But satellites orbiting close to Earth have such small coverage areas-ones that are constantly moving-that the signal received by one satellite will need to be bounced across the constellation and then back down to reach the right destination. Traditional geostationary satellites, or geosats, work by receiving a signal from one location on Earth and directly beaming it somewhere else within its coverage area. First, the satellites must be able to communicate with one another directly. While thatвЂ™s hard enough, a space-based network like SpaceXвЂ™s requires two more capabilities to be successful. вЂњYou need to launch enough satellites and space them out such that you can guarantee thereвЂ™s always one above the horizon.вЂќ вЂњWith these satellites, theyвЂ™re maybe over the horizon for 5 minutes,вЂќ says Zac Manchester, an assistant professor of aeronautics and astronautics at Stanford University. The trade-off for that expansive coverage is high latency and some degradation as the signal spreads out on its way down to Earth.ДЄn individual satellite in a LEO or VLEO constellation canвЂ™t be reached from a specific location most of the time, simply because Earth gets in the way-just as it does for distant ships, which appear to sink below the horizon when they travel far enough away. LEO and VLEO constellations require a radical rethinking of the way satellites communicate with one another and with stations on the ground.ДЄ traditional geostationary satellite can single-handedly provide continuous coverage for up to a third of the globe. SpaceX and other companies planning LEO and VLEO constellations, including Kepler Communications, LeoSat, and OneWeb, are betting that V band can nevertheless serve as a high-data-rate option for their near-Earth satellites.ДЄn untested spectral band isnвЂ™t the only technical hurdle.

The V band has been used for short, line-of-sight terrestrial applications, because the frequencies are too high to penetrate walls and because moisture in the atmosphere tends to absorb the signal over longer distances. The VLEO satellites, however, will make use of the V band, a higher frequency band ranging from 40 to 75В GHz. Federal Communications Commission has currently approved SpaceX to launch 4,425 of these communications satellites into low Earth orbit (LEO) and 7,518 more in very low Earth orbit (VLEO), for a total of nearly 12,000 satellites.ДЄccording to filings with the FCC, the LEO satellites will broadcast in the Ku (12- to 18-gigahertz) and Ka (26.5- to 40-GHz) spectral bands, which are typical bands for communications satellites.

There is a consensus that SpaceXвЂ™s business model, even more than the technical challenges it faces, could doom the constellation of satellites it plans to deploy. Outside observers arenвЂ™t as optimistic about SpaceXвЂ™s chances.

Starlink bandwidth