og ee : ▁ 1 2 0   km . ▁ ▁X - ray ▁astronom y ▁satellite ▁ ▁X - ray ▁astronom y ▁sat ell ites ▁study ▁X - ray ▁em issions ▁from ▁cel est ial ▁objects . ▁Sat ell ites , ▁which ▁can ▁detect ▁and ▁transmit ▁data ▁about ▁the ▁X - ray ▁em issions ▁are ▁deployed ▁as ▁part ▁of ▁branch ▁of ▁space ▁science ▁known ▁as ▁X - ray ▁astronom y . ▁Sat ell ites ▁are ▁needed ▁because ▁X - rad iation ▁is ▁absor bed ▁by ▁the ▁Earth ' s ▁atmosphere , ▁so ▁instruments ▁to ▁detect ▁X - ray s ▁must ▁be ▁taken ▁to ▁high ▁alt itude ▁by ▁bal lo ons , ▁sound ing ▁rock ets , ▁and ▁sat ell ites . ▁ ▁X - ray ▁teles cop es ▁and ▁mirror s ▁ ▁X - ray ▁teles cop es ▁( X RT s ) ▁have ▁varying ▁direction ality ▁or ▁imag ing ▁ability ▁based ▁on ▁gl ancing ▁angle ▁reflection ▁rather ▁than ▁ref raction ▁or ▁large ▁deviation ▁reflection . ▁This ▁limits ▁them ▁to ▁much ▁nar ro wer ▁fields ▁of ▁view ▁than ▁visible ▁or ▁U V ▁teles cop es . ▁The ▁mirror s ▁can ▁be ▁made ▁of ▁cer am ic ▁or ▁metal ▁fo il . ▁ ▁The ▁first ▁X - ray ▁teles cope ▁in ▁astronom y ▁was ▁used ▁to ▁observe ▁the ▁Sun . ▁The ▁first ▁X - ray ▁picture ▁( t aken ▁with ▁a ▁gra zing ▁inc idence ▁teles cope ) ▁of ▁the ▁Sun ▁was ▁taken ▁in ▁ 1 9 6 3 , ▁by ▁a ▁ro