Jordan Vinson, for the U.S. Army Garrison-Kwajalein Atoll’s Kwajalein Hourglass
NASA’s Wallops Flight Facility and astronomers, physicists and students from Pennsylvania State University and the University of Colorado-Boulder joined forces to launch a pair of custom-built spectrograph telescope payloads into the thermosphere from Roi-Namur earlier this month.
The Penn State team’s Water Recovery X-Ray Rocket (WRX-R) lifted off without a hitch from the Speedball pad on Roi at 10:40 p.m., April 4. It rode atop a NASA Terrier and Black Brant IX rocket assembly, flying 127 miles above the earth’s surface.
The launch of University of Colorado-Boulder’s payload, the Colorado High-resolution Echelle Stellar Spectrograph (CHESS), did not go as swimmingly. Its first 3-5 a.m. launch window opened up Friday, April 13, and a technical issue on the rocket forced managers to abort. The next day, strong, variable winds settled into the region, forcing campaign managers and safety personnel to scrub the launch three nights in a row—sometimes within mere seconds of liftoff.
Finally, at 4:47 a.m., April 17, during the final 13 minutes of the final launch window, the CHESS rocket’s first stage Terrier ignited, sending the payload nearly 180 miles from sea level and washing the south end of Roi in golden light and a deafening roar.
The University of Colorado-Boulder team, led by principal investigator Dr. Kevin France, designed the CHESS spectrograph to peer into translucent clouds of gas lying in what astronomers and astrophysicists call the interstellar medium, aka the matter between stars.
These thin gas clouds in the boondocks of space contain the fundamental building blocks of stars and planets. But in order to study them, astronomers must thrust telescopes out of the Earth’s atmosphere and orient them to bright, powerful stars lying behind these clouds. As the star’s light and stellar wind collide with the gas clouds, a telescope and spectrograph can view and record the chemical makeup of those clouds, along with their temperature and motion.
For the CHESS experiment, the target star was Gamma Ara, a young, 15-million-year-old giant, located in the southern sky constellation of Ara, near Scorpius.
“Gamma Ara possesses an unusually strong equatorial stellar wind that is injecting large amounts of material and kinetic energy into its immediate galactic environment,” France stated in an earlier NASA interview before flying out to Kwajalein Atoll.
His team worked with NASA’s Wallops Flight Facility staff to package the CHESS spectrograph and telescope into a payload and launch it into the thermosphere along a parabolic trajectory. During the 300 seconds the telescope stared at Gamma Ara, the spectrograph recorded precious data on the interaction between the star’s powerful stellar winds and the clouds of gas between Earth and Gamma Ara.
Minutes after liftoff, the payload had begun transmitting the data down to Reagan Test Site’s telemetry radars and monitors manned by NASA and University of Colorado-Boulder teams: The last-minute launch and payload separation were successful.
“We won the stat lottery,” wrote Michael Snap, of NASA Wallops Flight Facility, in a Facebook message to the Roi Rats who came out to watch the liftoff. A photo he sent out of a monitor in the group’s mission control room resembled television static. In reality, it was good data, France stated.
“That image shows that the rocket’s onboard attitude control system successfully acquired the Gamma Ara star field,” he stated. “Once we were on target, our ultraviolet spectrograph started taking data and observed over 10 million photons directly from Gamma Ara.”
While CHESS investigated the interstellar medium between Earth and Gamma Ara, Penn State’s WRX launch April 4 set out to record soft X-rays emanating from the remains of a supernova that lit up the Earths’ sky during the last ice age: the Vela Supernova Remnant.
Its past is similar to other stars with masses magnitudes greater than that of the sun. Toward the end of its lifespan, the remnant’s progenitor star in Vela lost the ability to generate enough energy to resist the ceaseless inward pull of gravity. By converting simple gases like hydrogen and helium into heavier elements through nuclear fusion, the star had maintained itself against gravity’s grip for a long stretch of time. But when its share of simpler elements was depleted, its gas tank went empty, and gravity pulled the star’s mass inward toward the body’s center of gravity, creating an immense amount of energy that caused the star to essentially explode.
During supernova events like this, most of the rest of the star’s mass is ejected outward into the interstellar medium and beyond. That mass—the elements created through nuclear fusion over the eons—winds up, literally, everywhere. All the elemental building blocks of every organism and rock and chemical compound on Earth and any planet in the known universe are made of the elements forged in the nuclear furnaces of stars, stellar explosions or mergers, and tossed out across the cosmos.
This is why supernovas are of vital interest to scientists: They are the figurative Johnny Appleseed’s of the universe.
However, supernova events are relatively rare, with only two or three stars exploding per century in a typical spiral galaxy like the Milky Way. Moreover, they are short-lived events, often visible from Earth for only weeks or months.
More permanent analogs for research are the ejected chemical remains of a supernova death. Travelling through space at extreme speeds, these elements comprise what is called a supernova remnant. The speeds of the ejected elements are so high that when they collide with other clouds of material in the interstellar medium, they produce a shockwave that heats the elements to temperatures as hot as 10 million Kelvin. These high temperatures, in turn, cause the emission of X-rays, which themselves radiate throughout the cosmos and are detected by X-ray telescopes, such as NASA’s Chandra X-ray Observatory. Those X-rays reveal much about not only the supernova remnant, but the original supernova itself. That’s the whole point of WRX, explained the experiment’s principal investigator, Dr. Randall McEntaffer, in between runs out to the Speedball pad April 4 in preparation for the launch.
After the WRX rocket lifted off , it flew 127 miles into the thermosphere, an altitude in which the spectrograph could peer at an unexamined 10-square-degree section of the Vela Supernova. For 280 seconds, the Penn State telescope sucked up X-rays, helping reveal the remnant’s chemical makeup, density, temperature and shock velocity, along with the energy of the original supernova and the mass of the progenitor star.
Staring at a laptop monitor during a round of celebratory drinks at the Outrigger, graduate students involved in the WRX experiment gushed over X-ray detector data already streaming in. Bright white pixels against a black background revealed captured X-rays emanating from the Vela Supernova Remnant. Dr. Abe Falcone, head of the WRX team’s X-ray detector group and a research professor at Penn State, looked over their shoulders, explaining the meaning behind the white blips on the monitor.
“The little dots are telling you where the X-rays are [on the detector]. Then we look for the particular energy of the X-rays [the team] cares about. … In addition to that, you’re looking at the position on the detector for the particular energy of the X-rays they care about. Because, as a result of the way this telescope is made, these X-rays are going to get diffracted into a particular position on that detector as a function of their energy.”
In short, by finding out what the energy of the X-ray is—or its particular frequency on the electromagnetic spectrum—the team can better understand the details it is after by studying the supernova remnant, Falcone explained.
“You have particular elements that you’re looking to see what the makeup is [of] that supernova remnant,” he said. “And if you can trace back to that, you start to understand the fundamental makeup of where these elements come from around the universe. … All of this pieces back to understanding the stellar structure, to understanding the formation of stars, therefore the formation of the structure of the universe.”
Strapping a telescope to a relatively small rocket sounds bizarre. On a suborbital trajectory, the spectrographs depended wholly on instrumentation controlling the payload’s yaw, pitch and roll so as to keep the telescope on target. Given that the types of spectrograph readings aimed for in these experiments are impossible to gather by telescopes inside the atmosphere, it makes sense that NASA and the research teams would go to so much trouble to launch a telescope way up into the thermosphere and splash it down into the ocean.
What sounds bizarre is the massive effort that goes into what amounts to a maximum of three or five minutes of data collection. Stable telescope or not.
Clarification of the grand purpose of the whole operation came from Ted Schultz, a research engineer with Penn State’s Department of Astronomy and Astrophysics. The truth is, he said, the gratings, or prisms, used inside the WRX spectrograph to characterize soft X-rays are the most advanced units employed in astronomy today—greater than even some of the capabilities of the Chandra X-ray Observatory, launched in 1999.
“The [optics] that we’re using [are] called gratings. We make them at Penn State,” Schultz said. “And they’re state of the art; there’s nothing better in the world. And you don’t really think about this little rocket … being better than a huge space telescope already up there. But it is. It actually performs better in certain colors than the best thing up in space right now.”
In other words, Schultz said, think of sounding rocket launches as a way of test driving new hardware and validating the technology’s membership aboard the next space-based X-ray telescope.
“You’ve got to prove that what you’ve got is going to work in space before they even give you the money to build the new one,” Schultz said. “So, we spend a lot of time trying to launch these bleeding edge things that no one has ever launched before. And I think that is the real value of the sounding rocket.”
Shooting telescopes into the upper limits of the atmosphere is nothing new for Wallops Flight Facility. The team performs many suborbital launches for astronomical research at the White Sands Missile Range in New Mexico, where land recoveries of the payloads are a cinch.
But the observation targets—Vela and Ara—for this sounding rocket campaign are too difficult to spot from White Sands’ latitude in the northern hemisphere, even at altitude. The constellations are simply too close to the horizon.
The solution? Head south, to Kwajalein Atoll, and launch.
Launching sounding rockets from Roi is, like the sounding rocket program itself, also nothing new. Dozens of NASA, Air Force and Navy suborbital launches have occurred from the island’s Speedball pad since the early 1960s.
What separated the WRX and CHESS experiments from the pack, however, was the need to recover and return the payloads from their open ocean landing spots. For these experiments, NASA employed a newly developed water recovery system in each rocket, enabling the payloads to float on the ocean’s surface after parachuting down from their dates in the thermosphere.
To begin the recovery process, Berry Aviation pilots and spotters took off from Kwajalein aboard a Fairchild Metroliner after each launch to search for the floating payloads. Following coordinates relayed by Wallops Flight Facility personnel, the pilots spotted the payloads and relayed their exact positions to the U.S. Army Vessel Great Bridge ship and crew.
Tasked with recovering the payloads near Rongerik Atoll, north of Kwajalein Atoll, the Great Bridge and crew endured days of roiling seas in high winds while the NASA and University of Colorado-Boulder teams scrubbed repeated attempts for the CHESS launch due to the winds. The earlier recovery of the WRX payload had gone as smoothly as possible. But when it came time to pluck the CHESS payload from the water, things were a little hairier, said Great Bridge Capt. Ron Sylvester.
“When it launched, it was 4:47 a.m., and the splash point was 32 nautical miles from our location with heavy seas and rain,” Sylvester stated.
After locating the payload a further eight miles away from the splash down point, divers jumped in the ocean to attach lines to it. Because the water was too rough to crane the payload onto the boat, the next-best option was to tow it 50 nautical miles into the shelter of the closest landmass—Rongerik Atoll—and then bring it aboard with the crane. It was a long, bumpy trip, the captain said. He and his crew were glad to get the payload back to Roi and then get themselves back home.
“The sea was angry that day, my friend,” Sylvester ended, quoting a classic “Seinfeld” episode. “Like an old man taking cold soup back at a deli.”
The NASA Wallops Flight Facility’s WRX and CHESS campaigns brought a few months of action—and two dazzling launches—to sleepy Roi, essentially doubling the island population in the process.
“This is my second time here,” said NASA Ground Safety Officer Seth Schisler a couple of hours before the WRX launch. “We’ve been coming back since 1989, actually. … We’re one of the few customers that comes out and uses these launch pads.”
Schisler and the rest of the Wallops team are no strangers to setting up camp in remote areas of the world to perform launches.
“We’re kind of all around the world on remote science,” Schisler said. “That’s one of the unique features that we have with the sounding rocket program. We’re a really cheap way to space and [with] a really quick timeframe.”
Outside of their home base launch pads at the Wallops Flight Facility along the Virginia coast, the team regularly launches from Alaska, and throughout its history, Wallops has launched sounding rockets everywhere, from Australia and New Zealand, to Bermuda and Greenland. Just last September, again at Roi, the Wallops team launched two rockets for the Waves and Instabilities from a Neutral Dynamo (WINDY) experiment.
This month’s WRX and CHESS experiments mark two more successful missions, and there will surely be more to come.