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Re: [Methane Hydrate Club] SOHO satellite update

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  • David
    ... I ll definitely keep up the reports, no matter what. There just might be days when I can t provide as much information as usual.
    Message 1 of 4 , Jun 21, 2003
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      --- In methanehydrateclub@yahoogroups.com, "mike" <mike@u...> wrote:
      > Keep us up on this. The solar reports have been absolutely priceless.
      >

      I'll definitely keep up the reports, no matter what. There just might
      be days when I can't provide as much information as usual.
    • David
      24-Jun-2003 The Solar and Heliospheric Observatory (SOHO) spacecraft expects to experience a blackout in the transmission of its scientific data during the
      Message 2 of 4 , Jun 24, 2003
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        24-Jun-2003 The Solar and Heliospheric Observatory (SOHO) spacecraft
        expects to experience a blackout in the transmission of its scientific
        data during the week of 22 June 2003. This is estimated to last for
        about two and a half to three weeks.

        Engineers are predicting this problem after detecting a malfunction in
        the pointing mechanism of the satellite's high-gain antenna (HGA),
        which is used to transmit the large amounts of data from SOHO's
        scientific observations to Earth.

        The SOHO spacecraft is operating as safely as before the problem
        occurred. Its low gain antenna, which does not need to be pointed in a
        specific direction (omni-directional), will be used to control the
        spacecraft and monitor both spacecraft and instrument health and safety.

        The anomaly in pointing the high-gain antenna was recently discovered
        when engineers detected a discrepancy between the commanded and
        measured antenna position. In normal conditions, the antenna must be
        able to move along two axes, vertical and horizontal. The horizontal
        movement was no longer taking place properly. The problem is probably
        due to a malfunction in the motor or gear assembly that steers the
        antenna.

        SOHO is located 1.5 million kilometers from Earth, slowly orbiting
        around the First Lagrangian point, where the combined gravity of the
        Earth and the Sun keep SOHO in an orbit locked to the Sun-Earth line.
        To transmit data, the SOHO high-gain antenna must rotate to have the
        Earth constantly in its field of view as the spacecraft and the Earth
        progress in their respective orbits.

        If the problem is not solved, the Earth will be left outside the HGA
        beam on a periodic basis, with similar blackouts occurring every three
        months.

        ESA and NASA engineers are currently assessing several options to
        recover the situation, or minimise the scientific data loss.

        **********

        For the purposes of my posts here, I'll still be able to provide the
        majority of information. I'll be able to report geomagnetic activity,
        solar wind data, and solar flare data. None of the current data
        information will be affected. What will be affected is the forecast
        information, and possibly information about whether or not a coronal
        hole is there. Coronal holes show up in the extreme UV images SOHO
        provides. Since UV light in this frequency range is blocked by the
        ozone layer, these images can't obtained from the ground. The TRACE
        (Transition Region and Coronal Explorer) satellite gathers data in the
        UV range, but it doesn't provide the same kind of images that SOHO does.
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