Durable Juno

Jupiter’s in­tense ra­di­a­tion called for a ro­bust, ar­moured space­craft

Sky at Night Magazine - - THE JUNO MISSION -

Ap­proach­ing Jupiter more closely than any other space­craft and sur­viv­ing the fiercest plan­e­tary mag­netic and ra­di­a­tion en­vi­ron­ment in the So­lar Sys­tem was al­ways go­ing to be a for­mi­da­ble chal­lenge. Most of Juno’s elec­tron­ics, in­clud­ing its RAD750 mi­cro­pro­ces­sor, are com­posed of ra­di­a­tion-re­sis­tant tan­ta­lum, with wiring sheathed in a cop­per and stain­less steel braid, all en­cased within the 10mm-thick walls of a cube­shaped ti­ta­nium vault. Al­though not im­pen­e­tra­ble, the vault re­duces ra­di­a­tion dam­age by 800 times.

For ex­tra ro­bust­ness, Juno’s hard­ware was built big­ger and ex­ter­nal com­po­nents – so­lar pan­els, cam­eras, sen­sors – re­ceived added pro­tec­tion, in­clud­ing 12mm-thick glass sheets. Ground-based elec­tron tests showed the so­lar pan­els would lose 0-15 per cent of their out­put at Jupiter, so were built 10-15 per cent big­ger. Over its life­time, the space­craft will en­dure the equiv­a­lent of 100 mil­lion den­tal X-rays.

“Juno is ba­si­cally an ar­moured tank,” says prin­ci­pal in­ves­ti­ga­tor Scott Bolton. “With­out its pro­tec­tive shield or ra­di­a­tion vault, Juno’s brain would get fried on the very first pass.”

Much of its 53.5-day or­bit is spent be­yond the worst ra­di­a­tion, but at per­i­jove it dives quickly through the sear­ing equa­to­rial re­gions. “We thread a nee­dle,” says Bolton. “By go­ing over the poles, we’re able to drop down in a small gap be­tween the at­mos­phere and these in­tense ra­di­a­tion belts.”

Just af­ter hav­ing had its ra­di­a­tion vault fit­ted over its propul­sion mod­ule, Juno is lifted on a ro­ta­tion fix­ture at Lock­heed Martin Space Sys­tems, Den­ver in June 2010

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