Space Communications Technology

Introduction

Satellite Communications Technology: Grainger engineers are connecting the world to tomorrow's technologies with satellites

Artificial intelligence. Quantum computing. The internet of things. The technological advances coming in the next few years will upend our society and forever change what we’re capable of.

These new technologies will depend on connection, whether to tandem devices or cloud services, to realize their full potential. Traditional networking depends on physical infrastructure, which is expensive to establish and challenging to construct for many parts of the world.

Fortunately, an alternative is right over our heads: outer space. A constellation of compact, inexpensive satellites can connect technologies all over the world while avoiding the difficulties of Earth-based networking.

Grainger engineers are facing this challenge from all angles – and altitudes – to make this vision reality.

On the International Space Station, 254 miles above Earth’s surface, Paul Kwiat is testing the limits of quantum hardware to show that reliable quantum networks can survive in the harsh radiation of outer space.

In low Earth orbits, 300 to 600 miles above us, Deepak Vashisht is innovating satellite-based computing and networking to allow real-time monitoring of environmental conditions and disasters.

Moving out to a point 1 million miles away from our planet, Lara Waldrop will take the most expansive pictures of our atmosphere ever in the first comprehensive study of the geocorona, advancing our understanding of space weather.

In addition to research, The Grainger College of Engineering is training the next generation of space industry engineers. From 2018 to 2024, Grainger Engineering benefited from the expertise of Michael Lembek, a veteran of the space industry who was instrumental in space systems engineering instructional programs.

Let’s take a look up and see how Grainger engineers are solving some of the loftiest problems.

Lara Waldrop

Getting the complete picture with the Carruthers Geocorona Observatory

Lara Waldrop is advancing space weather forecasting

Imagine that Earth is the size of an apple. The atmosphere, the layer of gas that insulates us from the harsh bleakness of outer space, would be about as thick as the apple’s skin.

At least, that’s what we thought for a long time.

That view was challenged in 1972 with a special camera deployed on the moon during the Apollo 16 mission. It was designed and built by George Carruthers, a three-time Illinois alum and one of the first Black Americans to receive an engineering doctorate, to capture ultraviolet light. It’s invisible to the naked eye, but it’s created wherever hydrogen atoms are energized. Since hydrogen is so light, it rises above all other gases and forms the topmost layer of the atmosphere. Carruthers wanted to know exactly how far this layer extends.

When the camera’s photograph was received, the results were shocking. Ultraviolet light showed up in the entire field of view. With subsequent observations, scientists now think the outermost hydrogen layer, named the geocorona, might extend at least 250,000 miles to the moon.

“In the apple analogy, you wouldn’t be able to wrap your arms around the geocorona,” said Lara Waldrop, a professor of electrical & computer engineering in Grainger Engineering. “It’s so vast that we don’t know where it ends. And we know next to nothing about it. Exactly four images have been taken to date.”

Understanding this layer is the key to solving several scientific questions – such as the ultimate fate of Earth’s atmosphere and how Mars transformed from a water-rich world to a desert – but the geocorona is at the center of a problem critical to satellite technology: space weather. Solar storms can destroy electrical components and severely disrupt communications, and predicting Earth's response to them requires a complete understanding of the entire atmosphere.

Waldrop is leading the Carruthers Geocorona Observatory, the first mission dedicated to understanding this layer and the first Illinois-led NASA mission. Currently scheduled to launch as early as April 2025, it will fly to a point 1 million miles away where the sun’s gravity precisely counteracts Earth’s, allowing it to remain in place for an extended amount of time. It will then turn around and take the furthest images ever of Earth’s atmosphere to study the geocorona.

Working with former aerospace engineering clinical professor Michael Lembeck, Waldrop led the development and implementation of the mission in partnership with the Space Sciences Laboratory at the University of California, Berkeley. Waldrop’s group is also collaborating with the Applied Research Institute at Illinois and Boston University to develop data analysis pipelines for the scientific aspects of the mission. It will also take advantage of the NASA Jet Propulsion Laboratory’s Deep Space Network to communicate with the researchers.

“The geocorona is Earth’s first line of defense,” Waldrop said. “Our atmosphere and our magnetic field are the reason we don’t experience the full power of the sun’s gas released in solar coronal mass ejections. If we’re going to continue exploring and working in space, we will need a firm understanding of the complete atmospheric system to minimize risk. Right now, we have computer models that seem to tell us what’s going on, but we have no way of knowing for sure until we can get a good look at the entire geocorona.”

The Carruthers mission will attempt to answer two scientific questions. The first relates to the evolution of Earth’s atmosphere as hydrogen escapes the surface, which naturally occurs as hydrogen dissociates from water. Understanding this escape process will give important insights into the evolution of planets with water, both for habitable exoplanets and what happened to worlds like Mars that formerly had water.

The second aims to understand how this layer interacts with the plasmas – gases so hot that the atoms dissociate into ions and electrons – from solar storms. When such solar storm plasmas hit Earth’s atmosphere, the electromagnetic interactions with the atmosphere can cause damage to electronics in space, disruptions in communications and GPS services on Earth, changes to the satellite orbits, and even widespread power outages.

“To understand how these events unfold in the atmosphere and how the atmosphere recovers from them, it is necessary to understand each layer, including the geocorona, because they all interact and influence each other,” Waldrop explained. “The Carruthers mission is critical in this regard because it’s filling a large and unacceptable gap in our knowledge of the atmosphere.”

A complementary instrument will be included on the same satellite. While the GeoCoronal Imager (GCI), the primary scientific payload, is looking at Earth, the Carruthers Observatory Student Solar Monitor will look back to the sun. Developed entirely by students in the Laboratory for Advanced Space Systems at Illinois under Lembeck’s supervision and at Boston University, it will collect data about the solar ultraviolet photons that produce the geocoronal glow measured by the GCI, allowing researchers to watch the complete process unfold.

Deepak Vasisht

Taking satellites to the edge

Deepak Vasisht is showing us the best ways to quickly get sensitive data

How do we fight wildfires when the tiniest shift in wind direction or change in humidity can drastically alter their course?

How can we keep track of agricultural fields too vast for people to regularly visit?

How can we monitor environmental developments large and complex as polar ice melting?

The answer to these and other questions may lie in space. A constellation of satellites in low-Earth orbit (LEO) at altitudes between 300 and 600 miles would enable us to study our planet with unprecedented detail.

Grainger Engineering computer science professor Deepak Vasisht explains, “The principle is actually very simple: by moving the camera closer to the object, you get a better photo. Current satellite constellations orbit at 12,000 or 22,000 miles, which allows us to see that there is a wildfire, for example. However, an LEO constellation would show in detail how the fire unfolds in real-time, making a huge difference in evacuation efforts and resource allocation to fight it.”

As the private space industry develops and orbital launch systems become more efficient, deploying Earth observation constellations in LEO is becoming feasible. However, using them for time-sensitive applications like wildfire monitoring is challenging due to networking and communications deficiencies.

Unlike ground-based networks, satellites cannot transmit information instantaneously. They must wait until they pass over a transmitter, where they “dump” as much information as possible before losing contact. Since LEO satellites move so quickly -- about 5 miles per second -- the contact window with the transmitter is very brief. In the wildfire example, a photograph can take hours to days to reach authorities, during which time the fire can significantly change.

Vasisht wants to cut this down to a minute. An expert in networking, he and his research group are working to reduce the latency in satellite communication through innovations in both satellite hardware and software. They have developed the Serval system to demonstrate how a constellation of LEO satellites could classify, prioritize and transmit images in a matter of minutes.

“We’re taking ideas from terrestrial networking and moving them into space for the first time,” Vasisht said. “One LEO satellite has limited compute capacity, so the idea of Serval is to distribute the load across satellites and even to ground stations. This way, the smaller, specialized satellite hardware – an ‘edge computer’ – is utilized as efficiently as possible.”

Classifying images based on their content and assigning priority is a perfect use for AI technology, but these algorithms require extensive resources to run. To perform such tasks in space, Serval splits them into two parts: one that depends on rapidly changing information, and one that depends on slowly changing information. The slowly changing part can be calculated in advance using ground-based computing resources then transmitted to the satellite to use as a baseline for the rapidly changing part.

For example, the AI algorithm to detect wildfires in California can be decomposed into “detect forests in California” – the slow part – and “detect fire” – the rapid part. The former is pre-computed on the ground and loaded onto the satellite, and the latter is evaluated on the satellite using an onboard GPU or other AI system.

This still leaves the problem of ensuring that the prioritized image is transferred in a timely manner. Serval addresses this by exploiting the predictability of orbital motion.

According to Vasisht, “It’s not like cellular service where a large group of transmitters move unpredictably. A satellite is subject to deterministic laws of motion, and its path can be calculated to very high precision. We can exploit this to create precise download schedules that make the most of the contact window.”

The research group found that the combination of distributed computing and precise network scheduling reduces the 50th percentile of transmission times from 47 hours to 2 minutes, with the 90th percentile reduced from 149 hours to 47 minutes. Moreover, the satellite compute load was reduced by 80%.

“This result is exciting for another reason: our scheme would broaden the scale of the internet of things,” Vasisht said. “Right now, networked devices can cover 5, maybe 10 miles. If they could connect to the cloud via satellites, they could cover 500 miles. Imagine if we had moisture sensors to study crops over entire regions, or sensors to track wildfires over their entire boundaries. We need efficient satellite networking to make this happen, and our work brings us a step closer.”

Graduate students Om Chabra, Ishani Javeja, Maleeha Masood and Bill Tao in Vasisht’s research group as well as computer science professor Indranil Gupta also contributed to the development of Serval.

Vasisht’s group collaborates with the company Planet, Inc. which operates around 200 LEO satellites. The research team used the company’s Planetscope imagery database to test their ideas.

This work was largely supported by Vasisht’s award “Networking and Compute for Next Generation Low-Earth Orbit Satellites” through the National Science Foundation’s CAREER program. Cisco and Microsoft also supported this work.

Paul Kwiat

Quantum goes even smaller with SEAQUE

Paul Kwiat is making quantum technology feasible for space

Communication links whose security is guaranteed by fundamental physics. New kinds of computers solving problems that can’t even be attempted today. These are just some of the things that technology based on the laws of quantum mechanics governing the world of atoms, molecules and light will be capable of.

Many of them will depend on networks that transmit quantum information over long distances. But how exactly do we get quantum information from Point A to Point B?

One option is fiber optic networks, commonly used to transmit data today. Quantum information is most conveniently transmitted in specially prepared light particles, or photons, and optical fibers are designed to direct light over long distances. But there is a drawback: the fibers absorb part of the light as it travels. This can be managed over shorter distances or for the high-intensity light pulses used in standard communications, but it’s fatal to long-range quantum communications. If a fiber optic quantum network connected Champaign, Ill., to Chicago, 1 in 10,000 transmitted photons would survive the journey.

Some researchers are exploring the use of intermediary “quantum repeater stations” to compensate for the losses, but there’s an alternative: space-based quantum networks in which photons are transmitted to and from satellites through the atmosphere, which absorbs much less light than optical fibers.

The most significant problem to solve with this option is exposure to the intense radiation of outer space. One high-energy particle is enough to damage sensitive quantum hardware, particularly photon detectors. Past quantum experiments in space have observed large increases in detector noise from radiation damage. While this might be addressed by physically shielding the system, this makes the satellite carrying it heavier and therefore more costly to launch into orbit.

A different solution will be explored by the Space Entanglement and Annealing Quantum Experiment (SEAQUE) led by Grainger Engineering professor Paul Kwiat, the John Bardeen Chair in Physics and Electrical Engineering. The project aims to demonstrate that radiation damage can be “healed” by using a laser to return the detector’s microscopic structure to its original state, a process called annealing. When combined with smaller electronics and quantum circuit elements, this makes for a very compact system.

“Past quantum space missions, such as the Chinese Micius satellite launched in 2016, were necessarily quite large,” Kwiat said. “In space, where every ounce makes a difference, this is a problem if we ultimately want to launch many satellites for a large-scale network. In contrast, the SEAQUE device is only about the size of a loaf of bread, and the entangled photon source it carries is like a small pack of gum. These miniaturized hardware components have never been flown in space before, but the real missing piece is a demonstration of annealing. We hope to give a proof of principle and show that it makes space quantum technology more feasible.”

SEAQUE is currently scheduled to launch on November 1, 2024, on a SpaceX rocket to the International Space Station, where it will stay for one year. During this time, the effects of radiation on the quantum hardware will be studied, and quantum annealing will be explored. After the year is over, the hardware will return to Earth for post-mission analysis.

Once in place, the experiment will proceed by using the SEAQUE device to perform a series of Bell tests – experiments designed to explicitly demonstrate entanglement, a crucial phenomenon underpinning quantum technology. Kwiat’s group has a long history of expertise in these experiments, having participated in one of the first “loophole-free” versions in 2015. In addition, group members were instrumental in Illinois’ Public Quantum Network demonstration in 2023, where Bell tests were performed by members of the public using a publicly accessible quantum node at the local Urbana Free Library.

While in space, SEAQUE will conduct repeated Bell tests. Researchers will track the quality of the results to determine how the system components degrade when continuously exposed to a space environment. They will also test using lasers to perform detector annealing.

“High-energy radiation can create defects in the chemical structure of materials, and quantum annealing aims to restore it by heating the material up and then cooling it down,” Kwiat explained. “Imagine that a ball has been knocked out of a bowl. To return the ball to the bowl, you need to give the ball energy. In annealing, this energy is provided by adding heat so the atoms in the material can return to their original positions.”

A research group in the University of Waterloo has demonstrated this principle on avalanche photodiodes – devices used to detect the low-intensity light used in quantum experiments – by heating them to 200 degrees Celsius in an oven for about an hour. SEAQUE will replicate this effect by heating the photodiodes with a high-power laser for just a minute, enabling the device to be made far more compact.

Kwiat collaborated on the project with former aerospace engineering clinical professor Michael Lembeck, whose research group developed the mission specifications and helped fabricate the system in their cleanroom environment.

“The requirements of space are far more stringent than we’re used to in our lab, so none of this would have been possible without Michael’s help,” Kwiat said. “His students showed us how to use the cleanroom and his industry contacts even helped us secure our ride up to space. We’re also extremely grateful to NASA’s Jet Propulsion Laboratory and Boeing, both of whom provided funding to make this project possible.”

The SEAQUE device has successfully completed vibration and extreme temperature testing with AEGIS Aerospace, and it is ready for the November 1 launch.

Kwiat reflected, “This whole effort has been several years in the making. It started when we were approached to design a space-bound quantum experiment but given a timeline of only 10 months. In retrospect, that was far too short a window, but we went for it anyway. We found new sponsors and collaborators and were finally able to complete the SEAQUE module. We’re definitely excited to see the payoff of our payload!”

SEAQUE is a tri-national effort. Kwiat’s Illinois research group is the scientific lead. Thomas Jennewein’s group at the University of Waterloo provided the avalanche photodiode single-photon detectors. Alex Ling’s group at the National University of Singapore provided the electronics that drive the liquid crystal polarization devices that enable the Bell test measurements.

Michael Lembeck

Training engineers to build for space

Michael Lembeck was instrumental in the space engineering educational program in Grainger Engineering

The rise of the space industry has sparked a need for engineers trained to design and operate space systems, including the satellites that will realize its promise. Grainger Engineering has been fortunate enough to benefit from the expertise of Michael Lembeck in both designing space systems and developing an educational program to train students in space technology.

Lembeck, who received bachelor’s, master’s and doctoral degrees in aerospace engineering from Illinois, has made significant contributions to both government and private space programs, including NASA’s return to the moon. He also has held many leadership positions in the industry. He brought his experience to Grainger Engineering, where he was a clinical professor of aerospace engineering until August 2024. He founded and led the Laboratory for Advanced Space Systems at Illinois (LASSI), which both developed research space systems and trained students.

“We tried to give students an experience that they will instantly recognize when they go to industry,” Lembeck said. “A lot of universities now have experiences that let students design small satellites, but, in LASSI, we always had the students working on missions that are used for meaningful research. We also prepared students by exposing them to the same pressures found in the space industry: there are only so many launch windows, and you don’t get any partial credit if you miss your date.”

LASSI was designed to give students as much control and responsibility as possible. Each mission had a graduate student serving as the system engineer with direct supervision of four or five undergraduate students working for course credit. Lembeck described his role as a “guardrail,” being there to give guidance but letting students take the lead.

In addition to the integral role LASSI played in the development of the Carruthers Geocoronal Observer Student Solar Monitor (COSSMo) and the Space Entanglement and Quantum Annealing Experiment (SEAQUE) missions, the laboratory also designed the hardware for a future mission sponsored by Fermilab. The Dark matter as a sterile NEutrino Search Satellite (DarkNESS) CubeSat mission, scheduled to launch in late 2025, will look to the center of our galaxy for evidence of sterile neutrinos, so-far-unobserved particles that have been hypothesized to be a significant component of dark matter.

“It’s really an incredible opportunity for our students: to have the chance to work on potentially Nobel Prize-winning science,” Lembeck said. “And it just goes to show the quality of the work that LASSI’s students strived for: not just educational experiences, but solving important problems first.”