News › Fraun­ho­fer IOF · Space mis­sion JUICE laun­ches into space with telescope from Jena to explore Jupi­ter and its moons

It is the lar­gest pla­net in our solar sys­tem and the­r­e­fore appro­pria­tely bears the name of the Greek father of the gods: Jupi­ter. No fewer than 92 moons orbit this pla­net, and new satel­li­tes are being dis­co­vered by rese­ar­chers all the time. Espe­ci­ally the moon Gany­mede, which is covered with ice, is in the focus of the sci­en­tists, because it has a spe­cial simi­la­rity to the earth.

To inves­ti­gate Gany­mede, but also the moons Cal­listo and Europa as well as Jupi­ter its­elf, the Euro­pean Space Agency is sche­du­led to launch a space probe on April 13 in the direc­tion of the giant pla­net, the »Jupi­ter Icy Moons Explo­rer« – in short: JUICE. To ful­fill its rese­arch mis­sion, a total of ten sci­en­ti­fic instru­ments are on board of the space­craft. One of them is the »Gany­mede Laser Alti­me­ter«, also known as GALA, which was co-deve­lo­ped by rese­ar­chers from Jena. The instru­ment is inten­ded to mea­sure the geo­gra­phic com­po­si­tion of Jupi­ter’s moon.

Explo­ra­tion of Jupi­ter’s moon Gany­mede using laser altimetry

»As part of the JUICE mis­sion, a laser alti­me­ter is being used for the first time as a high-pre­cis­ion metal optic for explo­ring Jupi­ter’s icy moon Gany­mede,« explains Dr. Ste­fan Risse, head of the Pre­cis­ion Opti­cal Com­pon­ents and Sys­tems depart­ment at Fraun­ho­fer IOF. »With a laser alti­me­ter, distances can be mea­su­red very pre­cis­ely, even over very long distances,« he con­ti­nues. »We hope to use it to gain new, fun­da­men­tal sci­en­ti­fic insights into the topo­gra­phy of Jupi­ter’s moon Gany­mede and the ques­tion of its ori­gin,« he adds.

To coll­ect this infor­ma­tion, GALA sends laser pul­ses to the moon from an orbit around Gany­mede – i.e., from about 500 kilo­me­ters – and recei­ves reflec­ted signals. From the tran­sit time of the pulse, the distance to the lunar sur­face can be deter­mi­ned and the topo­gra­phy cal­cu­la­ted. This requi­res a high-pre­cis­ion laser recei­ving unit. This was rea­li­zed by Fraun­ho­fer IOF in Jena tog­e­ther with HENSOLDT Optro­nics GmbH from Ober­ko­chen, Ger­many. For this pur­pose, Fraun­ho­fer IOF deve­lo­ped a spe­cial reflec­ting telescope that cap­tures the laser pul­ses that are reflec­ted back from the lunar sur­face. In this way, GALA can mea­sure the topo­gra­phy of Jupi­ter’s moon with a reso­lu­tion of less than 10 centimeters.

One par­ti­cu­larly important ques­tion that GALA could ans­wer in the future is whe­ther there are water depo­sits on Gany­mede: »The mea­su­re­ments with GALA take place at dif­fe­rent orbi­tal posi­ti­ons of the moon Gany­mede in rela­tion to Jupi­ter,« explains Dr. Hen­rik von Luko­wicz, head of the Pre­cis­ion Sys­tems rese­arch group at Fraun­ho­fer IOF. »If there were water below the sur­face, the tidal forces as a result of the moon’s motion would lead to a defor­ma­tion of the sur­face. This means GALA could pos­si­bly even prove the exis­tence of water.«

GALA is the first deep-space laser altimeter

The GALA laser alti­me­ter will be the worl­d’s first deep-space laser alti­me­ter to be deployed at a distance of appro­xi­m­ately one bil­lion kilo­me­ters from Earth. The mis­sion will take more than ten years: the JUICE probe will initi­ally need eight years to arrive in orbit around Jupi­ter. The sub­se­quent three years will be spent explo­ring Jupi­ter’s moons Europa, Cal­listo and Gany­mede, as well as Jupiter.

»On the way to Jupi­ter, the opti­cal telescope we have deve­lo­ped must cope with extreme envi­ron­men­tal con­di­ti­ons in ultra-high vacuum, cha­rac­te­ri­zed by enorm­ous acce­le­ra­tion during rocket launch, high tem­pe­ra­ture chan­ges and very strong cos­mic radia­tion,« says Dr. von Luko­wicz, explai­ning the spe­cial demands on opti­cal com­pon­ents in space. »The excel­lent opto-mecha­ni­cal pro­per­ties will make it pos­si­ble to explore Jupi­ter’s icy moons even under these chal­len­ging conditions.«

The JUICE mis­sion is sche­du­led to launch from ESA’s Kou­rou space­port in French Guiana on April 13 or April 15, 2023 at the latest. The car­rier rocket for the launch will be Ariane 5.

Award-win­ning coope­ra­tion bet­ween rese­arch and industry

The entire GALA sys­tem was deve­lo­ped and built under the lea­der­ship of the DLR Insti­tute of Pla­ne­tary Rese­arch. In addi­tion to HENSOLDT Optro­nics GmbH from Ober­ko­chen in Baden-Würt­tem­berg and Fraun­ho­fer IOF from Thu­rin­gia, other part­ners from Ger­many, as well as Japan, Switz­er­land and Spain are involved.

For the sci­en­ti­fic and entre­pre­neu­rial part­ner­ship espe­ci­ally bet­ween the com­pany HENSOLDT and the Fraun­ho­fer IOF, the team mem­bers invol­ved were hono­red with the Lothar Späth Award in Novem­ber 2021. The Lothar Späth Foun­da­tion pres­ents the award to coope­ra­tively crea­ted, out­stan­ding inno­va­tions in pro­ducts, pro­ces­ses and ser­vices in Baden-Würt­tem­berg and Thuringia.