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Re: [Methane Hydrate Club] SOHO satellite update

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  • mike
    Keep us up on this. The solar reports have been absolutely priceless. ... From: David To: methanehydrateclub@yahoogroups.com
    Message 1 of 4 , Jun 21, 2003
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      Keep us up on this. The solar reports have been absolutely priceless.

      -----Original Message-----
      From: "David" <b1blancer1@...>
      To: methanehydrateclub@yahoogroups.com
      Date: Sat, 21 Jun 2003 05:03:28 -0000
      Subject: [Methane Hydrate Club] SOHO satellite update

      > <html><body>
      >
      >
      > <tt>
      > There hasn't been anything new to speak of since yesterday. 
      > I'm<BR>
      > assuming, therefore, that the high-gain antenna remains a problem. <BR>
      > That's the antenna used to send data back to earth.  SOHO will NOT
      > be<BR>
      > lost if it can't be fixed.  Control of SOHO can still be
      > maintained<BR>
      > via the low-gain antenna.  However, the data transfer rate with
      > the<BR>
      > low-gain antenna is not high enough to return much in the way of<BR>
      > useful science data, except for some basic measurements.  No
      > images<BR>
      > could be sent back.<BR>
      > <BR>
      > Assuming worst case, that being that the high-gain antenna can only
      > be<BR>
      > moved slowly for a limited amount in slight steps, there will be
      > about<BR>
      > 18 days out of every three months that SOHO will be unable to
      > return<BR>
      > data.  Taking SOHO through a series of maneuvers at set times
      > may<BR>
      > improve that a little, but that also carries its own set of risks. <BR>
      > More will be known about that as the engineers have a chance to
      > sort<BR>
      > things out.<BR>
      > <BR>
      > As I mentioned before, while some SOHO functions could be taken
      > over<BR>
      > by other satellites, SOHO is unique in it's abilities, and there's<BR>
      > nothing currently up that can do everything that SOHO can. 
      > During<BR>
      > it's blackout periods, space weather forecasting will be
      > comprimised.<BR>
      > One important instrument that is unique to SOHO is LASCO, or Large<BR>
      > Angle Solar Coronagraph.  It has a disk that blocks out the light
      > of<BR>
      > the sun itself, allowing the corona to be studied.  While
      > other<BR>
      > satellites, like TRACE, can detect when a Coronal Mass Ejection has<BR>
      > occurred, only SOHO can be used to provide optical images of it.<BR>
      > <BR>
      > However, it is early in the game, and the folks at the Goddard<BR>
      > Spaceflight Center have been known to work miracles before, so stay<BR>
      > tuned.  I'll post more information as it is made available.<BR>
      > <BR>
      > <BR>
      > <BR>
      > </tt>
      >
      > <br>
      >
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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 2 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 3 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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