Following the launch of the Soviet Sputnik 1 on 4 October 1957, the Army Ballistic Missile Agency (ABMA) was directed to proceed with the launching of a satellite using the Juno I four-stage variant of the three-stage Jupiter-C, which had already been flight-tested in nose-cone re-entry tests for the Jupiter IRBM (intermediate-range ballistic missile).

Working closely together, ABMA and Jet Propulsion Laboratory (JPL) completed the job of modifying the Jupiter-C and building Explorer 1 in 84 days.

The case was heat-oxidized to a gold color and eight alternate stripes of white Rokide A (flame sprayed aluminum oxide) were used for temperature control.

The sub-carrier oscillators and Mallory mercury batteries for the low power transmitter were in the upper part of the nose cone.

Below these was the low power (10 mW, 108.00 MHz) transmitter for the carrier and sub-carrier signals, which used the stainless steel satellite skin as a dipole antenna.

[4] Below the nose cone was the detector deck, holding the Geiger-Mueller counter tube for the cosmic ray experiment, the command receiver, for recorder interrogations, high power playback transmitter (60 mW, 108.03 MHz) for interrogation response, cosmic ray experiment electronics, Mallory mercury batteries for the high power transmitter, and a 0.23 kg (0.51 lb), 5.7 cm (2.2 in) diameter magnetic tape recorder.

Near the bottom of the detector deck four circularly polarized turnstile stainless steel wire whip antennas protruded radially from the side of the spacecraft, equally spaced around the axis.

The instrument consisted of a single Geiger-Mueller tube, a scaling circuit to reduce the number of pulses, and a telemetry system to transmit the data to ground receiving stations.

The experiment had no onboard data storage device, and could only send telemetry to the ground when it was passing over an Earth receiving station, so some regions had no coverage during the flight.

The parameters determined were the influx rates of each size interval, the impinging velocity, the composition, and the density of the micrometeorite.

[6] Because of its symmetrical shape, Explorer 2 was selected for use in determining upper atmospheric densities as a function of altitude, latitude, season, and solar activity.

Density values near perigee were deduced from sequential observations of the spacecraft position, using optical (Baker-Nunn camera network) and radio and/or radar tracking techniques.

[7] The Explorer 2 satellite was equipped with four resistance thermometers that made direct temperature measurements, three external and one internal.

Additionally, the nose cone internal temperature could be indirectly estimated by measuring the frequency of the cosmic ray channel.

[8] The exterior temperature control was achieved by coating a fraction of the stainless steel satellite casing with an aluminum oxide ceramic (Rokide A).

[9] The launch vehicle was a Juno I, a variant of the three-stage Jupiter-C with an added fourth propulsive stage, which in this case was the Explorer 2.

The booster was equipped to spin the fourth stage in increments, leading to a final rate of 750 rpm about its long axis.

The spacecraft reentered the atmosphere and fell into the Atlantic Ocean near Trinidad, some 3,000 km (1,900 mi) from the launch site.