From NASA
Satellites that can fit in a backpack are shrinking technology, reframing satellite science, and providing valuable mission training and experience to the next generation of engineers.
They come in sizes small, micro, nano, and pico, with masses ranging from 500 kg (small) to 1 kg (pico). Over the past two years, global interest has grown rapidly in satellites that are a fraction of the size of Sputnik-1 (a beach ball weighing about 80 kg), ushering in a new era of missions and engineering opportunities.
Nanosats are not replacements for their larger counterparts—rather, they offer another approach to space flight. “People started saying, ‘Wait a minute, what else can I do with this?’” said Puig-Suari. “And it was just a chain reaction at that point.”