 thumb|260px|right|the x-ray solar corona as viewed by the yohkoh observatory yohkoh (ãããã, 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&nbsp;30, 1991 by the m-3s-5 rocket from kagoshima space center. it took its first image on september 13, 1991 21:53:40. ==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. many interesting new discoveries were also made.yohkoh science nuggets 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&nbsp;:yohkoh analysis guide version 2.9x / instrument manual. eds. m.d.morrison, r.d.bentley. 1999. * soft x-ray telescope (sxt) was an x-ray telescope with glancing incidence x-ray mirror and a ccd sensor. there was also a co-aligned optical telescope using the same ccd, but after the failure of the entrance filter in november 1992 it became unusable. the ccd is 1024Ã1024 pixels with pixel angular size of 2.45â³Ã2.45â³, point spread function core width (fwhm) was about 1.5 pixels (i.e. 3.7â³), field of view was 42â²Ã42â², which was a little larger than the whole solar disk. typical time resolution
1991_in_Japan 1991_in_spaceflight Artificial_satellites_formerly_orbiting_Earth Satellites_of_Japan Solar_telescopes Space_observatories Spacecraft_which_reentered_in_2005 X-ray_telescopes