The Contribution of Space Technologies to Arctic Policy Priorities

C.6 Science Satellite Systems Inventory The following pages contain templates of existing and planned science satellite systems. C.6.1 Existing Science Satellite Systems Gravity Recovery and Climate Experiment (GRACE) Facts in Brief Country: USA Operations: NASA Status: In operation, launched, March 2002

Mission Duration: Satellite design life of five years, however, system is currently still in operation. The duration of the mission is dependent on the health of the battery and the duration within each orbit when the battery is in use. It is currently being monitored on a weekly basis. Coverage: Arctic circumpolar region Orbit: two identical spacecrafts flying approximately 220 kilometers apart in a polar orbit 500 kilometres above the Earth Key Science Areas: map variations in the Earth’s gravity to inform our understanding of land mass variation, water currents and ice sheet and glacier activities Web link: http://science.nasa.gov/missions/grace/ The primary goal of the GRACE mission is to accurately map variations in the Earth’s gravity field over its lifetime. These detailed measurements of Earth’s gravity field will lead to discoveries about gravity and Earth’s natural systems. GRACE will be able to map the Earth’s gravity fields by making accurate measurements of the distance between the two satellites, using GPS and a microwave ranging system. It will provide scientists from all over the world with an efficient and cost-effective way to map the Earth’s gravity fields with unprecedented accuracy. The results from this mission will yield crucial information about the distribution and flow of mass within the Earth and its surroundings. The gravity variations that GRACE studies include: changes due to surface and deep currents in the ocean; runoff and ground water storage on land masses; exchanges between ice sheets or glaciers and the oceans; and variations of mass within the Earth, improved profile of Earth’s atmosphere. Due to an uneven distribution of mass inside the Earth, the Earth’s gravity field is not uniform - that is, it has «lumps». By far the largest is a flattening at the Polar regions, called the Earth’s oblateness. The GRACE Mission is assisting scientists to map out the precise location and size of these lumps, enabling greater understanding of the structure of the Earth. Additionally, GRACE data is also used to monitor the mass and location of water as it moves around on the surface of the Earth, cycling between the land, oceans, and polar ice caps. In particular, a recent Study (Jan/12) undertaken by NASA and the University of Washington, supported by data from the GRACE mission, allayed concerns that melting Arctic sea ice could be increasing the amount of freshwater in the Arctic enough to have an impact on the global «ocean conveyor belt» that redistributes heat around our planet Mission Duration: Originally 20 months, including a 3-month commissioning and calibration phase, followed by science measurement phases adapted to a long-eclipse hibernation period. In November 2010, granted an 18 month extension. Coverage: Global circumpolar region Orbit: Sun-synchronous, near-circular, dusk-dawn, low-Earth. Key Science Areas: Measurement of Earth’s gravity field and modeling the geoid with improved accuracy and spatial resolution. Web link: http://www.esa.int/esaLP/SEMRNIRHKHF_LPgoce_0.html GOCE’s main objective is to measure Earth’s gravity field and model the geoid with improved accuracy and spatial resolution. Data from this advanced gravity mission will improve knowledge of ocean circulation, which plays a crucial role in energy exchanges around the globe, sea-level change and Earth-interior processes. GOCE will also help to make significant advances in geodesy and surveying. This low-orbiting satellite is the first mission to employ the concept of ‘gradiometry’ – the measurement of acceleration differences over short distances between an ensemble of proof masses inside the satellite. GOCE is equipped with three pairs of ultra-sensitive accelerometers arranged in three dimensions that respond to tiny variations in the gravitational tug of Earth as it travels along its orbital path. The three axes of the gradiometer allow the simultaneous measurement of six independent but complementary components of the gravity fields. The satellite also carries an electric ion thruster system that continuously generates tiny forces to compensate for any drag the satellite experiences at low altitude. The gravity variations that GOGE studies will assist with the study of: oceanography, surveying and leveling, solid Earth physics, geodesy and sea-level research, and will contribute to furthering the understanding of climate change. GOCE is mapping variations in the gravity field with extreme detail and accuracy. This will result in a unique model of the ‘ geoid’, which is the surface of equal gravitational potential defined by the gravity field – crucial for deriving accurate measurements of ocean circulation and sea-level change, both of which are affected by climate change and subsequently impact Arctic interests

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Gravity field and steady-state Ocean Circulation Explorer (GOCE) Facts in Brief Country: EU Operations: ESA Status : In operation, launched March 2009

Mission Objectives

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Relevance to Arctic Interests

99 C. INVENTORY OF SPACE SYSTEMS