Joakim Espeland, CEO of QuadSAT explains how drones can be used for antenna testing in space applications
Satellite antenna testing is undergoing a revolution. Drone technology coupled with unique testing software could drastically change the way satellite antennas are tested. This new approach means that antennas can be tested anywhere – easily and effectively, something that has until now been complex and costly.
The Importance of antenna testing
To anyone involved in the testing industry, no matter the vertical, it is immediately apparent that testing is a critical part of any process. Satellite antennas are no exception and the impact of poor performing antennas is far-reaching. This is further impacted by the simple fact that space is getting more and more crowded, especially with the forthcoming launches in Low Earth Orbit (LEO).
As we see more satellites launching in LEO, the ground segment will be subject to different challenges and requirements which it is not at present able to deal with effectively. As opposed to Geosynchronous Earth Orbit (GEO) satellites that move with the Earth’s rotation, as a fixed point in the sky, seen from earth, LEO satellites move at a very high speed in orbit much closer above the Earth. This means that they are not a fixed point in the sky and that antennas are constantly tracking and re-pointing to maintain connectivity. The ground infrastructure is, therefore, much more complex, and the potential for things to go wrong has increased.
Naturally things do sometimes go wrong in every orbit. When they do, very often this could mean antennas pointing to the wrong satellites, which in turn causes satellite interference. It is widely reported that equipment failure is one of the biggest causes of interference, a problem that has caused massive challenges for the satellite industry for a number of years. There are a number of different types of interference, but the result of all of them is degradation, or in some cases, loss of service, sometimes even disrupting multiple services at one time.
Current testing practices
Currently, satellite antenna testing is carried out at large test ranges, often operated by academia or research institutions. There are a limited number of test sites and these can be costly to use for some manufacturers as it can be logistically difficult, and these advanced facilities are expensive to construct. The facilities are often in demand and manufactures could risk that if their antenna is not just right, they can experience delays in the validation process and ultimately going to market. There are a number of different stages of testing, the first being antenna model validation and approval to connect to a satellite network. This is carried out prior to deployment and typically done with a satellite operator or the Global VSAT Forum. This stage means transporting them to the test range. When you consider the size of some of the satellite antennas, these are not something you can simply put in the mail.
Many antennas operate in challenging environments. In these scenarios, the antennas are often covered by radomes for protection. Even slight inaccuracies in radome manufacturing processes affect the performance of the antenna it covers. The size and shape of radomes complicate testing at current test ranges because they often do not fit onto the test-bench where the antenna is installed. Also, the characteristics of Radomes can be changed by external factors, such as UV radiation, salt water, changing air pressure etc. These are all factors that are more challenging to test in a test range where the environment could be very different to the operational environment of the radome.
Satellite antennas are also subject to regular maintenance tests, especially for comms-on-the-move applications such as on aeroplanes or ships. This is a huge expense for operators and often results in significant downtime. The antenna must always be mobile, which in these environments often means laying on dedicated flights or voyages to enable accurate results in a realistic environment. Testing and calibration must also be performed by a specialist engineer, who must be transported to wherever in the world the vessel or aircraft is located – this soon becomes incredibly costly and seems incredibly antiquated in our modern age of automation and AI.
Could drones be the answer?
Here are some of the key ways in which drone technology can solve a number of challenges being faced by the satellite industry.
1. Changes in complexity
As mentioned above, LEO and MEO constellations are changing the complexity of antenna testing. Antenna laboratories and test ranges have not been designed with this paradigm shift in mind. This means that satellite constellation antenna manufacturers miss fundamental testing functionality to validate and test their systems according to LEO/ MEO tracking. Drones offer a simplistic way of performing such analysis by having test equipment moving freely in three dimensions.
2.Access to test facilities
Antenna manufacturers have few places in the world to test their antennas and these come with a number of challenges, as outlined above. The biggest risk antenna manufacturers face are challenges during the validation campaign. This can lead to delays to get to market, which can have serious financial implications for an antenna manufacturer. Drone technology means that antenna manufacturers can easily validate the antenna at their own facility, saving time and removing uncertainty when it comes to an antenna validation campaign.
3. Cost of maintenance
Maintenance tests are critical but time consuming and expensive. Minimising maintenance costs, while still identifying gradual degradation, will contribute to satellite engineers having to visit antenna sites less often. By using a drone system on already installed antennas, it will also help to keep satellite communication precise and any underperforming antenna will be quickly identified during routine maintenance. The antennas can be quickly adjusted and this will lead to a much healthier satellite network, with less interference and fewer unwanted signals for satellite operators.
The QuadSAT System
QuadSAT has been working closely with the satellite industry to develop a system that would meet stringent testing requirements, while drastically reducing the cost and complexity of antenna testing.
The system combines state of the art drone- and RF-technology with custom-developed software making automated antenna test and measurement available anytime and anywhere. It is composed of four elements:
• an RF payload – comprised of an antenna and a signal source. The purpose of the RF payload is to illuminate the antenna under test with a plane wave. The ability to precisely point the RF payload at the antenna under test is paramount.
• a receiver system – to determine how much power is received by the test antenna.
• a drone – this replaces the positioner in the standard antenna measurements and is accurately transporting the RF payload during measurements. It also comprises a flight computer and unique pre-flight path planning software.
• a base station – this carries out real-time monitoring of the flight and analytics of the measurement results, as well as other controlling functions, such as change of parameters, or error correction with the position navigation and timing (PNT) system
Revolutionising Satellite Testing
The satellite industry is at an exciting yet challenging time. There has been a steadily growing number of satellites in space over recent years and that number is set to increase dramatically over the months and years to come. With these launches, the satellite industry is likely to be key to enabling a number of next generation advances, such as 5G and the Internet of Things. However, it can only do that by reducing costs while continuing to ensure reliability of service. Using drones to complement other testing methods means that the industry can allow for the complexities of new and future systems, while keeping costs low and reliability high.