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21. LCRD - The Design: Ground | NASA's The Invisible Network Podcast

Season 1Episode 21Dec 22, 2021

In this fourth episode of a five-part series about NASA’s Laser Communications Relay Demonstration, we look at the LCRD ground segment, which consists of infrastructure in Hawaii, California, and New Mexico.

The Invisible Network Podcast Graphic

The Invisible Network Podcast Graphic

NARRATOR

In this fourth episode of a five-part series about the Laser Communications Relay Demonstration, we’ll look at LCRD’s ground segment, travelling across the Unites States to explore infrastructure in Hawaii, California, and New Mexico. We’ll encounter disparate and complex systems working harmoniously to empower LCRD’s flight system and its host spacecraft, the U.S. Space Force’s Space Test Program Satellite-6.

I’m Danny Baird. This is “The Invisible Network.”

NARRATOR

We begin our journey at the White Sands Complex in Las Cruces, New Mexico. There, NASA operates the entire LCRD system.

MIRIAM WENNERSTEN

My name is Miriam Wennersten, and I am the LCRD ground segment manager…

So, as the ground segment manager, I’m in charge of making sure that all of the pieces that are on the ground are ready to go — to be able to communicate with… LCRD… as a system. And so, part of LCRD was building the space component, but also the ground component. And there’s the ground stations and also the mission operations center, that’s kind of at the hub of it.

NARRATOR

The LCRD Mission Operations Center, or LMOC, controls the entire mission.

MIRIAM WENNERSTEN

It is the central brains of the LCRD system, when you think of LCRD as an entire system with both the flight payload and the ground segment. And the ground segment… consists of the LMOC, the two optical ground stations, and something called the PGLT, which is the payload-to-ground link terminal — and it actually connects to the spacecraft’s Ka-band link, the RF link…

The Ka-band link is actually the main link for the spacecraft itself. We are using that primarily as our command and telemetry link… We also have a lower speed link for telemetry that’s coming from the spacecraft.

NARRATOR

Both of those radio links — the high-data-rate Ka-band and lower data S-band telemetry link — support the entire STPSat-6 spacecraft, which hosts LCRD among other payloads and instruments. A separate facility nearby — the STPSat-6 Satellite Ops Center — operates the non-NASA payloads.

As for the LCRD Mission Ops Center:

MIRIAM WENNERSTEN

It’s a large room with several rows of consoles and there are multiple… stations for our operators with computer screens. And each one of those screens connects to a different subsystem of the LMOC… So we have something called the central ops monitoring and control — we call the COMAC — that is actually responsible for commanding the ground stations… and it also ultimately receives the spacecraft telemetry.

And so we’ll have a COMAC operator. We’ll have another person that is responsible for doing the planning of the different experiment events…

So, it’s a big room with a lot of computer screens. And we’ve got some big screens up on the wall for the purposes of showing what the weather is and things like that.

NARRATOR

In addition to the LMOC, White Sands also hosts the STPSat-6 Antenna and Ground Equipment, or SAGE, which supplies data to the LMOC. SAGE consists of the radio antennas that collect the spacecraft’s data, as well as the payload-to-ground link terminal, or PGLT, that Miriam mentioned.

KIM HAWKINS

My name is Kim Hawkins… I’m the SAGE mission readiness manager.

TJ CROOKS

My name is TJ Crooks. I’m a telecommunications engineer… and I’m the SAGE task monitor.

NARRATOR

Kim and TJ are two key players in the development of the radio antennas and related systems supporting STPSat-6 and LCRD.

TJ CROOKS

The antenna that we built at White Sands for the STPSat-6 mission is a 9.1 meter, S- and Ka-… dual band antenna. So, I oversaw the development of that antenna as well as the installation and certification of that antenna…

It’s very multi-disciplinary, as far as what goes into designing the ground system.

KIM HAWKINS

I’ve always been on the flight side before. This is the first time I’ve really gotten to see all that goes into the ground system… I am truly very fortunate to have been able to see both sides closely. There’s just so much going into the ground that I had — I mean, I knew it was there — but I didn’t fully appreciate it.

NARRATOR

Kim and TJ detailed the vast breadth of experience and expertise required to implement the radio systems for LCRD and STPSat-6. To begin a conversation about the optical communications component of LCRD, we journey west to Southern California, home to NASA’s Jet Propulsion Laboratory.

TOM ROBERTS

I’m Tom Roberts. I’m the manager of the Optical Ground Station-1 development and operations.

NARRATOR

Optical Ground Station-1 rests at the top of California’s Table Mountain among other JPL facilities dedicated to astronomy. For a variety of reasons, it’s the perfect location for an LCRD ground station.

TOM ROBERTS

Table Mountain happens to be a pretty good site. It’s easily accessible from JPL. It’s about 7500 feet elevation… so we get through a lot of the atmosphere… It also has a fairly good, cloud-free line-of-sight… Southern California, in general, is known for its good weather.

NARRATOR

Though relatively close to the Jet Propulsion Laboratory’s campus in Pasadena, getting to Table Mountain can still be a bit of a trek.

TOM ROBERTS

Well, there are two different ways to get to the actual telescope and the Table Mountain Facility in general. One is to go up the highway, which is this winding road. It’s idyllic. It’s beautiful. The scenery from this road is incredible.

It’s only about 60 miles, but it’s frequently closed off because of fires, or landslides, or snow. And so, generally speaking: it’s much easier to go a little further and to go around the Angeles National Forest and come in from behind.

The drive up there is beautiful. You go through a few small communities but you see a lot of geology — the Mormon Rocks, the Cajon Pass — and then when you get up to the telescope you’ve got this broad view of the entire sky…

The nights there are spectacular because you get all of the… dark skies that you need when you’re trying to do astronomy or optical communications — in some cases. And you’re far away from the city at that point.

NARRATOR

As for the Table Mountain telescope that will communicate data over laser links with LCRD:

TOM ROBERTS

This telescope that we have is designed specifically for optical communications. It’s what they call a very slow telescope. It has large focal ratio, which means that even though it’s one meter in diameter it sends a beam to focus 76 meters away…

And there are a few things that — when you look at the telescope — it’s not quite what you expect having seen a bunch of other telescopes. For one thing, it’s all painted white… and all of that is to cut down on the amount of… sunlight power that would get absorbed by the system and heat the system up. It reflects that sunlight away and gives it a nice even irradiance across the entire system. So, we don’t get those differential heating elements… that either would cause the mirrors to go out of alignment slightly or might cause turbulence in the atmosphere, which would give us more of a difficult time.

NARRATOR

The inner workings of that all-white exterior include technologies and systems that will allow the ground station to further prevent and mitigate the impacts that atmospheric turbulence and weather conditions might have on laser links flowing from LCRD to Table Mountain.

TOM ROBERTS

We’ve got a really good team that put together a state-of-the-art, adaptive optics system for coupling light from the spacecraft into a little single mode fiber that’s about 1/10 the diameter of the average human hair. So, it’s got to be able to do that with all the perturbations to the wavefront that comes down from the spacecraft as it goes through the atmosphere. And it’s a very tricky thing to do, but it makes this technology entirely possible.

An adaptive optics system uses a wavefront sensor to measure the amount of distortion to that electromagnetic wavefront that’s coming down from the spacecraft. And if we can measure that distortion, then we can send it through what’s called a deformable mirror, that actually changes its shape to take out those aberrations that the atmosphere induced.

And it has to do it very quickly… in order to take out the worst of the aberrations introduced by the atmosphere. That allows us to have a nice, pristine wavefront that we then couple down into that tiny little fiber opening.

NARRATOR

Essentially, the specialized mirror at Table Mountain can very rapidly change its shape to reduce or eliminate changes to LCRD’s signal as it passes through the atmosphere.

LCRD’s telescope at Table Mountain is actually part of a larger facility called the Optical Communications Telescope Laboratory. The laboratory has supported a number of optical communications experiments and demonstrations, including ones on the space station and in lunar orbit. But for LCRD, the telescope needed some upgrades to get to its current state.

TOM ROBERTS

I was actually the telescope lead responsible for making modifications to the telescope, and those modifications were in a lot of cases things to bring the telescope functional systems — its ability to point, etc. — up to a higher standard than we had before. Some of the things that we did was, we replaced some of the amplifiers in the system so that they were modern… pulse width modulation amplifiers, and we changed out some of the mirrors to have better reflectivity and better laser damage thresholds than we had before. Before they were all silver coated mirrors with a dielectric overcoat to protect them, but we really needed something that would transmit more of the light and not be damaged quite so easily with laser beams that we’re shooting off of the telescope mirrors.

NARRATOR

The Table Mountain telescope is part of a versatile system with a rich legacy supporting a wide variety of optical communications demonstrations. It just had to undergo a little modernization to support LCRD.

By contrast, Optical Ground Station-2, or OGS-2, was built from scratch for LCRD. That brings us to the next stop on our grand tour of LCRD’s ground segment: OGS-2 and Haleakalā, Hawaii.

RON MILLER

My name is Ron Miller and I was the OGS-2 lead for the LCRD mission.

OGS-2 is… basically a telescope and equipment on top of Haleakalā, [a volcano] in Maui, Hawaii, that’s used to receive and provide optical communications with the satellite.

NARRATOR

And why did NASA choose this specific location? Why Hawaii?

RON MILLER

The meteorological conditions at the top of the mountain. There’s very little dust and the air is quite good for laser communications. So, it’s about 10,000 feet up in the air, so you’re above a lot of the atmosphere. And most of the weather is below the summit at Haleakalā, so it’s very common to have a nice sunny day at the top and be cloudy around the midpoint of the mountain. Just the way the local meteorology works.

So, it’s a very good place to be and it also complements — weather-wise — some of the other sites… we have in the continental United States, because when they’re cloudy, Haleakalā is generally clear and vice versa.

NARRATOR

Building a ground station anywhere can be challenging. Building a ground station on the top of a mountain in the middle of the Pacific Ocean adds more complexity to the process.

RON MILLER

Some of the engineering challenges related to just even getting the telescope up the mountain. We had to get the telescope and the dome up a two-lane road that winds… up the mountain. So that was kind of interesting… Needed to get one of those big cargo jets to bring the units into Hawaii — that was an adventure in and of itself.

And then once we got on top of the mountain, things went very smoothly — there had to be some facility mods, of course, to get ready for it — but everything fit like a glove when we got up there.

NARRATOR

Beyond engineering and logistical challenges, there’s also a human element. Working at high altitudes places some unique physical strains on the engineers.

RON MILLER

I actually experienced some of the stuff. When you’re at 10,000 feet, the oxygen is — I think it’s 60% or so what you have on the ground —might be different than that number, but it’s thinner. And even people who have worked up there for years and years, every once in a while it just gets to you. And there’s oxygen [tanks] all over the place. So yeah, one day… I went up there and… I had the experience of having altitude sickness without doing anything…

The other fun thing that scared the heck out of us the first time we went up there is: there’s no cafeteria on top of the mountain, so you bring your lunch. So, we stopped at Subway and got a sub and some chips, and went up the hill. About two thirds of the way up the mountain, we hear this huge pop and all the bags of chips had exploded because the air pressure was less.

NARRATOR

With popping of bags of chips, we close our grand tour of LCRD’s ground segment. From a desert in New Mexico, through the forests of California, to a Hawaiian volcano, we’ve explored the systems that empower LCRD’s mission.

During development, the ground system teams had to overcome any challenges that came their way while ensuring every component operated as planned. That means that these disparate pieces of infrastructure needed to work cohesively to support the LCRD flight payload. This required collaboration, focus, and a strategic plan — the hallmarks of systems engineering.

Nick Cummings is a systems engineer on the LCRD mission.

NICK CUMMINGS

The work of a systems engineer is essentially to make a complex system work. So, many cases, we’re designing a system that’s made up of many parts that are constructed by many different people. So, you might have team of dozens or even hundreds of people working on different pieces that then all have to be assembled together to work as a system.

And if you don’t have a systematic approach to that process, then it would be very easy for people to make slightly different assumptions about how things are supposed to work. And then — when you put it together — it wouldn’t behave correctly.

And once you put it together, it obviously can be very complicated with all those moving parts. It could be hard to even figure out why it wasn’t working right. So systems engineering is the methodical way of making sure that doesn’t happen, making sure when you bring those pieces together, they work correctly.

NARRATOR

Systems engineering is a critical discipline at NASA. Systems engineers see the bigger picture of missions a million pixels wide. They ensure that every part of a mission works in concert — that individual components play well together; that ground systems and flight systems speak the same language; that one step follows the next on the road to mission success.

Together, LCRD’s flight and ground systems are proving the power and promise of optical communications technologies.

With the payload launched and ground segment at the ready, it’s time to look to the future of LCRD and of optical communications technologies in general. Tune in next week to learn about upcoming optical missions and development efforts.

NARRATOR

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.

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 Dec. 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.

Special thanks to Barbara Adde, SCaN Policy and Strategic Communications director, and all those who have lent their time, talent and expertise to making “The Invisible Network” a reality. Be sure to rate, review, and follow the show wherever you get your podcasts. For transcripts of the episodes, visit NASA.gov/invisible. To learn more about the vital role that space communications plays in NASA’s mission, visit NASA.gov/SCaN. And for more NASA podcast offerings, visit NASA.gov/podcasts.