William Brown, chief executive, Harris Corp.

PARIS — Harris Corp. has booked multiple hosted payloads to be flown on the Iridium Next constellation of mobile communications satellites in addition to the main aircraft-tracking payload the company is building, Harris Chief Executive William M. Brown said.

Melbourne, Florida-based Harris is under contract to build 81 Automatic Dependent Surveillance-Broadcast (ADS-B) air traffic monitoring units for the Iridium Next constellation, which is scheduled to be deployed into low Earth orbit between 2015 and 2017.

McLean, Virginia-based Iridium’s Aireon subsidiary, which has already taken on several air-navigation authorities as partners, will be operating the ADS-B service, in which Iridium is expected to retain a minority shareholding.

Iridium also hired Harris to create a payload support structure within certain volume, mass and power constraints given the constellation’s main mission of providing mobile voice and data communications.

But the Harris-designed structure is capable of handling more than just the Aireon hardware, making Iridium Next — with a planned 72 in-orbit satellites and nine ground spares — perhaps the biggest hosted payload opportunity ever offered.

In an April 29 conference call with investors, Brown said that in addition to the Aireon hardware, “we’ve also added other customers and so far have increased the number of payloads by almost 50 percent above the original contract, with the potential to add more, significantly increasing the value of this program.”

Iridium is counting on Aireon and other hosted payloads to provide revenue in the form of hosting fees and service fees.

Brown did not specify whether he was measuring hosted payloads by the number of customers, hardware units, revenue or some other metric.

In a May 1 email, Harris spokesman Sleighton Meyer said the 50 percent figure “referred to the quantity of hosted payloads on Iridium Next. The 50 percent number measures the quantity of hosted payloads that will support other missions over and above the 81 payloads originally announced by Aireon.” He did not respond to a request for further clarification.

The success of Aireon and the hosted payload opportunity in general has become critical to Iridium’s financial health in the next four years as it deploys the second-generation constellation and begins to generate revenue from it.

Five national air-navigation authorities in Canada and Europe have agreed to join Aireon as equity shareholders and partners, agreeing to invest a combined $270 million over time as Aireon hits its development milestones.

The U.S. Federal Aviation Administration is not one of them, however, and Iridium Chief Financial Officer Thomas J. Fitzpatrick said in a May 1 conference call that the FAA likely will be a customer, not an Aireon investor.

“We don’t envision the FAA as being a capital partner,” Fitzpatrick said. “The FAA would sign a contract with Aireon.” Iridium said the FAA’s evaluation of Aireon is continuing, but is not likely to lead to a contract until 2015 or 2016.

Peter B. de Selding was the Paris Bureau Chief for SpaceNews.