|Ed Sayadian, president of mission networks at Harris. Photo: Harris
[Avionics Today 03-22-2016] All over the United States operators are equipping slowly but surely with Automatic Dependent Surveillance-Broadcast (ADS-B) systems to comply with the upcoming Jan. 1, 2020 mandate. Meanwhile, Harris, the FAA contractor for ADS-B ground stations, has laid the groundwork for ADS-B equipage and is working to improve accuracy and expand coverage. As we approach the two-year anniversary of the implementation of the ADS-B ground infrastructure, Avionics Magazine sat down with Ed Sayadian, president of mission networks at Harris to discuss the ground network’s performance, surveillance gaps and how the company plans on expanding surveillance and capabilities in the coming year.
Avionics Magazine: How is the ADS-B system performing as we get closer to its two-year anniversary?
Sayadian: The performance has been good. We track performance and report it to the FAA and have been exceeding all the performance levels throughout the two-year period.
We have also invested in upgrading the underlying network to be more robust as well as to introduce some new technologies. One of the inherent risks with the initial network down-lay was that, while it was fully redundant, it used a single technology for routing and switching. The risk there is that if you have some kind of software bug in the management logic, it could propagate through both routing domains and cause a system-wide issue. Luckily, we never experienced that but it was a risk and it was the primary driver in investing for an upgrade to the underlying network. We moved to the state-of-the-art technology relative to network deployment, which has redundant networks but each of those networks use two separate technologies so we have a point-to-point Ethernet system and the private line system, each with separate routing domains, etc. Because of that, we are expecting even better performance moving forward.
Avionics Magazine: Is that update complete?
Sayadian: The update is 99 percent complete. We started at the beginning of calendar year 2015 in earnest. The transition was coordinated in lock-step with the FAA to move over the network. There are a few difficult locations and remote sites that require special attention still remaining, but the upgrade is essentially completed for all intents and purposes. We will likely finish the updates within the next month.
Avionics Magazine: Where are you looking to expand surveillance and/or the capabilities provided by the ground infrastructure over the next year and into the future?
Sayadian: Right now we have coverage that is at least equivalent to, and in a lot of cases greater than, the current radar coverage, which was the primary initial requirement for this system. We have 663 ground stations that are deployed and fully operational.
Our plans in terms of expansion include installing a couple of additional sites in the Gulf of Mexico. The initial deployment is considered coverage in the Northern half of the Gulf of Mexico. Recently we have implemented three sites around the Yucatan Peninsula in Mexico, to provide high altitude coverage in the southern part of the Gulf. We are expanding now to an oilrig in the lower part of Mexico to provide lower coverage in that southern part of the Gulf of Mexico.
We are implementing ADS-B coverage at eight new airports as part of the Airport Surface Surveillance Capability (ASSC) project. We are also implementing a new sight in the Aleutian Islands in Alaska on the Island of Adak.
We are just finishing up testing at Charlotte, NC., for not ADS-B, but a Multilateration (MLAT) capability, a navigation technique based on the measurement of the difference in distance to two stations at known locations that broadcast signals at known times, which leverages the ADS-B technology but also offers some additional flexibility in terms of equipage. It doesn’t necessarily rely on ADS-B message per se, but it receives either ASD-B or Mode S and Mode C messages and uses that differential of arrivals to derive positions. We have overlaid that in Colorado to provide expanded surveillance coverage as well and are in final testing in Charlotte to provide increased terminal coverage around the airport.
Further out, although not definitive yet, we are working with the FAA to look at expanding coverage to the Caribbean and provide essentially continuous coverage from Miami down to Puerto Rico and the U.S. Virgin Islands.
Last, we are looking at additional coverage in Minnesota and Wisconsin.
Avionics Magazine: Are there any coverage gaps in the system and, if so, where? Are you looking to expand to cover those gaps in the near future?
Sayadian: There are no real coverage gaps relative to the real requirement. We obviously don’t provide 100 percent coverage from 0 feet to 60,000 feet to everywhere across the U.S., but our requirement is to provide equivalent coverage to the legacy radar system and then where the FAA has ordered additional service volumes, we provide 100 percent coverage across those areas.
Avionics Magazine: Can you speak to any GPS/position accuracy issues?
Sayadian: I haven’t heard of any systemic issues. We did have a GPS event in late January that was felt across a variety of systems, not just aviation systems and not just ADS-B, but our system was able to coast through that. The receivers definitely experienced a timing issue, which was the result of a software error loaded into one of the GPS satellites by mistake, but the system was able to continue to provide surveillance positioning throughout the entire duration.
Otherwise, there was nothing that has come to the attention of Harris or the FAA program office when it comes to the accuracy for the pilots themselves.
We are confident that should any issues arise, the system will be able to tackle it. Generally speaking the accuracy of the GPS is sufficient to make sure the system works. There are integrity checks built into the system that would flag if the position accuracy went beyond the threshold or if there was an integrity issue flagged, we would be able to detect that in the ground system and be able to provide an error flag to the FAA, which would then fall back to the radar position.
Avionics Magazine: We have talked to helicopter operators that have said low-level airspace surveillance was not adequate as of one year ago. What is the status of low-level airspace coverage today?
Sayadian: We haven’t had any feedback from the community as to issues with the coverage. Currently, we have about 95 percent coverage in the northern half of the Gulf down to about 1,500 feet. As you get up to about 3,000 feet, it is essentially close to 100 percent coverage.
The ADS-B receivers were initially located on oilrig platforms that constituted the majority of helicopter traffic. Over the years certain drilling spots have dried out and things have moved, so those ADS-B ground stations are being re-worked in conjunction with the FAA and are being forwarded to us for action. We are in the process of relocating one of our ADS-B receivers from a legacy platform to a new platform because of the underlying operations. As I mentioned, we are also in the process of trying to add new sites to the southern part of the Gulf to expand coverage down further.
Avionics Magazine: How are you looking to expand the Flight Information System-Broadcast (FIS-B) and Traffic Information Service–Broadcast (TIS-B) aspects, if at all?
Sayadian: The majority of the activity in terms of expanding the inherent capability of ADS-B system proper, centers around FIS-B. We are in the process of adding five new weather products to the FIS-B broadcast distribution: lightning strikes, in-flight turbulence forecasting, icing forecasting, cloud top heights and then moving to a one-minute Automated Weather Observing System (AWOS) update.
In terms of TIS-B, we haven’t added any new functionality per se, but we have modified the TIS-B service so it can provide TIS-B graphic services to legacy receivers that aren’t fully DO-260B compliant. The requirement for ADS-B equipage was to be compliant to the latest RTCA documentation, DO-260B and the requirements around certain integrity levels and accuracy levels. There was some legacy equipment and avionics out there that did not fully meet those requirements and, hence, they were not provided TIS-B services per the specification. But through various discussions with the community, we are in the process of modifying the TIS-B service so those legacy avionics can also receive TIS-B until they have had time to upgrade.
Beyond what we are necessarily doing there is a lot of activity in the FAA that is trying to get the legacy ADS-B/TIS-B/FIS-B services to NextGen advanced operations, such as interval management, ground-based interval management, in-trail procedures, situational awareness, collision avoidance, etc. The current ground infrastructure does not require any modifications to the ADS-B service; instead activity around assessing new operations, approving the operations for safety and getting new procedures in place.
Avionics Magazine: Are there any new updates regarding space-based ADS-B?
Sayadian: The latest on space-based ADS-B is that we are working in conjunction with the FAA and Aireon, which develop and test a select set of new oceanic space service volumes at the tech center by December 2017. We have been working with the FAA to essentially leverage our ADS-B contract to be able to implement new oceanic-based service volumes. The way we would realize that is to subcontract with Aireon, acquire the Aireon data from the satellite system, bring that data into our U.S. FAA ADS-B system, validate it, ensure we have the appropriate security gateways and implementations in place, make sure we have any data transformation and formatting completed. The entire concept and associated underlying design is being put in place and will be tested at the tech center to ensure that those automation systems can receive and process the new oceanic data.
Beyond that, everything is still to be decided. Once it is tested, the FAA will likely move forward with actually ordering up those oceanic service volumes and providing the interfaces into the Advanced Technologies and Oceanic Procedures (ATOPS) systems in New York, Oakland, Miami and possibly up in Alaska. But right now, the focus is still on getting the concept down, design work done and completing testing by 2017.