Back from the dead
26th September - 23rd October, 1998.
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Back from the dead26th September - 23rd October, 1998. |
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Good question - the spacecraft might be fine but the more delicate instruments might still be damaged beyond all hope of repair. There is no use in having a working spacecraft without having any of the instruments working! It's a bit like having a fully working CD player but no CD's to listen to - useless. |
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| Some instruments, like the Coronal Diagnostic Spectrometer (CDS) where extremely hot! - above 80 degrees Centigrade (do you know how to measure a temperature and what units to use?)- enough to fry an egg! |
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Others were extremely cold. The Michelson Doppler Imager (MDI) got at least as low as -100 degrees Centigrade. It may have got colder but the thermometer stopped working because it was so cold! This is much much colder than any temperature ever measured on Earth. |
While SOHO was out of control, each instrument had to endure very different temperatures, some well out of the temperature range they were designed for - how well do you work at -100 degrees or +80 degrees Centigrade?
| Instrument switch on started on 5th October 1998. The first 8 to be switched on SUMER, VIRGO, GOLF, COSTEP, ERNE, UVCS, MDI and LASCO all came back just as good as they had been before the loss of SOHO. The next instrument to be switched on, EIT, came back even better than before! |
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How did this happen? Well, every so often EIT needs to be cleaned. They clean it by turning on its heaters which causes all the impurities (such as space dust) that have accumulated on the telescope to be boiled off. Since EIT was very much hotter than normal for almost three months this cleaned the instrument very well! Lucky for us! |
Look carefully at this EIT image and the rotating Sun images here. Notice anything strange?
| EIT confirmed that SOHO was pointing again at the Sun but still viewing the Sun at a strange angle. A later orbital manoeuver corrected this...... |
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