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A Group of Suitcase-Sized Satellites Will Transform Hurricane Tracking

Screenshot from "CYGNSS Overview," NASA Langley Research Center

Earlier this month, NASA launched a constellation of small satellites that will transform hurricane forecasting and enable new insights into storm formation and activity. Called the Cyclone Global Navigation Satellite System (CYGNSS), eight spacecraft, each the size of a carry-on suitcase, are flying over the tropics to measure and map ocean winds. Because of their altitude, heavy rain and storm surges are no obstacles to the satellites, and when hurricanes form, the spacecraft will be able to peer through walls of water into the storm’s core and continue to collect data—something no space-based system has ever done before.

“CYGNSS is a tool that will provide us 24/7 coverage of the tropical cyclone zone. It will improve our knowledge of how hurricanes grow so that we can better prepare and protect people in the path of each hurricane as it comes,” Christine Bonniksen, CYGNSS program executive with the Science Mission Directorate's Earth Science Division at NASA Headquarters, tells mental_floss.

THE RAIN BARRIER HAS BLOCKED OUR VIEW

Over the past several decades, there has been a steady improvement in storm track forecasting—or where storms will hit—and the National Hurricane Center’s error rate is half of what it was 20 years ago. The same cannot be said for storm intensity forecasting—how strong these storms will be. “If you look at the record for their intensity forecast, there has been very, very little improvement in the last 20 years,” said Chris Ruf, the principal investigator on the CYGNSS mission and a scientist at the University of Michigan, Ann Arbor. One of the primary reasons for this is that today’s satellites are unable to measure what’s going on in the inner core of hurricanes. “This has been identified for many years as a primary lacking ingredient in the numerical forecasts that are used by the National Hurricane Center. They wish they had information on the inner core of the storms and they don’t.”

Storm cores have so far been impenetrable because current wind-observing spacecraft cannot see through rain. This is because their on-board instruments emit signals at an 8-millimeter wavelength—about the same size as a large raindrop. When the signals encounter rain, they are simply scattered and absorbed. (Hurricane paths depend on environmental factors outside of the storm, which is why this rain shroud has not been an impediment to predicting where storms will hit.)

Additionally, it takes about three days for current systems to collect data to build a map of global wind speeds and precipitation. This is a big problem if you’re trying to track the rapid intensification of tropical storms and hurricanes, which can happen in a matter of hours. So until now, scientists have had to rely on so-called “Hurricane Hunter” aircraft to fly into the storm to perform wind speed reconnaissance.

THE CYGNSS SOLUTION

CYGNSS changes all of this by using GPS satellite signals, which were designed to penetrate heavy rains. GPS operates at a 19-centimeter wavelength—more than long enough to avoid rain interaction. When GPS satellite signals hit the ocean, they reflect back into space and are received by CYGNSS observatories. Think about the way the Moon reflects on a placid lake: When the lake is calm, the Moon's image is sharp. When the wind blows, the water roughens and the image diffuses. CYGNSS relies on a similar principle, reading the clarity of the GPS signals to reveal the characteristics of the wind. It measures the strength of the GPS signal as it scatters off the ocean surface to determine wind speed.

The eight CYGNSS observatory spacecraft operate evenly in a single orbital plane around the Earth. Each satellite has a payload called a Delay Doppler Mapping Instrument, a GPS receiver capable of tracking four different GPS signals simultaneously. Two antennas look down at reflected GPS signal and take measurements of the diffuse scattering, and from those derive the wind speed and activity. Meanwhile, one antenna looks up and receives a direct GPS satellite signal for geolocation. In essence, each 65-pound satellite is doing the work of four Hurricane Hunter airplanes. Collectively, CYGNSS is like a squadron of 32 such planes flying continuously over the tropics taking simultaneous measurements.

The system gives a total refresh of the entire tropical wind distribution map every seven hours, even under heavy precipitation. In a hurricane or tropical storm—including in areas with the highest wind speeds and the most powerful surges—CYGNSS can immediately answer questions about the storm size, intensity, and the reach of its strong winds. Moreover, because the satellite constellation has such expansive coverage of the Earth, it can collect massive amounts of data on the entire storm environment. There are three different data downlink points around the world, and the data can be downloaded from the satellites within the hour—an unprecedented timeframe.

HOW THE LAUNCH WENT DOWN

CYGNSS launched on the morning of December 15, 2016 from Cape Canaveral with the help of a Pegasus rocket, an air launch system. The rocket was mounted to the bottom of an L-1011 airplane called Stargazer that took off from a runway, just like any other plane you’ve ever seen. At 39,000 feet above the Atlantic Ocean, the plane released the Pegasus rocket, which ignited five seconds later and powered its way into space. The fairings hatched away and the deployment vehicle separated, and the eight small satellites released themselves in pairs over 30-second intervals. Ten minutes after separation, their solar arrays deployed. They then moved into position in orbit and began operation.

By 4:12 pm ET that same day, the CYGNSS team had successfully made contact with all eight satellites. "It is an amazingly rewarding feeling to spend such an intense and focused time working on CYGNSS and then, in a matter of just a few hours, have the entire constellation suddenly come to life," Ruf said in a brief mission update. "I am excited (and a little exhausted) and really looking forward to diving into the engineering data in the coming days, and then into the science data in the weeks to follow."

This is NASA’s flagship Earth Venture–class mission, which is a new NASA program designed for low-cost, high-technology suborbital (think aircraft and balloons) and orbital (CYGNSS) projects. Two previous missions of this class were aircraft designed for atmospheric research and communications. This is the first spaceborne Earth Venture endeavor. Southwest Research Institute in Boulder, Colorado runs CYGNSS mission operations, and science operations are run from the University of Michigan. The primary $160 million mission will run for two years—enough time to fill in blank spots in the hurricane dataset, get a grip on how storm cores intensify, and hopefully refine the forecast models that lives depend on.  

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7 Surprising Facts About Pluto
NASA/JHUAPL/SwRI
NASA/JHUAPL/SwRI

Pluto, the ninth planet of the classical solar system was, until 2015, largely a mystery—a few pixels 3.6 billion miles from the Sun. When NASA's New Horizons spacecraft arrived at the diminutive object in the far-off Kuiper Belt, planetary scientists discovered a geologist's Disneyland—a mind-blowing world of steep mountains, smooth young surfaces, ice dunes, and a stunning blue atmosphere. To learn more, Mental Floss spoke to Kirby Runyon, a planetary geomorphologist at the Johns Hopkins University Applied Physics Laboratory and a scientist on the NASA New Horizons geology team. Here is what you need to know about Pluto, the small world with the biggest heart in the solar system.

1. 248 EARTH YEARS = 1 PLUTO YEAR

At 1473 miles in diameter—about half the width of the United States—Pluto is the smallest of the nine classical planets and the largest discovered "trans-Neptunian object" (i.e., an object beyond the planet Neptune). As could be expected, it is cold on Pluto's surface: around -375°F. Its gravity is about 1/15 that of Earth. It has five moons: Charon, Nix, Hydra, Kerberos, and Styx. Charon is the largest of the moons by far, with a diameter about half that of Pluto. It takes about 248 Earth years for Pluto to circle the Sun, and during that time, its highly elliptical orbit takes it as far as 49 astronomical units from our star, and as close as 30.

2. THE DISNEY DOG IS CONNECTED TO THE PLANET.

Pluto the planet was discovered on February 18, 1930 by astronomer Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona. It was named later that year by Venetia Burney, an 11-year-old girl in England. She first learned of the new, nameless planet from her grandfather, who mentioned it while reading the newspaper. Burney was interested in Greek and Roman mythology at the time, and she immediately suggested Pluto.

Her grandfather was impressed, and mentioned it in a note to a friend of his, who taught astronomy at Oxford. The astronomy professor passed word to Lowell Observatory, and the astronomers there took an immediate liking to it. It helped that the first two letters of Pluto are the initials of the observatory's (then dead) founder, Percival Lowell. Note that Burney did not get the name from the Disney dog. Just the opposite: The dog, which premiered the same year as Pluto was discovered, was likely named by Walt to ride the planet's publicity wave. Scientists and cartoonists alike have yet to explain how the then-unseen planet and dog ended up being more or less the same color.

3. A PLUTO SYSTEM SPACE ELEVATOR IS TECHNICALLY POSSIBLE.

Space elevators are a science fiction staple, and advances in carbon nanotubes have made their prospects, if not likely, then certainly possible. The idea is to bring a large object such as an asteroid into a geostationary orbit at Earth's equator, and essentially connect that object and the Earth with a cable or structure. You could then lift things into orbit without the need for rockets. According to Runyon, the unique orbital characteristics of Pluto and Charon create interesting opportunities for the very, very distant future of engineering.

The two worlds are tidally locked. Charon's orbit is precisely the same duration as Pluto's rotation, meaning that if you stood on Pluto's surface, the moon would hover over the same spot, never rising or setting. "Because they are binary, tidally locked, literally orbiting each other in a perfect circle, you could build a space elevator that goes from one planet to the other, from Pluto to Charon," Runyon tells Mental Floss. "And it would touch the ground in both places, physically linking them. And you could literally climb a ladder from one to the other."

4. ITS HEART IS IN THE RIGHT PLACE—THE 40 PERCENT OF THE PLANET WE'VE SEEN.

In 2015, the New Horizons spacecraft arrived at the Pluto system and turned a few pixels into a real world. The famous first image released by NASA is not a straight-on shot from Pluto's side, with the top being the North Pole and bottom being the south. It is in reality a view from Pluto's higher latitudes, looking down. (The heart, in other words, is quite higher up on the planet than the picture suggests.) Because New Horizons was a flyby craft and not an orbiter, planetary scientists don't know what 40 percent of the planet looks like.

5. ITS BIZARRE ORBIT AND ROTATION ARE A MYSTERY.

The traditional classroom solar system model of a light bulb as the Sun and planets on wires extending from it represents a nice flat orbital plane known as the ecliptic, and for most of the solar system, that's pretty close to the truth. But not for Pluto, which has a 17-degree inclination relative to the ecliptic. Moreover, like Uranus, its rotation is tipped on its side, and it rotates backward (east to west). No one knows why, according to Runyon. "It's probably the result of an ancient impact," he says. "One not strong enough to disrupt planet but enough to tip on its side. This might have been the Charon-forming impact, which would be similar to how our moon is formed."

6. WE WERE WRONG ABOUT ITS ATMOSPHERE …

Astronomers have long known that Pluto has an atmosphere. During stellar occultations (that is, when it moves in front of stars), astronomers can see the star dim, and then completely go out, and then reappear dimly, and then return to its full brightness. That dimming is caused by the planet's atmosphere. Astronomers are furthermore able to track its density over time. Because Pluto is so far from the Sun, the ice on its surface sublimates: It goes from a solid directly to a gas without first becoming a liquid. When Pluto reached perihelion (as close to the Sun as its gets in an orbit) in 1989, the expectation was that the atmosphere would begin to collapse entirely: that it would freeze out, basically, and fall to the surface.

"A good comparison is when it snows on Earth," says Runyon. "Snow is basically the water vapor in the atmosphere freezing out and falling to the surface, leaving Earth's atmospheric density slightly lower than it would be otherwise." In Pluto's case, the thought was that the complete atmosphere would freeze out and fall onto the planet's surface.

It didn't happen. "Pluto's atmosphere is denser than we thought it would be," Runyon explains. "Even now as it's moving farther from the Sun, its atmosphere is puffier than ever." One model says that while the atmosphere does thin as ices fall to the surface, it never completely freezes and falls.

7. … WHICH IS ELECTRIC BLUE.

Scientists on the New Horizons team didn't expect to see Pluto's atmosphere during the flyby. "When we spun New Horizons around after closest approach and looked back at Pluto—being basically backlit from the Sun—we could see the atmosphere," he says. "We knew we'd be able to detect it, but to see it, and to see that the sunrise and sunset on Pluto is this ethereal electric blue—nobody anticipated that." Runyon says that the New Horizons found discrete atmospheric layers that could be traced for hundreds of miles. "Pluto has what's called a stably stratified atmosphere. The coldest layer is on the bottom and it gets warmer as you go up," he says.

"In science, you test hypotheses, but before you can even do that you need to figure out what's there in the first place. To me, that's the most exciting part of science. The most exciting part of space exploration is to see something for the first time, and that's what New Horizons was. And to turn around and look back at the Sun and see a beautiful atmosphere with the gorgeous layers through it is just astonishing," he says. 

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Voyager 1's Back Thrusters Just Fired Up for the First Time in 37 Years
NASA/JPL-Caltech
NASA/JPL-Caltech

Imagine trying to start a car that's been sitting in a garage for decades—and the car is 13 billion miles away. That's what NASA attempted to do this week with the Voyager 1 spacecraft—and it worked.

Four of the thrusters on Voyager 1—the only human-made object ever to reach interstellar space—have been dormant since 1980, just three years after it and its twin probe, Voyager 2, were launched into the universe bearing the sights, sounds, and music of Earth on the Golden Record.

For the past 40 years, Voyager 1 has been using "attitude control thrusters" to keep the spacecraft's antenna oriented to Earth so that it can communicate with us, and us with it. The thrusters fire tiny pulses lasting for just milliseconds. For the past three years, they've been degrading, worrying the Voyager team.

Propulsion experts Carl Guernsey and Todd Barber, from NASA's Jet Propulsion Laboratory in Pasadena, California, considered different interventions and how the spacecraft might respond to them. They proposed attempting to start the four "trajectory correction maneuver," or TCM, thrusters located on the back of the spacecraft, hoping they could take over the job of correctly orienting Voyager. In the early days of the mission, these thrusters, identical in size and functionality to the attitude control thrusters, were used to keep the probe's instruments targeted on Jupiter, Saturn, and their moons as the spacecraft flew by them.

They pored over decades-old data and deciphered outdated software code to make sure they could attempt to turn on the TCM thrusters without causing damage to Voyager. Then, on Tuesday, engineers fired them up and tested their ability to orient the spacecraft, using 10-millisecond pulses. They had to wait 19 hours and 35 minutes for the data to make it to Earth, but eventually they got the good news: The TCM thrusters were up to snuff.

Now that the back thrusters are operational, Voyager 1 just got another two to three years of life, Suzanne Dodd, mission project manager at NASA's Jet Propulsion Laboratory, said in a statement. The plan is to shift the orientation work to the TCM thrusters in stages beginning in January. Each requires a heater to operate, and turning on the heaters requires power, which is a strain on the aging probe. So when there's no longer enough power for them, the job will switch back to the attitude control thrusters.

The engineers will likely attempt the same move with Voyager 2 when its attitude control thrusters start to break down; currently, they're in better shape than Voyager 1's. Now in the periphery of our solar system in what's known as the heliosheath, Voyager 2 will enter interstellar space in the next few years. As the twin crafts fly deeper into the universe at more than 36,000 mph, they'll keep talking to Earth for at least a little while longer. 

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