NASA News: NASA Cold Weather Airborne Campaign to Measure Falling Snow


WASHINGTON - Beginning Jan. 17, NASA will fly an airborne science
laboratory above Canadian snowstorms to tackle a difficult challenge
facing the upcoming Global Precipitation Measurement (GPM) satellite
mission -- measuring snowfall from space.

GPM is an international satellite mission that will set a new standard
for precipitation measurements from space, providing next-generation
observations of worldwide rain and snow every three hours. It is also
the first mission designed to detect falling snow from space.

"Snow is notoriously hard to measure as it falls," said Walter
Petersen, the GPM ground validation scientist at NASA's Wallops
Flight Facility in Virginia. "Snowflakes contain varying amounts of
air and water, and they flutter, wobble and drift as they leave the clouds."

Knowing how "wet" a snowflake is allows scientists to measure overall
water content. A wet, heavy snow can shut down a city, and melted
snow is a crucial source of freshwater in many areas.

Working with Environment Canada, NASA's GPM Cold-season Precipitation
Experiment (GCPEx) will measure light rain and snow in Ontario from
Jan. 17 to Feb. 29. The field campaign is designed to improve
satellite estimates of falling snow and test ground validation
capabilities in advance of the planned launch of the GPM Core
satellite in 2014.

NASA's DC-8 airborne science laboratory will fly out of Bangor, Maine,
carrying radar and a radiometer that will simulate the measurements
to be taken from space by GPM. At an altitude of 33,000 feet (10
kilometers), the DC-8 will make multiple passes over an extensive
ground network of snow gauges and sensors at Environment Canada's
Center for Atmospheric Research Experiments north of Toronto.

The GCPEx field experiment will help scientists match measurements of
snow in the air and on the ground with the satellite's measurements.

"We will be looking at the precipitation and the physics of
precipitation, such as snowflake types, sizes, shapes, numbers and
water content," Petersen said. "These properties affect both how we
interpret and improve our measurements."

GPM's Core satellite is being built at NASA's Goddard Space Flight
Center in Greenbelt, Md., with instruments provided by NASA and its
mission partner, the Japanese Aerospace and Exploration Agency
(JAXA). The spacecraft will orbit Earth at a 65-degree inclination,
covering the world from the Antarctic Circle to the Arctic Circle.

GPM will carry a microwave radiometer and a dual-frequency
precipitation radar that distinguishes a snowflake's size and shape,
which affects how much water it holds. Knowing these microphysical
properties will lead to more accurate estimates of rain and snowfall,
especially during winter and at high latitudes where snow is the
dominant form of precipitation.

The Ontario region is prone to both lake effect snow squalls and
widespread snowstorms. If the opportunity exists, the DC-8 also will
fly over blizzards along the northeastern United States. While the
DC-8 flies above the clouds, two other aircraft, one from the
University of North Dakota and another from Canada, will fly through
the clouds, measuring the microphysical properties of the raindrops
and snowflakes inside.

Advanced ground radars will scan the entire air column from the clouds
to the Earth's surface.

"These multiple measurements of snowfall provide a complete picture, a
complete model, of the snowfall process from top to bottom," Petersen said.

NASA's Dryden Flight Research Center in Edwards, Calif., manages the
DC-8 flights for the GCPEx mission. The aircraft is based at the
center's aircraft operations facility in Palmdale, Calif. NASA's
Marshall Space Flight Center in Huntsville, Ala., is providing
aircraft tracking and guidance through the Real Time Mission Monitor,
as well as GCPEx real-time data and personnel support for the ground
instruments in Canada.

For more information on the GCPEx ground validation, visit:



NASA's Kepler Mission Finds Three Smallest Exoplanets

WASHINGTON -- Astronomers using data from NASA's Kepler mission have
discovered the three smallest planets yet detected orbiting a star
beyond our sun. The planets orbit a single star, called KOI-961, and
are 0.78, 0.73 and 0.57 times the radius of Earth. The smallest is
about the size of Mars.

All three planets are thought to be rocky like Earth, but orbit close
to their star. That makes them too hot to be in the habitable zone,
which is the region where liquid water could exist. Of the more than
700 planets confirmed to orbit other stars -- called exoplanets --
only a handful are known to be rocky.

"Astronomers are just beginning to confirm thousands of planet
candidates uncovered by Kepler so far," said Doug Hudgins, Kepler
program scientist at NASA Headquarters in Washington. "Finding one as
small as Mars is amazing, and hints that there may be a bounty of
rocky planets all around us."

Kepler searches for planets by continuously monitoring more than
150,000 stars, looking for telltale dips in their brightness caused
by crossing, or transiting, planets. At least three transits are
required to verify a signal as a planet. Follow-up observations from
ground-based telescopes also are needed to confirm the discoveries.

The latest discovery comes from a team led by astronomers at the
California Institute of Technology in Pasadena. The team used data
publicly released by the Kepler mission, along with follow-up
observations from the Palomar Observatory, near San Diego, and the
W.M. Keck Observatory atop Mauna Kea in Hawaii. Their measurements
dramatically revised the sizes of the planets from what originally
was estimated.

The three planets are very close to their star, taking less than two
days to orbit around it. The KOI-961 star is a red dwarf with a
diameter one-sixth that of our sun, making it just 70 percent bigger
than Jupiter.

"This is the tiniest solar system found so far," said John Johnson,
the principal investigator of the research from NASA's Exoplanet
Science Institute at the California Institute of Technology in
Pasadena. "It's actually more similar to Jupiter and its moons in
scale than any other planetary system. The discovery is further proof
of the diversity of planetary systems in our galaxy."

Red dwarfs are the most common kind of star in our Milky Way galaxy.
The discovery of three rocky planets around one red dwarf suggests
that the galaxy could be teeming with similar rocky planets.

"These types of systems could be ubiquitous in the universe," said
Phil Muirhead, lead author of the new study from Caltech. "This is a
really exciting time for planet hunters."

The discovery follows a string of recent milestones for the Kepler
mission. In December 2011, scientists announced the mission's first
confirmed planet in the habitable zone of a sun-like star: a planet
2.4 times the size of Earth called Kepler-22b. Later in the month,
the team announced the discovery of the first Earth-size planets
orbiting a sun-like star outside our solar system, called Kepler-20e
and Kepler-20f.

For the latest discovery, the team obtained the sizes of the three
planets called KOI-961.01, KOI-961.02 and KOI-961.03 with the help of
a well-studied twin star to KOI-961, or Barnard's Star. By better
understanding the KOI-961 star, they then could determine how big the
planets must be to have caused the observed dips in starlight. In
addition to the Kepler observations and ground-based telescope
measurements, the team used modeling techniques to confirm the planet

Prior to these confirmed planets, only six other planets had been
confirmed using the Kepler public data.

NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's
ground system development, mission operations and science data
analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., managed
the Kepler mission's development.

For information about the Kepler Mission, visit:



Hubble Solves Mystery On Source Of Supernova In Nearby Galaxy

WASHINGTON -- Using NASA's Hubble Space Telescope, astronomers have
solved a longstanding mystery on the type of star, or so-called
progenitor, which caused a supernova seen in a nearby galaxy. The
finding yields new observational data for pinpointing one of several
scenarios that trigger such outbursts.

Based on previous observations from ground-based telescopes,
astronomers knew the supernova class, called a Type Ia, created a
remnant named SNR 0509-67.5, which lies 170,000 light-years away in
the Large Magellanic Cloud galaxy.

Theoretically, this kind of supernova explosion is caused by a star
spilling material onto a white dwarf companion, the compact remnant
of a normal star, until it sets off one of the most powerful
explosions in the universe.

Astronomers failed to find any remnant of the companion star, however,
and concluded that the common scenario did not apply in this case,
although it is still a viable theory for other Type Ia supernovae.

"We know Hubble has the sensitivity necessary to detect the faintest
white dwarf remnants that could have caused such explosions," said
lead investigator Bradley Schaefer of Louisiana State University
(LSU) in Baton Rouge. "The logic here is the same as the famous quote
from Sherlock Holmes: 'when you have eliminated the impossible,
whatever remains, however improbable, must be the truth.'"

The cause of SNR 0509-67.5 can be explained best by two tightly
orbiting white dwarf stars spiraling closer and closer until they
collided and exploded.

For four decades, the search for Type Ia supernovae progenitors has
been a key question in astrophysics. The problem has taken on special
importance during the last decade with Type Ia supernovae being the
premier tools for measuring the accelerating universe.

Type Ia supernovae release tremendous energy, in which the light
produced is often brighter than an entire galaxy of stars. The
problem has been to identify the type of star system that pushes the
white dwarf's mass over the edge and triggers this type of explosion.
Many possibilities have been suggested, but most require that a
companion star near the exploding white dwarf be left behind after
the explosion.

Therefore, a possible way to distinguish between the various
progenitor models has been to look deep in the center of an old
supernova remnant to search for the ex-companion star.

In 2010, Schaefer and Ashley Pagnotta of LSU were preparing a proposal
to look for any faint ex-companion stars in the center of four
supernova remnants in the Large Magellanic Cloud when they discovered
the Hubble Space Telescope already had taken the desired image of one
of their target remnants, SNR 0509-67.5, for the Hubble Heritage
program, which collects images of especially photogenic astronomical targets.

In analyzing the central region, they found it to be completely empty
of stars down to the limit of the faintest objects Hubble can detect
in the photos. Schaefer suggests the best explanation left is the
so-called "double degenerate model" in which two white dwarfs collide.

The results are being reported today at the meeting of the American
Astronomical Society in Austin, Texas. A paper on the results will be
published in the Jan. 12 issue of the journal Nature.

There are no recorded observations of the star exploding. However,
researchers at the Space Telescope Science Institute in Baltimore,
Md. have identified light from the supernova that was reflected off
of interstellar dust, delaying its arrival at Earth by 400 years.
This delay, called a light echo of the supernova explosion also
allowed the astronomers to measure the spectral signature of the
light from the explosion. By virtue of the color signature,
astronomers were able to deduce it was a Type Ia supernova.

Because the remnant appears as a nice symmetric shell or bubble, the
geometric center can be determined accurately. These properties make
SNR 0509-67.5 an ideal target to search for ex-companions. The young
age also means that any surviving stars have not moved far from the
site of the explosion.

The team plans to look at other supernova remnants in the Large
Magellenic Cloud to further test their observations.

The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. NASA's Goddard Space
Flight Center manages the telescope. The Space Telescope Science
Institute (STScI) conducts Hubble science operations. STScI is
operated for NASA by the Association of Universities for Research in
Astronomy, Inc., in Washington, D.C.

For more information about Hubble, visit:



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