PARIS — Four O3b Networks broadband satellites are likely to be launched in mid-December aboard a Europeanized Russian Soyuz rocket, replacing two European Galileo navigation spacecraft in what industry officials say is a rare symbiosis between the two constellations.

The O3b and Galileo programs are not in the same business but have been in an occasionally rough competition for access to the Europeanized Soyuz. Each has had its share of satellite-related delays, and each has tried to muscle its satellites to the head of the Soyuz queue.

O3b is based in Britain’s Channel Islands and its principal shareholder is commercial satellite fleet operator SES of Luxembourg, which is the world’s second-largest fleet operator by revenue and as such is always a priority customer for Europe’s Arianespace launch consortium. Arianespace operates the Europeanized Soyuz from Europe’s Kourou, French Guiana, spaceport.

The Galileo positioning, navigation and timing constellation is owned by the European Union’s executive commission, which has become the biggest single customer for Evry, France-based Arianespace, both because of Galileo and because of the Copernicus network of Earth observation satellites.

Galileo had secured the December Soyuz slot, to be followed by an O3b Soyuz launch in early 2015.

But in recent weeks, following a bungled orbital injection of two Galileo satellites in August, Galileo managers have concluded that they would like to test these two spacecraft more fully before continuing with the constellation’s launch. The testing should last until sometime in January, officials said.

For Galileo, then, it is important to wait before launching further satellites. For O3b, the opposite is true. Four of the eight satellites in orbit have a defect that is likely to shorten their lives, leading program managers to switch off two of them. A six-satellite constellation is sufficient to offer O3b’s Ka-band broadband service for now.

Adding the final four satellites currently under construction for O3b will add to the safety margin. Ultimately O3b has enough spectrum rights for its unusual 8,000-kilometer-altitude equatorial orbit to field more than 100 satellites if the business develops.

The company is about to receive a $300 million insurance claim because of the defect on the first four satellites, and SES has indicated it would support investing these funds into the business, likely in the form of another satellite order.