19. LCRD – The Dream | NASA’s The Invisible Network Podcast
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Working from home over the past year or so, I’ve never been more aware of the importance of my high-speed internet connection. Most of the time, I enjoy a reasonably fast, fiber-optic connection, which allows me unfettered access to the files and systems I need to do my work. If I need to upload a large video file to a server or download a slide deck full of high-resolution images, I usually have no trouble logging into NASA’s virtual private network and getting the job done.
Having just turned 30, I’m not so young that I don’t appreciate the speed of my internet connection. I can’t imagine what this pandemic would have been like had I needed to rely on the dial-up internet my family had in the 1990s and early 2000s. Back then, the time it took to download an album or a video game from the web could seem interminable.
The fiber-optics that serve as the backbone for today’s terrestrial internet didn’t appear overnight. Through diligent and persistent innovation, engineers developed and implemented these systems, which send pulses of lasers densely packed with information through cables made of glass or plastic.
In parallel, NASA’s space communications community has been creating systems that allow spacecraft to send their data over lasers — minus the cables, of course. Free-space optical communications — so named because the lasers flow freely through space — offers similar benefits to fiber-optics and can take missions from dial-up to high speed connections.
In this second episode of a five-part series about the Laser Communications Relay Demonstration, we’ll dive deeper into the benefits of optical communications for space users and glean the goals of the mission overall.
I’m Danny Baird. This is “The Invisible Network.”
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Gerald Bawden serves as program scientist in the Earth science division at NASA Headquarters in Washington.
GERALD BAWDEN
I’m responsible for NASA’s Earth science radar systems. These are satellites that are looking at everything from earthquakes and volcanic eruptions, looking at changes in biomass on the Earth, and cryosphere.
NARRATOR
NASA’s fleet of orbiting Earth science satellites generate invaluable insights about our changing planet. Their data informs everything from long-term research into climate change, to real-time information about natural disasters as they occur.
GERALD BAWDEN
NASA’s Earth science satellites provide a context… We see what’s going on, where it’s going, and being able to go ahead and measure it… So, these are our eyes in space…
If it wasn’t for… the satellite data, we would not be able to go ahead and see these changes of what’s going on in the world. So it’s impressive what we can do with it.
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Earth science satellites can generate a lot of data and continue to generate more as engineers develop higher resolution science instruments. Over the years, NASA has refined ways of getting the ever-increasing volume of scientific information onboard these spacecraft to scientists on the ground.
GERALD BAWDEN
The challenges of getting data down to the ground are multi-leveled… What it really comes down to the download bandwidth. So, if we think of a kind of like an internet connection coming into your house. If we go old school and you’ve got a modem coming in, we used to have very slow modems and then they got faster and faster. The data that was coming in was just trickling down. That’s like our satellites were — I’ll say — back in the 1970s.
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In the days before digital instruments — when satellites used film — engineers had to be even more creative about getting their data down.
GERALD BAWDEN
They actually dropped the film out of the satellite and was retrieved down on Earth… as technology improves over time, we’re able to get more and more data. So, it’s this bandwidth piece.
We’ve gone from that to now where we’re collecting… terabytes of data every day. And so we’re going from very small… modem speeds that I was talking about earlier, up to really the fiber-optic speeds. And so that’s where I think laser communication is really going to help expand… the research field because we’ll actually have this higher data bandwidth.
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What is laser communications? It’s a technology that will empower scientists with more data than ever before.
GERALD BAWDEN
If you really take a look at what the Earth science needs are — so this is now trying to look at the future of NASA’s Earth Science needs. Everybody wants bigger, badder, faster type capabilities. And the scientists that have pride and help put together NASA’s missions are no different…
I kind of use this water tower as an analogy… where the water represents the data and you want to get that out of the tower. If you’ve got a small hose, you could only do it so quickly… It’s goning to take a long time to get all the data. So what we need to be able to do is open the bottom of the satellites, so you can get a ton of data off the satellites within a few minutes.
NARRATOR
And what does more data mean for research?
GERALD BAWDEN
We’re going to be able to go and do a lot more exciting science. So, instead of looking at just large-scale processes, we’re able to start looking in, and zeroing in, on some of the smaller level things that actually contribute to the larger scale.
There’s a lot of — I’ll say — interconnectivity among the different processes. We got fires that are burning that’s putting smoke up in the air. That smoke comes out, it lands on snow and ice, so you increase the melting on the snow and ice. And then… now we’ve got more water that’s coming out the mountains… There’s a lot of interconnectivity that the added data volume and quality of data we’ll be able to go ahead and enable.
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The Laser Communications Relay Demonstration, or LCRD, which launched this December, is helping to mature optical communications so that missions across the agency can deliver more data to scientists like Gerald Bawden. As he so eloquently put it, it’s like opening up the bottom of the satellites so that more data can flow to the ground at once. The higher frequency of these infrared laser links can provide 10 to 100 times higher data rates than comparable radio frequency systems. That means that missions using optical can downlink more data-per-second than ever before.
Optical communications technologies are not new. If you went back and listened to episode 11 of this podcast, “Reflections,” you’d learn about 1992’s Galileo Optical Experiment, one of NASA’s earliest optical communications tests.
If you listened to episode 2, “Lemnos,” you’d learn about the Lunar Laser Communications Demonstration, or LLCD, which flew aboard the Lunar Atmosphere and Dust Environment Explorer, or LADEE, in 2013. That mission is considered the predecessor to LCRD in many ways, but LCRD is taking optical communications one step further.
LCRD principal investigator, Dave Israel:
DAVID ISRAEL
LCRD was chosen as a mission in August of 2011, actually, and at that time… we were already building the Lunar Laser Communications Demonstration mission that was to fly on the LADEE spacecraft.
So LADEE did fly was very successful in 2013. And it demonstrated the technology of laser comm and even, you know, all the way to and from lunar orbit, and set all sorts of records, and performed extremely well.
However, that was a short-duration technology demonstration mission. And so — even though the basic technology was proven with LADEE — because it was such a short duration, there still were — and still are — lots of questions about longer term operational use.
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It’s those exact questions that LCRD is addressing. The goal of the mission is the further refine operational use of optical communications, testing capabilities and limitations.
SABINO PIAZZOLLA
Okay, my name is Sabino Piazzolla, and I am here at the Jet Propulsion Laboratory. I’m an optical engineer.
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Sabino also serves as a co-investigator on LCRD. He’s worked on a host of NASA optical communications experiments and demonstrations and looks forward to refining the science behind optical communications with LCRD.
SABINO PIAZZOLLA
We know that the laser beam can propagate through the atmosphere, but there is… a lot of things that need to be still studied, like interaction with… turbulence… etc. So, this is one thing that LCRD is going to provide. And, we’re going to understand that with this limitation of propagation… through the atmosphere, what is the best that we can achieve in terms of data rate and performances.
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Due to their lower frequency, radio waves don’t interact with the atmosphere as strongly as laser light does, so those interactions must be studied. To move towards operational use of optical communications, engineers need to understand and overcome the challenges of things like transmitting through cloud coverage or turbulent air.
SABINO PIAZZOLLA
One way to limit the effect of the optical turbulence is to use a technology that we are currently using for LCRD, which is called adaptive optics. So, adaptive optics is a way… to compensate for the distortion or the aberration of light that’s experienced when it is propagated through atmosphere.
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In addition to issues of atmospheric distortion, engineers must compensate for a phenomenon called beam wander.
SABINO PIAZZOLLA
Beam wander is caused by the fact that the refractive index for the atmosphere is not constant… because of the different temperature distribution in the… atmosphere.
NARRATOR
If engineers can predict the wander of the beam based on the atmospheric conditions, they can compensate for it, assuring clear transmissions.
Atmospheric distortion and beam wander are just two of the relative unknowns that LCRD hopes to address over the life of the mission. There’s also the issue of modulation schemes — the ways NASA embeds data onto the lasers. There’re questions about the data rates that can be achieved under operational conditions. There’re also the unknown questions that engineers won’t even know to ask until LCRD is on orbit and transmitting data.
To encounter these questions, mission engineers developed LCRD as a versatile platform. It’s the perfect tool for investigators and guest experimenters to test and refine optical communications technologies while developing future optical missions. Beginning next episode, we’ll take a look at the design and architecture of LCRD, starting with the flight systems. The week after, we’ll take a look at the ground architecture that ties it all together.
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Thank you for listening. Do you want to connect with us? The Invisible Network team is collecting questions about laser communications from listeners like you! We’re putting together a panel of NASA experts from across the Space Communications and Navigation community to answer your questions.
If you would like to participate, navigate over to NASA SCaN on Twitter or Facebook and ask your question using the hashtag AskSCaN. That’s @ NASA SCaN, N-A-S-A-S-C-A-N, on social media, with the hashtag AskSCaN, A-S-K-S-C-A-N.
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This LCRD-focused season of “The Invisible Network” debuted after the launch of the U.S. Space Force’s Space Test Program Satellite-6 on December 7, 2021. LCRD is led by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in partnership with NASA’s Jet Propulsion Laboratory in Southern California and the MIT Lincoln Laboratory. LCRD is funded through NASA’s Technology Demonstration Missions program, part of the Space Technology Mission Directorate, and the Space Communications and Navigation (SCaN) program at NASA Headquarters in Washington, D.C.
The podcast is produced by SCaN at Goddard with episodes written and recorded by me, Danny Baird. Editorial support provided by Katherine Schauer. Our public affairs officers are Lora Bleacher, Kathryn Hambleton, and Clare Skelly of the Space Technology Mission Directorate.
SOURCE: NASA
