Space technology

Third generation of important climate satellite on the way

The GRACE satellites have been feeding the world with important climate data for over 20 years. Now the third generation is being manufactured, and DTU is supplying important instruments.

The GRACE satellites fly approximately 500 km above the Earth's surface and detect changes in the Greenland ice sheet, groundwater deposits and the amount of water in large lakes and rivers, among other things. Visualisation: NASA/JPL-Caltech

Thursday 12 December 2024

Lotte krull

Since 2002, two generations of NASA’s GRACE satellites have provided important knowledge about the freshwater cycle on Earth. It is a cycle that includes ice and meltwater, among other things, and which has a major impact on the climate system. Now the third generation of GRACE satellites is being manufactured.

The satellites measure changes in the Earth’s gravitational field. Gravity varies slightly on Earth, partly because its mass is not evenly distributed. Areas with mountains and ice caps generally have a greater gravity because they have a greater mass locally. This direct correlation between mass distribution and local gravity means that changes such as melting ice can therefore be detected by the satellites.

As a PhD student, Senior Researcher Valentina Barletta from DTU was among the first European researchers to start using data from GRACE 20 years ago. A data source she still uses in her research.

“The GRACE missions are probably one of the most successful missions when it comes to Earth observations. Measurements of gravity provide a unique insight into how the land, ice, and water masses change, and we can monitor how the ice melts and the sea rises,” says Valentina Barletta.

We’re refining the technology all the time to constantly improve the star cameras—typically 10 times per generation.

Professor John Leif Jørgensen DTU Space

DTU delivers star cameras

DTU supplies equipment for the GRACE satellites: a special version of star cameras which help to detect the changes in the gravitational field with very high precision.

For the registration, the Earth’s varying gravitational field is exploited by letting two satellites fly after each other with a distance of about 180 km between them. Variations in the local gravitational field will affect the speed of first one and then the other satellite, resulting in changes in the distance between the two satellites.

It is these changes that can be translated into changes in the mass under the satellites.
The distance between the satellites is measured with a laser, which requires an extremely precise positioning of the two satellites, and this can be carried out with the help of the star cameras.

“We have supplied star cameras for both GRACE missions, and we’re now developing the new star cameras that will be included in the third generation of GRACE. We’re refining the technology all the time to constantly improve the star cameras—typically 10 times per generation,” says Professor John Leif Jørgensen from DTU Space.

In the first GRACE mission, DTU equipment achieved a precision corresponding to 1/100 of the thickness of a hair. In the GRACE satellites in orbit today—GRACE-FO—DTU’s instrument makers achieved a precision of 1/10,000 of a hair.

The third generation of GRACE satellites—GRACE-C—is expected to enter into orbit in 2028.

Facts

About the GRACE Missions

GRACE stands for Gravity Recovery and Climate Experiment.

2002: The first GRACE mission sent into orbit.

2018: Launch of second generation of GRACE—GRACE Follow-On (GRACE-FO).

2028: Expected launch of third generation of GRACE—GRACE-C.

Topic

Space technology

Space technology is an area of increased interest from both government and industry and it’s an international position of strength for DTU. Space research not only gives us a better understanding of the universe but also of our own planet.

DTU conducts research in a wide range of areas within space technology, such as space exploration, climate monitoring and security. DTU has also developed instruments and equipment for a wide range of space missions.

Contact

Valentina Roberta Barletta Senior scientist vrba@dtu.dk

John Leif Jørgensen Professor and Head of Measurement and Instrumentation Mobile: +45 93510315 jlj@space.dtu.dk