Re: [Methane Hydrate Club] SOHO satellite update
- Keep us up on this. The solar reports have been absolutely priceless.
From: "David" <b1blancer1@...>
Date: Sat, 21 Jun 2003 05:03:28 -0000
Subject: [Methane Hydrate Club] SOHO satellite update
> There hasn't been anything new to speak of since yesterday.
> 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
> lost if it can't be fixed. Control of SOHO can still be
> via the low-gain antenna. However, the data transfer rate with
> low-gain antenna is not high enough to return much in the way of<BR>
> useful science data, except for some basic measurements. No
> could be sent back.<BR>
> Assuming worst case, that being that the high-gain antenna can only
> moved slowly for a limited amount in slight steps, there will be
> 18 days out of every three months that SOHO will be unable to
> data. Taking SOHO through a series of maneuvers at set times
> 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
> things out.<BR>
> As I mentioned before, while some SOHO functions could be taken
> by other satellites, SOHO is unique in it's abilities, and there's<BR>
> nothing currently up that can do everything that SOHO can.
> it's blackout periods, space weather forecasting will be
> 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
> the sun itself, allowing the corona to be studied. While
> 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>
> 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>
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- --- In email@example.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.
- 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
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
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.