\tEnabling & Support<\/p>\n
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On 28 September<\/a>, ESA\u2019s\u00a0Juice<\/a>\u00a0mission reached another important Jupiter-bound milestone with its penultimate gravity\u00a0assist\u00a0manoeuvre: a flyby of Earth. This encounter, however, was not only an essential step on the road to Jupiter, but an opportunity to rehearse the observations and operations that will define Juice\u2019s exploration of the Jovian system.\u00a0\u00a0<\/p>\n Since its launch on 14 April 2023, Juice has been making its way towards Jupiter and its icy moons, where it will arrive in 2031. But getting there is not straightforward.<\/p>\n \u201cIf you want to go directly to Jupiter, you need to reach a certain velocity,\u201d explains Arnaud Boutonnet, ESA Juice Mission Analyst. \u201cThis is why you need gravity assist manoeuvres.\u201d<\/p>\n These manoeuvres use a planet\u2019s gravity to alter a spacecraft\u2019s course and speed. With its recent Earth gravity assist, Juice has now completed three of four planned flybys<\/a>.<\/p>\n Following its Venus flyby, Juice had enough speed relative to Earth, but was not yet heading in\u00a0the right direction.\u00a0This latest flyby effectively steered the spacecraft around 20 degrees towards Jupiter, ahead of a final adjustment during its last Earth flyby in 2029.<\/p>\n But the milestone was about more than navigation. It also gave mission teams a valuable opportunity to rehearse for the operational and science challenges awaiting Juice at Jupiter.<\/p>\n \t\t\t\t\t\t\tJuice flies by Earth \u2013 the complete path<\/a><\/p>\n \tA rehearsal in the dark<\/p>\n This past August, many witnessed the spectacular\u00a0total solar eclipse<\/a>\u00a0that swept over Greenland, Iceland, Spain and parts of Portugal. For observers on Earth, totality lasted just over two minutes.<\/p>\n Spacecraft encounter eclipses too.<\/p>\n During its Lunar Earth gravity assist in 2024, Juice experienced a 32 minute long eclipse. Its recent Earth flyby, however, broke a new mission record.<\/p>\n Before closest approach, Juice slipped into Earth’s shadow, spending three hours in full umbra and six in partial shadow. More importantly, the eclipse closely resembled conditions Juice will encounter at Jupiter, giving the Flight Control Team a rare opportunity to test future operational strategies years before arrival.<\/p>\n \u201cFlybys have become fairly routine for the mission, but they still require a great deal of preparation. We’ve been preparing for this one for more than a year,\u201d says Juice Spacecraft Operations Manager Angela Dietz.<\/p>\n The eclipse turned that preparation into a rehearsal for Jupiter.<\/p>\n \tTotal eclipse of the charge<\/p>\n \t\t\t\t\t\t\tJuice solar cells with cover glass and grounding network of tiny wires<\/a><\/p>\n Juice is powered\u00a0by two large\u00a0so<\/a>lar arrays<\/a>, which together make up 85\u00a0squared\u00a0metres. This is roughly\u00a0half\u00a0the area of a volleyball court.\u00a0Those arrays will be essential at Jupiter, where sunlight is just 3% as intense as it is at Earth, and eclipses can last up to five hours.\u00a0<\/p>\n \u201cThis was our first opportunity to test those prolonged eclipse conditions in flight,\u201d says Angela.\u00a0<\/p>\n Months in advance, the Flight Control Team at the European Space Operations Centre (ESOC) rehearsed eclipse and contingency scenarios while Science Operations Teams from the European Space and Astronomy Centre (ESAC) prepared instruments for observations and calibration activities.\u00a0<\/p>\n On the evening of 27 September, as Juice entered the penumbra at 21:30 CEST, flight operators at ESOC monitored the drop in solar-array power and rise in battery use as the telemetry came in via ESA’s Cebreros\u00a0Estrack\u00a0deep space antenna.\u00a0\u00a0<\/p>\n After the three-hour umbra phase, the battery power dropped to 54% before the solar arrays resumed power generation at 04:14 CEST. With the operational limit set at 35% and the spacecraft behaving nominally, the result exceeded\u00a0expectations.<\/p>\n \u201cThe power data we got from this flyby is very important because it will be used for future Jupiter eclipse simulations,\u201d explains Paula Betriu, Juice Science Operations Engineer working at ESAC for Starion Spain.\u00a0<\/p>\n But the eclipse was about more than simply keeping the spacecraft alive.<\/p>\n \t\t\tJuice\u2019s September 2026 Earth flyby: the movie \tScience beyond survival<\/p>\n At Jupiter, Juice will need to continue carrying out science even during long periods of darkness.<\/p>\n \u201cInitially we thought we would not have enough power for the payloads. But after we looked into it further, we realised we could keep several instruments active and make full use of the opportunity,\u201d recalls Angela.<\/p>\n
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