Overview

Jikiken (EXOS-B) was developed by the Institute of Space and Aeronautical Science of the University of Tokyo (currently ISAS/JAXA).
It is to study the deep magnetosphere (a region with a radius of 60,000 to 70,000 km around the Earth) and to participate in the International Magnetospheric Study Program (IMS) conducted from 1976 to 1979.
It was launched on September 16, 1978 by the M-3H rocket from the Kagoshima Space Center (now the Uchinoura Space Center), and conducted cooperative observations with Kyokko (EXOS-A) as part of the International Magnetospheric Study (IMS) program, before completing operations in 1985.

The main objective is to study wave and particle interactions in the Earth’s magnetosphere and plasmasphere.

The satellite weighs 90 kg, has a 38-hedron body with a height of 0.6 m and a face-to-face dimension of 0.75 m, and is equipped with four 60 m long extendable antennas spaced 90 degrees apart on its sides.
After launch, the satellite began to extend its antennas on September 23, but due to a rise in temperature of the control circuit and other problems, the satellite gave up the full extension and terminated the extension when the length of the two antennas reached the same level.

It was injected into a long elliptical orbit with a perigee altitude of 227 km, apogee altitude of 30,056 km (initial), and inclination of 31 degrees, and orbited at a speed of 524 minutes per revolution.

Observation Instruments

Natural Plasma Waves-astronomy mode (NPW-A)

NPW-A is an instrument for observing naturally occurring plasma waves.
Using a long dipole antenna (51 m - 51 m antenna), it receives hectometre (HF) and decametre (MF) waves from planets such as Jupiter and Saturn, and kilometer (LF) waves from Earth in the frequency range of 20 kHz to 3 MHz.

Natural Plasma Waves-VLF mode (NPW-B)

NPW-B is an instrument for observing plasma waves in the very low frequency (VLF) band. This instrument can capture VLF band phenomena such as whistlers, chorus, and hiss.
A wideband VLF receiver with a long dipole antenna receives VLF waves up to 10 kHz.

Stimulated Plasma Wave experiment (SPW)

SPW is an instrument for observing artificially stimulated plasma waves. The instrument applies 30 - 300 W oscillating electrolytic pulses (10 kHz - 3 MHz) to a dipole antenna to induce plasma instabilities and observe the resulting wave conduction characteristics and particle heating. This allows detailed analysis of the wave-particle interaction.

VLF Doppler Technique (DPL)

DPL is a technique for observing plasma waves using the Doppler shift in the VLF band. The instrument receives VLF electromagnetic waves (NWC 22.3 kHz) from the ground and measures their Doppler shift in a narrow bandwidth phase measurement to detect plasma ducts in the magnetosphere, electron temperature, and electron density distribution.

Magnetic Field measurement (MGF)

The MGF is designed to observe the geomagnetic vector field and its variations using a fluxgate magnetometer mounted on the apex of a 1.5 m boom to measure the direction and intensity of the magnetic field in the magnetosphere with high accuracy. It also uses sun and earth detectors to determine the satellite’s attitude. It measures the x, y, and z components of the magnetic field with measurement ranges of ±51,200, ±8,000, ±1,048, and ±256 gamma and a resolution of ±2 gamma (maximum sensitivity).

Impedance and Electric Field measurement (IEF)

The IEF is a device for measuring the electric field within the plasmasphere.
The Frequency Swept Impedance Probe (IEF-I) provides the basic data for calibrating natural plasma wave detectors and for estimating their transmission efficiency for plasma wave stimulation. One of the main purposes of this probe is to measure electron density independently of all other techniques, which can be done accurately by canceling stray capacitance.
The Electric Field Measuring Instrument (IEF-F) measures the electric field using a cylindrical probe with electrodes at the tip of a 51 m - 51 m dipole antenna. The satellite body is coated with a conductive material to eliminate local electric fields and accurately measure the natural electric field. It can also detect variations in the satellite potential excited by SPWs and CBEs.

Controlled Beam Emission experiment (CBE)

CBE is an instrument that emits a beam of electrons to control the spacecraft’s electric potential and provide accurate measurements of low-energy particles. The instrument emits electron beams from 0 eV to 200 eV (0 - 1 mA) to control the potential of the plasma around the spacecraft, thereby improving the measurement of particles and electric fields. It also aims to observe the plasma waves excited by the electron beam using NPW.

Energy Spectrum of the Particles (ESP)

ESP is an instrument for analyzing the energy spectrum of particles. A hemispherical electrostatic energy analyzer measures the energy distribution of electrons in the 5 eV - 10 KeV range, and a cylindrical analyzer measures the energy distribution of ions in the 20 eV - 30 KeV range. With these instruments, we observe the spatial distribution and temporal variation of particle fluxes in the magnetosphere, as well as changes in the distribution of particles excited by SPW and CBE.
The instruments play an important role in observing the behavior of particles associated with wave phenomena.

Achievements

The Jikiken observations have yielded the following important results:

1. Mechanism of auroral kilometer waves: Data on the formation mechanism of auroral kilometer waves was collected.
2. Plasma Pose Formation: A better understanding of the process of plasma pose formation was obtained.
3. Wave and Particle Interactions: A detailed picture of wave and particle interactions in the magnetosphere was obtained.
4. International Cooperation: Communication and data exchange with foreign scientific satellites such as GEOS took place.
5. Reception of low-frequency signals: Successful reception of low-frequency signals transmitted from the South Pole contributed to the study of the interaction between plasma and waves in the magnetosphere.

These results have greatly advanced our understanding of physical phenomena in the Earth’s magnetosphere and plasmasphere.