was a half-ton Kanopus-V-IK remote sensing satellite (for monitoring surface conditions and heat), one of five Russia is putting into orbit in the next few years. But the other 72 satellites were micro-satellites, most of them weighing less than ten kg (22 pounds) and weighing (all together) nearly as much as the Kanopus. The record for this sort of mass nano-satellite launch was set by an Indian PSLV-XL rocket in February when it put 101 small (average weight 7 kg/15 pounds) satellites and three larger ones (by weight, most of what was put into orbit) into orbit. What makes the Soyuz micro-satellite launch so important is that the Soyuz is the most frequently used satellite delivery rocket ever, with over 1,800 launches to date. The Indian PSLV is similar in design and function to the Soyuz 2.1 and has been in use since the mid-1990s with 41 launches and a 93 percent success rate.
Since the 1960s most news about satellites concentrated on the very large (often over ten tons) birds. But since the 1990s there has been enormous growth in the use of smaller (under 100 kg/220 pounds) satellites. Called nano and micro satellites the number launched increased more than 6o percent a year from 2010 to 2016 and given current trends over 3,000 of these smaller satellites are expected to go up in the next decade. One reason these smaller satellites are so cheap is that most are built locally by people who do not specialize in satellite construction. This is related to the fact that the low cost means more risks can be taken in the design and construction of these satellites. While larger satellites have a useful life measured in years, smaller birds are built to last for a few weeks or months. The low cost and ease of construction means that more organizations worldwide can design and build satellites. All this experimentation has led to many useful advances in satellite design that have been adapted for larger satellites. At the same time these smaller satellites are increasingly going up to replace or complement larger satellites.
The earliest (1950s and early 60s) satellites were similar in size to the larger nano-satellites, mainly because the available rockets back then could not put anything larger into orbit. In the late 1990s several countries in the West (especially the U.S.) began developing very small satellites again mainly because the technology had improved to the point where small was affordable and useful. The earliest of these developed by the U.S. Department of Defense were called CubeSats. That is, their volume was no more than one liter (10x10cm or 4.1x4.1 inches) and weighed no more than 1.3 kg (three pounds). The military got the idea from the increasing use of commercial nanosatellites (which weigh no more than 6.8 kg/15 pounds). The U.S. military launched its first CubeSats in 2008 (piggybacking with a larger bird).
It was quickly proven that CubeSats could be used for photo or electronic surveillance, or communications. The rapid advances in communications and sensor technology in the early 21st century made it possible to build a useful reconnaissance satellite weighing less and less. A tiny satellite like this includes solar panels to provide power. A British firm pioneered this technology in the 1990s and made it possible to get scientific satellites in orbit for a fraction of the usual price. Since 2008 nearly a thousand CubeSats (or similar designs) have been launched and the number is increasing each year. Thus most of the 173 micro-satellites used in the recent Soyuz and PSLV launches were based on the CubeSat design. That standardization also allowed for the establishment of standards for placing many micro-satellites in a rockers final stage, another factor in keeping delivery costs down.
The problem with these microsatellites is the cost of getting them into orbit. The cheapest way to launch these small birds is via a solid fuel ICBM (preferably one that is being retired). Even there, the launch cost is going to be about $20 million per satellite. That's why even smaller satellites became popular, because they were compact enough to be piggybacked with a larger satellite. This is becoming the most common way to launch the tiny satellites, keeping the cost down to under $10,000 per microsatellite. Launching dozens of them using a retired Russian ICBM has also proved economical. Thus in mid-2014 a retired Russian ICBM (a 217 ton RS-20/SS-18) launched a record 37 satellites at once (actually at 30 second intervals) after the third stage achieved the intended 630 kilometer high orbit. The RS-20 has a max satellite payload of nearly three tons. That means the average satellite weighed about 60 kg (132 pounds). Some of the 37 satellite were quite a bit heavier and most of the 37 were microsatellites (under 10 kg/22 pounds).
The Indian PSLV mass microsat launch cost about $100,000 (average) each if you go by weight being put into orbit. But because the primary cargo for the PSLV and Soyuz rockets is larger commercial satellites the micro-satellites can usually go up at a large discount or free. As more micro-satellite designs demonstrate a commercial use there will be more rockets going up carrying only (or primarily) micro-satellites and all will pay an appropriate (according to weight and shape) launch fee.
Russia was fortunate to have a new version of the Soyuz rocket (Soyuz 2.1v) ready for regular service by 2014. This one uses a new engine and digital guidance system. Soyuz remains a popular launcher for putting satellites into orbit and has survived and thrived because of constant upgrades like this. Soyuz is still the most frequently used rocket for putting commercial payloads into orbit. The most notable Soyuz use is to supply the international space station (ISS). The Soyuz/Progress space vehicle weighs about seven tons and can deliver 2.7 tons of cargo and also serve as a rescue craft to get people back to earth. The Soyuz spacecraft has become the model for more recent designs that hope to compete.
Micro-satellites also have the advantage of being much more difficult to be tracked from the ground and that helped pay for a lot of the early work on micro-satellite design. If there are successful wartime satellite attacks, then the micro-satellites and nanosatellites can be sent up to replace the war losses. The lightweight satellites (from CubeSats to 200 kg minisats) can be put in orbit using smaller, solid fuel, boosters. The U.S. Navy proposed using the ICBMs fired from SSBNs (ballistic missile carrying nuclear subs), which can be put to work much more quickly than the usual liquid fueled launcher. But the solid fuel ICBMs can only put a ton or more into orbit. With CubeSats and nanosatellites, this is not a problem. There are now standard micro-satellites (mainly based on CubeSat) that are sold ready for the installation alongside the regular payload (a larger satellite).