Overview

“Oozora” (EXOS-C) is a middle atmosphere observation satellite developed by the Institute of Space and Astronautical Science (ISAS) with the objectives of elucidating the structure and composition of the Earth’s middle atmosphere, observing the magnetosphere, and participating in the International Program on Observations of the Middle Atmosphere (MAP), which was carried out from 1982 to 1985.
It was launched on February 14, 1984 by the M-3S Rocket No. 4 from the Kagoshima Space Center (currently Uchinoura Space Center), and completed its operation on December 26, 1988.

It was an octagonal prism weighing 207 kg, 0.88 m tall, with face-to-face dimensions of 1.09 m, and was equipped with an extendable 20 m antenna.
It orbited in an elliptical orbit with a perigee of 354 km, an apogee of 865 km, and an inclination of 75 degrees, completing one revolution in 97 minutes.

Observation Instruments

IRA, ALA, BUV, and LAS are primarily intended to elucidate the structure and organization of the middle atmosphere.
PPS, ESP, HEP, NEI, TEL, and PLR are primarily intended to elucidate the interactions between precipitating charged particles, ionospheric plasma, and the atmosphere in the polar regions and over the South Atlantic geomagnetic anomaly.

InfraRed atmospheric band Airglow radiometer (IRA)

IRA is a radiometer for observing airglow in the infrared band.
IRA measures the mesospheric ozone profile by using the O₂ 1.27 μm emission from the tmospheric limb.
It also measures the CO₂ 15 μm radiation with the thermistor bolometers to get information on the satellite attitude and the tangential heights of the line of sight of the sensors.
This instrument is capable of analyzing the distribution and variations of trace components in the atmosphere.

Aerosol Limb Absorption (ALA)

ALA is an instrument that observes the absorption characteristics of atmospheric aerosols.
It is a two-channel sun photometer with wavelengths of 600 nm and 1000 nm, and the detectors for each channel use two-dimensional CCD image sensors to obtain a vertical resolution of the order of 1 km.
The absorption spectrum of sunlight is used to measure the vertical distribution of aerosols. This makes it possible to identify the concentration and type of aerosols in the atmosphere.

Backscattered middle UltraViolet radiation from the terrestrial atmosphere (BUV)

BUV consists a concave grating spectrometer and a interference filter photometer to observe solar ultraviolet light scattered by the Earth’s atmosphere.
It measures scattered light in the ultraviolet wavelength band (250 nm - 320 nm) between 80 degrees north and 80 degrees south latitude, and analyzes the state of the ozone layer in the atmosphere and the ultraviolet transmission characteristics.

Limb-Atmospheric infrared Spectrometer (LAS)

LAS observes the infrared spectrum of the atmosphere and analyzes the distribution of trace components in the atmosphere and temperature profiles.LAS は、大気の赤Its objective is to globally observe H₂O, CO₂, CH₄, O₃, N₂O, and aerosols in the middle atmosphere.

Planetary Plasma Sounder (PPS)

PPS is an instrument for observing the acoustic properties of interplanetary plasma. It measures the propagation characteristics of sound waves in plasma and analyzes the density and temperature of plasma.
Using orthogonal 40m (tip-to-tip) antennas and a 100 kHz to 16 MHz swept-frequency receiver and a 500 Hz to 20 kHz swept-frequency VLF receiver, it operates for two main purposes: receiving natural plasma waves (NPWs) at both high frequency and VLF, and observing active plasma waves (SPWs) using a high-power (up to 300 W) RF pulsed transmitter.

Energy Spectra of the low energy Particles (ESP)

ESP is designed to measure the energy spectrum and the pitch-angle distribution of electrons
over the energy range of 6 eV to 16 keV and positive ions from 200 eV to
16 keV.
It measures the energy distribution of particles and analyzes the radiation environment around the Earth.

High Energy Particle fluxes (HEP)

HEP is an instrument to observe the flux of high-energy particles and analyze the effects of cosmic rays and the solar wind.
It consists of two identical silicon detector telescopes (S-1 and S-2). One (S-1) of the telescopes is mounted on the spacecraft and looks along the positive z axis (anti-sun direction), the other telescope (S-2) is mounted perpendicular (-y axis) to telescope S-1.
It observe the flux and energy spectrum of electrons (0.19 - 3.2 MeV), protons (0.64 - 35 MeV), and He ions (4 - 140 MeV).

Number density of Electron by Impedance Probe (NEI)

NEI is an instrument that observes the electron number density using an impedance probe.
It is designed to measure the effective capacitance of a rod-shaped probe with a length of 45 cm and a diameter of 2 cm over a sweep frequency range from 0.1 MHz to 16 MHz.
This instrument measures the electron density in plasma with high precision and analyzes the plasma characteristics.

ELectron Temperature probe (TEL)

TEL is an instrument that observes electron temperature.
It measures the temperature of electrons in plasma and analyzes the energy state of the plasma.

Power Line Radiation (PLR)

The PLR ​​is a device for observing radiation from power lines. It consists of a loop antenna and a receiving unit, and can receive the fundamental frequencies (50Hz and 60Hz) of power line radiation using three narrowband filters.
PLR data has been useful in research into the effects of electromagnetic interference.

MU rador Monitor (MUM)

MUM is an instrument that observes the atmosphere using the MU radar.
It analyzes the dynamics of the atmosphere by measuring wind speed and temperature in the atmosphere.
MUM data has contributed to research into atmospheric physics.

Achievements

Ohzora provided valuable data on the observation of the absorption spectrum of sunlight by trace components in the middle atmosphere, and on high-energy particles in the polar regions and the South Atlantic magnetic anomaly, making a significant contribution to our understanding of the Earth’s atmosphere and electromagnetic environment.