Japanese Robots Land on Asteroid Ryugu

 Sept. 22,, 2018: This weekend, Japan made history by deploying two rovers on the surface of a near-Earth asteroid. The mechanical explorers dropped from their mothership, Hayabusa2, less than 100 meters above Ryugu, and now they are hopping across the space rock’s cratered landscape. This picture was taken by Rover-1A in mid-hop:

Hopping is necessary because the asteroid’s gravity is too weak for simple rolling.  Instead of wheels, the rovers have rotating motors inside that allow them to shift their momentum and, thus, make little jumps across the asteroid’s rugged surface. Mission controllers are taking great care that the rovers, which measure 18 cm by 7 cm and weigh only 1 kg, do not fly into space.

As historic as this achievement is, it is only the beginning: Rover-1A and 1B are on a reconnaissance mission for two more robots slated to land later this year.  In October, Hayabusa2 will release MASCOT (Mobile Asteroid Surface Scout), a larger lander made by the German Aerospace Center. MASCOT will be followed, in turn, by another Japanese robot.


Above: Hayabasa2 photographs its own shadow on the asteroid. Credit: JAXA

Exploring Ryugu is important. Classified as a potentially hazardous asteroid, this 900-meter wide space rock can theoretically come closer to our planet than the Moon. This makes it a potential target for asteroid mining. Hayabasa2 will discover what valuable metals may be waiting there. Ryugu is also a very primitive body, possibly containing a chemical history of the formation of our solar system billions of years ago.

Launched in December 2014, Hayabusa2 reached asteroid Ryuga in June of this year. It is scheduled to orbit the asteroid for about a year and a half before returning to Earth in late 2020, carrying samples of Ryugu for analysis by researchers. Stay tuned for updates!

Student-Built Space Weather Satellite Targets Killer Electrons

Sept. 20, 2018: Last Saturday, a Delta II rocket blasted off at dawn from the Vandenberg AFB in California. Soon thereafter NASA reported the successful deployment of the ICESat-2 satellite, designed to make 3D laser images of Earth’s surface.

Here’s what most news stations did not report: A pair of tiny satellites were tucked inside the rocket, and they were successfully deployed as well. Built by students at UCLA, ELFIN-A and ELFIN-B are now orbiting Earth, monitoring the ebb and flow of “killer electrons” around our planet.

“We’ve just received our first downlink of data from ELFIN-A,” reports Ryan Caron, Development Engineer at UCLA’s Department of Earth, Planetary, and Space Sciences. Click to listen:

ELFIN-science-orbit-cutaway_strip

That may sound like ordinary static, but the signal is full of meaning. As mission controllers turn on ELFIN’s science instruments, the static-y waveforms will carry unique information about particles raining down on Earth from the inner Van Allen Radiation Belt.

“Sensors onboard our two cubesats detect electrons in the energy range 50 keV to 4.5 MeV,” says Caron. “These are the so-called ‘killer electrons,’ which can damage spacecraft and cause electrical disruptions on the ground. They also give rise to the majestic aurora borealis.”

“ELFIN is doing something new,” says Vassilis Angelopoulos, a UCLA space physicist who got his doctorate at UCLA and serves as ELFIN’s principal investigator. “No previous mission was able to measure the angle and energy of killer electrons as they rain down on Earth’s atmosphere. ELFIN will help us investigate how disturbances called ‘Electromagnetic Ion Cyclotron waves’ knock these electrons out of the Van Allen Belts and scatter them down toward Earth.”

ELFIN-A and ELFIN-B are cubesats, each weighing about eight pounds and roughly the size of a loaf of bread. They are remarkable not only for their cutting edge sensors, but also for their origin. The two satellites were almost completely designed and built by undergraduate students at UCLA. Working for more than 5 years, a succession of 250 students created the two Electron Losses and Fields Investigation CubeSats –“ELFIN” for short.

“Just seeing all the hundreds of hours of work, the many sleepless nights, the stressing out that you’re not going to make a deadline — just seeing it go up there … I’m probably going to cry,” says Jessica Artinger, an astrophysics major and geophysics and planetary science minor who helped build the satellites and witnessed their launch.

The ELFIN website has interactive tools so the public can track and listen to the spacecraft as it passes overhead twice a day. The CubeSats are expected to remain in space for two years, after which they will gradually fall out of orbit and burn up in the atmosphere like shooting stars.

ELFIN has been supported with funding from the National Science Foundation and NASA, with technical assistance from the Aerospace Corporation among other industry partners and universities.

 

Equinox Cracks in Earth’s Magnetic Field

Sept. 14, 2018: The northern autumnal equinox is only a week away. That means one thing: Cracks are opening in Earth’s magnetic field. Researchers have long known that during weeks around equinoxes fissures form in Earth’s magnetosphere. Solar wind can pour through the gaps to fuel bright displays of Northern Lights. Here’s an example from Yellowknife, Canada:

“On Sept. 5-6, we could see auroras in the sky all night long, with a bright outburst of pink shortly after midnight,” says photographer Yuichi Takasaka.

During the display, a weak stream of solar wind was blowing around Earth. At this time of year, that’s all it takes. Even a gentle gust can breach our planet’s magnetic defenses.

This is called the the “Russell-McPherron effect,” named after the researchers who first explained it. The cracks are opened by the solar wind itself. South-pointing magnetic fields inside the solar wind oppose Earth’s north-pointing magnetic field. North and South partially cancel one another, opening a crack. This cancellation can happen at any time of year, but it happens with greatest effect around the equinoxes. Indeed, a 75-year study shows that September is one of the most geomagnetically active months of the year–a direct result of “equinox cracks.”

NASA and European spacecraft have been detecting these cracks for years. Small ones are about the size of California, and many are wider than the entire planet. There’s no danger to people on Earth. Our planet’s atmosphere intercepts the rush of incoming particles with no harm done and a beautiful afterglow.

Stay tuned for more Arctic lights as autumn approaches.

Realtime Aurora Photo Gallery

Rads on a Plane: New Results

Sept. 18, 2018: Many people think that only astronauts need to worry about cosmic radiation. Not so. Ordinary air travelers are exposed to cosmic rays, too. Every day, radiation from deep space enters Earth’s atmosphere and penetrates the walls of aircraft. A recent study from the Harvard School of Medicine found that flight attendants have a higher risk of cancer than members of the general population, and the International Commission on Radiological Protection has classified pilots as occupational radiation workers.

How much radiation do you absorb? Spaceweather.com and the students of Earth to Sky Calculus have been working to answer this question by taking cosmic ray detectors onboard commercial airplanes. Flying since 2015, we have collected more than 22,000 GPS-tagged radiation measurements over 27 countries, 5 continents, and 2 oceans.

maps

(A) A global overview of our flights. This map shows where we have been. (B) To show the density of our data, we zoom in to the Four Corners region of the USA. There are three major hubs in the map: Phoenix, Las Vegas, and Denver. You can’t see them, however, because they are overwritten by pushpins.

Here is what we have learned so far:

  1. Radiation always increases with altitude, with dose rates doubling every 5000 to 6000 feet. This make sense: The closer you get to space, the more cosmic rays you will absorb.
  2. At typical cruising altitudes, cosmic radiation is 40 to 60 times greater than natural sources at sea level.
  3. Passengers on cross-country flights across the USA typically absorb a whole body dose equal to 1 or 2 dental X-rays.
  4. On international flights, the total dose can increase ~five-fold with passengers racking up 5 to 6 dental X-rays.

Our database is a powerful tool for investigating cosmic rays in the atmosphere. For instance, this plot compares aviation radiation over the tropics vs. the Arctic:

arctic_tropics

We see that the Arctic is a high radiation zone. This comes as no surprise. Researchers have long known that particles from space easily penetrate Earth’s magnetic field near the poles, while the equator offers greater resistance. That’s why auroras are in Sweden instead of Mexico. Generally speaking, passengers flying international routes over the poles absorb 2 to 3 times more radiation than passengers at lower latitudes.

Our database also allows us to investigate differences between individual countries. This plot, for instance, compares Sweden, the USA and Chile:

countries

As an Arctic country, Sweden has the most radiation–no surprise.  The continental USA straddles the middle–again, no surprise. A mid-latitude country can be expected to have middling radiation. Chile, however, is more of a puzzle.

Although Chile does not cross the equator, it has some of the lowest readings in our database. This phenomenon is almost certainly linked to Chile’s location on the verge of the South Atlantic Anomaly–a large distortion in Earth’s magnetic field that affects radiation levels. We are actively investigating the situation in Chile with additional flights, and will report our results in a future blog.

Because our home base is in the USA, we spend a lot of time flying there. In fact, our US dataset is so dense, we can investigate regional differences across the country. This plot compares radiation over New England vs. the Southwest:

newengland_southwest

The two curves are indistinguishable below ~30,000 feet, but at higher altitudes they diverge. By the time a plane reaches 40,000 feet, it would experience 30% more radiation over New England than the same plane flying above the desert Southwest. According to our measurements so far, New England is the “hottest” region of the continental USA, radiation-wise, with the Pacific Northwest a close second.

Perhaps the most important outcome of our work so far is E-RAD–a new predictive model of aviation radiation. We can now predict dose rates on flights in areas where we have flown before. Because it is constantly updated with new data, E-RAD naturally keeps up with variables that affect cosmic rays such as the solar cycle and changes in Earth’s magnetic field.

Here is an example of a recent flight we took from Baltimore to Las Vegas, comparing E-RAD’s predictions with actual measurements:

eradvreality

The two agree within 10% for most of the flight. These errors are constantly shrinking as we add new readings to our database.

The results in this report are offered as a preview of what we are learning. Our database is growing almost-daily with new flights to new places, and we will have more results to share in the weeks and months ahead.

Visit RadsonaPlane.com for updates.

Green Comet Makes Closest Approach to Earth

Sept. 9, 2018: On Sept. 10th, Comet 21P/Giacobini-Zinner (“21P” for short) makes its closest approach to Earth in 72 years–only 58 million km from our planet. The small but active comet is easy to see in small telescopes and binoculars shining like a 7th magnitude star. Michael Jäger of Weißenkirchen, Austria, photographed 21P approaching our planet on Sept. 9th:

“Comet 21P is currently in the constellation Auriga,” says Jäger. “I caught it just as it was passing by star clusters M36 and M38.”

The comet’s close approach to Earth coincides with a New Moon, providing a velvety-dark backdrop for astrophotography. The best time to look is during the dark hours before sunrise when the constellation Auriga is high in the eastern sky. If you have a GOTO telescope, use these orbital elements to point your optics. Detailed sky maps can help, too.

Shining just below the limit of naked-eye visibility, the comet will remain easy to photograph for the rest of September. If you can only mark one date on your calendar, however, make it Sept. 15th. On that night, 21P will cross directly through the middle of the star cluster M35 in the constellation Gemini. Astronomer Bob King writing for Sky and Telescope notes that “the binocular view should be unique with the rich cluster appearing to sprout a tail!”


Click to view an interactive 3D orbit of 21P/Giacobini-Zinner. Credit: NASA/JPL

21P/Giacobini-Zinner is the parent of the annual Draconid meteor shower, a bursty display that typically peaks on Oct. 8th. Will the shower will be extra-good this year? Draconid outbursts do tend to occur in years near the comet’s close approach to the sun. However, leading forecasters do not expect an outburst this year despite the comet’s flyby. In case they are mistaken, many eyes next month will be on the shower’s radiant in the constellation Draco.

Got a picture of Comet 21P/Giacobini-Zinner? Submit it here.

159 Years Ago, A Geomagnetic Megastorm

Sept. 2, 2018: Picture this: A billion-ton coronal mass ejection (CME) slams into Earth’s magnetic field. Campers in the Rocky Mountains wake up in the middle of the night, thinking that the glow they see is sunrise. No, it’s the Northern Lights. People in Cuba read their morning paper by the red illumination of aurora borealis. Earth is peppered by particles so energetic, they alter the chemistry of polar ice.

Hard to believe? It really happened 159 years ago. This map shows where auroras were sighted in the early hours of Sept. 2, 1859:

As the day unfolded, the gathering storm electrified telegraph lines, shocking technicians and setting their telegraph papers on fire. The “Victorian Internet” was knocked offline. Magnetometers around the world recorded strong disturbances in the planetary magnetic field for more than a week.

The cause of all this was an extraordinary solar flare witnessed the day before by British astronomer Richard Carrington. His sighting on Sept. 1, 1859, marked the discovery of solar flares and foreshadowed a new field of study: space weather. According to a NASA-funded study by the National Academy of Sciences, if a similar “Carrington Event” occurred today, it could cause substantial damage to society’s high-tech infrastructure and require years for complete recovery.

carrsket

In Sept. 1859, this large sunspot unleashed a record-setting solar flare. Sketch by R. C. Carrington.

Could it happen again? In fact, a similar event did happen only 6 years ago. On July 23, 2012, a powerful explosion on the sun hurled a Carrington-class CME away from the sun. Fortunately, it missed. “If it had hit, we would still be picking up the pieces,” says Prof. Daniel Baker of the University of Colorado, who summarized the event at NOAA’s Space Weather Workshop in 2014.

In a paper published just a few months ago, researchers from the University of Birmingham used Extreme Value Theory to estimate the average time between “Carrington-like flares.” Their best answer: ~100 years, a value which suggests we may be overdue for a really big storm.