How It Works - UK (2020-05)

How It Works 053

DID YOU KNOW? In2012, satellite data showed there were twice as many emperor penguins in Antarctica than thought

E

versincethelaunchofthefirstsatellite,

Sputnik,bytheUSSRinOctober1957,

thousandsmorehaveorbited– and

remainorbiting– theEarth.Wedon’ttendto

hearaboutreconnaissance,orspysatellites

though,andastheirmissionsareclassified,

theirequipmentandcapabilitiesareoftennot

disclosed.Hundredsofthesesecretivespiesin

thesk yhavebeenlaunchedsincethe1960s.

Spysatellitesareusedforbothmilitar yand

intelligencepurposes,includingdetectingtroop

movements,monitoringthedismantlingof

nuclearweaponsandradiosignals,spotting

missilelaunchesandprov idingprecise

positionalinformation.Fly inghighabovethe

surfaceofEarth,theseeyesarefreetoscanthe

groundbeloww iththeirmostimportantasset

• theironboardcamera.It’sestimatedthatthese
  satellitescanseeobjectsonthegroundthatare
  justtencentimetresacross– enoughtoseean
  indiv idualpersonina crowd.Theseusethe
  sametechnolog ythat’sinyoursmartphone– a
  charge-coupleddev ice(CCD)– a sensorthat
  convertslightintoelectricalsignals.Theseare
  storedonthesatellite’sonboardcomputeruntil
  it cansendtheencr y ptedinformationbackto
  theground.Satellitesmustalsohavea sourceof
  power,inmanycaseseithersolarornuclear,and
  a meansofcontrollingtheiraltitude,suchasv ia
  thrusters.Therearealsoradio-listeningspy
  satellitesthatcanlistentoradiosignalsthat are
  being transmitted by another satellite.

A KH-9satelliteimageofanairfield

near Moscow, taken in 1979

© NRO

Themorerecent‘Keyhole’spysatellites

are thought to resembletheHubble

Space Telescope

© NASA