Explorer 41 (IMP-G) was a spin-stabilized satellite placed into a high-inclination, highly elliptical orbit to measure energetic particles, magnetic fields, and plasma in cislunar space.

The line of apsides and the satellite spin vector were within a few degrees of being parallel and normal, respectively, to the ecliptic plane.

The acceptance cones for the channel multipliers had full-angles of approximately 30° with axes of symmetry 60° off the spacecraft spin axis.

The D3 element of the telescope became noisy on 29 September 1969, and the condition continued until the spacecraft emerged from first shadow on 5 January 1970.

[8] An electrostatic analyzer and an E-cross-B velocity selector normal to the spacecraft spin axis were used to separately determine proton and alpha particle spectra in the solar wind.

The instrumentation consisted of a 10 cm (3.9 in)-diameter Neher-type integrating ionization chamber and three pairs of Geiger–Müller tubes (GM).

The experiment performed normally from launch until the spacecraft decayed from orbit on 23 December 1972, except that the ionization chamber operated intermittently throughout the mission.

[10] This experiment used a dE/dx versus E telescope with one thin and two thick surface-barrier, solid-state detectors and an anticoincidence plastic scintillator counter.

Protons stopping in the thin detector (and particles penetrating it) were measured by passing the output signal through an eight-level energy threshold discriminator.

There were also two solid-state detectors that looked along the spacecraft spin axis and that were identical except for differences in the covering foil thicknesses.

Spectral information was gathered by subjecting the output signals from each detector to eight-level energy threshold discrimination.

The detector system consisted of a cylindrical electrostatic analyzer (LEPEDEA detector) and Bendix Corporation continuous channel multiplier (channeltron) array, and an Anton 213 Geiger–Müller tube designed to survey the intensities of electrons with E>40 keV in the outer magnetosphere.

A complete scan of the spectrum for four directions in a plane perpendicular to the spacecraft spin axis required 307.2-seconds.

[12] This experiment was designed to observe positive ion intensities in the solar wind, within the magnetosheath, and in the geomagnetic tail using a modified low-energy proton and electron differential energy analyzer (LEPEDEA detector).

[13] In this experiment, a four-element solid-state telescope with an acceptance cone half angle of 20° was mounted normal to the spacecraft spin axis.

The experiment performed normally until 30 January 1970, when a Goddard Space Flight Center (GSFC) power supply failure limited the useful data gathered to protons between 0.5 and 5-MeV, alpha particles between 4 and 18-MeV, and electrons between 0.3 and 3-MeV.

Three detectors measured the omnidirectional fluxes of protons and alpha particles with energy per nucleon values above 10, 30, and 60-MeV.

Resultant hourly averaged fluxes have been published in Solar-Geophysical Data (National Oceanic and Atmospheric Administration (NOAA), Boulder, Colorado) on a rapid basis.

Fluxes of 1- to 10-MeV/nucleon protons and alpha particles were measured in the lower and upper discrimination states, respectively.

[15] A boom-mounted triaxial fluxgate magnetometer measured magnetic fields in the interplanetary medium, in the magnetosheath, and in the geomagnetic tail.

Measurement of the energy spectra of magnetic field fluctuations was accomplished through a computation of the autocorrelation function in an onboard digital processor.

[16] It recorded important data on one of the most potent solar proton events of the Space Age in early August 1972.