For a quater of a century, the ESA NASA Solar & Heliospheric Observatory (SOHO) has been essential in helping the scientists understand the heart of our system, the Sun.
The SOHO mission was launched 25 years ago & to celebrate it, ESA compiled a wonderful mosaic of images.
“SOHO has been a cornerstone of modern solar physics and launched many careers including my very own,” said professor Peter Gallagher, Director of Dunsink Observatory in Dublin, Ireland & Head of Astrophysics at the Dublin Institute for Advanced Studies (DIAS).
“My research group & lots of others, still use SOHO data 25 years later. It’s a tremendous mission.”
As an evidence, about 6000 scientific papers have been published based on SOHO data.
SOHO was launched on 2 December 1995 & was only designed to last for 2 years. But the spacecraft showed itself to be a workhorse and the mission was so successful that ESA & NASA decided to prolong its life several times, granting several mission extensions.
Astrophysicist Karl Battams, principal investigator for one among SOHO’s instruments, the LASCO coronagraph, said on Twitter that when he was an undergrad (in approx. 2001), his astronomy professor “told us that if we had any solar physics textbooks published before SOHO, we should not use them for her class. SOHO literally rewrote the books on solar physics!”
Some highlights of SOHO’s revelations are:
• First images ever of a star’s convection zone & of the structure of sunspots below the surface.
• The most detailed & precise measurements of the temperature structure, the interior rotation and gas flows in the solar interior.
• Discovering new dynamic solar phenomena like coronal waves & solar tornadoes.
• Revolutionizing our ability to forecast space weather by abandoning to 3 days’ notice of Earth-directed disturbances & playing a lead role in the early warning system for space weather.
• Monitoring the impact of solar-variability on Earth’s climate.
The mission was launched to provide a comprehensive look at our Sun and was specially designed to assist understand the flow of energy & material from the Sun, the solar radiation & coronal mass ejections.
The main goals were to determine the structure & dynamics of the solar interior, learn more about the solar corona and to find out where the solar wind is produced & the way it is accelerated.
The scientific payload of SOHO comprises 12 complementary instruments developed & furnished by an international consortium of 29 institutes from 15 countries.
More than 1500 scientists in countries around the world are either directly involved in SOHO’s instruments or have used SOHO data in their research programs.
LASCO, the Large Angle & Spectrometric Coronagraph has recorded over 1.5 million images since the mission started. During a Reddit AMA to celebrate the anniversary, Battams was asked if has any favorite images.
“There are numerous mind-blowing images that I absolutely cannot pick a single one,” he said. But he highlighted two favorites.
The first is one from the LASCO C2 coronagraph & was taken 1998, [above]. It shows a stunning helical structure in a coronal mass ejection (CME).
The another shows a CME reaching out towards comet C/2002 V1 (NEAT) back in 2003. “This was a rare instance where the CME actually passed right over the comet & we saw a touch interaction between the CME & the comet tail,” Battams said during the AMA. “CMEs are entirely harmless to comets structurally but the magnetic flux embedded in them can fiddle with dust in the comet tails.”
But SOHO’s 25 years haven’t been with a couple of nail-biting incidents. Two & a half years after launch in June 1998, the mission almost ended following a routine spacecraft maneuver.
Contact was lost, the mission was thought to be over. But the engineering & science teams worked painstakingly for 3 months, and eventually used a way called bistatic radar to find out & re-establish contact with SOHO.
They used the Arecibo Observatory in Puerto Rico to transmit a sign toward SOHO and one among the region Network dishes in Goldstone, California acted as a receiver, locating the spacecraft’s echo & tracking it using radar techniques.
The team managed to bring the mission back online-with all of the instruments surviving the extreme temperatures of the blackout. The rescue was one among the most dramatic rescue actions in space, perhaps second only to Apollo 13.
But then just a month after the spacecraft was back online, all three of the spacecraft’s stabilizing gyroscopes failed igniting a new race against the time to save the mission. The team developed new software that would control SOHO without the necessity of gyroscopes & the spacecraft was returned to full operations.
But ever since, SOHO has remained a stalwart and is now working together with other solar missions like the Solar Dynamics Observatory, STEREO & the Parker Solar Probe. The SOHO team hopes that in 5 years, we will celebrate more new imagery & data on the mission’s 30th anniversary.
This article was originally published by Universe Today.
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