Qinetiq has completed final testing of the ion thrusters that will enable a European space mission to measure and map the Earth’s gravity field in far greater detail than ever previously achieved.
Qinetiq’s T5 ion thrusters will provide high precision drag compensation for the European Space Agency (ESA) GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) spacecraft, due for launch later this year. The data captured by GOCE will contribute significantly to our understanding of the Earth’s structure, climate and the impacts of climate change.
GOCE will measure the Earth’s gravity field and model the geoid, or average sea level, with extremely high accuracy and spatial resolution. A precise model of the Earth’s geoid is crucial for deriving accurate measurements of ocean circulation, sea-level change and terrestrial ice dynamics, all of which are affected by climate change. The geoid is also used as a reference surface from which to map all topographical features on the planet.
Qinetiq was awarded a £4.6m contract by Astrium, ESA’s prime contractor for the GOCE platform, in 2001 to provide the two Ion Thruster Assemblies (ITAs) for the spacecraft. By using Qinetiq’s T5 ion thruster the spacecraft will be able to compensate for the drag experienced in orbit, thereby allowing highly accurate measurements of the Earth’s gravity field.
Travelling at 8km/s and operating at an orbital altitude of 240km, the spacecraft will experience a small but significant disturbance in its motion from atmospheric drag. This disturbance is constantly changing so continuous and precise compensation is needed to allow the highly sensitive accelerometers on board to map the earth’s gravitational field.
An improved knowledge of gravity anomalies will contribute to a better understanding of the Earth’s interior, such as the physics and dynamics associated with volcanism and earthquakes and also further our knowledge of land uplift due to post-glacial rebound.
In addition to the precision provided by the T5 thrusters, the ion engines are mass efficient, requiring only 40kg of propellant for the entire 20-month duration of the mission. This is achieved by ejecting xenon gas propellant out of the thrusters at a velocity in excess of 40,000 m/s, which is at least 10 times faster than any other conventional rocket thruster employing volatile chemicals, such as those used on the Space Shuttle.
In addition to providing the T5 thrusters, Qinetiq has produced control software and algorithms for the GOCE propulsion system. Qinetiq is also supporting the testing of the complete propulsion sub-system, the Ion Propulsion Assembly (IPA), of which the ITA is a key component and for which Astrium has overall responsibility.
Qinetiq is currently working with partners to qualify its T6 thruster, an even more advanced electric propulsion system aimed at enabling deep space missions and capable of extending the operational life of the next generation of commercial communications satellites.