Orbit viewer · Episode 1 · 1957–1958

Sputnik 1 and Explorer 1, orbit by orbit

The first Soviet and the first American satellite, drawn from the orbit figures in NASA History Office records. Drag to turn the Earth, scroll or pinch to zoom.

Sputnik 1
Explorer 1
Elapsed 00:00:00
Sputnik 1 orbits 0.00
Explorer 1 orbits 0.00
Craft size exaggerated · orbit shape to scale
USSR · launched 4 October 1957

Sputnik 1

Mass
83.6 kg
Perigee
228 km
Apogee
947 km
Inclination
65.6°
Period
96.17 min
Kepler check

Figures are the first orbit determined by the Moscow Coordination-Computation Center. The apogee came out about 80 km lower than planned because the engine cut off early.

Sources: NASA History Office, Siddiqi, "Korolev, Sputnik, and the IGY" (orbit) · Chronology 1957–58 (date, mass)

USA · launched 31 January 1958

Explorer 1

Mass
14 kg (30.66 lb)
Perigee
224 mi · 360 km
Apogee
1,575 mi · 2,535 km
Inclination
not shown
Period
114.9 min
Kepler check

Explorer 1 found the Van Allen radiation belts. Its inclination is not yet confirmed from a primary source, so this view draws its orbit in the equatorial plane.

Sources: NASA History Office, Explorer-I characteristics (orbit, mass) · Chronology 1957–58

The first six months, to scale