▁radio astr onomy . ▁Explorer ▁ 3 8 ▁was ▁launched ▁as ▁part ▁of ▁the ▁Ex pl or ers ▁program , ▁being ▁the ▁first ▁of ▁the ▁ 2 ▁sat ell ites ▁R AE . ▁Explorer ▁ 3 8 ▁was ▁launched ▁on ▁ 4 ▁July ▁ 1 9 6 8 ▁from ▁V anden berg ▁Air ▁Force ▁Base , ▁California , ▁United ▁States , ▁with ▁a ▁D elta ▁J ▁ro cket . ▁ ▁Space craft ▁Explorer ▁ 3 8 ▁measured ▁the ▁intensity ▁of ▁cel est ial ▁radio ▁sources , ▁particularly ▁the ▁Sun , ▁as ▁a ▁function ▁of ▁time , ▁direction ▁and ▁frequency ▁( 0 . 2 ▁M Hz ▁to ▁ 2 0   M Hz ). ▁The ▁space craft ▁was ▁gravity ▁gradient ▁orient ed . ▁The ▁space craft ▁weight ▁was ▁, ▁and ▁average ▁power ▁consumption ▁was ▁ 2 5 ▁W . ▁It ▁carried ▁ 2 ▁ ▁long ▁V - ant enn as , ▁one ▁facing ▁toward ▁the ▁Earth ▁and ▁one ▁facing ▁away ▁from ▁the ▁earth . ▁A ▁ ▁long ▁di pole ▁anten na ▁was ▁orient ed ▁tang entially ▁with ▁respect ▁to ▁the ▁earth ' s ▁surface . ▁ ▁The ▁space craft ▁was ▁also ▁equ ipped ▁with ▁one ▁ 1 3 6   M Hz ▁te lem etry ▁turn st ile . ▁The ▁on board ▁experiments ▁consisted ▁of ▁four ▁step - fre quency ▁R yle - V on berg ▁rad iom eters ▁operating ▁from ▁ 0 . 4 5   M Hz ▁to ▁ 9 . 1 8   M Hz , ▁two ▁mult ich annel ▁total