Re­lay Satel­lite

China Pictorial (English) - - Buzzwords - Edited by Li Zhuoxi

The word “re­lay” in “re­lay satel­lite” refers to ex­pand­ing the dis­tance of net­work trans­mis­sion by send­ing or for­ward­ing data sig­nals.

A re­lay satel­lite, some­times re­ferred to as “the satel­lite of satel­lites,” is a kind of com­mu­ni­ca­tion satel­lite used to trans­mit mas­sive vol­umes of data. By pro­vid­ing data re­lay, teleme­try, track­ing and com­mand (TT&C) ser­vices for space­craft and satel­lites, it greatly im­proves the ef­fi­ciency and emer­gency re­sponse ca­pa­bil­i­ties of var­i­ous satel­lites. The tech­nol­ogy en­ables real-time data trans­mis­sion of re­sources satel­lites and en­vi­ron­men­tal satel­lites, earn­ing more warn­ing time for ma­jor nat­u­ral dis­as­ters.

Early on the morn­ing of May 21, 2018, China suc­cess­fully launched the world’s first re­lay satel­lite named Que­qiao (“Mag­pie Bridge”) in or­bit around the moon, which will pro­vide a com­mu­ni­ca­tion link between the earth and the planned Chang’e-4 lu­nar probe that will soft-land on and ex­plore the moon’s mys­te­ri­ous far side at the end of 2018.

The re­lay satel­lite will solve a ma­jor dif­fi­culty in lu­nar ex­plo­ration. The tidal forces of the earth slowed the moon’s ro­ta­tion to the point where the same side al­ways faces the earth. The other side, most of which is never vis­i­ble from the earth, is known as the “dark side” of the moon.

Due to shield­ing from the moon it­self, the de­tec­tor land­ing on the far side of the moon can­not di­rectly re­al­ize TT&C com­mu­ni­ca­tion and data trans­mis­sion with the earth.

The Que­qiao re­lay satel­lite will as­sist the con­trol cen­ter on the earth to en­hance con­trol of the lu­nar probe to en­sure a smooth land­ing.

May 21, 2018: Tech­ni­cians ready the Que­qiao re­lay satel­lite for launch at the Xichang Satel­lite Launch Cen­ter in the Liang­shan Yi Au­tonomous Pre­fec­ture, Sichuan Prov­ince. That same day, a Long March-4c rocket car­ry­ing the re­lay satel­lite was suc­cess­fully launched from the satel­lite launch cen­ter. VCG

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