May 19 2016
From The Space Library
NASA’s KORUS-OC Campaign Takes to Seas
In a South Korean port, two research ships are being equipped with instruments that will measure sunlight interacting with the ocean and capture the microscopic life that ebbs and flows with the currents. As part of the Korea-United States Ocean Color (KORUS-OC) expedition, scientists from the Korean Institute of Ocean Science and Technology (KIOST), NASA and other U.S. institutions are launching an 18-day field campaign to characterize the daily changes of the seas surrounding South Korea.
"The ocean is very dynamic, and changes happen on very short time scales – from minutes to hours," said Antonio Mannino of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, one of the campaign’s lead scientists.
One of the dynamic players that KORUS-OC will focus on is phytoplankton, the tiny plants at the base of the marine food web that also play a key role in Earth’s carbon cycle. To get a complete picture of a day-in-the-life of these organisms, the campaign’s researchers will combine ship-based and airborne observations with data from a South Korean satellite called the Geostationary Ocean Color Imager (GOCI), which takes hourly measurements eight times a day. While satellites carrying instruments like the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) provide ocean color information, they collect information once a day. GOCI is the only geostationary satellite sensor – meaning that it observes a fixed area, instead of orbiting the globe – that has the proper instrument capabilities to measure ocean color throughout a day.
Korean and NASA-supported researchers are hoping to better understand how oxygen and carbon flow between the ocean and atmosphere, and the role that phytoplankton plays in these and other processes, said Joe Salisbury, a research associate professor at the University of New Hampshire, Durham, and KORUS-OC’s chief scientist.
"We’ll have our feet right in the water, with the best instruments available to science, characterizing the process itself – how the carbon is moving and changing," Salisbury said. Phytoplankton play a role in absorbing carbon dioxide from the atmosphere, sometimes taking it out of the carbon cycle as they die and sink to the bottom of the ocean. And although individuals are tiny, the sheer number of them means that about half of the oxygen that people breathe was produced by phytoplankton.
KORUS-OC will investigate phytoplankton with instruments that measure the light reflected from the ocean. Because different species of phytoplankton absorb different wavelengths of light, the measurements will allow scientists to get a picture of the mix.
The two research vessels – a smaller one that ventures out during the day and returns to port at night, and a larger one that will go out for the entire time – will be equipped with dozens of instruments to measure the ocean and atmosphere. In addition to the optical measurements, researchers will gather data on the water salinity, temperatures, particulate matter and pollutant concentration, dissolved gasses and more. They’ll dip devices into the ocean to take samples, and classify which phytoplankton are where. Some ship instruments will also look upward – to measure aerosols and trace gases in the atmosphere.
The field work is a sister campaign to the KORUS-AQ effort focusing on air quality, and will also include flights of NASA’s B-200 aircraft over some of the same routes as the ships. The plane will carry two Goddard instruments developed by Ball Aerosopace to look down at the ocean color and atmosphere, called the Geostationary Trace gas and Aerosol Sensor Optimization (Geo-TASO) and the Multi-slit Optimized Spectrometer (MOS). These add an intermediary set of measurements between the ships and the satellite.
As the tides, currents, upwelling and winds move coastal waters around, the researchers will use this range of tools to monitor changes in the phytoplankton and ocean chemistry and biology. These changes can shed light on connections between ocean properties and harmful algal blooms, oil spills, pollution, fisheries and more.
NASA is developing future ocean color-monitoring satellites, and the KORUS-OC mission is designed to provide information about what kind of capabilities those satellites should have, Mannino said. The campaign could also lead to information about what instrument wavelengths, timing and sensitivities are best for other ocean color satellites as well.
"We know there’s going to be variability through the day, because of the tides, the dynamics of surface currents, the activity of the living organisms within the ocean," Mannino said. "The question is, what sensitivity do the satellite sensors need to be, in order to detect it?"
The agreement between NASA and the Korean ocean science agency goes beyond the May 20 through June 6, 2016, field campaign. The two countries have signed a memorandum of understanding, which provides KIOST’s approval for NASA’s Ocean Biology Processing Group at Goddard to process data from the GOCI satellite instrument into ocean color products. Goddard’s Ocean Biology Distributed Active Archive Center will provide the raw and processed data products, for free, to researchers worldwide.
NASA Mini-Balloon Mission Maps Migratory Magnetic Boundary
During the Antarctic summer of 2013-2014, a team of researchers released a series of translucent scientific balloons, one by one. The miniature membranous balloons – part of the Balloon Array for Radiation-belt Relativistic Electron Losses, or BARREL, campaign – floated above the icy terrain for several weeks each, diligently documenting the rain of electrons falling into the atmosphere from Earth’s magnetic field.
Then in January 2014, BARREL's observations saw something never seen before. During a fairly common space event called a solar storm – when a cloud of strongly magnetic solar material collides with Earth's magnetic field – BARREL mapped for the first time how the storm caused Earth’s magnetic field to shift and move. The fields’ configuration shifted much faster than expected: on the order of minutes. These results were published in the Journal of Geophysical Research on May 12, 2016. Understanding how our near-Earth space environment changes in response to solar storms helps us protect our technology in space.
During this solar storm, three BARREL balloons were flying through parts of Earth’s magnetic field that directly connect a region of Antarctica to Earth’s north magnetic pole – these parts of the magnetic field are called closed field lines, because both ends are rooted on Earth. One BARREL balloon was on a field line with one end on Earth and one end connected to the sun’s magnetic field, an open field line. And two balloons switched back and forth between closed and open field lines throughout the solar storm, providing a map of how the boundary between open and closed field lines moved as a result of the storm.
“It’s very difficult to model that open-closed boundary,” said Alexa Halford, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This will help with our simulations of how magnetic fields change around Earth, because we’re able to state exactly where we saw this boundary.”
We live in the extended atmosphere of a magnetically active star – which, in part, means that we’re constantly in the path of the sun’s outflow of charged particles, called the solar wind.
Most of the solar wind particles are fairly slow, but even the fastest particles – accelerated to high speeds by explosions on the sun or pushed along by clouds of solar material – are deflected away from Earth’s surface by our planet’s magnetic field. Most of Earth’s magnetic field has a foot point in a region near Antarctica, called the south magnetic pole. Much of this magnetic field loops up out into space, but then connects back to Earth at the north magnetic pole, near the Arctic Circle. This looped part of the magnetic field – the closed magnetic field – creates a barrier against charged particles, repelling them from reaching Earth.
But a smaller portion of Earth’s magnetic field is open, connecting to the sun’s magnetic field, instead of curving back toward Earth. It’s this open magnetic field that gives charged particles from the sun a path into Earth’s atmosphere. Once particles are stuck to an open field line, they can rocket down into the upper atmosphere to collide with neutral atoms, creating a type of aurora.
The boundary between these open and closed regions of Earth’s magnetic field is anything but constant. Due to various causes – such as incoming clouds of solar material – the closed magnetic field lines can realign into open field lines and vice versa, changing the location of the boundary between open and closed magnetic field lines.
Scientists have known that the open-closed boundary moves, but it’s hard to pinpoint exactly how, when, and how quickly it changes – and that’s where BARREL comes in. The six BARREL balloons flying during the January 2014 solar storm were able to map these changes, and they found something surprising – the open-closed boundary moves relatively quickly, changing location within minutes.
BARREL was designed to study how electrons from Earth’s radiation belts – vast swaths of particles trapped in Earth’s magnetic field hundreds of miles above the surface – can make their way down into the atmosphere. The BARREL campaign is primarily tasked with supplementing observations by NASA’s Van Allen Probes, which are dedicated to studying these radiation belts. However, solar energetic electrons happen to be in the same energy range as those radiation belt electrons, meaning that BARREL can see both.
“The scientists used balloon observations of solar particles entering Earth’s magnetic field to locate the outer boundary of Earth’s magnetic field, many tens of thousands of miles away,” said David Sibeck, a space scientist at Goddard and mission scientist at NASA for the Van Allen Probes. “This isn’t what BARREL was intended for, but it’s a wonderful bonus science return.”
The Antarctic is dotted with ground-based systems that, like BARREL, can measure the influx of radiation belt electrons. But because of their design, these detectors are overwhelmed by solar protons – which generally far outnumber solar electrons during solar particle events – meaning they’re unable to differentiate between the particles that come from the sun versus those that come from the radiation belts. On the other hand, BARREL is finely tuned to see electrons, meaning that the accompanying barrage of solar protons doesn’t drown out the electrons in BARREL’s detectors.
“Protons create signatures in a very small energy range, while electron signatures show up in a wide range of energies,” said Halford. “But the electron energies are usually well below the proton energy, so we can tell them apart.”
It is possible – but unlikely – that complex dynamics in the magnetosphere gave the appearance that the BARREL balloons were dancing along this open-closed boundary. If a very fast magnetic wave was sending radiation belt electrons down into the atmosphere in short, stuttering bursts, it could appear that the balloons were switching between open and closed magnetic field lines.
However, the particle counts measured by the two balloons on the open-closed boundary matched up to those observed by the other BARREL balloons – hovering on closed or open field lines only – strengthening the case that BARREL’s balloons were actually crossing the boundary between solar and terrestrial magnetic field.
New Hubble Portrait of Mars
Bright, frosty polar caps, and clouds above a vivid, rust-colored landscape reveal Mars as a dynamic seasonal planet in this NASA Hubble Space Telescope view taken on May 12, 2016, when Mars was 50 million miles from Earth. The Hubble image reveals details as small as 20 to 30 miles across.
The large, dark region at far right is Syrtis Major Planitia, one of the first features identified on the surface of the planet by seventeenth-century observers. Christiaan Huygens used this feature to measure the rotation rate of Mars. (A Martian day is about 24 hours and 37 minutes.) Today we know that Syrtis Major is an ancient, inactive shield volcano. Late-afternoon clouds surround its summit in this view.
A large oval feature to the south of Syrtis Major is the bright Hellas Planitia basin. About 1,100 miles across and nearly five miles deep, it was formed about 3.5 billion years ago by an asteroid impact.
The orange area in the center of the image is Arabia Terra, a vast upland region in northern Mars that covers about 2,800 miles. The landscape is densely cratered and heavily eroded, indicating that it could be among the oldest terrains on the planet. Dried river canyons (too small to be seen here) wind through the region and empty into the large northern lowlands.
South of Arabia Terra, running east to west along the equator, are the long dark features known as Sinus Sabaeus (to the east) and Sinus Meridiani (to the west). These darker regions are covered by dark bedrock and fine-grained sand deposits ground down from ancient lava flows and other volcanic features. These sand grains are coarser and less reflective than the fine dust that gives the brighter regions of Mars their ruddy appearance. Early Mars watchers first mapped these regions.
An extended blanket of clouds can be seen over the southern polar cap. The icy northern polar cap has receded to a comparatively small size because it is now late summer in the northern hemisphere. Hubble photographed a wispy afternoon lateral cloud extending for at least 1,000 miles at mid-northern latitudes. Early morning clouds and haze extend along the western limb.
This hemisphere of Mars contains landing sites for several NASA Mars surface robotic missions, including Viking 1 (1976), Mars Pathfinder (1997), and the still-operating Opportunity Mars rover. The landing sites of the Spirit and Curiosity Mars rovers are on the other side of the planet.
This observation was made just a few days before Mars opposition on May 22, when the sun and Mars will be on exact opposite sides of Earth, and when Mars will be at a distance of 47.4 million miles from Earth. On May 30, Mars will be the closest it has been to Earth in 11 years, at a distance of 46.8 million miles. Mars is especially photogenic during opposition because it can be seen fully illuminated by the sun as viewed from Earth.
The biennial close approaches between Mars and Earth are not all the same. Mars' orbit around the sun is markedly elliptical; the close approaches to Earth can range from 35 million to 63 million miles.
They occur because about every two years Earth's orbit catches up to Mars' orbit, aligning the sun, Earth, and Mars in a straight line, so that Mars and the sun are on "opposing" sides of Earth. This phenomenon is a result of the difference in orbital periods between Earth's orbit and Mars' orbit. While Earth takes the familiar 365 days to travel once around the sun, Mars takes 687 Earth days to make its trip around our star. As a result, Earth makes almost two full orbits in the time it takes Mars to make just one, resulting in the occurrence of Martian oppositions about every 26 months.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.
NASA’s Van Allen Probes Reveal Long-term Behavior of Earth’s Ring Current
New findings based on a year's worth of observations from NASA’s Van Allen Probes have revealed that the ring current – an electrical current carried by energetic ions that encircles our planet – behaves in a much different way than previously understood.
The ring current has long been thought to wax and wane over time, but the new observations show that this is true of only some of the particles, while other particles are present consistently. Using data gathered by the Radiation Belt Storm Probes Ion Composition Experiment, or RBSPICE, on one of the Van Allen Probes, researchers have determined that the high-energy protons in the ring current change in a completely different way from the current’s low-energy protons. Such information can help adjust our understanding and models of the ring current – which is a key part of the space environment around Earth that can affect our satellites.
“We study the ring current because, for one thing, it drives a global system of electrical currents both in space and on Earth’s surface, which during intense geomagnetic storms can cause severe damages to our technological systems," said lead author of the study Matina Gkioulidou, a space physicist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “It also modifies the magnetic field in near-Earth space, which in turn controls the motion of the radiation belt particles that surround our planet. That means that understanding the dynamics of the ring current really matters in helping us understand how radiation belts evolve as well.”
The ring current lies at a distance of approximately 6,200 to 37,000 miles (10,000 to 60,000 km) from Earth. The ring current was hypothesized in the early 20th century to explain observed global decreases in the Earth’s surface magnetic field, which can be measured by ground magnetometers. Such changes of the ground magnetic field are described by what's called the Sym-H index.
“Previously, the state of the ring current had been inferred from the variations of the Sym-H index, but as it turns out, those variations represent the dynamics of only the low-energy protons,” said Gkioulidou. “When we looked at the high-energy proton data from the RBSPICE instrument, however, we saw that they were behaving in a very different way, and the two populations told very different stories about the ring current.”
The Van Allen Probes, launched in 2012, offer scientists the first chance in recent history to continuously monitor the ring current with instruments that can observe ions with an extremely wide range of energies. The RBSPICE instrument has captured detailed data of all types of these energetic ions for several years. “We needed to have an instrument that measures the broad energy range of the particles that carry the ring current, within the ring current itself, for a long period of time,” Gkioulidou said. A period of one year from one of the probes was used for the team’s research.
“After looking at one year of continuous ion data it became clear to us that there is a substantial, persistent ring current around the Earth even during non-storm times, which is carried by high-energy protons. During geomagnetic storms, the enhancement of the ring current is due to new, low-energy protons entering the near-Earth region. So trying to predict the storm-time ring current enhancement while ignoring the substantial pre-existing current is like trying to describe an elephant after seeing only its feet,” Gkioulidou said.
The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, built and operates the Van Allen Probes for NASA's Science Mission Directorate. RBSPICE is operated by the New Jersey Institute of Technology in Newark, New Jersey. The mission is the second mission in NASA's Living With a Star program, managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland.
