LEO’s Impact on Testing at the Ground Segment

The Race to LEO Mega Constellations

Since 2019, we’ve seen the first satellites of LEO mega constellations being launched into orbit. Reflecting the increase in consumer demand for connectivity in recent years, we’ve heard of plans to launch large constellations of satellites into LEO in order to deliver low latency and geographically wide-reaching coverage to consumers. With LEO becoming a reality, many questions have been raised in terms of the technical and operational challenges being delivered by low altitude satellites. At a lower orbital altitude, the satellite will be switching from one teleport to the next to deliver a continuous feed; ground segments will have to track satellites across the sky and perform handovers to and from other teleports. Managing a dynamic system increases complexity within ground segment management. What does this mean when managing spectrum at the ground segment? Can we expect LEO to have different requirements in terms of testing and calibration? What can we expect from the technology receiving LEO signals?

Similar Objectives - Operational Changes

As with satcom in any orbit, the key objective is to deliver a seamless service to consumers. Without the ground segment and satellite communicating effectively, signal degradation will impact service delivery. Radio frequency interference has been an ongoing challenge within satcom and there have been many products and solutions created to prevent RFI in GEO. With GEO’s ‘static’ positioning above the teleport, mispointing of antennas, poor-quality equipment and human error have often been the challenges to overcome.

Although the industry may still be faced with these issues at LEO, there is an added complexity in terms of switching and tracking at the ground segment. Management and monitoring systems, as well as in-depth and regular testing, will drive the success of LEO ground segments. As with any antenna, subtle changes to the pointing can have a large impact on RF up/downlinking. However, the ramifications of errors will be magnified in the intricate infrastructures of LEO.

Another consideration when assessing the landscape of LEO is frequency; LEO mega constellations are primarily utilising Ku and Ka bands as they offer greater throughput in smaller dishes. However, the need for test and measurement increases with greater directivity as it increases the likelihood of RFI and the severity of its impact on services. This once again highlights this importance of managing the ground segment correctly. RFI is incredibly unforgiving and ultimately impacts on the service received by customers.

The management of RFI and spectrum in GEO has improved as testing and monitoring has become more sophisticated. So, as we look ahead, it’s obvious that these must play a role as we establish the LEO ground segment. However, in terms of testing, how different will our solutions need to be?

Adapting the Testing Regimes

Within testing regimes, there certainly is crossover between GEO and LEO methods. Static tests see the same methods monitoring similar data at ground segments for both orbits; antenna radiation diagrams are measured in both LEO and GEO. However, LEO has significantly more data to consider due to the antenna tracking a moving satellite signal. Due to this, additional testing of the dynamic pointing systems will be required at these ground segments.

Tracking accuracy and satellite acquisition quality during the ground segment handovers will need to be tested and monitored to ensure the integrity of the system. This will be critical in ensuring that the satellites are handed over smoothly within a set window of action. The testing of LEO ground segments requires a full raster view of the antenna and not just principal cuts; the entire performance of the dish will be used for tracking, and therefore needs observing. With mega constellations being such large networks, coordination between the whole ecosystem must be precise.

Additionally, it is looking likely that flat panel antennas (FPAs) with be utilised within LEO. On top of the aforementioned challenges within LEO, questions have been raised around the industry’s ability to manage FPAs to high standards. There have been many question marks left over FPAs, with there being a lack of a uniform approach to their testing and management within the industry. FPAs need a wider scope of testing which can monitor pointing angles over time. Subtle pattern changes caused by graceful degradation could have significant effects at LEO as it could result in service interruption through mis-tracking and RFI.

As with all elements of satcom, cost efficiencies are hugely important to operators. Historically, we have seen the high costs associated with testing act as a deterrent which ultimately causes wider problems, not only for the non-testing ground segment operators, but for satcom users as a whole. Costly testing regimes could impact on the financial viability of a business, therefore the industry must deliver low-cost and flexible solutions to promote testing and calibration within LEO.

The role of UAVs

UAVs are now being utilised within GEO to deliver testing at the ground segment. Using UAV technology to complete testing regimes is appealing as it brings testing to the antenna, as opposed to having to move the antenna to a testing regime. This reduces the costs associated with downtime and the logistics of transporting antennas. So, is UAV antenna testing suitable for LEO?

Here are some of the ways the flexibility offered by UAVs within testing fits LEO requirements:

• LEO satellites appear dynamic above the ground segment and drones can be used to create testing paths that can mimic the movement of satellites. This enables accurate data to be collated.
• Drones testing solutions have already been adapted to cater for Ku and Ka band to service LEO requirements.
• Drones enable low-cost testing; something which is going to be hugely important when managing testing regimes across thousands of ground segments.
• The complexity of switching and tracking means that testing of the raster view must not be omitted. UAVs can easily deliver this type of testing.
• Flat Panel Antennas are a popular choice within the coms-on-the-move sector, which is anticipated to be a significant user of LEO. UAVs can offer the wider scope of testing required by FPAs to keep track of pattern changes, as well as in-depth testing at critical operation points.

The Future of the Ground Segment

As an industry, we’re in a great position; we have decades of experience in which we have developed solutions to mitigate problems at the ground segment for GEO. We know how to identify RFI, we know the causes often stem from poor quality equipment and human error and we know the importance of monitoring and testing systems. As we look forward to LEO, it’s important to recognise the similarities - and the differences - between the orbits’ interactions with the teleport and deliver solutions to enable LEO to live up to its potential as a revolutionary communications network that can be of benefit to us all.

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