Explorer 10 was a cylindrical, battery-powered spacecraft instrumented
with two fluxgate magnetometers and one rubidium vapor magnetometer
extending from the main spacecraft body, and a Faraday cup plasma
probe. The mission objective was to investigate the magnetic fields
and plasma as the spacecraft passed through the earth's magnetosphere
and into cislunar space. The satellite was launched into a highly
elliptical orbit. It was spin stabilized with a spin period of 0.548
s. The direction of its spin vector was 71 deg right ascension and
minus 15 deg declination. Because of the limited lifetime of the
spacecraft batteries, the only useful data were transmitted in real
time for 52 h on the ascending portion of the first orbit. The
distance from the earth when the last bit of useful information was
transmitted was 42.3 earth radii, and the local time at this point was
2200 h. All transmission ceased several hours later.