Taiyo

List all Taiyo datasets

Solar Radiation and Thermospheric Satellite (SRATS) "Taiyo"

Mission Descriptions

Overview

Taiyo (SRATS) is a satellite developed by the Institute of Space and Astronautical Science (ISAS) of the University of Tokyo for research in upper atmospheric physics. Its purpose was to observe solar soft X-rays, solar vacuum ultraviolet radiation, ultraviolet geocoronal emission lines, and more. Taiyo was launched on February 24, 1975, from the Kagoshima Space Center (now Uchinoura Space Center) by the M-3C-2 rocket. The satellite re-entered the Earth's atmosphere and was destroyed on June 29, 1980, ending its mission.

The satellite weighs 86 kg and has an octagonal prism shape with a diameter of about 70 cm and a height of about 71 cm. It orbited in an elliptical orbit with a periapsis altitude of 260 km, an apoapsis altitude of 3,140 km, and an inclination of 32 degrees, completing one orbit approximately every 120 minutes.

The mission aimed to systematically observe data related to the ionosphere, such as the Sun's Lyman-alpha radiation, X-rays, the Earth's ultraviolet albedo, the composition of positive ions, and the density and temperature of electrons and ions.

Observation Instruments

Solar X-Ray Detector (SXR)

The SXR is an X-ray detector designed to observe solar X-rays produced by solar flares. It is sensitive to X-rays in two energy ranges, 5.9-9.5 keV and 9.5-11.5 keV, with an area of 3 square cm and a time resolution of about 8 seconds. It is also sensitive to charged particles, allowing it to study the distribution of charged particles in the radiation belts and the nature of precipitating particles in orbit when Taiyo is near its periapsis.

Intensity Monitor for Solar Hydrogen Lyman-α Radiation (SXU)

The SXU measures the intensity of hydrogen Lyman-alpha radiation from the entire Sun. It consists of an ion chamber with a special input control mask and associated electronics. The ion chamber has a magnesium fluoride glass window and is filled with nitric oxide gas, making it sensitive to a narrow spectral band, including the Lyman-alpha line. The special mask maintains the detector's angular response within 1% accuracy. The electronics measure the ion chamber's output current, holding the maximum output value for 4-second intervals, and transmit this data via telemetry. The Lyman-alpha line (121.6 nm) is used to probe the physical state of the Sun's chromosphere and transition region.

Geocoronal and Middle Ultraviolet Radiometers (GMV)

Taiyo carries two middle ultraviolet radiometers (MUV) and four vacuum ultraviolet photon counters (GUY). Although the research objectives differ, the data acquisition and processing systems are common, and their observation modes are similar, so the combined experimental system is often referred to as GMV.

Middle Ultraviolet Radiometer (MUV)

The MUV measures solar light reflected from ozone in the Earth's atmosphere in the middle ultraviolet range (255 nm and 290 nm). This helps study the vertical distribution of ozone in the upper atmosphere.

Vacuum Ultraviolet Photon Counter (GUV)

The GUV measures the Earth's geocorona in the vacuum ultraviolet range at wavelengths of He+ 30.4 nm, He 58.4 nm, O+ 83.3 nm, O 130 nm, and H 102.6 nm.

Bennett Ion Mass Spectrometer (CPI)

The CPI is a Bennett-type ion mass spectrometer that measures the mass and relative concentration of ions in the Earth's upper atmosphere. It is used to separate the masses of H+, He+, and O+ ions and determine their relative abundances.

Retarding Potential Analyzer (RPA)

The RPA measures the density and temperature of positive ions. It uses a trap with three grids, applying a 1.5 kHz voltage and a 1-second sweep voltage to the grids and measuring the collected current at 1.5 kHz.

Electron Temperature Probe (TEL)

The TEL is a type of resonance rectification probe that measures the temporal and spatial variations in electron temperature. It can measure temperatures up to 4000 K.

Gyro-Plasma Probe (IMP)

The IMP measures the spatial distribution and variations in electron density. It uses a high-frequency impedance probe that sweeps frequencies from 300 kHz to 16.1 MHz every 125 milliseconds.

Achievements

Taiyo provided data on the typical plasma environment of the Earth during periods of low solar activity over approximately five years. It achieved its objective of observing the Sun's Lyman-alpha line intensity, among other parameters.

Additionally, international collaborative research was conducted with the West German AEROS-B satellite, enhancing the data obtained from similar observations.

The data collected by Taiyo has been a valuable resource for ionospheric research and has provided a fundamental dataset contributing to subsequent space science research.

Refereneces

Instrument paper