Aireon begins intensively testing orbiting space-based ADS-B payloads

After being handed complete control of its space-based ADS-B transceiver payload on one of the first 10 orbiting Iridium NEXT low-earth orbit communications satellites on 24 February, Aireon expects to receive control of another seven payloads “roughly over the next month” for testing, once Iridium has raised the satellites to their operational orbits.

Speaking to RGN, Aireon CEO Don Thoma says that after the first 10 satellites were launched on 14 January – on a SpaceX Falcon 9 booster launched from Vandenberg AFB in California – Iridium monopolized testing of the satellites until late February so that it could verify their orbital dynamics and ensure the satellites were functioning properly.

However, on 25 January, Aireon was able to turn on its payloads on the 10 orbiting satellites briefly to confirm they were functioning and to allow the payloads to perform self-testing. This process activated the payloads’ antennas briefly and in the short periods during which the antennas were active they transmitted thousands of ADS-B position reports from 150 aircraft, Aireon being able to receive and decode each message.

Describing those early glimpses of the Aireon payloads’ capabilities as “tantalizing”, Thoma adds, “We were amazed at what we could see,” because the company hadn’t expected to receive any live ADS-B messages from the payloads during self-testing. One encouraging early sign was that during that early testing the payloads captured live ADS-B messages from a commercial flight landing at an airport in Sweden, demonstrating their ability to detect aircraft operating at low altitudes in high-density terminal airspace.

Anything before last Friday [24 February] was snippets of data,” says Thoma. Since then the trickle of early position reports has become a flood. Once Aireon assumed complete control of one of its space-based ADS-B payloads, in the 62 hours which followed it received and decoded almost 5 million ADS-B position reports, from more than 17,000 different aircraft.

It is far too early in the payload performance-testing and data validation process for Aireon to determine if the space-based ADS-B data it is receiving has reached air traffic management (ATM) surveillance-grade accuracy. “That’s a really rigorous process, which will need months and months of data,” says Thoma. However, Aireon is already seeing ADS-B position reports from aircraft in every operating environment – including oceanic, polar and high-density terminal airspace.

Aireon is receiving ADS-B messages from commercial, business and general aviation aircraft. Even more encouraging is that one payload managed to pick up ADS-B messages from an aircraft some 3,500km (2,175mi) away, though the nominal maximum reception range of the Harris-manufactured payload is 1,200mi. “It shows what a good job Harris did in making the payloads,” says Thoma.

Aireon and Harris performed the initial payload testing and will remain deeply involved in the process as more NEXT satellites are launched and after 45-60 days are pushed to their final orbits. However, Aireon is now sending data for validation to customer (and future lead shareholder) Nav Canada and the UK air navigation service provider (ANSP) NATS, as well as to the FAA, a long-term program partner in Aireon’s space-based ADS-B effort. All are involved with Aireon in proving the system’s end-to-end capabilities.

On 6 March Aireon will begin space-based ADS-B integration testing with Thales on that company’s TopSky – ATM Solutions automation platforms, used by more ANSPs than any other ATM platform. Integration testing is also beginning with the FAA Technical Center at Atlantic City, New Jersey on the FAA’s Advanced Technology and Oceanic Procedures oceanic-airspace automation platform.

Aireon will soon broaden its sharing of data for performance-validation purposes to other early ANSP customers for its space-based ADS-B ATM surveillance data feeds. These include Aireon shareholders the Irish Aviation Authority, Denmark’s Naviair and Italy’s ENAV. Each will validate Aireon’s space-based ADS-B data for its performance compared with their existing ground-based ADS-B s or other ATM systems, the ATM surveillance-grade performances of which are known exactly.

As more of the eventually planned 75 orbiting NEXT satellites are raised to their operational orbits, Aireon will connect live to other customers and ANSPs with which it has operational validation agreements. “It’s a phased program and we’ll keep growing it as more satellites and connections are put in place,” says Thoma.

This second phase of capturing rapidly growing amounts of space-based ADS-B messages and intensifying data validation will see Aireon connecting live with customers such as the Civil Aviation Authority of Singapore, Curaçao’s Dutch Caribbean Air Navigation Service Provider, South Africa’s Air Traffic Navigation Services, Isavia of Iceland and the Seychelles Civil Aviation Authority. Aireon will also connect to Airways New Zealand, with which it recently signed an operational-validation agreement. Aireon also has a memorandum of understanding with Air Services Australia.

Continuing payload-testing by Aireon will see the company “look at various types of avionics – to learn how well we see [signals from aircraft ADS-B] transponders with the minimum requirement of 125W, to the 500W units” in large aircraft, says Thoma. Another part of the effort will see “how we collect information in high-density traffic, high-noise environments”.

Much of this effort will involve Nav Canada and the FAA Technical Center in Atlantic City, both of which will fly highly instrumented aircraft to assist Aireon’s performance and validation effort. Aireon also has an agreement with an operator on the US West Coast to flight-test an aircraft in the Western and Midwest USA for  these purposes. Additionally, Nav Canada is making available a “golden transponder” it operates in Iqaluit in Canada’s Northwest Territories. This unit can vary its power and antenna configuration with known performance validation, useful capabilities for calibrating and verifying Aireon’s space-based ADS-B signals.

Perhaps Aireon’s most important cooperation of all is its effort to provide space-based ADS-B performance metrics and statistical analysis for the European Aviation Safety Agency (EASA), with which Aireon is working “to get the service certified as a surveillance source”, according to Thoma. Aireon began working with EASA six months ago and over the coming 18 months, as more NEXT satellites and their Aireon payloads are orbited in seven more planned launches, EASA will perform a series of rigorous audits of Aireon’s space-based ADS-B data feeds.

“Over the next year, our plan is to collect … data and fully understand it,” says Thoma. “We have a very flexible system, so we need to fine-tune it.” Aireon expects that as more satellites are launched it will understand much more about the payloads’ capabilities and operational reliability, so that by the time later NEXT launches occur, Aireon will have learned lessons that will simplify and speed its testing of the payloads. “We purposely built into the design lots of knobs we can turn to optimize the performance of the system.”

Testing will culminate in about 18 months, when the Aireon payloads on the last five planned orbiting NEXT satellites become fully operational. The last launch, now tentatively planned for June 2018, will require Aireon to perform final verification-testing of its entire space-based ADS-B system, in a “run-for-the-money” exercise to demonstrate the system’s full operational performance. The fact the last NEXT launch is now scheduled to happen 18 months from now instead of just over 12 months, as a result of the SpaceX launch “anomaly” on 1 September 2016, indicates that the originally planned orbiting schedule for the NEXT constellation has slipped by at least four months.


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1 Comment

  1. Ben

    Once it matures, is the Aireon system going to be able to provide Mode-S georeferencing through multilateration? I’ve got to think that by the very dynamic nature of LEO satellites, MLAT wouldn’t work based on the the requirement to have very precise fixed positions of multiple Mode-S sensors to triangulate. However, those satellite scientists and engineers are a clever bunch and it wouldn’t surprise me at all if they developed some algorithm based solution.