[3] The purposes of the mission were: (1) to investigate solar-terrestrial relationships at the outermost boundaries of the Earth's magnetosphere, (2) to examine in detail the structure of the solar wind near the Earth and the shock wave that forms the interface between the solar wind and the Earth's magnetosphere, (3) to investigate motions of and mechanisms operating in the plasma sheets, and (4) to continue the investigation of cosmic rays and solar flare effects in the interplanetary region near 1 AU.

The three spacecraft carried a number of complementary instruments for making measurements of plasmas, energetic particles, waves, and fields.

The mother/daughter portion of the mission consisted of two spacecraft (ISEE-1 and ISEE-2) with station-keeping capability in the same highly eccentric geocentric orbit with an apogee of 23 Earth radii (Re).

[1] During the course of the mission, the ISEE-1 and ISEE-2 orbit parameters underwent short-term and long-term variations due to solar and lunar perturbations.

[3] This experiment was intended to study quasi-static electric fields and low-frequency plasma waves in the plasmasphere, magnetosphere, magnetosheath, and solar wind.

The double-probe floating-potential technique was applied using long-wire antenna probes with an effective electric field baseline of 179 m (587 ft).

[5] This experiment was designed to determine, by using identical instrumentation (see ISEE-2) on the mother/daughter spacecraft, the spatial extent, propagation velocity, and temporal behavior of a wide variety of particle phenomena.

[7] This experiment was designed, in conjunction with a similar instrument (1977-102B-01) provided by G. Paschmann of Max Planck Institute for flight on the daughter spacecraft, to study the plasma velocity distribution and its spatial and temporal variations in the solar wind, bow shock, magnetosheath, magnetopause, magnetotail, and magnetosphere.

Two of them, viewing in opposite directions, produce complete 2D velocity distribution measurements of both protons and electrons every spacecraft revolution.

Two sensors were used: a 4 cm (1.6 in)-diameter, CsI scintillator system and a 6-cm2, solid-state (Cadmium telluride (CdTe)) array.

At the lower energies, charge states of heavy ions in the high-speed (> 500 km/s (310 mi/s)) solar wind were determined.

"ULEZEQ" (ultralow-energy Z, E, and Q) was a combination of an electrostatic analyzer and a dE/dx vs E system with a thin-window proportional counter and a position-sensitive solid-state detector.

[10] This experiment was designed to study, by means of identical instrumentation on the mother/daughter spacecraft, the spatial and temporal variations of the solar wind and magnetosheath electrons and ions.

[11] This experiment was designed to identify and to study plasma instabilities responsible for acceleration, source and loss mechanisms, and boundary and interface phenomena throughout the orbital range of the mother/daughter satellites.

A proton telescope and an electron spectrometer were flown on each spacecraft to measure detailed energy spectrum and angular distributions.

These detectors used silicon surface-barrier, totally depleted solid-state devices of various thicknesses, areas, and configurations.

After an antenna had been momentarily excited at one of the characteristic frequencies of the plasma in which it was immersed, a pronounced "ringing" was observed.

In this experiment, the transmitter was designed to step through 128 sub-bands, covering the characteristic resonance frequencies of the plasma, from 0.3 to 50.9-kHz, and from 0 to 353-kHz.

The phase was compared against a phase-coherent signal transmitted from the mother to the daughter by modulation onto a carrier of frequency high enough to be unaffected by the ambient plasma (272.5-MHz).

The instrumentation consisted of four main elements: (1) a narrow-band sweep-frequency receiver with 32 frequency steps in each of four bands from 100-Hz to 400-kHz, a complete sweep required 32 seconds; (2) a high-time-resolution spectrum analyzer with 20 channels from 5.62-Hz to 31.1-kHz for electric field and 14 identical channels from 5.62-Hz to 10-kHz for magnetic field information, the electric and magnetic channels were sampled simultaneously; (3) a wave-normal analyzer to provide components for computing the wave normal and the Poynting flux, this analyzer had a 10-Hz bandwidth, and covered 32 frequencies from 100-Hz to 5-kHz; and (4) a wide-band receiver to condition electric and magnetic waveforms for transmission to the ground via the special-purpose analog transmitter, this receiver also provided the signals for long-baseline-interferometer measurements between ISEE-1 and ISEE-2.

[14] The objective of this experiment was to study quasi-static and low-frequency electric fields in the plasmasphere, magnetosphere, magnetosheath, and solar wind.

Measurements were made of the potential difference between a pair of 8 cm (3.1 in) diameter vitreous carbon spheres which were separated by 73.5 m (241 ft) and mounted on the ends of wire booms in the satellite spin plane.

[15] The magnetic fields investigation selected for ISEE-1 and ISEE-2 had as its principal objectives the study of the magnetic signatures of magnetospheric phenomena and magnetohydrodynamic waves in and around the magnetosphere, and to provide supporting data for other experiments on the spacecraft such as the electric field, particle and plasma wave investigations.

Two triaxial systems of 127° cylindrical electrostatic analyzers were used to make three-dimensional measurements of the electron distribution function.

[17] This experiment was intended to provide data to study interactions between discrete Very low frequency (VLF) waves and energetic particles in the magnetosphere.

Injection of the waves beyond the ionosphere was assured by transmitter location in a region where the magnetic lines of force are open: in this case, the Siple Station, Antarctica.

The injected signal and any stimulated VLF emissions were recorded through a loop antenna by a 1 to 32-kHz broadband receiver on the satellite.