mercredi 30 décembre 2015

Hubble Views Two Galaxies Merging

NASA - Hubble Space Telescope patch.

Dec. 30, 2015

This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the galaxy NGC 6052, located around 230 million light-years away in the constellation of Hercules.

It would be reasonable to think of this as a single abnormal galaxy, and it was originally classified as such. However, it is in fact a “new” galaxy in the process of forming. Two separate galaxies have been gradually drawn together, attracted by gravity, and have collided. We now see them merging into a single structure.

As the merging process continues, individual stars are thrown out of their original orbits and placed onto entirely new paths, some very distant from the region of the collision itself. Since the stars produce the light we see, the “galaxy” now appears to have a highly chaotic shape. Eventually, this new galaxy will settle down into a stable shape, which may not resemble either of the two original galaxies.

Related link:

Wide Field Planetary Camera 2:

For images and more information, visit:

Image Credits: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt/Text Credits: European Space Agency/Ashley Morrow.

Season' Greetings,

mardi 29 décembre 2015

NASA Looks at Deadly Weather Over the U.S.

NASA / JAXA - GPM Mission logo.

Dec. 29, 2015

NASA's Global Precipitation Measurement or GPM mission core satellite analyzed extreme weather that affected the U.S. over the course of five days. Heavy rainfall, flooding and tornado outbreaks affected areas of the United States from the Southwest through the Midwest from December 23 to 27, 2015.

NASA Looks at Deadly Weather Over the U.S.

Video above: This animated NASA rainfall analysis from Dec. 23 to 27, 2015, showed highest rainfall totals of almost 938 mm (36.8 inches) were measured by IMERG in the state of Alabama. Video Credits: NASA/JAXA/SSAI, Hal Pierce.

GPM is an international satellite mission between NASA and the Japan Aerospace Exploration Agency to provide next-generation observations of rain and snow worldwide every three hours.

An analysis was made of the rainfall that occurred during the period from December 21 to 28, 2015. This analysis used data generated by NASA's Integrated Multi-satellitE Retrievals for GPM (IMERG). This analysis showed that during the past week the highest rainfall totals of almost 938 mm (36.8 inches) were measured by IMERG in the state of Alabama.

Image above: A NASA rainfall analysis from Dec. 23 to 27 showed highest rainfall totals of almost 938 mm (36.8 inches) were measured by IMERG in the state of Alabama. Image Credits: NASA/JAXA/SSAI, Hal Pierce.

The GPM satellite passed above a line of tornadic thunderstorms moving through the Midwest on December 23, 2015 at 2232 UTC (5:32 p.m. EST). GPM's Microwave Imager (GMI) and Dual-Frequency Precipitation Radar (DPR) instruments had an excellent view of the violent weather occurring near the center of the satellite's swath.  The supercell thunderstorm that moved from northern Mississippi into Tennessee generated two tornadoes. Fourteen deaths alone occurred with tornadoes that hit Benton, Mississippi on December 23, 2015.

GPM's Radar (DPR Ku band) revealed the intensity of thunderstorms within this line of powerful storms. Many of those thunderstorms contained heavy showers that were returning 45 dBZ values or greater to the satellite (dBZ values (decibels of Z) represent the energy reflected back to the GPM satellite). At NASA's Goddard Space Flight Center in Greenbelt, Md. the data was used to create a color enhanced 3-D view of the GPM radar's slice through the line of storms.

The low pressure area that brought the severe weather moved into the Great Lakes region on Dec. 29 bringing rain and snow from the Middle/Upper Mississippi.

Valleys across the Great Lakes and into New England.

Image above: GPM data was used to create this color enhanced 3-D slice through a line of storms on Dec. 23 that spawned tornadoes in Mississippi. Image Credits: NASA/JAXA/SSAI, Hal Pierce.

The National Weather Service Weather Prediction Center (NWS/WPC) in College Park Md. stated in the Dec. 29 Short Range Forecast Discussion that residual flooding and/or the threat for flooding will persist from Oklahoma to Illinois. NWS/WPC noted that several rivers across the Midwest were out of their banks on Dec. 29. Several locations along the Mississippi River from St. Louis down to the delta are anticipating major flooding, possibly even breaking record flood levels. For updated forecast summaries from NWS/WPC, visit:

For more information about GPM, visit:

Images (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Hal Pierce/Rob Gutro/Karl Hille.


Long March 3B launches Gaofen-4 satellite, ends 2015 launches year

CASC - China Aerospace Science and Technology Corporation logo.

December 28, 2015

Chinese Long March 3B Rocket Successfully Launches Gaofen-4

A Chinese Long March 3B Rocket blasted off from the Xichang Satellite Launch Center on Monday December 28, lifting the Gaofen-4 satellite into orbit to have a watchful eye on Planet Earth, becoming China’s first remote sensing satellite operated from Geosynchronous Orbit.

The launch involved the orbiting of a geostationary remote sensing bird, known as Gaofen-4 (GF-4). It was launched from the Xichang Satellite Launch Center at 16:05 UTC.

China Launches High Definition Earth Observation Satellite

Gaofen-4 is China’s first geosynchronous orbit remote sensing satellite featuring a visible light and infra-red staring optical imager with a common optical system.

The optical resolution is better than 50 meters, while the infrared resolution is better than 400 meters. GF-4 can provide an imaging area of 7,000 km × 7,000 km with individual scene covering an area of 400 km × 400 km, and with capacity for high temporal resolution remote sensing monitor at minute-level. Launch mass is 4,600 kg. Gaofen-4 will be operational for 8 years.

Gaofen 4 satellite

Gaofen 4 was positioned in geostationary orbit with optical and infrared staring imagers for continuous observations of China and surrounding regions, such as disaster monitoring, meteorological observation agriculture, national security, etc.

Monday’s mission was the 222th flight of the Long March rocket series and the 34th liftoff overall for the 3B version. It’s also the 9th launch from Xichang this year.

For more information about China Aerospace Science and Technology Corporation (CASC), visit:

Images, Video, Text, Credits: CASC/CCTV+/Günter Space Page/ Aerospace.


lundi 28 décembre 2015

Wisps Under the Rings

NASA - Cassini Mission to Saturn patch.

Dec. 28, 2015

Dione's beautiful wispy terrain is brightly lit alongside Saturn's elegant rings.

The "wisps" are relatively young fractures on the trailing hemisphere of Dione's (698 miles or 1123 kilometers across) icy surface. See PIA06162 and PIA06163 for higher resolution views of Dione's wispy terrain.

This view looks toward the anti-Saturn side of Dione. North on Dione is up. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 15, 2015.

The view was obtained at a distance of approximately 1.1 million miles (1.7 million kilometers) from Dione. Image scale is 7 miles (11 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

Related links:

PIA06162: Dione's Surprise:

PIA06163: Highest Resolution View of Dione:

For more information about the Cassini-Huygens mission visit or . The Cassini imaging team homepage is at and ESA's website:

Image, Text, Credits: NASA/JPL-Caltech/Space Science Institute/Tony Greicius.

Season' Greetings,

Boulders on a Martian Landslide

NASA - Mars Reconnaissance Orbiter (MRO) patch.

Dec. 28, 2015

The striking feature in this image, acquired by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter on March 19, 2014, is a boulder-covered landslide along a canyon wall. Landslides occur when steep slopes fail, sending a mass of soil and rock to flow downhill, leaving behind a scarp at the top of the slope. The mass of material comes to rest when it reaches shallower slopes, forming a lobe of material that ends in a well-defined edge called a toe.

This landslide is relatively fresh, as many individual boulders still stand out above the main deposit. Additionally, while several small impact craters are visible in the landslide lobe, they are smaller in size and fewer in number than those on the surrounding valley floor. The scarp itself also looks fresh compared to the rest of the cliff: it, too, has boulders, and more varied topography than the adjacent dusty terrain.

Just to the north of the landslide scarp is a similarly-shaped scar on the cliffside. However, there is no landslide material on the valley floor below it. The older landslide deposit has either been removed or buried, a further indicator of the relative youth of the bouldery landslide.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project and Mars Science Laboratory Project for NASA's Science Mission Directorate, Washington.

More information and image products:

For more information about Mars Reconnaissance Orbiter (MRO), visit:

Image, Text, Credits: NASA/JPL/University of Arizona/Caption: HiRISE Targeting Specialists/Sarah Loff.


Europe’s first decade of navigation satellites

ESA - Galileo Programme logo.

28 December 2015

Ten years ago today saw the launch of Europe’s very first navigation satellite. A decade of hard work later, more than a third of the Galileo constellation has followed it into orbit and a ground network sharpening the satnav system’s accuracy encompasses the globe.

GIOVE-A, short for Galileo In-Orbit Validation Element-A, was launched by Soyuz from Baikonur cosmodrome in Kazakhstan on 28 December 2005.


“Much work had already taken place on the ground, but GIOVE-A marked the first time that Galileo hardware went into orbit,” recalls Didier Faivre, heading ESA’s navigation directorate.

“It had a crucial role: to claim operating frequencies that had been set aside for Galileo by the International Telecommunications Union, to demonstrate essential technologies such as Galileo’s rubidium atomic clock, and to gather data on the radiation-rich environment of medium-altitude orbit, which was a relatively unknown region for Europe.

“So GIOVE-A opened the way to all that followed – the follow-up GIOVE-B in 2008, and then the launches of the Galileo satellites proper – a total of six double-satellite launches from 2011 to earlier this month, with 12 satellites placed in orbit so far, on the way to the full 30-satellite constellation.

Didier Faivre

“Our three launches this year doubled the number of satellites in orbit, and the pace of progress is set to increase further in 2016, when we will see Ariane 5 called on to launch Galileo for the first time, doubling the number of satellites released on each flight.”

Progress in space has been mirrored on Earth, with the establishment of Galileo’s ground segment: two control centres in Fucino, Italy, and Oberpfaffenhofen, Germany, sit at the heart of a worldwide network of ground stations.

This ground segment, as one of the most complex infrastructures ever overseen by ESA, has the task of keeping all the satellites healthy and their navigation signals synched – the timing system accurate to a few billionths of a second that provides the submetre precision.

GIOVE-A liftoff

Sensor stations to monitor Galileo signals and return data to the control centres are required all across the vast footprint of the system. Their locations range from the Arctic to Antarctic to lonely mid-ocean islands, all connected back to Europe via satellite.

Initial Galileo services are set to be available during next year. New generations of commercial satnav receivers are already ‘Galileo-ready’, having received extensive technical checks from ESA’s Navigation Laboratory.

And national governments are already preparing to make use of Galileo’s Public Regulated Service – PRS, the most secure and precise class of service, restricted to authorised users. Belgium, France, Italy and the UK have all performed their own PRS acquisitions and positioning testing.

GIOVE-A on ground

As for GIOVE-A, the satellite that started it all, its ESA mission concluded in 2012, once the first four Galileo satellites followed it to orbit. Remarkably, it is still operational, controlled by builder Surrey Satellite Technology Ltd in the UK.

In the past it has carried out tests of high-altitude satnav detection. Its radiation monitor continues monitoring the medium-altitude orbit environment, helping to forecast the future long-term performance of its Galileo descendants.

Related links:

Tests of high-altitude satnav detection:

Launching Galileo website:

Galileo Tour:

EC Galileo website:

European GNSS Agency:

Far-out space navigation from sideways satnav signals:

Surrey Satellite Technology Limited:

Galileo: the future becomes reality - brochure (PDF):

Images, Text, Credits: ESA/J. Mai/Surrey Satellite Technology Ltd.

Season's Greetings,