ESA's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was operated in an extremely low Earth orbit down to 229 km altitude to map the Earth's gravity field. As anticipated, on 21 st Oct 2013 drag-free control stopped owing to the depletion of fuel for GOCE's ion propulsion system. To get the most out of what was still a fully functional spacecraft designed to fly in a drag environment, ESA kept operating the mission as long as possible in the ensuing orbital decay phase. Exceeding all expectations, the S/C remained functional and contact could be maintained down to extreme altitudes of little over 100 km, less than 1.5 hours before re-entry. This allowed collecting a set of most valuable data prior to GOCE's demise on 11 th Nov 2013 close to the Falkland Islands. The paper presents the preparation and execution of this unique operations campaign.
An effort to escort students in learning some abilities, awareness, ideas, approach and skills is called teaching." [1] According to the literature [2], the transmission of knowledge occurs mainly according to three methodologies, that are strongly influenced by the context of reference, the physical space and the relationships between the different actors.
<p>The European Space Agency (ESA)&#8217;s wind mission, Aeolus, was launched on 22 August 2018. It is a member of the ESA Earth Explorer family and its main objective is to demonstrate the potential of Doppler wind Lidars in space for improving weather forecast and to understand the role of atmospheric dynamics in climate variability. Aeolus carries a single instrument called ALADIN: a high sophisticated spectral resolution Doppler wind Lidar which operates at 355 which is the first of its kind to be flown in space.</p>
<p>Aeolus provides profiles of single horizontal line-of-sight winds (primary product) in near-real-time (NRT), and profiles of atmospheric backscatter and extinction. The instrument samples the atmosphere from about 30 km down to the Earth&#8217;s surface, or down to optically thick clouds. The required precision of the wind observations is 1-2.5 m/s in the troposphere and 3-5 m/s in the stratosphere while the systematic error requirement be less than 0.7 m/s. The mission spin-off product includes information about aerosol and cloud layers. The satellite flies in a polar dusk/dawn orbit (6 am/pm local time), providing ~16 orbits per 24 hours with an orbit repeat cycle of 7 days. Global scientific payload data acquisition is guaranteed with the combined usage of Svalbard and Troll X-band receiving stations.</p>
<p>After almost five years in orbit and despite some performance issues related to its instrument ALADIN, Aeolus has achieved all its scientific objectives and gone beyond its original designed life-time in space. Positive impact on the weather forecast has been demonstrated by multiple NWP centres world-wide, with four European meteorological centres now are assimilating Aeolus winds operationally, paving the way to its successor: EPS-Aeolus. Aeolus data is being used with success over a number of innovative research streams with growing scientific impact on literature.</p>
<p>The status of the Aeolus mission will be presented including the last main challenge to re-enter the satellite from space with an assisted scenario instead of an uncontrolled one, as initially foreseen by design.</p>
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