Creative Writing

Kamikaze Electrons: NASA's BARREL Mission

An article, written by myself, covering NASA's BARREL campaign, studying dangerous particles from our Sun that surround Earth in the magnetosphere. - - - BARREL is a balloon-based Mission of Opportunity to augment the measurements of NASA's RBSP spacecraft. BARREL seeks to measure the precipitation of relativistic electrons from the radiation belts during 2 multi-balloon campaigns, operated in the southern hemispheres (option for 3rd northern hemisphere campaign). During each campaign, 5-8 long-duration balloons would be aloft simultaneously over a one-month period to provide measurements of the spatial extent of the relativistic electron precipitation and to allow an estimate of the total electron loss from the radiation belts. Observations are planned for when the balloon-array will be conjugate with the RBSP spacecraft, such that direct comparison is possible between one another.
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   T owering 15 stories above the Antarc-tic landscape, the white balloon castsa long, dark shadow across the snow.  The ground crew makes nal preparations forlaunch, lling the balloon with helium and secur - ing its cargo. In one uid motion, the workers freethe balloon from the Earth. Rising into the air, itbecomes a fading silhouette in a cloudless sky.Meanwhile, millions of kilometers away, thefocus of this launch begins its own journey. Agust of high-energy particles blows out of the sunand into the solar system. A few of these particlesmake a beeline for Earth. The balloon expands in the thin air of the up -per atmosphere. The sun’s warm light charges the solar panels, giving life to the scientic instru - ments hanging in a box of insulating foam below the balloon. Winds catch the large surface of the balloon like a sail, blowing it along its two-week  circumnavigation of Antarctica.Earth’s magnetic eld snatches an electron from the sun’s outburst and throws it into a turbulent sea of particles that surrounds our planet. Spi - raling wildly, the electron follows a suicidal pathtoward certain destruction. With a burst of light,the electron crashes into the atmosphere. Its fatetriggers a spark of electrical current inside one of the scientic instruments—unveiling new details about how the sun can disturb the delicate cocoon within which our planet resides.  This is a new NASA mission called BARREL.In a series of several dozen ights in the Antarcticsummers of 2012-13 and 2013-14, BARREL willexplore the invisible world of the heavens that af  - fects nearly every component of our modern lives. Its goal is to better understand the dangerous solar particles that engulf our planet, especially dur - ing the sun’s piques of violence. The mission also will break new ground for NASA, which typically funds big single space projects, rather than a suiteof smaller, mass-produced payloads. “We’re vulnerable to the space environment. Understanding the dynamics and how that affectsour technology is becoming more and more im - portant for modern society,” says physicist RobynMillan of Dartmouth College, BARREL’s princi - pal investigator. “We need to understand the [dy  - namics] well enough to make better predictions.” Living with a Star Electronics and people have become insepara -ble. Air travel, power grids, satellite television, and cellular networks may seem robust, but they are allsensitive to the high-energy particles shot from the sun at a million tons per second. “Disturbances in Earth’s magnetic eld act likea giant particle accelerator, so some of the par - ticles end up moving very, very fast—almost atthe speed of light,” says David Smith, professorof physics at the University of California, SantaCruz, and researcher on the BARREL mission.“[They’re] very penetrating, and enough of themcan do a lot of harm to a person. But they canalso harm electronics.” The radiation from an intense solar stormshouldn’t make you run for a lead umbrella. Solarstorms inict their most damage electronically. In1962, Telestar-1 became the rst satellite casualty from a solar outburst, short-circuited by the so -lar wind. A 1989 event triggered a massive power outage in Quebec, affecting millions of residentsand costing billions of dollars to repair. The most violent eruptions from the sun in recorded his - tory, if they were to happen today, could do more than $1 trillion in damage to the world’s electronic infrastructure.“The potential for these geomagnetic storms todamage systems is greater than [ever],” says Brett Anderson, a Dartmouth College graduate student working on BARREL. “Almost on a daily basis,our society is putting more and more satellites into space. The more assets we send into space, themore important it becomes to understand space  weather and to be able to predict it.”Earth has a natural defense from these damag  -ing particles: the magnetosphere, a donut-shaped blanket wrapped around the planet. Earth’s mag  - netic eld directs particles—such as electrons car - ried by the solar winds—into the magnetosphere’sradiation belts, like rainwater owing into a reser -  voir. Without the magnetosphere, harmful solarparticles would bombard Earth’s surface. Understanding how these solar particles behave near Earth is critical. “These electrons are part of  our environment, so we’d like to understand what processes inuence their presence, their num - bers and their energies,” says BARREL scientistMichael McCarthy, a professor of physics at theUniversity of Washington. Into the Radiation Belts Despite the impact of solar activity on soci - 2 Kamikaze Electrons  An artist’s rendition of Earth’s magnetosphere. Earth’s magnetosphere protects our planet from charged particles that blow out of the sun. The particles can cause damage to satellites and other electronics. BARREL 3  ety, there are still large gaps in our knowledge. ANASA satellite campaign called Radiation BeltStorm Probes (RBSP) will work in tandem withBARREL to expose the interior dynamics of radiation belts. Two identical RBSP satellites will be launched into orbit within the belts in August 2012, measuring the movement and types of par -ticles there. The magnetosphere lies outside Earth’satmosphere for mostof its length, except near the north and south poles. Electronsspiral within Earth’s radiation belts in tight orloose loops. Electrons with tighter spirals bouncelike ping-pong balls back and forth between the northern and southern hemispheres. The looser the spiral, the more likely the electron will cascadeinto Earth’s atmosphere at one of the poles andbecome a “loss.”“Out in space, all sorts of phenomena will knock an electron into a loose spiral around a magnetic eld line,” says Smith. “It will follow [the eld line] right down into the atmosphere andthen—crash!—it makes gamma rays that we candetect.” Accurate models of the radiation belts arecrucial in predicting the impact of solar storms.However, they lack a precise input for how quickly particles escape from the radiation belts. This isimportant information for calculating when it’ssafe to send astronauts through the belts after asolar storm. While the RBSP satellites will measuremany processes inside the radiation belts them - selves, they will not detect the loss rate of par -ticles. “The satellite can see a certain amount of elec - trons,” says Smith. “That could be because thoseelectrons have been out there forever, or thatsome keep coming in and out.”So scientists had to get creative. Just as waterows in and out of res -ervoirs, particles enterand exit the radiation belts. If researchers cangure out how many  electrons leave the belts, they will gain clarity onthe number of electrons coming in to replenish the losses.“The whole idea is seeing where the radiation belts come from by guring out how and why [electrons] decay and disappear from the belt,”says Smith. “You can’t understand where it comesfrom unless you understand where it’s going.” Into the Skies  To detect those electron losses, researchersmust reach the area where the electrons collide  with the atmosphere, high above the poles. Start - ing in December 2012, BARREL scientists willlaunch a helium-lled balloon every other day from the South African Antarctic Station (SANAEIV) and the British Antarctic station, Halley Bay.Each balloon will ascend 36 kilometers above theEarth—more than four times the height of MountEverest—to its cruising altitude. There, it will stay aloft for about two weeks. If all goes well, eetsof balloons will circle Antarctica throughout thesummer months (December through February) in2012-13 and 2013-14, allowing the team to scan alarge area of the southern sky for electron losses.“A magic moment will happen each time RBSPand a BARREL payload are on opposite ends of amagnetic eld line,” says Smith. “At that moment,you know that the waves and plasma propertiesseen by RBSP are causing the electron [losses] yousee at BARREL.” A 23-kilogram payload the size of a dorm-roommini-refrigerator will dangle from each balloon.Each payload is a self-contained box with aninstrument to gauge electron losses. Solar panelsattach to each side of the payload, powering theinstruments. Inside the payload’s hard foam exte - rior is a scintillator made of sodium iodide, whichcreates an electrical pulse from each gamma ray itabsorbs after an electron loss. A satellite modem— complete with its own telephone number—beamsthe information back to researchers in the UnitedStates.BARREL team members will monitor the statusof each payload around the clock to ensure thehealth of each balloon. If one of them falls toolow in the sky or drifts into the ight path of air - lines, it gets cut down for safety reasons. A small explosive charge attached to each balloon can be remotely detonated, dropping the payload to theground. Unless the payloads fall near a researchbase, they’ll remain on the Antarctic ice. 4 Kamikaze Electrons  You can’t understand whereit comes from unless you understand where it’s going.  The Radiation Belt Storm Probes and the radiation belts surrounding Earth. The twin satellites willorbit through the radiation belts collecting data to better understand the effects of solar activity. BARREL 5   The goal is for each balloon to drift by theSouth Atlantic Anomaly, a weak spot in Earth’smagnetic eld that creates a data “sweet spot”between South America and Africa. The team willtake advantage of winds that circulate east-to- west around the Antarctic continent. By launching slightly upwind of the South Atlantic Anomaly,each balloon will sail around the South Pole andthrough the sweet spot for a few days of peak exposure to electron-sparked gamma rays. “The radiation belts come down closer to the atmosphere [in the South Atlantic Anomaly] thananywhere else,” says Smith. “If you go just below it along the Antarctic coast, you can not only seeparticles that rain down at that point, you can alsosee particles drifting around from other places inthe radiation belt.”  An Unexpected Discovery One type of loss consists of the very-high-ener - gy electrons, which pose the greatest risk to satel - lites. Discovering what makes them pour out of the radiation belts in abrupt waves is a key focusof BARREL.Scientists might never have learned of thoselosses if not for a lucky accident during a 1996balloon ight. Michael McCarthy was part of aFrench campaign called INTERBOA, which ew balloons carrying scientic instruments 35 kilome - ters above Scandinavia. At rst the campaign saw  no interesting data. Then, something unexpectedhappened. “We observed for a brief time this funny littlenoise spike, and that was all we got for severaldays,” says McCarthy. “We went back and looked at [the spike]. The more we looked, the more in- teresting it became.”McCarthy took his X-ray data to Jason Foat, aUC Berkeley researcher on the mission, whosegamma-ray data from the same ight lled in thegaps. “We put those two pieces of information together and we both saw something at the same time—it was real,” McCarthy recalls. “It wasn’tnoise.”Because the puzzling spike was isolated, theresearchers could study it more easily. They foundthat it came from an unexpected downpour of  energetic electrons. No one had ever seen this before; indeed, no one had thought to look foranything at such high energies.“It was an accident that we found this,” says Mc - Carthy. “We had to gure out more about it.”In the years following INTERBOA, several science missions attempted to better understand these sudden bursts of electron losses. But notuntil ten years later did a group of scientists fromacross the country, united by common history  and passion, assemble a proposal that would be- come the forerunner of a new way of thinking atNASA. This project grew into BARREL: the Bal - loon Array for RBSP Relativistic Electron Losses. Rolling Out BARREL  After NASA announced the Radiation BeltStorm Probes satellite mission, the agency beganlooking into other projects that could work withthe satellites on space-weather physics. Smith andMcCarthy had previously done research togetherin Antarctica. BARREL’s principal, Robyn Millan,had worked with both on her thesis project at UC 6 Kamikaze Electrons Members of the BARREL team and ground crew prepare to launch a research balloon in 2009. Theballoons are launched from Antarctica and travel for about two weeks collecting data. BARREL 7
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