Solar Radiation and Thermospheric Satellite
Japanese satellite studied solar radiation and upper atmosphere.
The Japanese space probe Taiyo, meaning "Sun," was also designated the Solar Radiation and Thermospheric Satellite (SRATS) and Shinsei-3. Built by the University of Tokyo’s Institute of Space and Astronautical Science (ISAS), it launched from Kagoshima Space Center aboard an M-3C-2 rocket on February 24, 1975. Its research focused on the upper atmosphere, solar X-ray and ultraviolet radiation, and the ionosphere. After completing its work, Taiyo fell back to Earth on June 29, 1980.
Weighing 86 kg, the satellite was shaped like an octagonal cylinder, or prism. It traveled in an elliptical orbit inclined at 32 degrees, with a low point of 260 km and a high point of 3,140 km. Its main tasks involved studying solar X-rays, ultraviolet light, and the distribution of ions and electrons high above the planet.
Taiyo carried seven scientific instruments. The Solar X-Ray Detector (SXR) observed X-rays in two energy bands (5.9–9.5 keV and 9.5–11.5 keV) and tracked charged particles near Earth’s radiation belts. The Lyman-alpha Radiation Monitor (SXU) measured solar hydrogen Lyman-alpha emissions to study the Sun’s chromosphere. The Geocoronal and Middle Ultraviolet Radiometers (GMV) included the Middle Ultraviolet Radiometer (MUV), which measured sunlight reflected by atmospheric ozone, and the Vacuum Ultraviolet Photon Counter (GUV), which analyzed geocoronal light. The Bennett Ion Mass Spectrometer (CPI) identified H+, He+, and O+ ions in the upper atmosphere. The Retarding Potential Analyzer (RPA) used voltage sweeps across ion traps to determine ion density and temperature. The Electron Temperature Probe (TEL) recorded electron temperature variations, with a maximum measurement of 4000 K. Finally, the Gyro-Plasma Probe (IMP) measured electron density by analyzing high-frequency impedance.
Quick Facts
- Operator
- ISAS
- Mission Type
- Solar-terrestrial research
- Manufacturer
- Nippon Electric Company
- Launch Mass
- 86 kg
- Launch Date
- February 24, 1975, 05:25 UTC
- Launch Rocket
- M-3C No. 2
- Launch Site
- Kagoshima Space Center
- End Date
- June 29, 1980
- Orbit Reference
- Geocentric
- Orbit Regime
- Low Earth/Medium Earth
- Orbit Periapsis
- 260 km
- Orbit Apoapsis
- 3,140 km
Facts from the source article.
Lore & Background
Taiyo was an octagonal cylindrical satellite weighing 86 kg, placed into an elliptical orbit with a periapsis of 260 km and an apoapsis of 3,140 km at a 32-degree inclination. Its primary mission was to investigate solar X-rays, ultraviolet radiation, and the distribution of ions and electrons in the Earth's upper atmosphere. The spacecraft carried seven science instruments to achieve these goals.
The instrument suite included a Solar X-Ray Detector (SXR) that observed solar X-rays in two energy ranges (5.9-9.5 keV and 9.5-11.5 keV) and measured charged particles near the radiation belts. A Lyman-alpha Radiation Monitor (SXU) measured solar hydrogen Lyman-alpha radiation to study the Sun's chromosphere. The Geocoronal and Middle Ultraviolet Radiometers (GMV) combined a Middle Ultraviolet Radiometer (MUV) for reflected solar light from ozone and a Vacuum Ultraviolet Photon Counter (GUV) for geocoronal emissions.
Additional instruments included a Bennett Ion Mass Spectrometer (CPI) that identified H+, He+, and O+ ions, a Retarding Potential Analyzer (RPA) for ion density and temperature, an Electron Temperature Probe (TEL) capable of measuring up to 4000 K, and a Gyro-Plasma Probe (IMP) that analyzed electron density distribution through high-frequency impedance measurements.
Reader's Guide
The Solar Radiation and Thermospheric Satellite (Taiyo) represents an early Japanese effort in space-based solar and atmospheric research. Its comprehensive instrument package allowed simultaneous measurements of solar radiation and ionospheric plasma, contributing to the understanding of solar-terrestrial interactions. The satellite's data on solar X-rays, Lyman-alpha radiation, and ion composition helped characterize the upper atmosphere's response to solar activity. By operating from 1975 to 1980, Taiyo provided a multi-year dataset that supported studies of the ionosphere and thermosphere. Its legacy lies in demonstrating the capability of Japanese space science and laying groundwork for later missions. The mission's results were published in journals such as the Journal of Geomagnetism and Geoelectricity, with detailed instrument descriptions and initial findings documented by the principal investigators.
Did You Know?
- Taiyo was also known as Shinsei-3 and means 'Sun' in Japanese.
- The satellite had an octagonal cylindrical shape and weighed 86 kg.
- It carried seven science instruments, including a Bennett Ion Mass Spectrometer that identified H+, He+, and O+ ions.
- The Electron Temperature Probe could measure electron temperatures up to 4000 K.
More in Missions to the Sun 1-21
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