When the seven-minute window of opportunity finally opened, Raha Riazati was ready.
This May, Caltech researchers tested an important step toward an ambitious plan to beam energy from an orbiting satellite down to Earth. Riazati, then a third-year undergraduate at the Institute, had spent months designing and building the ground-station equipment that would play a key part in the detection experiment. As the Space Solar Power Demonstrator (SSPD-1) prepared to pass 300 miles directly above the Gordon and Betty Moore Laboratory, Riazati and a small group of Caltech engineers were gathered on the building’s rooftop where they had spent the past few hours hurriedly setting up equipment.
Seven minutes was the sliver of time the team had to detect the weak microwave test signal beamed from SSPD-1 back to Earth. For a few anxious moments, nothing happened, but then after about three long minutes had passed, success: the ground station antennae Riazati helped design picked up the signal, prompting a round of cheers and high fives.
“After we put all the equipment back, which took about another hour or so, I went back to my dorm room,” recalls Riazati, who is now a fourth-year undergraduate. “That was when it clicked in my head that this project I’d been working on for over a year and a half had finally worked and that we’d gotten this groundbreaking result. I was like, ‘Wow, that was pretty awesome.’”
Launched in January, SSPD-1 is the first spaceborne prototype from Caltech’s Space Solar Power Project (SSPP). It carries three onboard experiments, each designed to test key technologies for an orbital power station capable of harvesting sunlight in space and directing it down to Earth. Riazati worked in the lab of Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering, who is a co-director of SSPP, along with Caltech aeronautical engineer Sergio Pellegrino and nanophotonic expert Harry Atwater. Hajimiri leads the team behind one of SSPD-1’s experiments, the Microwave Array for Power-transfer Low-orbit Experiment (MAPLE).
MAPLE comprises a series of flexible lightweight microwave power transmitters designed to transmit energy between different locations. It achieved this primary goal on March 3, in an experiment that beamed energy between a transmitter and two receiver arrays; the power was then converted to direct current (DC) electricity and used to illuminate a pair of LEDs. The May detection experiment, which aimed to show that SSPD-1 could direct the power down to Earth, was not the focus of the initial tests. But it was the kind of high-risk, high-reward side project that Caltech is known for as well as a chance to allow an undergraduate with less than two years of electrical engineering experience to be part of that team, another signature Caltech feature.
Initially a chemistry major, Riazati had switched to electrical engineering after a first-year class on the subject sparked her interest. She first encountered Hajimiri while taking his EE 44 class in her second year. One day after class, she approached him to discuss doing research in his lab. Hajimiri connected Riazati with a graduate student, Austin Fikes, who was then leading the MAPLE development. Eventually, Riazati was tasked with designing ground station equipment for a detection experiment.
Her project consisted of two primary components: designing, testing, and assembling a telescope mount that would allow the team to track the SSPD-1 with great precision and create a radio frequency receiver chain that would permit the detection of the faint microwave signal sent by the spacecraft. “These two parts required two different skill sets, yet she mastered both,” says Jesse Brunet, a graduate student in Hajimiri’s lab who worked with Riazati.
“Raha is a highly motivated student who takes the time to make sure her work is done well,” Brunet added. “As a co-worker, I could rely on her to plan tests and solve problems just as I could with the graduate students in our lab.”
Riazati’s time in the lab was made possible by a Caltech Summer Undergraduate Research Fellowship (SURF), a 10-week program in which students are given a stipend that allows them to immerse themselves in a specific research project with a faculty mentor. Riazati did her SURF research in the summer of 2022. “You’re signed up for a 40-hour commitment a week,” she says. “I would basically do research from 9 to 5 or 6 every day. I think if I hadn’t done that, I wouldn’t have been able to make as much progress as quickly as I did.”
Looking back, Riazati praises the lab’s collaborative spirit. “Everyone is so incredibly brilliant,” she says. “For a lot of the parts in the project that I had to work on, it was my first exposure to those fields and topics, but I could just walk up to anyone in the lab and ask for help, and they would be more than willing to set aside time to walk me through some of the steps or some of the equipment that I needed to use, or point me to papers or articles that I could read to get more information on the topic.”
Riazati remembers one piece of valuable advice that Fikes offered after she had finished the initial design for the ground station but kept going back to tweak it.
“At a certain point toward the end of the summer, Austin told me, ‘You just need to get something out so we can test it. Because if we just keep designing forever, even if we design the perfect product, which is impossible to do, there’s always going to be some sort of issue, and then we test it and something goes wrong, and we won’t have time to fix it.’”
That lesson stuck with her. “Stopping myself from continuously going back and tweaking little things in the design was definitely pretty challenging, but at a certain point you have to have a design freeze and step back, get it made, and then get into testing.”
This past summer, Riazati interned at an aerospace firm that designs satellites, and she credits her ground station experience with providing the foundational knowledge necessary for her present role. But she isn’t finished with SSPP just yet.
“I’d like to still be involved with those parts of the project,” she says, “and I’m still doing my senior thesis with Professor Hajimiri in his lab.”
Written by Ker Than
Source: Caltech