The Solar and Heliospheric Observatory (SOHO) is a joint mission between the European Space Agency (ESA) and NASA. The mission is to observe the sun and enable analysis of solar events. The spacecraft, built by Matra and launched by NASA, was launched on Dec 2, 1995. SOHO moves around the Sun in step with the Earth, by slowly orbiting around the First Lagrangian Point (L1), where the combined gravity of the Earth and Sun keep SOHO in an orbit locked to the Earth-Sun line. The L1 point is approximately 1.5 million kilometers away from Earth (about four times the distance of the Moon), in the direction of the Sun.
There have been several close calls - Control of the spacecraft was lost in June 1998, and only restored three months later through efforts of the SOHO recovery team. All 12 instruments were still usable, most with no ill effects. Two of the three on-board gyroscopes failed immediately and a third in December 1998. After that, new on-board software that no longer relies on gyroscopes was installed in February 1999. It allowed the spacecraft to return to full scientific operations, while providing an even greater margin of safety for spacecraft operations. The mission control team at the Goddard Space Center has been phenomenal in extending the mission from a three year design life to over 13 years.
SOHO is invaluable because it provides early warning of the dangerous Corona Mass Ejections (CME)s that can jeopardize earth's increasingly susceptible space and surface infrastructure. CMEs are when the sun releases billions of tons of electrified gas into space at speeds up to 1000 km/h. If they hit Earth, these immense clouds can cause large magnetic storms in our magnetosphere and upper atmosphere. Such a strike can damage satellites, disrupt telecommunications, endanger astronauts, lead to corrosion in oil pipelines and cause current surges in power
lines.
The solar storm of 1859 is the most powerful solar storm recorded in history. The CME traveled to earth in just 18 hours in comparison to an average CME which takes a three day journey. Wiki tells that the CME caused telegraph wires in North America and Europe to short out, causing widespread fires. The auroras were so strong they were seen in the Rocky Mountains, awakening gold miners who thought it was morning. The great storm: solar tempest of 1859 revealed adds the 1859 storm was two orders of magnitude greater than any in recent history. It also warns that after a similar event today, some of our communications systems "could be like beachfront houses after a hurricane."
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