Mapping planet Earth for better positioning: ESA’s GENESIS mission

Written by Copernical Team Thursday, 20 October 2022 09:43

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ESA’s Navigation Directorate is planning a new satellite whose results will enable the generation of an updated global model of Earth – the International Terrestrial Reference Frame, employed for everything from land surveying to measuring sea level rise – with an accuracy down to 1 mm, while tracking ground motion of just 0.1 mm per year. This improvement, at a stroke, will have a major impact in multiple navigation and Earth science applications, including enhancing the precision of the Galileo navigation system. This mission, called GENESIS, is being proposed to ESA’s Council Meeting at Ministerial Level next

“But now by operating all of them together from the same satellite, with the instruments duly calibrated and synchronised, we can identify and correct for these biases over time, reaching much more accuracy and stability overall. GENESIS will in turn become a dynamic space geodetic observatory, which efficiently complements the existing ground-based infrastructure, providing a breakthrough in improving the accuracy and consistency of the Earth reference frame.”

Combined scientific measurements

GENESIS will embark the following geodetic payloads, today used to fix the position of observing stations:

Global Navigation Satellite System receiver	Satellite navigation, otherwise known as satnav, is one of the most widely-used geodetic techniques. Positioning of a given site is fixed continuously, using multiple satnav constellations for added accuracy, and over time becomes more and more precise down to millimetre scale, additionally revealing gradual drifts due to Earth movement.
Satellite Laser Ranging	This measurement method involves bouncing laser pulses off a retroreflector aboard a satellite, then measuring its two-way travel time to fix the distance the laser light has shone, down to a few millimetres.
DORIS receiver	France’s Doppler Orbitography and Radiopositioning Integrated by Satellite or DORIS system has been in operation for the past three decades and has become a standard data source for the ITRF. DORIS signals from satellites are compared to those coming from 60-strong receiver station network spaced across the planet in terms of their ‘Doppler shift’ – rising in frequency upon approach and sinking when moving away – to fix their relative position down to centimetre scale.
VLBI	Very Long Baseline Interferometry, or VLBI, began as a radio astronomy technique where observations of celestial objects such as quasars from multiple radio telescopes are combined together precisely to yield resolution equivalent to a single giant telescope. For geodesy the technique can be reversed so that the precise timings of joint observations of celestial targets can derive the exact distance between the sites. An artificial radio source aboard GENESIS will therefore serve as a common target for multiple VLBI stations down on Earth, broadcasting on at least two frequency bands.

One or more of these instruments, once duly qualified and characterised with the GENESIS mission, could also potentially be flown on future Galileo satellites.