PocketQube Satellite Scans the Atmosphere for Electrosmog Pollution
Academic Team Sends Pocket-Sized Satellite into Orbit
The PocketQube miniature satellite class packs a powerful payload into a tiny housing that fits inside a pant pocket. A Budapest University of Technology and Economics (BME) team designed one that measured a mere 5 centimeters (nearly 2 inches) on each side and weighed under 250 grams (8.82 ounces).
When BME’s SMOG project development started in 2013, other groups launched an initial wave of PocketQube satellites, but none had successfully completed a mission. The Hungarian team led by András Gschwindt, an honorary associate professor in BME’s Department of Broadband Infocommunications and Electromagnetic Theory, included more than a dozen students.
They named their satellite SMOG-P for its ability to detect electromagnetic (EM) pollution from Earth. It sported six solar panels, an onboard computer, a lithium-ion battery, and additional electrical components, but no built-in propulsion, thrusters, or backup battery.
“The first law of space missions is that you cannot say, ‘Joe, please go fix this with a wrench.’ You have to make sure it fully operates on the first try,” said Viktor Józsa, who has been with the project since 2014 and is currently an associate professor in the university’s Department of Energy Engineering. “There’s usually no second chance.”
The team set out to design a mini satellite that could withstand high G-forces during launch as well as extreme temperatures while orbiting Earth in the sun’s glare and its frigid shadow. Students participating in the project used MATLAB® to simulate launch and a thermal network modeling approach in Simulink® to analyze worst-case scenarios in the long term.
On December 6, 2019, SMOG-P hitched a ride into space with support from corporate sponsors and entered low-Earth orbit, becoming the first operational PocketQube in the world. “We showed that this satellite class works and is affordable,” Józsa remembered. “We didn’t need expensive space-grade instruments, just engineering knowledge.”
Small Pockets, Big Research Goals
Professor Robert Twiggs from Morehead State University is known as the father of the CubeSat for his pioneering work on the 10 cm (almost 4 in) devices, called picosatellites. He later co-developed the even tinier PocketQube in 2009 with a state consortium to spur space research opportunities for STEM students.
Advancements in integrated circuits (ICs) have spurred further opportunities for these tiny satellites. Today’s ICs only consume microamps while delivering precise measurements. Józsa praised the PocketQube satellite class for allowing rapid lightweight space technology development at a low cost, especially when gathering less than 1 megabyte of data per orbit. Amateur radio equipment can pick up PocketQube signals.
“If your measurement only requires a small amount of energy, PocketQube is an economical platform,” said Józsa, who was the SMOG project’s mechanical engineering group leader until 2017 and now primarily assists with thermal engineering and mechanical tasks.
Although the launch cost can vary, the SMOG-P launch was around $20,000. Parts for BME’s satellite mainly came from commercial vendors and weren’t space-grade, which helped keep the price tag fairly low. The project received support from more than three dozen sponsors. The price of the components and manufacturing was comparable to the launch cost.
Undergraduate students participating in the SMOG project got to watch their satellite head into orbit before graduation. “Seeing it lifting off and beeping in a few years is truly exciting,” Józsa said. “But we had to deliver useful data, not just show that we could make a functional small satellite.”
Józsa pointed out that the space environment near our planet is quite noisy. The BME team aimed to use their PocketQube satellite for measuring the electromagnetic waste that escapes Earth, focusing on the 430–860 MHz range typically used by digital TV stations. Called electrosmog, this cacophony can interfere with communications across devices, prompting large companies to develop more and more powerful technologies that, in turn, consume greater amounts of energy.
Electrosmog isn’t a life-threatening problem, Józsa clarified. But the group in Hungary is shedding light on the issue’s seriousness, especially for global broadcasting corporations. SMOG-P contained equipment to measure electrosmog and transmit that data back to Earth so engineers could analyze the frequencies emitted.
“The telecommunications industry doesn’t have the largest slice of the electrical consumption cake, but telecommunication suffers from the excessively noisy world,” Józsa said. “It’s a complicated topic, though, because by just decreasing power consumption, you lose information transmission capabilities. The way forward is advanced antenna design.”
High-Stakes Satellite Modeling
Before it could take its first measurement, the miniature satellite had to survive unbelievably intense conditions. “The most critical point is separation from the rocket during the first launch stage, which is like a hammer hitting the satellite load,” Józsa explained. “You also have to make sure the satellite doesn’t collide with other satellites on the rocket or the main load, endangering the launch.”
If the satellite didn’t slingshot into orbit from the launch rocket correctly, it could become dangerous debris. Although the International Space Station can maneuver to avoid collisions with space junk, which is pretty frequent these days, a PocketQube satellite traveling at 8 kilometers (about 5 miles) per second would be right at the detection limit for the North American Aerospace Defense Command’s space monitors.
Once in orbit, the battery of SMOG-P must stay above 0° Celsius (32° Fahrenheit) in a space environment that could dip to -270° C (-454° F) or else sensitive components might fail. At the same time, the satellite needed to stay below the battery’s upper temperature limits. With such a narrow range and high stakes, the Hungarian team turned to Model-Based Design.
“On the thermal side, ambient temperature isn’t something we can recreate easily,” explained Ágnes Welsz, a BME energy engineering student on the SMOG project team who was involved in thermal model design as well as design verification before she graduated. “We had to get creative and research how to make that model work.”
Early in her studies, Welsz gained familiarity with thermodynamics and heat transfer topics, but MATLAB and Simulink were completely new to her. After experimenting with built-in Simulink models, she decided the best way to make the model was by creating blocks from scratch. Through researching, watching online tutorial videos, and consulting with Józsa, Welsz added details to the model.
Welsz, Józsa, and other team members ultimately built a cross-connected thermal network in Simulink with 11 nodes, leveraging the block diagram environment’s interactive programming to gain a clear overview of a complex network. This allowed them to devise onboard logic for mounting the battery on the other side of the printed circuit board (PCB) containing the communications and spectrum analyser subsystem, securing its safe operation. The team simulated hundreds of orbits to produce long-term thermal balance predictions that would keep the satellite’s components above their minimum operation temperatures. The team recently made the Simulink model and SMOG project code available on File Exchange.
The mechanical motion of the release from the picosatellite bay also required simulation. Spinning too fast means the solar panels’ maximum power point tracking system can’t keep up and the incoming power won’t be sufficient. The SMOG project participants ran MATLAB scripts to ensure that the launch from the pod would be smooth.
Interoperability with other software supported the project as well. “Temporal functions simulated the satellite’s orbit and rotation, providing the boundary conditions,” Józsa said. “But since there was no fully operational satellite of this size at the time to provide data for validation, we verified our calculations through finite element method analysis in ANSYS Workbench.”
Using MATLAB and Simulink meant the team could perform complex analyses with simple models. “MATLAB has tremendous online materials. It offers the best support of any software out there,” Józsa said, adding that he didn’t need to pose new programming questions because the active community had already posted answers to any problems that came up during the modeling of the communications and spectrum analyzer subsystems.
Model-Based Design tools ended up being incredibly useful for Welsz. “Now I am confident that I can solve nearly any challenge in MATLAB,” she said.
Academic Space Research Takes Off
Twiggs personally congratulated the BME team on their success with SMOG-P. The satellite deorbited at the end of September 2020—an intentionally short trip that was just long enough to monitor radiated radio frequency signals from Earth.
During its mission, the pocket-sized satellite scanned the entire Earth’s surface twice daily, collecting and transmitting enough spectrum monitor subsystem data for researchers to produce a global electrosmog map within weeks. A minuscule onboard radiation dosimeter measured how much radiation hit the electronics during orbit, allowing the team to check for excess exposure.
The SMOG project subsequently developed a similar PocketQube satellite, SMOG-1, which was launched on March 22, 2021, and the first signals were received on March 24. Its orbit is nearly circular at a 550 km altitude, which is a higher trajectory than SMOG-P. Although this newer satellite could technically remain in orbit for more than 20 years, the solar panels and commercial-grade components degrade much sooner. Lower energy capture over time would end communication with Earth, so the design for SMOG-1 contained soft iron insert prototypes on the sides to accelerate deorbiting and ensure the device wouldn’t turn into circling space junk for an excessively long time.
After sending a final transmission on June 23, 2022, SMOG-1’s mission was complete, Józsa said, adding that the group collected a huge data set on temperatures and frequency from the satellite.
Since the SMOG project began, the team published an article about the satellite modeling in the scientific journal, Applied Thermal Engineering. Their paper received international attention and has been cited numerous times, including in an analysis of the International Space Station’s Alpha Magnetic Spectrometer.
During its mission, the pocket-sized satellite scanned the entire Earth surface twice daily, collecting and transmitting enough spectrum monitor subsystem data for researchers to produce a global electrosmog map within weeks.
Even though Hungary isn’t necessarily known for space exploration, the project represented a giant leap for the country. Józsa sees a correlation with Hungary formally becoming a European Space Agency member in 2015, followed by the success of the first Hungarian satellite called MaSat-1, also developed at BME. More recently, he said, researchers from neighboring countries Slovakia and Serbia asked the group for satellite development guidance.
The team’s work also led to BME introducing a new space engineering master’s degree program. “Most of the project team members contribute to the space engineering program by giving lectures and teaching the upcoming generation,” Józsa said. “It takes time, but I think the Hungarian engineers who graduated here can easily join large-scale European and American projects.”
High-level research collaborations through the SMOG project offer university students valuable insights for making informed decisions about their careers. BME engineering students can gain a clearer sense about whether to pursue a PhD and remain in academia or apply their skills to solving industry problems. After graduation, Welsz studied electrical engineering for her master’s degree and then went to work for Tesla on large-scale energy storage.
Józsa’s trajectory shifted since the project’s early days as well. He joined the Department of Energy Engineering Combustion Research Group to tackle what he called humanity’s problem of the 21st Century: sustainable energy.
In the near-term, he sees a bright future for miniature research satellites as components continue shrinking. “There is no limit to scientific missions that help make our lives better,” he said. “The possibilities are approaching infinity now.”