The Celestri Multimedia LEO System was a planned

Low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

(LEO)

satellite constellation A satellite constellation is a group of artificial satellites working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global coverage, such that at any time everywhere on Earth at least one sa ...

, which was intended to offer global, low-latency broadband Internet services via

Ka-band The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum defined as frequencies in the range 26.5–40 gigahertz (GHz), i.e. wavelengths from slightly over one centime ...

radio links.''Application for Authority to Construct, Launch and Operate the Celestri Multimedia LEO System, A Global Network of Non-Geostationary Communications Satellites Providing Broadband Services in the Ka Band'', filed June 1997 with the Federal Communications Commission, Motorola Global Communications, Inc., Chandler, Arizona. It was planned by

Motorola Motorola, Inc. () was an American Multinational corporation, multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent p ...

circa 1997-1998 as one of the earliest "Internet in the sky" constellations, and as a successor to the company's

Iridium satellite constellation The Iridium satellite constellation provides L band voice and data information Pass (spaceflight), coverage to satellite phones, pagers and integrated transceivers over the entire surface of Earth. Iridium Communications owns and operates the Sa ...

, but never built or launched. The Celestri constellation was envisioned to consist of 63 operational satellites in 7

orbital plane The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) an ...

s, inclined at 48° with respect to the Equator, plus up to 7 in-orbit spares. Satellites in each plane would follow circular orbits at an altitude of 1400 kilometers. Each satellite was envisioned to contain all hardware and software needed to route traffic throughout the network, including Earth-to-space in the 28.6-29.1 GHz and 29.5-30.0 GHz bands, space-to Earth in the 18.8-19.3 GHz and 19.7-20.2 GHz bands, and space-to-space connections via optical inter-satellite links. Satellites were expected to employ

phased array In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving th ...

antennas supporting 432 uplink beams and 260 downlink beams per satellite, provided by

Raytheon Raytheon Technologies Corporation is an American multinational aerospace and defense conglomerate headquartered in Arlington, Virginia. It is one of the largest aerospace and defense manufacturers in the world by revenue and market capitaliza ...

, to communicate with Celestri ground stations, which would have equivalent antenna aperture sizes from 0.3 to 1 meter to support communications at rates from 2.048 to 155.52 Mbps. Celestri's anticipated cost was $12.9 billion. In May 1998, Motorola announced that it was dropping its plans for the Celestri system, and instead would invest $750 million in the rival

Teledesic Teledesic was a company founded in the 1990s to build a commercial broadband satellite internet constellation. Using low-Earth-orbiting satellites small antennas could be used to provide uplinks of as much as 100 Mbit/s and downlinks of up to 720 ...

constellation. The combined project was ultimately abandoned in 2003.de Selding, Peter B.
Teledesic Plays Its Last Card, Leaves the Game
. Space News, July 14, 2003.

References

Communications satellite constellations {{spacecraft-stub