JPL, Airbus continue with GRACE-C to measure Earth’s gravity field

NASA’s Jet Propulsion Laboratory (JPL) is working with the German Space Agency, and the craft will be built at the German Aerospace Center (DLR).

During its planned five year lifetime, the GRACE-C (Gravity Recovery And Climate Experiment-Continuity) Mission will observe the Earth’s groundwater, oceans, ice sheets, and land shift, month-to-month. This will be done by measuring changes in the planet’s gravity field.

It consists of two identical satellites flying around 200 km apart at an orbit altitude of 500 km with an inclination of 89 degrees. Each satellite will measure approximately 3 x 2 x 1 metres and weigh around 600 kg.

“It is amazing to think that, without looking down at Earth, two satellites more than 200 km away from each other, can tell us how quickly our ice sheets are melting,” said Alain Fauré, Head of Space Systems at Airbus.

“In environmental monitoring, continuity is key. The valuable data provided by the previous GRACE missions is testament to their success and it is great news that Airbus continues to be part of this international mission providing the tools to measure how our climate is evolving.”

Specifically, Airbus Defence and Space in Friedrichshafen will design, build and deliver the satellites to the launch site. The contract also includes Launch and Early Orbit Phase (LEOP) support for NASA/JPL. The mission will be operated by the German Space Operations Center (GSOC) of DLR.

The launch date for GRACE-C is planned to be no earlier than late 2028 and will take place in the USA.

The partnership between the two organisations has been in place for more than 20 years: it started in 2002 with GRACE and continues with GRACE-FO (Follow-On), which was launched in 2018.

Airbus highlights that GRACE-C is a rebuild of the two GRACE Follow-On satellites with upgraded avionics, including the joint US-German Laser Ranging Interferometer (LRI), already flown on GRACE Follow-On as an experimental payload. This will now be the main ranging instrument.

GRACE-C

The method of the mission is described as follows.

Like with its predecessors, the GRACE-C mission will precisely measure small distance changes between the flying satellites due to gravity variations. This will be measured with an unprecedented precision, says the company, down to the micron.

As the pair of satellites circle the Earth, areas of slightly stronger gravity will affect the spacecraft’s positions and the distance between them.

The extremely precise microwave ranging system will detect such changes and should enable the mapping of Earth’s gravity field with “unmatched accuracy”, says Airbus.

“Over the months and years, the comparison of these gravity maps, or the evolution of mass concentrations, will enable scientists to assess the global water balance, including groundwater tables and ice sheets, and the influence of climate change. It will also provide insights into deep and surface currents in oceans and ocean height contributors.”

Image: Airbus – GRACE-C Mission will succeed GRACE and GRACE-FO in measuring the Earth’s gravity field

See also: Airbus buys out OneWeb from AOS jv, satellite manufacturing facility