A first-of-its-kind satellite, designed and built by Boston University engineers, on Monday morning hitched a ride aboard a NASA rocket launched from Vandenberg Space Force Base in California. Over the next five to six years in orbit, about 340 miles above our planet's surface, the shoebox-size satellite containing an X-ray telescope will capture images of where the magnetic fields of the Earth and the sun meet in space.
Known as CuPID, which stands for Cusp Plasma Imaging Detector, the satellite is designed to capture images that will help scientists learn more about the way energy from the sun is transferred into the near-Earth space environment. The team behind the satellite's development has been led by Brian Walsh, a BU College of Engineering professor of mechanical engineering, and supported by a $2.4 million, four-year NASA grant. In addition to BU engineers, the team is made up of collaborators from NASA's Goddard Space Flight Center, Johns Hopkins University, Drexel University, and Merrimack College.
"It's not every day that the hardware you have been working on for four years, the software you have written, the computer you have been talking to every day, is closed up in its launch vehicle going somewhere you'll never see it again," says Emil Atz, a BU graduate student pursuing a PhD in mechanical engineering in Walsh's lab. "It's bittersweet….I can't imagine the feeling I will have during launch or during first pass [in orbit] when we make contact with CuPID. I will probably cry."
CuPID's launch date was moved several times due to weather and other scheduling issues-perhaps serendipitously. "The launch was originally supposed to be on [my] wedding day," Atz says. "I asked the launch provider if they could move the launch or if they could find an appropriate stand-in for me at the wedding-he said neither was likely. Fortunately for me-and my lovely wife-but unfortunately for the launch provider, the launch had to be delayed [until September 27]."
X-ray imaging is not a new technology for observing earth and space phenomena. But previous orbiting telescopes have been limited by their field of view, capturing images of specific areas one by one. CuPID is the first such satellite to have a wide field of view, which will allow scientists to study the boundary between the Earth and the sun's magnetic fields using much bigger, more comprehensive images.
"CuPID will image the invisible," Walsh says. "For decades, scientists have studied a process called magnetic reconnection." As charged particles emitting from the sun collide with Earth's atmosphere, electrons are exchanged and X-rays are given off. During periods of high solar activity, charged particles can leak into the Earth's atmosphere, potentially putting satellites and astronauts in harm's way.
"The more we roam and observe our universe, the more we see [magnetic reconnection] occurring and controlling phenomena everywhere from the surface of the sun, to the black holes, to the 'magnetic bubble' or magnetosphere surrounding the Earth," Walsh says. "It has been studied routinely through pinpoint measurements…but we've never been able to image the process as a whole with a zoomed-out view." He adds that CuPID will help scientists "answer a fundamental question: Under what conditions does reconnection occur in explosive bursts versus a steady continuous hum?"
Another remarkable feature of CuPID? It's size. It's about as big as a shoebox, whereas other X-ray telescopes tend to be closer to the size of school buses to accommodate their imaging hardware.
"X-rays are notoriously hard to focus onto a detector," Walsh says. "They just pass through or get absorbed by the types of lenses we wear in our glasses. For several decades, researchers have used a [so-called] Wolter focusing technique…[which] can provide a great image but is large, heavy, and produces a narrow field of view, a fraction of a degree in the sky."
To capture and focus wide-field images from its tiny package, CuPID employs a new type of imaging element called lobster-eye optics.
"Working closely with scientists and engineers from NASA Goddard, Johns Hopkins, and the University of Leicester in the UK, [we developed] lobster-eye focusing," Walsh says. "This technique uses a slumped piece of thin glass with tiny pores, each roughly the size of a human hair. Each pore has the ability to focus an X-ray coming through. The technique is similar to how the eye of a lobster works with many pores, hence the name."
The lobster-eye lens allows CuPID to make wide-field-of-view X-ray images at a fraction of the size and weight of traditional focusing tools, Walsh says.
To make sure that CuPID withstands the violent and bumpy launch, and its journey in orbit, the BU team put the satellite through rigorous testing.
"Vibration testing is pretty exciting, but you never want an exciting result," Atz says. "The best result is when nothing happens. We were required to shake CuPID extremely hard. When you shake things that hard they make this noise that you can't unhear. It's like the satellite is screaming."
Fortunately for CuPID and its engineers, the vibration test mimicking the bumpy ride to space didn't result in any damage to the satellite. To see how CuPID would fare in orbit required a different approach.
"We use a vacuum chamber that reaches high vacuum, nearly the vacuum of space," Atz says. "In the chamber, we test our instruments with energetic particles created by either radioactive sources, or an X-ray generator. These help us to calibrate the instruments to what they will see in orbit. That chamber is our workhorse of the lab. When we are running tests, that chamber will be running for months at a time."
For Atz, the experience of working on CuPID has shaped where he wants his career to go. "I just want to build satellites….I think the future has many, many more satellites with my initials hidden somewhere on the hardware or in the software," he says with a smile.
