There are more than 5,465 operational satellites in orbit around Earth today. These satellites are performing the critical work necessary to drive advances in communications, Earth observation, technology development, navigation and more. But to do this effectively, the equipment on these satellites must be reliable and calibrated to the highest level of accuracy.
When a satellite is launched into space, the sensitive communication equipment on board—known as the payload—undergoes significant stress. Extreme heat, vibration and other variables can affect the calibration and accuracy of these antennas, receivers and transmitters. As a result, they must be tested in-orbit to ensure their continued accuracy.
Calian has been building in-orbit test (IOT) systems for the operators and manufacturers of the satellite industry since the early days of satellite communications. These systems have been an integral part of the satellite industry for more than 30 years, providing a reliable method for evaluating the performance of satellite payloads after launch. These systems ensure that the performance of the payload meets the required specifications once it has been launched into orbit and has reached its destination in its orbital slot.
Measurements performed in orbit are much more complex than they are when the equipment is still in the factory. Testing these systems has typically taken weeks, or even months, to complete. But as satellite technology has evolved, so too have these IOT systems, keeping pace with the increasing frequency and throughput of modern satellites and reducing the time it takes to test them.
Early Days of IOT
In the early days of in-orbit testing, C/L band payloads were the norm. These payloads were characterized by their bent-pipe design, which meant that they simply received and transmitted signals without any processing or routing. Testing systems involved small transponders and a simple text-based user interface and even featured support for dot matrix printers.
The introduction of X-band, Ku, and digital payloads brought higher frequencies and larger transponders to the table. These payloads also had more complex routing capabilities, requiring more logic to test them, including loading carriers and power ramping. These technological improvements required more interactive user interfaces, allowing the monitoring of multiple windows as well as support for PDF reports.
The next generation of IOT testing systems was built to accommodate bent-pipe Ka payloads, which had even higher frequencies and larger transponders. These systems also considered the impact of rain fade and atmospheric conditions on the performance of the payload. This required advanced algorithms and specialized hardware to accurately measure and correct for these factors.
Present and Future
High-throughput satellites and software-defined satellites have become the norm in the industry today. For this reason, current testing systems are designed to handle digital Ka payloads, which can have thousands of carriers per transponder and the ability to load thousands of carriers at once. These payloads have greatly expanded the capabilities of satellite communications and have driven the need for even more advanced IOT testing systems. The latest iteration of these systems is designed to work with ultra-high frequency V-band payloads, which have ultra-wide transponders and even more complex routing capabilities.
“We’ve evolved our test systems in order to meet the demands for higher throughput, faster measurements and a quicker pace to the overall testing campaigns with the newest payloads,” says Peter Waskowic, Vice President of Satcom Products at Calian. “The measurements are accurate and fast, but also flexible enough to test the satellite once it has reached its ultimate destination.”
Galileo IOT System
An example of a Calian IOT system currently installed in Belgium and Germany tests the Galileo GNSS constellation of mid-Earth orbit satellites used for global positioning. These satellites require extremely accurate measurements so that their end users—people with a GNSS-enabled cell phone, for example—receive reliable positioning data.
“There were very high accuracy requirements for that system,” says James Mantyka, Senior Systems Designer at Calian, who led the project. “We were proud that we met, or beat, all the expectations for that system,” he says.
In addition to the high requirements for accuracy, the mid-Earth orbit and constellation nature of the Galileo satellites added several requirements. The Galileo IOT system had to accommodate pass management—knowing which satellites are overhead and which are connected—which required added logic. Built-in telemetry interfaces take telemetry from the satellite and use them in the IOT measurement techniques. Signals from the satellite help the system to determine the next step in the measurement process. Calian also built custom analysis tools into the system, such as a mechanism for translating position signals into data for measurement.
Over the past 30 years, the evolution of Calian IOT testing systems has kept pace with developments in satellite technology. As satellite payloads have become more sophisticated, testing systems have had to evolve to keep up. These IOT systems play a crucial role in the satellite industry and affect the lives of everyone on Earth in some way. These IOT systems will continue to play an essential role in the satellite industry for years to come.
