Recently CNN.co.jp reported the following:
ＮＡＳＡ、レーザー実証装置を打ち上げ 宇宙通信に革新もたらす可能性
2021.12.08 Wed posted at 20:30 JST
（ＣＮＮ） 宇宙空間で不可視のレーザーを使用する計画はまるでＳＦの世界のことのように聞こえるかもしれないが、これは現実だ。
ＮＡＳＡの「レーザー通信中継実証装置」は、太陽系各地で行われる将来のミッションとの通信のあり方に変革をもたらす可能性がある。
ＮＡＳＡによると、これらのレーザーを使うことで、かつてない高解像度の動画や写真を宇宙から送信できるようになる可能性があるという。
実証装置は米東部時間の７日午前５時１９分、国防総省宇宙試験プログラムの人工衛星に搭載されてフロリダ州ケープカナベラルから打ち上げられた。打ち上げはもともと５日に予定されていたが、ロケット推進剤の地上貯蔵システムで漏出が見つかり日程が変更となった。漏出は７日の打ち上げ前に修復された。
ＮＡＳＡは１９５８年以来、飛行士や宇宙探査機との交信に電波を使ってきた。電波の有効性は実証済みだが、宇宙ミッションはかつてなく複雑になり、収集する情報も増えている。
赤外線レーザーの特徴をつかむには、遅くてイライラするダイヤルアップとは対照的な光通信の高速インターネットを思い浮かべれば良い。レーザー通信なら地表上空３万５４０６メートルの対地同期軌道から、毎秒１．２ギガバイトのスピードでデータを送信できる。これは映画丸１本を１分未満でダウンロードする速度に相当する。
これによりデータ伝送速度は電波の１０～１００倍に向上する。我々の目に見えない赤外線レーザーは電波より波長が短いことから、一度により多くのデータを送信できる。
現在の電波システムを使った場合、火星の完全な地図の送信に要する時間は９週間だが、レーザーなら９日間で送信できる可能性がある。
地上のレーザー受信施設にとって一つ障害になるのが雲や乱気流といった大気の乱れで、大気中を伝わるレーザー信号に干渉する場合がある。受信機２基の設置場所に遠隔地が選ばれたのはこれを念頭に置いた対応であり、どちらも標高が高く気象条件が良いことが決め手となった。
実際に宇宙ミッションの支援を開始するまでには２年間の試験や実験が必要となる。国際宇宙ステーション（ＩＳＳ）には将来的に光通信装置が搭載され、科学実験のデータを人工衛星を介して地球に送ることが可能になりそうだ。
Translation
(CNN) The plan to use an invisible laser in outer space might sound like a thing in the science fiction world, but it was a reality.
NASA's "Laser communication relay experimental
device" had the potential to revolutionize the future missions and communication ways to be done
in various parts of the solar system.
According to NASA, this laser had the potential to send
unprecedented high-definition videos and photos from space.
An experimental device was launched from Cape Canaveral,
Florida at 5:19 am EST on the 7th, on board was an artificial satellite of the
Department of Defense Space Test Program. The launch was originally scheduled
for the 5th, but was changed due to a leak found in the rocket propellant
ground storage system. The leak was repaired before the launch on the 7th.
NASA had been using radio waves to communicate with aviators
and space probes since 1958. Although the effectiveness of radio waves had been
proven, space missions were more complex than ever and more information was
being collected.
In order to capture the characteristics of infrared laser,
thought of the high-speed Internet of optical communication as opposed to slow
and frustrating dial-up. With laser communication, data could be transmitted at
a speed of 1.2 gigabytes per second from a geosynchronous orbit of 35,406
meters above the surface of the earth. This corresponded to the speed of
downloading a whole movie in less than a minute.
As a result, the data transmission speed would be improved
10 to 100 times compared to that of radio waves. Infrared laser that was
invisible had a shorter wavelength than radio waves, so it could transmit more
data at any one time.
When using the current radio systems, it took nine weeks to
send a complete map of Mars, but if it was laser, it could be sent in nine
days.
This "Laser communication relay experimental
device" would be NASA's first terminal-to-terminal laser relay system that
sent and received data from space to two optical ground stations in Table
Mountain, California and Haleakala in Hawaii. These ground stations had
telescopes that converted the light received from the laser into digital data.
One obstacle to laser receiving facilities on the ground was
the atmospheric turbulence such as clouds and eddy, which could interfere with
laser signals transmitted through the atmosphere. With this in mind, a remote
location was selected as the installation location for the two receivers, the
deciding factor was that the altitude was high and the weather conditions were
good.
When the satellite arrived in orbit, a team at the Operations Center in Las Cruces, New Mexico would activate the laser communication relay experimental device, and prepared to send the test data to the ground station.
Two years of testing and experimentation could be required
before the actual starting of support for the Space Mission. The International
Space Station (ISS) could be equipped with optical communication equipment for
the future, and it was likely that it might be possible to send scientific
experiment data to the earth via artificial satellites.
Since the experimental device acts as a relay satellite,
future spacecraft would not need to be equipped with an antenna with a direct
line of sight to the earth. This could ease the size, weight, and power
conditions required for future spacecraft communications, which might lead to a
reduction in launch costs and an increase in the storage for putting observing
equipment.
So, NASA's
"Laser communication relay experimental device" has the potential to
revolutionize the future space missions and way of communication. Laser has the
potential to send unprecedented high-definition videos and photos from space to earth in
a very short period of time.
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