An astrophysicist and his team build a sounding rocket—from scratch—in a lab on the Homewood campus.
By Douglas Birch
By Douglas Birch
Photos by Will Kirk
If all goes according to plan, Stephan McCandliss will be at White Sands Missile Range in New Mexico one chilly night in December watching a rocket carry his latest experimental telescope into space.
Over the past 24 years McCandliss, a research professor in the Department of Physics and Astronomy, has flown 14 of his one-of-a-kind, hand-built instruments on a NASA sounding rocket. They soar above the Earth’s light-filtering atmosphere for five or six minutes before parachuting their payloads back to Earth.
“How is it that out of a universe composed of particles, which at a fundamental level are indistinguishable from each other, does this rich complexity and life emerge?”
—Stephan McCandliss, Research Scientist
Most of the time, his innovative ultraviolet telescopes have worked as planned and have returned in one piece. McCandliss is doing everything he can think of to make sure nothing goes wrong on his 15th flight, which will carry a telescope that, he hopes, will one day open a new window on the history of the cosmos.
On the telescope’s maiden flight, McCandliss and crew plan to aim it at the picturesque Great Barred Spiral Galaxy, formally known as NGC1365, to study how ultraviolet light escapes from galaxies. It’s part of his broader goal of better understanding how stars, galaxies, and gas and dust clouds have emerged from the chaos of the early universe.
But in rocket science, as in life, things don’t always go according to plan.
On a shelf in his office at the Homewood campus’s Bloomberg Center for Physics and Astronomy, he keeps a few souvenirs of misadventures past.
He picks out an electrical connector he rigged up for a sounding rocket launch in Woomera, Australia, in 1995 on a mission to observe the Southern Hemisphere’s Large Magellanic Cloud. The connector arced during the flight and interrupted the high voltage to its ultraviolet light detectors. A television station, meanwhile, was transmitting on the same frequency as the rocket’s ground controllers, interrupting communications. A second planned flight was scrubbed.
The 57-year-old astrophysicist—a member of the world’s small guild of space astronomy instrument builders—pointed to the soot at the contact point burned by the electrical arc. “This was something that I thought was going to work,” says the California native. He adds with characteristic sardonic humor: “And I was thinking stupid.”
When it comes to his work, McCandliss is ready to tolerate a degree of risk. Carefully calculated risks, to be sure. Risks that can advance the state of the art of rocket science. But risks nonetheless.
He’s built ultraviolet telescopes with experimental configurations, advanced detectors, and novel optical coatings. And he’s used them to study nearby objects like the comet Hale-Bopp, which lit up the sky in 1997; and the doughnut-shaped ring around Jupiter caused by volcanoes on Io, one of its moons. He’s also focused on binary stars, red giants, and clouds of intergalactic gas and dust. The mirror technology he’s helped develop has been incorporated into satellites like the Hopkins Ultraviolet Telescope and the Far Ultraviolet Spectroscopic Explorer.
Like McCandliss’ previous telescopes, FORTIS—for Far-Ultraviolet Off-Rowland Telescope for Imaging and Spectroscopy—has some novel features. First, it will test a prototype of a new shutter system that NASA plans to use on the $8 billion James Webb Space Telescope, which can capture light from 43 separate targets at the same time. The telescope also is designed to take both ultraviolet images and spectrographs of its celestial targets.
“What we are trying to do here is understand the emergence of complexity,” he says. “How is it that out of a universe composed of particles, which at a fundamental level are indistinguishable from each other, does this rich complexity and life emerge? That really is the fundamental reason we do astronomy.”
And he hopes to accomplish all this in the five minutes or so FORTIS has to conduct its observations as it streaks across the vacuum of space before plunging back toward the New Mexican desert.
With so much riding on such a brief space flight, McCandliss wants to ensure that his instrument’s novel design and advanced technology produce as much science and as few nasty surprises as possible. “It’s always the things you didn’t think about that get you,” he says. “So you try to make yourself bulletproof by thinking about as many things as you can that might go wrong.” And of course fixing them.
But FORTIS is, after all, an experiment, and there are no guarantees. And for McCandliss that is part of the point of sounding rocketry.
Flagship space science projects like the Webb telescope cost billions, and the careers of dozens of scientists and engineers may hang in the balance. Mission planners and researchers are of necessity risk-averse. Even the small- and medium-sized scientific satellites launched by NASA’s Explorer program can cost roughly $100 million to $200 million, and failure carries a heavy price tag.
The FORTIS telescope by comparison will cost only about $3.2 million to build and another $2 million to launch. McCandliss says the relatively low cost and short lead-time—of a year or so for most sounding rocket missions—means there is room for the kind of reasonable gambles critical to progress in any field.
Pitching sounding rocket missions is a little like trying to find venture capital for a Silicon Valley startup. “I’ve got to be able to take my crazy ideas—and these ideas for the sounding rocket program are entrepreneurial—so I basically think them up myself and then I present them to the peer review,” he says. “And they say, ‘Good idea,’ or ‘Jeez, you ought to think about this some more.…’ Ultimately, you just keep plugging away, and if you’re clever enough they say go ahead and we’ll fund you.”
McCandliss began working on FORTIS in 2004 and completed assembly in May, with the help of Johns Hopkins staff engineer Russell Pelton, graduate students Brian Fleming and Keith Redwine, and members of the Physics and Astronomy Machine Shop and Instrument Development Group.
Since then, he and his team have disassembled, tested, tweaked, and reassembled the device at least twice. In August, they took the telescope down to NASA’s Wallops Flight Facility near Chincoteague Island, Virginia, for a “shake table” test, to make sure it can stand the stress of being blasted into space, and dress rehearsals for the telescope’s operations during flight.
The work can be challenging, says Fleming, who has worked with McCandliss for six years and participated in two launches. The 29-year-old Alaska native spent 10 months working with engineers at Goddard Space Flight Center adapting the Webb’s shutter array to FORTIS. The upcoming launch will mark the first time the array has flown in space.
Despite the pressure of preparing for the mission, Fleming says that sounding rocket work has given him the rare chance to participate in every phase of building and operating a space telescope. “It’s sort of a tough way to be an astronomer, but on the other hand you get to play with more toys,” he says, adding that he is determined to see the instrument launched before he graduates.
Redwine, 23, of Massachusetts and a graduate of Columbia University, has spent the past three years working with McCandliss. The FORTIS mission will mark his first rocket launch—if you don’t count the model rockets he and his father built when he was a boy. “I’m excited,” Redwine says. “I’m going to try not to mess anything up.”
As with any space shot, every detail of FORTIS has to be sweated. Take the telescope’s carefully polished primary mirror. Bolt it too loosely to the housing and it can bang around during launch, McCandliss says. Ratchet it too tightly in place, and it can warp.
The astrophysicist also worries about the metal skin of the rocket heating up through friction in flight, which could cause the telescope inside to expand, contract, or warp. If the distance between FORTIS’ primary and secondary mirrors changes by more than a thousandth of an inch, McCandliss says, it will significantly degrade the focus.
One day, he hopes to launch a later-generation FORTIS telescope on a satellite mission. Like many astrophysicists, he was excited by last year’s announcement from the National Reconnaissance Office that it was giving NASA two surplus 2.4 meter telescopes, designed and built for use in spy satellites.
“I could throw away the secondary and tertiary stuff and just use the primary mirror, and we could make FORTIS a 2.4 meter telescope, and that would be,” he says, pausing for effect—“awesome.”
In the community of ultraviolet astronomers, there is even talk of building a huge 8-meter space telescope.
Johns Hopkins has a long tradition of ultraviolet astronomy, which doesn’t always produce pretty pictures but can reveal a lot about a star or other object’s chemical composition, movement, and temperature.
One problem for astronomers working in the wavelength is that most ultraviolet light is absorbed by the Earth’s atmosphere, meaning that for all practical purposes their observations have to be done from space. And while the Hubble Space Telescope, which is still operating, and Hopkins’ Far Ultraviolet Spectroscopic Explorer, which is not, have studied the universe in the ultraviolet range of the spectrum, McCandliss says these wavelengths remain relatively unexplored.
The shortage of UV telescopes in orbit, he argues, has limited our understanding of the last 10 billion years or so of the evolution of the cosmos. Stars and galaxies in the process of being born or dying, for example, tend to be hot and they glow brightly in the ultraviolet.
With this in mind, he’s tried to design FORTIS as a satellite-ready telescope. He’s tried to make it as light as possible, for one thing. And he’s avoided using magnetically susceptible materials anywhere in the instrument because spacecraft builders worry that they can interfere with magnetic devices used to stabilize satellites.
“We operate in this interface between art and engineering,” he says. “I’m a scientist, right? So artists, they do something once and it’s called art. If you do it twice, it’s called science. After that, it’s engineering.”
Stephan McCandliss was born in Salinas, California, where his parents settled down after World War II. His father, Robert McCandliss, was active in the California Farm Bureau and ran a feedlot. But in the late 1960s, a recession in the cattle industry and a certain missionary zeal inspired him to join a U.S. government-run program to help bring modern agricultural methods to rural areas of Vietnam.
Robert McCandliss’ family couldn’t join him in the war-torn country, but to be closer to him, his wife and the five youngest of his seven children moved to Taiwan, where Stephan attended Taipei American School.
Stephan McCandliss recalls spending a lot of time in his sophomore year at the University of Washington worrying about his dad, who was evacuated from the roof of the American embassy in Saigon eight hours before the city fell to the North Vietnamese troops. That was the morning of April 30, 1975.
He quit school shortly thereafter, frazzled both by his father’s ordeal and the mediocre grades he had earned during that stressful year. He intended to travel around the world, he says, but it soon dawned on him that he needed to support himself. So he spent two years sorting packages for the United Parcel Service in the Seattle area.
After that, he returned to the University of Washington and focused on schoolwork.
“I ended up digging my way out of the bad grades,” he recalls. He also started building his first instrument, a wobbling secondary mirror for a radio telescope designed to study the microwave background radiation, the faint echo of the Big Bang.
He discovered that he was good at making telescopes, but at one point told his boss, University of Washington astrophysicist Paul Boynton, that he wanted to work on theory. “Paul just looked at me and said, ‘Kid, there’s a lot of people out there who can [do theory] badly. But there aren’t that many people who can do instrumentation well.’ So, I kind of took that to heart I guess, though I always kind of felt frustrated by it. But that’s what I do well.”
As a doctoral student at the University of Colorado, Boulder, in the 1980s, McCandliss worked on improving the processing of signals from devices called microchannel plate detectors, glass plates honeycombed with holes 10 times thinner than a human hair. The plates convert photons into electrical pulses. (The basic technology was developed by the military for night-vision equipment.) “These are sort of the workhorse of ultraviolet astronomy,” he says.
At Hopkins, McCandliss worked with several prominent senior faculty members, including Professor William Fastie, sometimes called the father of the university’s space program and a key figure in the creation—and repair in orbit—of the Hubble Space Telescope. It was through Fastie that Hopkins joined the NASA sounding rocket program soon after it began in the late 1950s, eventually forming the core of an elite group of space-faring universities.
The Hopkins physics and astronomy department also has a long tradition of instrument design, especially in the field of spectroscopy, the study of spectra, which break up white light into a continuous series of colors. By the late 19th century, astronomers were already using spectrographic diffraction gratings—reflective plates burnished with thousands of fine grooves—to study the temperature and chemical composition of stars.
Since coming to Hopkins 23 years ago, McCandliss has gotten married, had two children, and like many others, struggled to balance the demands of his work and his life. He runs four or five miles most afternoons, swims, and commutes by bike from his home in the city’s Medfield neighborhood.
At work, he has focused on building advanced spectroscopic instruments to study far-ultraviolet emissions from the faint gas and dust clouds surrounding comets, planets, and stars. Those observations have provided the data for seven doctoral theses as well as follow-on observations by both ground-based and space-based satellites. On average, he’s been involved in a NASA launch about every other year.
Today, the NASA program is at a crossroads. Like many federal programs it faces budgetary headwinds in Washington. It may also soon face competition from commercial space companies, which are in line to receive some federal space research dollars.
McCandliss and others say the program provides a unique training ground for young astrophysicists because they can participate in every phase of the creation of a new instrument, from the original idea to the launch. “This is literally the seed corn for the future of NASA science,” says H. Warren Moos, professor of astrophysics and principal investigator on the Far Ultraviolet Spectroscopic Explorer satellite. “This is where the young scientists come from.”
Around midnight sometime in mid-December, a Terrier-Black Brant rocket is scheduled to blast off from Launch Complex 36 at the Army’s White Sands Missile Range, where captured Nazi scientists once helped the U.S. test German V2 rockets after World War II.
The rocket’s two-stage motor will burn for 46 seconds and drop away. After another 14 seconds of flight, the rocket will toss out counterweights, like an ice skater extending her arms, to stop the hurtling vehicle from spinning.
Explosive bolts will fire a few seconds later and free the half-ton, 24-foot-long payload section from the motor as FORTIS continues its soar.
At around one minute, 24 seconds into the flight, after reaching an altitude of nearly 73 miles, the payload’s “gate valve” or rear hatch will open, and seconds later FORTIS will start collecting photons and making images.
During the five minutes or so it spends furiously slurping images and data from the Great Barred Spiral Galaxy, FORTIS will reach a maximum altitude of about 173 miles (by comparison, the Hubble Space Telescope orbits Earth at around 350 miles).
After FORTIS thumps to Earth in the scrublands of New Mexico, McCandliss and his team will fly to the landing site aboard a couple of vintage military helicopters. The Hopkins-NASA team will disassemble the telescope into two pieces, install them on special carriers, load them on the helicopters, and head back to the launch site.
That’s how it is supposed to work, anyway. In practice, of course, things may not run so smoothly.
Missions have been delayed or, as in Woomera, scrubbed because of technical glitches. Rockets sometimes go awry, and instruments have malfunctioned. Hours before one Hopkins launch at White Sands, the crew discovered that someone had left several loose washers in an onboard control box that caused the rocket’s steering jets to switch on and off at random. The goof set the mission back several months.
“For this launch, there are too many things that are going to keep me up at night,” Fleming says. “Too many to mention.”
For McCandliss, it is “the big problem in astrophysics.”
For about 400,000 years after the Big Bang, space was filled with a soup of elementary particles. As the universe gradually cooled and matter coalesced, protons began pairing with electrons to form vast clouds of atomic hydrogen. Gravity gradually began to concentrate and heat up the gas, which still makes up about three-quarters of the observable universe.
Between about 300 million and 1 billion years after the Big Bang, the first stars, galaxies, and quasars began to burn. The energy they generated started stripping electrons off hydrogen, turning neutral atoms of the gas into electrically charged ions. Researchers call this era the “reionization” of the universe because it returned most hydrogen back to its aboriginal ionized state.
And this process is almost a complete mystery.
“This was an epoch where the first stars or maybe some exotic objects lit up the universe and burned through all this neutral hydrogen and ripped all the electrons off of the protons,” McCandliss says. “And so the universe is mainly ionized right now.”
But it’s not clear how this process may have worked. Neither is it clear, he says, whether there were enough photons produced during this epoch to ionize the universe’s vast reservoir of hydrogen.
The astrophysicist hopes that FORTIS can help settle these questions. One strategy, he says, is to look for clues in nearby ancient dwarf galaxies, which may have had their growth halted when the hydrogen feeding their growth was bombarded with radiation. That could provide clues about how the early universe evolved.
But those observations depend on FORTIS. And FORTIS will face its first critical test during the upcoming rocket launch. What will he do if his ambitious 15th sounding rocket mission runs into trouble?
“If they don’t, we will fix it and move on,” he says.