Mission type Heliophysics COSPAR ID 1991-062A Website Yohkoh home page Launch date 30 August 1991 Inclination 31.3° Names Solar-A (before launch | SATCAT no. 21694 Launch mass 390 kilograms (860 lb) Inclination 31.3° Period 1.6 hours Launch site Uchinoura Space Center | |
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Similar TRACE, Hinode, Solar and Heliospheric Observatory, Solar Maximum Mission, Tenma | ||
Annular eclipse observed by yohkoh the world s first space satellite to provide solar images
Yohkoh (ようこう, Sunbeam in Japanese), known before launch as Solar-A, was a Solar observatory spacecraft of the Institute of Space and Astronautical Science (Japan), in collaboration with space agencies in the United States and the United Kingdom. It was launched into Earth orbit on August 30, 1991 by the M-3S-5 rocket from Kagoshima Space Center. It took its first image on September 13, 1991 21:53:40.
Contents
- Annular eclipse observed by yohkoh the world s first space satellite to provide solar images
- Yohkoh soft x ray telescope
- Description
- Instruments
- References
Yohkoh soft x ray telescope
Description
The satellite was three-axis stabilized and in a near-circular orbit. It carried four instruments: a Soft X-ray Telescope (SXT), a Hard X-ray Telescope (HXT), a Bragg Crystal Spectrometer (BCS), and a Wide Band Spectrometer (WBS). About 50 MB were generated each day and this was stored on board by a 10.5 MB bubble memory recorder.
Because the SXT utilized a charge-coupled device (CCD) as its readout device, perhaps being the first X-ray astronomical telescope to do so, its "data cube" of images was both extensive and convenient, and it revealed much interesting detail about the behavior of the solar corona. Previous solar soft X-ray observations, such as those of Skylab, had been restricted to film as a readout device. Yohkoh therefore returned many novel scientific results, especially regarding solar flares and other forms of magnetic activity.
The mission ended after more than ten years of successful observation when it went into its "safehold" mode during an annular eclipse on December 14, 2001 20:58:33 and the spacecraft lost lock on the sun. Operational mistakes and other flaws combined in such a way that its solar panels could no longer charge the batteries, which drained irreversibly; several other solar eclipses had successfully been observed.
On September 12, 2005 the spacecraft burned up during reentry over South Asia. The time of reentry, as provided by the U.S. Space Surveillance Network, was 6:16 pm Japan Standard Time (JST).
Instruments
Yohkoh carried four instruments :
The CCD is 1024×1024 pixels with pixel angular size of 2.45″×2.45″, point spread function core width (FWHM) was about 1.5 pixels (i.e. 3.7″), field of view was 42′×42′, which was a little larger than the whole solar disk. Typical time resolution was 2 s in flare mode and 8 s in quiet (no flare) mode, the maximum time resolution in 0.5 s.
For spectral discrimination, STX employed wide-band filters installed on a filter wheel. There were five usable filter positions: 1265 Å-thick Al filter (2.5 Å–36 Å pass band), Al/Mg/Mn filter (2.4 Å–32 Å), 2.52 μm Mg filter (2.4 Å–23 Å), 11.6 μm Al filter (2.4 Å–13 Å), 119 μm Be filter (2.3 Å–10 Å). Before the entrance filter failure in November 1992 three more filter positions were available: no analysis filter (2.5 Å–46 Å), Wide band optical filter (4600 Å–4800 Å), Narrow band optical filter (4290 Å–4320 Å).