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General Relativity Experiment with Galileo satellites 5 and 6 (GREAT)

We report on a new test of the gravitational redshift and thus of local position invariance, an integral part of the Einstein equivalence principle, which is the foundation of general relativity and all metric theories of gravitation. We use data spanning 1008 days from two satellites of Galileo, Europe’s global satellite navigation system (GNSS), which were launched in 2014, but accidentally delivered on elliptic rather than circular orbits. The resulting modulation of the gravitational redshift of the onboard atomic clocks allows the redshift determination with high accuracy.

France

15/710

SYRTE
General Relativity Experiment with Galileo satellites 5 and 6 (GREAT)

The GREAT project provides an improved test of Einstein's theory of General Relativity by analyzing the relativistic gravitational redshift as observed in the clock data from GSAT-0201 and GSAT-0202. These satellites have been injected into highly eccentric orbits following a launch mishap, providing us with the unique chance to perform an important test of fundamental physics. The gravitational redshift describes the slowing down of the ticking rate that a clock experiences in a gravitational potential. This effect is a fundamental aspect of Einstein's theory of General Relativity.

Germany

15/711

ZARM
Feasibility of Operational use of Satellite Laser Ranging observations for GNSS orbit determination and time synchronisation and GNSS Science

Within the framework of ESA’s Alcantara initiative international R&D Studies were funded.

Austria

AO5-b

AUSTRIAN ACADEMY OF...
Future Concepts for Galileo Search-and-Rescue Space and Ground Segment (Parallel b)

While the MEOSAR is moving to FOC with Galileo satellites that are equipped with SAR transparent payloads, ESA is already investigating its future Galileo-2 (G2G) system for new features. In this framework, one of the aims of the ESA study on Future Concepts for Galileo Search And Rescue was to define a preliminary design of a new SAR payload capable of processing both First Generation Beacon (FGB) and future Second Generation Beacon (SGB) signals.

France

15/708-b

Thales Alenia Space
Future Concepts for Galileo Search-and-Rescue Space and Ground Segment (Parallel a)

MEOSAR is a system designed to locate emergency beacons anywhere on the Earth in order to coordinate rescue efforts for people, vehicles and facilities in distress. It works by evaluating the time and the frequency of the beacon signal upon arrival at the receiver. From these the relative distance and velocity of the sender can be calculated if sufficient data points have been collected. It is beneficial to receive the beacon on several different spacecraft to optimise the accuracy of the trace.

Germany

15/708-a

OHB System AG
Disposal strategies analysis for MEO orbits

The Medium Earth Orbit (MEO) region, home of the operational Global Navigation Satellite Systems (GNSS) GPS and Glonass, is becoming more and more exploited with the advent of the European Galileo and the Chinese Beidou constellations, both in their build-up phase. The sensitive applications of the navigation satellites and the absence of any natural sink mechanism, such as the atmospheric drag, call for a careful debris prevention policy able to preserve the MEO environment, avoiding in the future the problems now already faced by the LEO and the Geostationary Orbit (GEO) environments.

Italy

12-604-01

IFAC-CNR

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