Earth Gravitational Observatory–Crosslink Occultation system (EGO-XO)

Note: Please note that this is an “archived project” and is no longer updated. This article is meant for historical purposes only.

NASA needs instruments with improved sensitivity for measuring Earth gravity. These measurements will allow NASA to better understand the movement of water on the surface and in the atmosphere and many other aspects of Earth dynamics. In addition to increasing the sensitivity, increasing the sampling and reducing the cost of these measurements is a key need.

The Earth Gravitational Observatory–Crosslink Occultation system (EGO-XO) is an integrated Earth observational array that will continuously map Earth’s time-varying gravitational field to unprecedented resolution in both space and time, and perform next-generation LEO-LEO crosslink radio occultation of the atmosphere. These tasks will be executed concurrently through the exchange of tailored radio signals or crosslinks among small fleets of nanosats.

The EGO-XO Tipping Point project will develop and test a laboratory version of the crosslink ranging system broadcasting at two frequencies: one near the H2O absorption line at 22.7 GHz, the second at a frequency 2-3 times higher. The precise frequencies will be selected during the initial detailed design phase. From the demonstration instrument EGO-XO will produce a design for a full flight instrument together with a design for a complete nanosat to house the instrument and conduct operational missions. EGO-XO will also conduct studies of the science and commercial benefits of different configurations of spacecraft as a basis for future EGO-XO deployments.

GeoOptics and EGO-XO partners at Tyvak and JPL will deliver a system design that can achieve an order of magnitude improvement on GRACE-FO gravity mapping precision with small fleets of nanosats, each less than one-third the linear dimension and one-tenth the mass of the GRACE-FO satellites. The major deliverable for this project is a functioning laboratory version of the dual-frequency range and range rate measurement system, including transmitters and integrated receiver-processor, capable of making range rate measurements of the required precision.

An operational EGO-XO system would dramatically improve monitoring of the continual redistribution of water in all its forms (ice, liquid, and vapor) below, on, and above the surface of the Earth, allowing major improvements in water resource planning and climate change monitoring. It will also be a key resource in monitoring internal Earth dynamics and assessing hazards from volcanoes, earthquakes, and tsunamis, among many other things.

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