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SOHO satellite update

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  • David
    There hasn t been anything new to speak of since yesterday. I m assuming, therefore, that the high-gain antenna remains a problem. That s the antenna used to
    Message 1 of 4 , Jun 20, 2003
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      There hasn't been anything new to speak of since yesterday. I'm
      assuming, therefore, that the high-gain antenna remains a problem.
      That's the antenna used to send data back to earth. SOHO will NOT be
      lost if it can't be fixed. Control of SOHO can still be maintained
      via the low-gain antenna. However, the data transfer rate with the
      low-gain antenna is not high enough to return much in the way of
      useful science data, except for some basic measurements. No images
      could be sent back.

      Assuming worst case, that being that the high-gain antenna can only be
      moved slowly for a limited amount in slight steps, there will be about
      18 days out of every three months that SOHO will be unable to return
      data. Taking SOHO through a series of maneuvers at set times may
      improve that a little, but that also carries its own set of risks.
      More will be known about that as the engineers have a chance to sort
      things out.

      As I mentioned before, while some SOHO functions could be taken over
      by other satellites, SOHO is unique in it's abilities, and there's
      nothing currently up that can do everything that SOHO can. During
      it's blackout periods, space weather forecasting will be comprimised.
      One important instrument that is unique to SOHO is LASCO, or Large
      Angle Solar Coronagraph. It has a disk that blocks out the light of
      the sun itself, allowing the corona to be studied. While other
      satellites, like TRACE, can detect when a Coronal Mass Ejection has
      occurred, only SOHO can be used to provide optical images of it.

      However, it is early in the game, and the folks at the Goddard
      Spaceflight Center have been known to work miracles before, so stay
      tuned. I'll post more information as it is made available.
    • mike
      Keep us up on this. The solar reports have been absolutely priceless. ... From: David To: methanehydrateclub@yahoogroups.com
      Message 2 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 3 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 4 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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