海外の宇宙ニュース：#WEBBWOWの1年
幼いころ体験したようなクリスマスの感動は、大人になって再び味わうことは出来ないと言われます。ですが2021年12月25日に空を見上げていた天文学者たちは、そうは思わなかったでしょう。この日、史上最強の宇宙望遠鏡が打ち上げられようとしていました。
幼いころ体験したようなクリスマスの感動は、大人になって再び味わうことは出来ないと言われます。ですが2021年12月25日に空を見上げていた天文学者たちは、そうは思わなかったでしょう。この日、史上最強の宇宙望遠鏡が打ち上げられようとしていました。
幼いころ体験したようなクリスマスの感動は、大人になって再び味わうことは出来ないと言われます。ですが2021年12月25日に空を見上げていた天文学者たちは、そうは思わなかったでしょう。この日、史上最強の宇宙望遠鏡が打ち上げられようとしていました。
DESTINY＋ミッションで地上観測を主担当する吉田二美（よしだふみ）氏が、研究者とアマチュア天文家との協力をリードし小惑星フェートン（Phaeton）による恒星掩蔽現象（星食）の観測を成功させたことを評価されて、ホーマー・F・ダボール賞を受賞されました。
衝突まで17日-2022年９月上旬、世界中の科学者たちは、ある重要な問いに向き合っていました。万が一、必要に迫られたら、、地球上の生命が危機にさらされるとしたら、、私たちは地球を守れるのだろうか？それを見極めるときが来たのです。
「物体が高いところから低いところに落ちるとき、重力ポテンシャルを失うことで運動エネルギーを得る」これは宇宙最大の構造である銀河団（銀河クラスター）の形成について説明した文です。銀河団の中で何が起きているのか。これは長い間不明でしたが、来年度に打ち上げが予定されているX線分光撮像衛星XRISM（クリズム）によって新たな展開が期待できそうです。
NASAの小惑星探査機Lucy（ルーシー）がトラブルに見舞われたのは、昨年10月の打ち上げ直後のことです。打ち上げ後に起こる問題は、Lucyに限ったことではありません。ミッションを成功に導くには？ ISASの研究者らがその経験を語りました。
二つの小惑星。二つの国。二つの偉大なミッション！JAXAの「はやぶさ２」と NASAの「OSIRIS-REx」はリュウグウとベンヌという2つの異なる小惑星を探査しました。今週、両チームのメンバーが、SNS上で、これまでに判明したことに関連する皆さんの質問にお答えします。
6月8日、欧州宇宙機関（ESA）は、Comet Interceptor （コメット・インターセプター）ミッションの検討段階が終了し2029年の打ち上げを目指して正式に製造組み立てを開始することが承認されたと発表しました。Comet InterceptorはESAが主導、JAXAも参加するミッションで、ISASのComet Interceptorチームはこのニュースを心待ちにしていました。
大型ロケット「SLS」(Space Launch System）の初号機打ち上げに向け、期待が高まってきています。全長98mの巨大ロケットには、ISASが開発するOMOTENASHI（おもてなし）と EQUULEUS（エクレウス）という、とても小さな２体のロボットたちが乗り込むことになります。
太陽電池パネルに積もったちりが、これまで多くの「火震」を検出してきたNASAの火星着陸機InSightが今夏、その役目を終えることを告げています。ですが地球以外での天体における地震観測は、InSightとともに終わるというわけではありません。ISASの研究者が語ります。
Jim served as a safety diver at Marshall Space Flight Center. (NASA)
“How I got involved in the repair of Hubble is that I’m a scuba diver!”
While studying at the University of Iowa in the late 1970s, Jim Green joined the university scuba club. It was an activity that would ultimately lead to Green being involved in several of the most famous space repairs in history.
In 1980, Green began his first position at NASA at the Marshall Space Flight Center. A short while later, Green was visited by his parents who had asked for a tour of the facilities. The seemingly innocent request sent Green into a fluster.
“A tour! I know what happens in my building, but there’s fifty buildings here. I don’t know what they do! I have no idea what the Marshall Space Flight Center does, what are you talking about?!” laughs Green. “I can show you my pencil and… my computer terminal!”
A clever solution was to assign the task to a more experienced party. Just outside the Marshall Space Flight Center was the US Space and Rocket Center that took visitors on tours of the neighbouring NASA facility. When Green’s parents arrived, the family boarded a bus to take the official tour of Green’s institute.
The tour bus wove through the Marshall Space Flight Center and eventually reached a building that contained a huge tank of water stretching 23m across down to 12m in depth. This was a neutral buoyancy pool where astronauts could practice working in space wearing a full spacesuit while being suspended in the water.
“I look into a porthole and I go, I’ve got to get in this tank!” recalls Green. “How do I get in this tank and dive?”
To support the astronauts during the training exercises, safety and utility divers were needed in the water. And as it happened, many of the current team of divers were retiring that year. With his extensive scuba diving experience in the difficult visibility conditions of the quarries, lakes and rivers of Iowa, Green’s application to join the team was accepted. A few times a week he would then receive a phone call at this desk to dive the next day.
“They’d call me up and say, can you dive tomorrow? I’d look at my schedule, and I’d say great,” remembers Green. “And I’d have a morning dive or an afternoon dive that would last anywhere from 80 minutes to 120 minutes.”
Once in the tank, Green’s job as a safety diver was to weight the astronaut to balance the buoyancy of their spacesuit until they were perfectly suspended in the water. Green would then stay by the astronaut through the exercise to ensure that they were never put at risk.
One such dive was for the spacewalk in 1993 that would fix the flaw in the Hubble Space Telescope’s primary mirror. Yet, the mission Green most clearly remembers was the repair of the Solar Maximum Mission (SMM).
Solar Maximum had launched in February 1980, but a failure in the attitude control late that year sent the satellite into a spin. In 1984, a Shuttle crew intercepted the spacecraft and repaired the fault.
“The repair of SMM was unbelievable!” says Green. “They built the Manned Manoeuvring Unit—the unit that fits on your back, and you literally are the spacecraft—they built that to repair SMM!”
The Manned Manoeuvring Unity (MMU) is the astronaut propulsion pack that is seen in the movie “Gravity” being used by George Clooney’s character. It was the job of NASA astronaut George “Pinky” Nelson to use the MMU to get Solar Maximum safely into the Shuttle’s payload bay where it could be repaired.
“The spacecraft has these solar panels, and it’s spinning,” describes Green. “So Pinky Nelson had to corkscrew his way in, all the way to the satellite itself, and connect. Then he had to use his thrusters to slow the spin down, and pull the spacecraft over to the Shuttle and stick it in the bay. We practiced that in the tank!”
Despite a series of challenges during the mission, Solar Maximum was a successfully repaired. The mission ran for another five years, until the end of 1989.
Green would ultimately perform around 150 dives over five years to support astronauts in the neutral buoyancy tank.
“I had a blast!” he recalls. “We did all kinds of spectacular stuff like this.”
The Intrepid being inflated from the nearby hydrogen gas generators at the Lowe Balloon Camp on Dr. Gaines’s farm (Library of Congress)
“Everyone has hobbies and one of my hobbies is Civil War Balloons.”
During the American Civil War, balloons crewed by aeronauts were used for reconnaissance. Soaring a thousand feet above the ground, the balloons provided an elevated look-out from which the location of the opposition’s troops and artillery could be seen.
Fascinated by the aeronautical technology being developed in that era, Green was searching for references to the balloons in the newspaper archives held at the US Library of Congress. It was there he found that balloons were not the only notable phenomena in the sky in 1859.
“The late August, early September papers were filled with aurora stories, no matter what newspaper you read,” exclaims Green.
The papers referenced an event dubbed “The Great Aurora of 1859” and Green swiftly realised this must be far more wide-spread then any recent phenomena.
“The news at the time was very local,” he explains. “So if a newspaper in New Orleans mentions an aurora flying overhead, it’s local. They’re not talking about a place in Canada.”
Green’s findings pointed to the occurrence of a solar superstorm in which violent eruptions on the Sun’s surface had engulfed our planet in a cloud of high energy plasma, and generated a huge aurora that stretched from the poles and down towards the equator.
It has previously been well known that the Sun releases a continuous stream of high energy particles into space, known as the solar wind. Upon reaching the Earth, these particles are caught in our planet’s magnetic field and spiral down towards the poles. As they hit the atmosphere, light is emitted in characteristic colours of greens and reds to form the northern and southern lights, also known as the aurora borealis and australis. But views of the aurora typically require you to be far north or far south, with few opportunities for sightings in the US outside Alaska.
Solar storms where clouds of plasma explode from the Sun had also regularly been recorded, but even these had never produced an aurora as globally visible as that of the Great Aurora of 1859. Overall, our nearest star was mistakenly believed to be quite quiescent.
The publication of Green’s findings in the US records triggered a search by scientists of global historical archives. Sightings of an aurora far from the north and south poles were discovered in multiple reports, dating back to even to Assyrian and Babylonian tablets in 500 and 600 BC.
“One of the telltale signs is a very low latitude red aurora. That’s what happens during superstorms,” describes Green. “And there were these comments of people on the ground looking up, seeing a red aurora, and that ends up being written about.”
But superstorms are not merely a pretty phenomenon. As the charged particles from the solar storm spread out across the sky to form the Great Aurora of 1859, they generated electric currents which disrupted telegraph stations. If such a storm were to occur today, the damage would be much more severe as our technology is now heavily reliant on far more vulnerable communication satellites.
“Space weather then takes on a new dimension,” explains Green. “It can become a threat to our technology.”
Recognition of the dangers of solar storms has led to improvements in satellite design, and space weather is now monitored to provide warning for big events. However, a large superstorm would certainly cause significant damage both in space and to ground equipment such as the power grids.
“In the 1980s this was nowhere on the scene,” notes Green. “We now recognise that the Sun can really put it out!”
