vendredi 22 juin 2018

Crew Researching Microbes and Plants For Space and Earth Benefits












ISS - Expedition 56 Mission patch.

June 22, 2018

The Expedition 56 crew members researched microbes and plants today and conducted more eye exams to benefit future space residents as well as people on Earth. The Cygnus space freighter continues to be packed for its release in July as robotics controllers get ready to inspect the vehicle.


Image above: Flying over Brazil, seen by EarthCam on ISS, speed: 27'616 Km/h, altitude: 403,22 Km, image captured by Roland Berga (on Earth in Switzerland) from International Space Station (ISS) using ISS-HD Live application with EarthCam's from ISS on June 22, 2018 at 21:21 UTC. Image Credits: Orbiter.ch Aerospace/Roland Berga.

NASA astronaut Serena Auñón-Chancellor stowed genetically modified microbes in a science freezer that will be analyzed for their ability to compete with petrochemical production processes on Earth. Flight Engineer Ricky Arnold, also from NASA, thinned plants for the Plant Habitat-1 experiment that is comparing plants grown in microgravity to those grown on Earth.


Image above: Astronaut Alexander Gerst is seated in the Columbus laboratory module participating in the Grip study. Grip is researching how the nervous system adapts to microgravity. Observations may improve the design of safer space habitats and help patients on Earth with neurological diseases. Image Credit: NASA.

Arnold and Auñón-Chancellor later joined Commander Drew Feustel for more eye checks. The trio used optical coherence tomography to capture 2D and 3D imagery of the eye to help doctors understand how living in space affects eyesight.

European Space Agency astronaut Alexander Gerst was packing Cygnus with trash and old gear today ahead of its July 15 release.

Related links:

Plant Habitat-1: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=2032

Grip study: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1188

Expedition 56: https://www.nasa.gov/mission_pages/station/expeditions/expedition56/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Text, Credits: NASA/Mark Garcia/Orbiter.ch Aerospace/Roland Berga.

Best regards, Orbiter.ch

Charon at 40: Four Decades of Discovery on Pluto’s Largest Moon












NASA - New Horizons Mission logo.

June 22, 2018

Charon at 40: The Discovery of Pluto’s Largest Moon

Video above: The largest of Pluto's five moons, Charon, was discovered on June 22, 1978, by James Christy and Robert Harrington at the U.S. Naval Observatory in Flagstaff, Arizona – only about six miles from where Pluto itself was discovered at Lowell Observatory. They weren't even looking for satellites of Pluto – Christy, examining a series of grainy telescope images, trying to refine Pluto's orbit around the Sun. Christy and others tell the story of this amazing scientific find, which fueled Pluto’s transformation from a telescopic dot into an actual planetary system – and a source of many discoveries to come. Video Credit: NASA.

The largest of Pluto's five moons, Charon, was discovered 40 years ago today by James Christy and Robert Harrington at the U.S. Naval Observatory in Flagstaff, Arizona – only about six miles from where Pluto itself was discovered at Lowell Observatory. They weren't even looking for satellites of Pluto – Christy was trying to refine Pluto's orbit around the Sun.

Before NASA’s New Horizons spacecraft flew through the Pluto system in July 2015, many New Horizons scientists expected Charon to be a monotonous, crater-battered world. Instead, they found a landscape covered with giant mountains, vast canyons, a strange polar cap, surface-color variations and landslides.

“Even if Pluto wasn’t there, Charon would have been a great flyby target by itself,” said Will Grundy, a New Horizons science team co-investigator from Lowell Observatory in Flagstaff, Arizona. “It’s a far more exciting world than we imagined.”

It would have taken serious imagination to see much of anything in the grainy telescope plates of Pluto that U.S. Naval Observatory astronomer James Christy was checking 40 years ago to refine Pluto’s orbit. But on June 22, 1978, Christy did notice something – a small bump on one side of Pluto.


Image above: What a difference 40 years makes. An enhanced color image of Charon from data gathered by the New Horizons spacecraft in 2015 shows a range of diverse surface features, significantly transforming our view of a moon discovered in 1978 as a “bump” on Pluto (inset) in a set of grainy telescope images. Image Credits: U.S. Naval Observatory; NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

As he looked at other images he saw the bump again and again, only this time moving from one side of Pluto to another. Further examination showed the bump seemed to move around Pluto, cycling back and forth over Pluto's own rotation period – 6.39 days. He figured either Pluto possessed a mountain thousands of miles high, or it had a satellite in a synchronous orbit. In the 48 years that had passed since Clyde Tombaugh discovered Pluto at Lowell Observatory in 1930, no evidence of any moon of Pluto had ever been spotted.

The Naval Observatory detailed the next steps to confirm the possible moon in a 1998 story about the 20th anniversary of the discovery: Christy scoured the observatory's image archives and found more cases where Pluto appeared strangely elongated. He measured the angle (from north) where the elongations appeared, while his colleague Robert Harrington calculated what the answer "should be" if the elongation was caused by an orbiting satellite.

Their calculations matched. But to be sure, they waited for the Naval Observatory's 61-inch telescope to make one more confirmation. And on July 2, 1978, new images showed the elongation due to a satellite right where it was supposed to be. They announced their discovery to the world five days later.


Image above: Forty years after his important discovery, Jim Christy holds two of the telescope images he used to spot Pluto’s large moon Charon in June 1978. A close-up photo of Charon, taken by the New Horizons spacecraft during its July 2015 flyby, is displayed on his computer screen. Image Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Art Howard/GHSPi.

An Important Discovery

The discovery of Charon fueled Pluto’s evolution from a telescopic dot into an actual planetary system – and a source of many discoveries yet to come.

About the size of Texas, Charon is the largest moon in the solar system relative to its parent planet. Together, Pluto and Charon were the first known double planet – or binary – two bodies that orbit a common center of gravity. Modeling also shows that Pluto-Charon formed by giant impact, very much like the Earth-Moon system.

Naming a Moon

Tradition allows a moon’s discoverer to suggest a name for the new satellite to the International Astronomical Union (IAU). Christy wanted to name it after his wife, Charlene, known as “Char” to friends and family. "I’m always thinking about physics, electrons and protons," Christy recalled. "I added an '-on' to it and said I could name it Charon."

While wondering whether the name Charon would be approved, Christy checked the dictionary and found “Charon” was actually a real term — the mythological ferryman who carried souls across the river Acheron, one of the five mythical rivers that surrounded Pluto's underworld. With that, he knew the name would be a perfect fit for a companion of Pluto and made that linkage known to the IAU, which approved the name Charon.

“A lot of husbands promise their wives the moon," Charlene Christy said, "but Jim actually delivered.”


Image above: Jim Christy points to the photographic plate on which he discovered Pluto’s largest moon, Charon, in 1978. Image Credits: U.S. Naval Observatory.

NASA Photo Feature:

Meet Pluto’s Moon Charon
https://solarsystem.nasa.gov/news/466/10-things-calling-all-pluto-lovers/

Charon’s size and proximity to Pluto helped the push to send a mission to Pluto and see, close up, something for the first time. “The importance of the discovery of Charon really cannot be underestimated,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute in Boulder, Colorado. “We on the New Horizons team owe a big debt of gratitude to Jim Christy for his landmark discovery.”

In passing just about 18,000 miles (29,000 kilometers) from Charon on July 14, 2015, New Horizons completely transformed our view of the moon. High-resolution images of Charon’s Pluto-facing hemisphere revealed a belt of fractures and canyons that stretches more than 1,000 miles (1,600 kilometers) across the entire face of Charon and, likely, onto the moon's far side. Four times as long as the Grand Canyon, and twice as deep in places, these faults and canyons indicate a titanic geological upheaval in Charon’s past.

What’s in the Names?

Learn about Charon’s Surface Features
http://pluto.jhuapl.edu/Multimedia/Science-Photos/image.php?page=1&gallery_id=2&image_id=536

An especially cool feature is Charon’s reddish polar coloring. Methane gas escapes from Pluto’s atmosphere and becomes “trapped” by the moon’s gravity and freezes to the cold, icy surface at Charon’s pole. Chemical processing by ultraviolet light from the Sun then transforms the methane into heavier hydrocarbons and eventually into reddish organic materials called tholins.

"Who would have thought that Pluto is a graffiti artist, spray-painting its companion with a reddish stain that covers an area the size of New Mexico?" asked Grundy, lead author of a 2016 paper on the phenomenon in the journal Nature.

For Christy – who, with Charlene, was recognized by a packed auditorium at the Johns Hopkins Applied Physics Lab in Maryland when the first close-up images of Charon were revealed – the transformation of Charon from a grainy blob into a real world over the past 40 years has been nothing short of amazing.

“When you go from this little blur in which you don’t actually see anything, to the enormous detail New Horizons sent back,” Christy said, “it’s incredible.”

Related links:

Pluto: http://www.nasa.gov/mission_pages/newhorizons/main/index.html

Dwarf Planets: https://www.nasa.gov/subject/3143/dwarf-planets

New Horizons: http://www.nasa.gov/mission_pages/newhorizons/main/index.html

Video (mentioned), Images (mentioned),Text, Credits: NASA/Bill Keeter.

Greetings, Orbiter.ch

Chaotic Clouds of Jupiter












NASA - JUNO Mission logo.

June 22, 2018


This image captures swirling cloud belts and tumultuous vortices within Jupiter’s northern hemisphere.

NASA’s Juno spacecraft took this color-enhanced image at 10:23 p.m. PDT on May 23, 2018 (1:23 a.m. EDT on May 24), as the spacecraft performed its 13th close flyby of Jupiter. At the time, Juno was about 9,600 miles (15,500 kilometers) from the planet's cloud tops, above a northern latitude of 56 degrees.

The region seen here is somewhat chaotic and turbulent, given the various swirling cloud formations. In general, the darker cloud material is deeper in Jupiter’s atmosphere, while bright cloud material is high. The bright clouds are most likely ammonia or ammonia and water, mixed with a sprinkling of unknown chemical ingredients.

A bright oval at bottom center stands out in the scene. This feature appears uniformly white in ground-based telescope observations. However, with JunoCam we can observe the fine-scale structure within this weather system, including additional structures within it. There is not significant motion apparent in the interior of this feature; like the Great Red Spot, its winds probably slows down greatly toward the center.

Juno orbiting Jupiter

Citizen scientists Gerald Eichstädt and Seán Doran created this image using data from the spacecraft’s JunoCam imager.

JunoCam's raw images are available for the public to peruse and process into image products at http://www.missionjuno.swri.edu/junocam

More information about Juno is at:

https://www.nasa.gov/juno and http://missionjuno.swri.edu

Image, Animation, Credits: NASA/Tony Greicius/JPL-Caltech/SwRI/MSSS/Gerald Eichstädt /Seán Doran.

Greetings, Orbiter.ch

jeudi 21 juin 2018

Crew Studies How Space Affects Time Perception, Exercise and Eyesight Today












ISS - Expedition 56 Mission patch.

June 21, 2018

Quite a wide variety of science activities took place today aboard the International Space Station exploring time perception, exercise and eyesight. The Expedition 56 crew members also worked on station plumbing, stowed satellite deployer gear and checked out communications gear.

Two-time station resident Alexander Gerst started his morning helping doctors understand how living in space alters time perception and impacts crew performance. Later he strapped himself into an exercise bike and attached electrodes to his chest to monitor his pulmonary function during the workout session.


Image above: This fish-eye lens view from a window on the Cupola shows the U.S. Cygnus commercial space freighter with its cymbal-like Ultra-Flex solar arrays attached to the Unity module. To its right is the Soyuz MS-09 spacecraft docked to the Rassvet module. Image Credit: NASA.

NASA astronauts Ricky Arnold, Drew Feustel and Serena Auñón-Chancellor teamed up for eye exams with an ultrasound device to study microgravity’s effects on eyesight. The scans were downlinked real-time to scientists on Earth observing the retina and optic nerve while monitoring the health of the astronaut’s eyes.

Auñón-Chancellor started her day changing out a filter and valve in the station’s bathroom located in the Tranquility module. She then checked out Wi-Fi gear connected to antennas installed during a March 29 spacewalk after assisting Feustel in the Japanese Kibo lab module. The duo stowed gear after Wednesday’s successful deployment of a satellite to demonstrate space junk clean up.

Arnold was set to install radio frequency tags today to improve tool tracking but that task was postponed till after the Cygnus cargo ship departs July 15. He then moved on to emergency communication tests with control centers around the world before light maintenance work on a 3D manufacturing device.

Related links:

Time perception: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7504

Satellite: https://www.nasa.gov/mission_pages/station/research/experiments/2456.html

Expedition 56: https://www.nasa.gov/mission_pages/station/expeditions/expedition56/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Image (mentioned), Text, Credits: NASA/Mark Garcia.

Best regards, Orbiter.ch

Red Nuggets’ Are Galactic Gold for Astronomers












NASA - Chandra X-ray Observatory patch.

June 21, 2018

About a decade ago, astronomers discovered a population of small, but massive galaxies called “red nuggets.” A new study using NASA’s Chandra X-ray Observatory indicates that black holes have squelched star formation in these galaxies and may have used some of the untapped stellar fuel to grow to unusually massive proportions.

Red nuggets were first discovered by the Hubble Space Telescope at great distances from Earth, corresponding to times only about three or four billion years after the Big Bang. They are relics of the first massive galaxies that formed within only one billion years after the Big Bang. Astronomers think they are the ancestors of the giant elliptical galaxies seen in the local Universe. The masses of red nuggets are similar to those of giant elliptical galaxies, but they are only about a fifth of their size.


Image above: Artist's illustration and X-ray image of "red nugget" galaxy Mrk 1216. Image Credits: X-ray: NASA/CXC/MTA-Eötvös University/N. Werner et al., Illustration: NASA/CXC/M. Weiss.

While most red nuggets merged with other galaxies over billions of years, a small number managed to slip through the long history of the cosmos untouched. These unscathed red nuggets represent a golden opportunity to study how the galaxies, and the supermassive black hole at their centers, act over billions of years of isolation.

For the first time, Chandra has been used to study the hot gas in two of these isolated red nuggets, MRK 1216, and PGC 032673. They are located only 295 million and 344 million light years from Earth respectively, rather than billions of light years for the first known red nuggets. This X-ray emitting hot gas contains the imprint of activity generated by the supermassive black holes in each of the two galaxies.

“These galaxies have existed for 13 billion years without ever interacting with another of its kind,” said Norbert Werner of MTA-Eötvös University Lendület Hot Universe and Astrophysics Research Group in Budapest, Hungary, who led the study. “We are finding that the black holes in these galaxies take over and the result is not good for new stars trying to form.”

Astronomers have long known that the material falling towards black holes can be redirected outward at high speeds due to intense gravitational and magnetic fields. These high-speed jets can tamp down the formation of stars. This happens because the blasts from the vicinity of the black hole provide a powerful source of heat, preventing the galaxy’s hot interstellar gas from cooling enough to allow large numbers of stars to form.

The temperature of the hot gas is higher in the center of the MRK 1216 galaxy compared to its surroundings, showing the effects of recent heating by the black hole. Also, radio emission is observed from the center of the galaxy, a signature of jets from black holes. Finally, the X-ray emission from the vicinity of the black hole is about a hundred million times lower than a theoretical limit on how fast a black hole can grow – called the “Eddington limit” – where the outward pressure of radiation is balanced by the inward pull of gravity. This low level of X-ray emission is typical for black holes producing jets. All these factors provide strong evidence that activity generated by the central supermassive black holes in these red nugget galaxies is suppressing the formation of new stars.

Chandra X-ray Observatory. Animation Credits: NASA/CXC

The black holes and the hot gas may have another connection. The authors suggest that much of the black hole mass may have accumulated from the hot gas surrounding both galaxies. The black holes in both MRK 1216 and PGC 032873 are among the most massive known, with estimated masses of about five billion times that of the Sun, based on optical observations of the speeds of stars near the galaxies’ centers. Furthermore, the masses of the MRK 1216 black hole and possibly the one in PGC 032873 are estimated to be a few percent of the combined masses of all the stars in the central regions of the galaxies, whereas in most galaxies, the ratio is about ten times less.

“Apparently, left to their own devices, black holes can act a bit like a bully,” said co-author Kiran Lakhchaura, also of MTA-Eötvös University.

“Not only do they prevent new stars from forming,” said co-author Massimo Gaspari, an Einstein fellow from Princeton University, “they may also take some of that galactic material and use it to feed themselves,”

In addition, the hot gas in and around PGC 032873 is about ten times fainter than the hot gas around MRK 1216. Because both galaxies appear to have evolved in isolation over the past 13 billion years, this difference might have arisen from more ferocious outbursts from PGC 032873's black hole in the past, which blew most of the hot gas away.

“The Chandra data tell us more about what the long, solitary journey through cosmic time has been like for these red nugget galaxies,” said co-author Rebecca Canning of Stanford University. “Although the galaxies haven’t interacted with others, they’ve shown plenty of inner turmoil.”

A paper describing these results in the latest issue of the Monthly Notices of the Royal Astronomical Society journal and is available online (http://lanl.arxiv.org/abs/1711.09983). NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Read More from NASA's Chandra X-ray Observatory: http://chandra.harvard.edu/photo/2018/mrk1216/

For more Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra

Image (mentioned), Animation (mentioned), Text, Credits: NASA/Lee Mohon/Marshall Space Flight Center/Molly Porter/Chandra X-ray Center/Megan Watzke.

Greetings, Orbiter.ch

Rosetta Image Archive Complete












ESA - Rosetta Mission patch.

21 June 2018

All high-resolution images and the underpinning data from Rosetta’s pioneering mission at Comet 67P/Churyumov-Gerasimenko are now available in ESA’s archives, with the last release including the iconic images of finding lander Philae, and Rosetta’s final descent to the comet’s surface.

The images were delivered by the OSIRIS camera team to ESA in May and have now been processed and released in both the Archive Image Browser and the Planetary Science Archive.

Rosetta’s final images

The Archive Image Browser also hosts images captured by the spacecraft’s Navigation Camera, while the Planetary Science Archive contains publicly available data from all eleven science instruments onboard Rosetta – as well as from ESA’s other Solar System exploration missions.

The final batch of high-resolution images from Rosetta’s OSIRIS camera covers the period from late July 2016 to the mission end on 30 September 2016. It brings the total count of images from the narrow- and wide-angle cameras to nearly 100 000 across the spacecraft’s 12 year journey through space, including early flybys of Earth, Mars and two asteroids before arriving at the comet.

 Comet on 2 September 2016 from 2.1 km

The spacecraft’s trajectory around the comet changed progressively during the final two months of the mission, bringing it closer and closer at its nearest point along elliptical orbits. This allowed some spectacular images to be obtained from within just two kilometres of the surface, highlighting the contrasts in exquisite detail between the smooth and dusty terrain, and more consolidated, fractured comet material.

One particularly memorable sets of images captured in this period were those of Rosetta’s lander Philae following the painstaking effort over the previous years to determine its location. With Rosetta flying so close, challenging conditions associated with the dust and gas escaping from the comet, along with the topography of the local terrain, caused problems with getting the best line-of-sight view of Philae’s expected location, but the winning shot was finally captured just weeks before the mission end.

Can you spot Philae in this image?

In the mission’s last hours as Rosetta moved even closer towards the surface of the comet, it scanned across an ancient pit and finally sent back images showing what would become its resting place. Even after the spacecraft was silent, the team were able to reconstruct a last image from the final telemetry packets sent back when Rosetta was within about 20 m of the surface.

“Having all the images finally archived to be shared with the world is a wonderful feeling,” says Holger Sierks, principal investigator of the camera. “We are also pleased to announce that all OSIRIS images are now available under a Creative Commons license.”

Interview with Rosetta’s camera team

“The final set of images supplements the rich treasure chest of data that the scientific community are already delving into in order to really understand this comet from all perspectives – not just from images but also from the gas, dust and plasma angle – and to explore the role of comets in general in our ideas of Solar System formation,” says Matt Taylor, ESA’s Rosetta project scientist. “There are certainly plenty of mysteries, and plenty still to discover.”

Notes for editors:

The OSIRIS images are released under the Creative Commons Attribution-ShareAlike 4.0 (CC BY-SA 4.0) license. To view a copy of this license, please visit https://creativecommons.org/licenses/by-sa/4.0/

Related links:

Archive Image Browser: http://imagearchives.esac.esa.int/

Planetary Science Archive: https://archives.esac.esa.int/psa/#!Home%20View

Creative Commons: https://creativecommons.org/licenses/by-sa/4.0/?

ESA Rosetta: http://www.esa.int/Our_Activities/Space_Science/Rosetta

Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

End of mission FAQ: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_s_grand_finale_frequently_asked_questions

Images, Videos, Text, Credits: ESA/Markus Bauer/Matt Taylor/Max Planck Institute for Solar System Research in Göttingen, Germany/Holger Sierks/ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA (CC BY-SA 4.0).

Best regards, Orbiter.ch

Hubble proves Einstein correct on galactic scales












ESA - Hubble Space Telescope logo.

21 June 2018

Most precise test of general relativity outside the Milky Way

Image of ESO 325-G004

An international team of astronomers using the NASA/ESA Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope has made the most precise test of general relativity yet outside our Milky Way. The nearby galaxy ESO 325-G004 acts as a strong gravitational lens, distorting light from a distant galaxy behind it to create an Einstein ring around its centre. By comparing the mass of ESO 325-G004 with the curvature of space around it, the astronomers found that gravity on these astronomical length-scales behaves as predicted by general relativity. This rules out some alternative theories of gravity.

How gravitational lensing acts as a magnifying glass — diagram

Using the NASA/ESA Hubble Space Telescope and European Southern Observatory’s Very Large Telescope (VLT), a team led by Thomas Collett (University of Portsmouth, UK), was able to perform the most precise test of general relativity outside the Milky Way to date.

Two methods of measuring the mass of a galaxy

The theory of general relativity predicts that objects deform spacetime, causing any light that passes by to be deflected and resulting in a phenomenon known as gravitational lensing. This effect is only noticeable for very massive objects. A few hundred strong gravitational lenses are known, but most are too distant to precisely measure their mass. However, the elliptical galaxy ESO 325-G004 is amongst the closest lenses at just 450 million light-years from Earth.

Hubble illuminates cluster of diverse galaxies

Using the MUSE instrument on the VLT the team calculated the mass of ESO 325-G004 by measuring the movement of stars within it. Using Hubble the scientists were able to observe an Einstein ring resulting from light from a distant galaxy being distorted by the intervening ESO 325-G004. Studying the ring allowed the astronomers to measure how light, and therefore spacetime, is being distorted by the huge mass of ESO 325-G004.

Artist’s impression of massive object distorting spacetime

Collett comments: “We know the mass of the foreground galaxy from MUSE and we measured the amount of gravitational lensing we see from Hubble. We then compared these two ways to measure the strength of gravity — and the result was just what general relativity predicts, with an uncertainty of only nine percent. This is the most precise test of general relativity outside the Milky Way to date. And this using just one galaxy!”

Pan across ESO 325-G004

General relativity has been tested with exquisite accuracy on Solar System scales, and the motions of stars around the black hole at the centre of the Milky Way are under detailed study, but previously there had been no precise tests on larger astronomical scales. Testing the long range properties of gravity is vital to validate our current cosmological model.

Interview with Thomas Collett about the research

These findings may have important implications for models of gravity alternative to general relativity. These alternative theories predict that the effects of gravity on the curvature of spacetime are “scale dependent”. This means that gravity should behave differently across astronomical length-scales from the way it behaves on the smaller scales of the Solar System. Collett and his team found that this is unlikely to be true unless these differences only occur on length scales larger than 6000 light-years.

Hubble Space Telescope (HST). Animation Credits: ESA/NASA

“The Universe is an amazing place providing such lenses which we can use as our laboratories,” adds team member Bob Nichol (University of Portsmouth). “It is so satisfying to use the best telescopes in the world to challenge Einstein, only to find out how right he was.”

More information:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

This research was presented in a paper entitled “A precise extragalactic test of General Relativity” by Collett et al., to appear in the journal Science.

The international team is comprised of: Thomas E. Collett (Institute of Cosmology and Gravitation, University of Portsmouth, UK), Lindsay J. Oldham (Institute of Astronomy, University of Cambridge, UK, and Harvard College, Harvard-Smithsonian Center for Astrophysics, USA), Russell Smith (Centre for Extragalactic Astronomy, University of Durham, UK), Matthew W. Auger (Institute of Astronomy, University of Cambridge, UK), Kyle B. Westfall (ICG, Portsmouth, UK, and University of California, Santa Cruz, USA), David Bacon (ICG, Portsmouth, UK), Robert C. Nichol (ICG, Portsmouth, UK), Karen L. Masters (ICG, Portsmouth, UK), Kazuya Koyama (ICG, Portsmouth, UK) and Remco van den Bosch (Max Planck Institute for Astronomy, Garching, Germany).

Links:

Hubblecast 110 Light: New test of Einstein’s general relativity:
https://www.spacetelescope.org/videos/heic1812a/

Science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1812/heic1812a.pdf

ESO release: http://eso.org/public/news/eso1819

Hubblesite release: http://hubblesite.org/news_release/news/2018-27

NASA/ESA Hubble Space Telescope: https://www.spacetelescope.org/

European Southern Observatory (ESO): https://www.eso.org/public/

Very Large Telescope (VLT): https://www.eso.org/public/teles-instr/paranal-observatory/vlt/

Images, Animation (mentioned), Text, Credits: ESA/Hubble/Mathias Jäger/University of Portsmouth (UK)/Bob Nichol/Thomas Collett/ESO/M. Kornmesser/NASA/The Hubble Heritage Team (STScI/AURA)/Videos: ESO/L. Calçada/NASA, ESA, and The Hubble Heritage Team (STScI/AURA)/University of Portsmouth (UK).

Best regards, Orbiter.ch

The secret spatial aims of the Swiss army












Swiss Army logo.

June 21, 2018

The army thought for a while to launch its own satellite. The project did not succeed but a "space cell" was born from this failure.

The Swiss army has space projects. To put it into practice, it even set up in 2017 a "space cell", reveals Thursday the RTS (Radio Television Swiss). The latter discovered by investigating the subject that the Department of Defense had been in negotiation with the start-up S3 (Swiss Space Systems) which offered launch satellites at broken prices. Through these discussions, the army planned to acquire its own satellite or, failing that, to obtain images provided by the company's & agencies. Objective: not to buy pictures abroad and thus gain independence.


Army spokesman Daniel Reist says negotiations with S3 have remained "at an early stage". Meanwhile, the company sank into a resounding bankruptcy. But the army did not end its space project so far. It created a "space cell", made up of eleven militia officers, more than half of whom also worked for the S3 start-up.

Related article:

Swiss Space Systems: bankruptcy confirmed
https://orbiterchspacenews.blogspot.com/2017/01/swiss-space-systems-bankruptcy-confirmed.html

Swiss Space Systems unveils small reusable satellite launch system
https://orbiterchspacenews.blogspot.com/2013/03/swiss-space-systems-unveils-small.html

Image, Text, Credits: NXP/Orbiter.ch Aerospace/Roland Berga.

Best regards, Orbiter.ch

Prolific Sea-Observing Satellite Turns 10










OSTM Jason-2 Mission logo.

June 21, 2018

An international oceanography satellite that is tracking the ongoing rise in global sea level marks its 10th year in orbit yesterday.

Designed for a three-to-five-year mission, the joint U.S./European Ocean Surface Topography Mission (OSTM) on the Jason-2 satellite has now made more than 47,000 trips around our home planet, measuring sea level change across the globe, observing ocean currents, studying climate phenomena such as El Nino and La Nina, and monitoring the long-term rise in global mean sea level. In January 2016, it was joined in orbit by its follow-on mission, Jason-3. NASA's Jet Propulsion Laboratory in Pasadena, California, manages NASA's portion of both missions.


Image above: Illustration of the U.S./European Ocean Surface Topography Mission (OSTM)/Jason-2 satellite, which marked its 10th year in orbit on June 20. Image Credits: NASA-JPL/Caltech.

In July 2017, Jason-2 began a new science mission when it was maneuvered into a slightly lower orbit. In this new orbit, Jason-2 is collecting data along a series of very closely spaced ground tracks, just 5 miles (8 kilometers) apart. It will take just over a year for Jason-2 to complete one cycle of these new ground tracks, which provide a very accurate and high-resolution estimate of the mean sea surface. The pull of gravity from underwater mountains and other features of the sea floor helps to shape the mean sea surface. These new surface measurements are already being used by scientists to improve maps of the shape and depth of the sea floor, resolving many previously unknown seamounts and other geologic features on the ocean bottom. The new maps will also allow for advances in ocean modeling, naval operations and solid Earth dynamics.

Jason-2 data from the new orbit are used by operational agencies to provide societal and strategic benefits, such as real-time information used for deriving ocean currents; improving marine, fishery and naval operations; and calculating tropical cyclone heat potential to improve forecasts of the intensity of tropical hurricanes and cyclones.

"Along with Jason-3, Jason-2 has extended the record of global sea level rise into a third decade," said Glenn Shirtliffe, Jason-2 project manager at JPL.

NASA is currently working with its partners -- the European Space Agency, the National Oceanic and Atmospheric Administration, the Centre National d'etudes Spatiales and the European Organisation for the Exploitation of Meteorological Satellites -- on future generations of satellite altimeters. The instruments are projected for launch in the next decade. They include the Sentinel-6/Jason Continuity of Service (Jason-CS) and Surface Water and Ocean Topography (SWOT) missions.


Image above: Latest image from OSTM/Jason-2's successor satellite, the U.S./European Jason-3, showing sea surface height with respect to the seasonal cycle and the long-term trend. Blue/magenta colors indicate lower-than-normal sea levels, while yellow/red colors indicate higher-than-normal sea levels. Image Credits: NASA/JPL-Caltech.

"In addition to measuring ocean circulation and revealing the ocean's role in Earth's climate, Jason-2 and Jason-3 measure the rise in global sea level caused by global warming," said Josh Willis, JPL oceanographer and NASA's project scientist for both missions. "Melting ice and expanding seawater drive global sea levels higher and higher each year. The rise has become a powerful reminder of how fast humans are changing the climate. These missions keep our finger on the pulse of climate change."

Other significant science results from the Jason-2 mission include studies of ocean circulation; the ties between the ocean and the atmosphere; and improved global climate forecasts and predictions.

"The 10th anniversary of the launch of Jason-2 is also a landmark in the development of operational oceanography, as this was the first Jason mission involving two operational agencies, EUMETSAT and NOAA," said EUMETSAT Director-General Alain Ratier. "This paved the way for the transition from highly successful research missions to an operational altimeter system, which has now turned to reality with Jason-3, Jason-CS/Sentinel-6 and Sentinel-3 providing data until 2030."

"After 10 years of excellent service, we're excited that Jason-2 is continuing to help forecast hurricane intensity and monitor winds and waves, while taking on a new mission of mapping unexplored parts of the ocean," said Eric Leuliette, NOAA's Jason program and project scientist.

For more information on Jason-2 and other satellite altimetry missions, visit:

http://sealevel.jpl.nasa.gov/ and https://www.aviso.altimetry.fr/en/missions/current-missions/jason-2.html

OSTM/Jason-2 is a joint satellite mission operated by CNES, EUMETSAT, NOAA and NASA.

Images (mentioned), Text, Credits: NASA/JPL/Alan Buis.

Greetings, Orbiter.ch

mercredi 20 juin 2018

New Satellite, Space Research and Cargo Missions Fill Crew Agenda












ISS - Expedition 56 Mission patch.

June 20, 2018

The International Space Station deployed a satellite this morning to demonstrate the potential of removing space junk. Back inside the orbital lab, the Expedition 56 crew explored space physics, studied human research and conducted an emergency drill.


Image above: Astronaut Serena Auñón-Chancellor collects breath samples to analyze and measure red blood cell function for the Marrow investigation. Image Credit: NASA.

A new satellite was deployed into space today from outside the Japanese Kibo laboratory module. Officially named the NanoRacks-Remove Debris satellite, it will explore using a 3D camera to map the location and speed of space debris. It will also deploy a net to capture a nanosatellite that will simulate space junk.

NASA astronaut Ricky Arnold worked inside the Microgravity Science Glovebox to troubleshoot gear today for a semiconductor crystal growth experiment. Alexander Gerst, of the European Space Agency, set up dosimeters and measured the station’s acoustic levels to understand the effects on crews.

Arnold later joined fellow Soyuz MS-08 crewmates Drew Feustel of NASA and Oleg Artemyev of Roscosmos for an emergency drill. The trio practiced evacuating the station in their Soyuz crew ship in the unlikely event of an emergency.

International Space Station (ISS). Image Credits: NASA/STS-132

U.S. and Russian cargo ships are due to launch to the space station this summer. Another cargo craft is due to end its stay at the orbital lab next month. SpaceX is counting down to a June 29 launch of its Dragon cargo ship. Roscosmos will launch its Progress 70 cargo craft on July 9. Finally, the Cygnus space freighter attached to the Unity module is due to end its stay July 15.

Related links:

Marrow: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1673

NanoRacks-Remove Debris satellite: https://www.nasa.gov/mission_pages/station/research/experiments/2456.html

Semiconductor crystal growth: https://www.nasa.gov/mission_pages/station/research/experiments/316.html

SpaceX: https://www.nasa.gov/spacex

Expedition 56: https://www.nasa.gov/mission_pages/station/expeditions/expedition56/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Text, Credits: NASA/Mark Garcia.

Best regards, Orbiter.ch

Martian Dust Storm Grows Global: Curiosity Captures Photos of Thickening Haze










NASA - Mars Science Laboratory (MSL) logo.

June 20, 2018

A storm of tiny dust particles has engulfed much of Mars over the last two weeks and prompted NASA’s Opportunity rover to suspend science operations. But across the planet, NASA’s Curiosity rover, which has been studying Martian soil at Gale Crater, is expected to remain largely unaffected by the dust. While Opportunity is powered by sunlight, which is blotted out by dust at its current location, Curiosity has a nuclear-powered battery that runs day and night.

The Martian dust storm has grown in size and is now officially a "planet-encircling" (or "global") dust event.


Image above: A self-portrait by NASA's Curiosity rover taken on Sol 2082 (June 15, 2018). A Martian dust storm has reduced sunlight and visibility at the rover's location in Gale Crater. A drill hole can be seen in the rock to the left of the rover at a target site called "Duluth." Image Credits: NASA/JPL-Caltech/MSSS.

Though Curiosity is on the other side of Mars from Opportunity, dust has steadily increased over it, more than doubling over the weekend. The atmospheric haze blocking sunlight, called "tau," is now above 8.0 at Gale Crater — the highest tau the mission has ever recorded. Tau was last measured near 11 over Opportunity, thick enough that accurate measurements are no longer possible for Mars' oldest active rover.

For NASA's human scientists watching from the ground, Curiosity offers an unprecedented window to answer some questions. One of the biggest: Why do some Martian dust storms last for months and grow massive, while others stay small and last only a week?

“We don’t have any good idea,” said Scott D. Guzewich, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, leading Curiosity's dust storm investigation.

Curiosity, he points out, plus a fleet of spacecraft in the orbit of Mars (Odyssey, MRO, Maven and ESA's Mars Express and GTO), will allow scientists for the first time to collect a wealth of dust information both from the surface and from space. The last storm of global magnitude that enveloped Mars was in 2007, five years before Curiosity landed there.


Animation above: In June 2018 NASA's Curiosity Rover used its Mast Camera, or Mastcam, to snap photos of the intensifying haziness the surface of Mars, caused by a massive dust storm. The rover is standing inside Gale Crater looking out to the crater rim. The photos span about a couple of weeks, starting with a shot of the area before the storm appeared. Animation Credit: NASA.

In the animation above, Curiosity is facing the crater rim, about 18.6 miles (30 kilometers) away from where it stands inside the crater. Daily photos captured by its Mast Camera, or Mastcam, show the sky getting hazier. This sun-obstructing wall of haze is about six to eight times thicker than normal for this time of season.

Curiosity's engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, have studied the potential for the growing dust storm to affect the rover's instruments, and say it poses little risk. The largest impact is to the rover's cameras, which require extra exposure time due to the low lighting. The rover already routinely points its Mastcam down at the ground after each use to reduce the amount of dust blowing at its optics. JPL leads the Mars Science Laboratory/Curiosity mission.


Image above: Two images from the Mast Camera (Mastcam) on NASA's Curiosity rover depicting the change in the color of light illuminating the Martian surface since a dust storm engulfed Gale Crater. The left image shows the "Duluth" drill site on Sol 2058 (May 21); the right image is from Sol 2084 (June 17). The cherry red color is due to red dust grains in the atmosphere letting red light through to the surface, but not green or blue, and to different exposure times for the two images. Image Credits: NASA/JPL-Caltech/MSSS.

Martian dust storms are common, especially during southern hemisphere spring and summer, when the planet is closest to the Sun. As the atmosphere warms, winds generated by larger contrasts in surface temperature at different locations mobilize dust particles the size of individual talcum powder grains. Carbon dioxide frozen on the winter polar cap evaporates, thickening the atmosphere and increasing the surface pressure. This enhances the process by helping suspend the dust particles in the air. In some cases, the dust clouds reach up to 40 miles (60 kilometers) or more in elevation.

Though they are common, Martian dust storms typically stay contained to a local area. By contrast, the current storm, if it were happening on Earth, is bigger than North America and Russia combined, said Guzewich.

The dust storm may seem exotic to some Earthlings, but it’s not unique to Mars. Earth has dust storms, too, in desert regions such as North Africa, the Middle East and the southwest United States.

But conditions here prevent them from spreading globally, said Ralph A. Kahn, a Goddard senior research scientist who studies the atmospheres of Earth and Mars. These include the structure of our thicker atmosphere and stronger gravity that helps settle dust. Earth also has vegetation cover on land that binds the soil with its roots and helps block the wind and rain that wash the particles out of the atmosphere.

Related articles:

NASA Encounters the Perfect Storm for Science
https://orbiterchspacenews.blogspot.com/2018/06/nasa-encounters-perfect-storm-for.html

Shades of Martian Darkness
https://orbiterchspacenews.blogspot.com/2018/06/shades-of-martian-darkness.html

Opportunity Hunkers Down During Dust Storm
https://orbiterchspacenews.blogspot.com/2018/06/opportunity-hunkers-down-during-dust.html

Related links:

Mars Science Laboratory (Curiosity): https://www.nasa.gov/mission_pages/msl/index.html

Mast Camera: https://mars.nasa.gov/msl/mission/instruments/cameras/mastcam/

Images (mentioned), Animation (mentioned), Text, Credits: NASA/Karl Hille/Goddard Space Flight Center, by Lonnie Shekhtman.

Greetings, Orbiter.ch

Once in a Blue Dune












NASA - Mars Reconnaissance Orbiter (MRO) logo.

June 20, 2018


Sand dunes often accumulate in the floors of craters. In this region of Lyot Crater, NASA's Mars Reconnaissance Orbiter (MRO) shows a field of classic barchan dunes on Jan. 24, 2018.

Just to the south of the group of barchan dunes is one large dune with a more complex structure. This particular dune, appearing like turquoise blue in enhanced color, is made of finer material and/or has a different composition than the surrounding.

The map is projected above at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 34.7 centimeters (13.7 inches) per pixel (with 1 x 1 binning); objects on the order of 104 centimeters (40.9 inches) across are resolved.] North is up.

This is a stereo pair with https://www.uahirise.org/ESP_053406_2295

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 Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

Image, Text, Credits: NASA/Tony Greicius/JPL-Caltech/Univ. of Arizona.

Greetings, Orbiter.ch

XMM-Newton finds missing intergalactic material












ESA - XMM-Newton Mission patch.

20 June 2018

After a nearly twenty-year long game of cosmic hide-and-seek, astronomers using ESA’s XMM-Newton space observatory have finally found evidence of hot, diffuse gas permeating the cosmos, closing a puzzling gap in the overall budget of ‘normal’ matter in the Universe.

While the mysterious dark matter and dark energy make up about 25 and 70 percent of our cosmos respectively, the ordinary matter that makes up everything we see – from stars and galaxies to planets and people – amounts to only about five percent.

 Detecting the warm-hot intergalactic medium

But even this five percent turns out to be quite hard to track down.

The total amount of ordinary matter, which astronomers refer to as baryons, can be estimated from observations of the Cosmic Microwave Background, which is the most ancient light in the history of the Universe, dating back to only about 380 000 years after the Big Bang.

Observations of very distant galaxies allow astronomers to follow the evolution of this matter throughout the Universe’s first couple billions of years. After that, however, more than half of it seemed to have gone missing.

“The missing baryons represent one of the biggest mysteries in modern astrophysics,” explains Fabrizio Nicastro, lead author of the paper presenting a solution to the mystery, published today in Nature.

“We know this matter must be out there, we see it in the early Universe, but then we can no longer get hold of it. Where did it go?”

XMM-Newton

Counting the population of stars in galaxies across the Universe, plus the interstellar gas that permeates galaxies – the raw material to create stars – only gets as far as a mere ten percent of all ordinary matter. Adding up the hot, diffuse gas in the haloes that encompass galaxies and the even hotter gas that fills galaxy clusters, which are the largest cosmic structures held together by gravity, raises the inventory to less than twenty percent.

This is not surprising: stars, galaxies and galaxy clusters form in the densest knots of the cosmic web, the filamentary distribution of both dark and ordinary matter that extends throughout the Universe. While these sites are dense, they are also rare, so not the best spots to look for the majority of cosmic matter.

Astronomers suspected that the ‘missing’ baryons must be lurking in the ubiquitous filaments of this cosmic web, where matter is however less dense and therefore more challenging to observe. Using different techniques over the years, they were able to locate a good chunk of this intergalactic material – mainly its cool and warm components – bringing up the total budget to a respectable 60 percent, but leaving the overall mystery still unsolved. 

The cosmic budget of ‘ordinary’ matter

Fabrizio and many other astronomers around the world have been on the tracks of the remaining baryons for almost two decades, ever since X-ray observatories such as ESA’s XMM-Newton and NASA’s Chandra became available to the scientific community.

Observing in this portion of the electromagnetic spectrum, they can detect hot intergalactic gas, with temperatures around a million degrees or more, that is blocking the X-rays emitted by even more distant sources. 

For this project, Fabrizio and his collaborators used XMM-Newton to look at a quasar – a massive galaxy with a supermassive black hole at its centre that is actively devouring matter and shining brightly from X-rays to radio waves. They observed this quasar, whose light takes more than four billion years to reach us, for a total of 18 days, split between 2015 and 2017, in the longest X-ray observation ever performed of such a source.

“After combing through the data, we succeeded at finding the signature of oxygen in the hot intergalactic gas between us and the distant quasar, at two different locations along the line of sight,” says Fabrizio.

“This is happening because there are huge reservoirs of material – including oxygen – lying there, and just in the amount we were expecting, so we finally can close the gap in the baryon budget of the Universe.”

This extraordinary result is the beginning of a new quest. Observations of different sources across the sky are needed to confirm whether these findings are truly universal, and to further investigate the physical state of this long-sought-for matter.

Cosmic web

Fabrizio and his colleagues are planning to study more quasars with XMM-Newton and Chandra in the coming years. To fully explore the distribution and properties of this so-called warm-hot intergalactic medium, however, more sensitive instruments will be needed, like ESA’s Athena, the Advanced Telescope for High-Energy Astrophysics, scheduled for launch in 2028.

“The discovery of the missing baryons with XMM-Newton is the exciting first step to fully characterise the circumstances and structures in which these baryons are found,” says co-author Jelle Kaastra from the Netherlands Institute for Space Research.

“For the next steps, we will need the much higher sensitivity of Athena, which has the study of the warm-hot intergalactic medium as one of its main goals, to improve our understanding of how structures grow in the history of the Universe.”

“It makes us very proud that XMM-Newton was able to discover the weak signal of this long elusive material, hidden in a million-degree hot fog that extends through intergalactic space for hundreds of thousands of light years,” says Norbert Schartel, XMM-Newton project scientist at ESA.

“Now that we know these baryons are no longer missing, we can’t wait to study them in greater detail.”

Notes for editors:

“Observations of the missing baryons in the warm–hot intergalactic medium” by F. Nicastro et al is published in Nature. DOI: 10.1038/s41586-018-0204-1 

Nature: https://www.nature.com/articles/s41586-018-0204-1

ESA’s XMM-Newton: http://sci.esa.int/xmm-newton/

Images, Text, Credits: ESA/Markus Bauer/Norbert Schartel/SRON – Netherlands Institute for Space Research/Jelle S. Kaastra/Istituto Nazionale di Astrofisica (INAF)/Fabrizio Nicastro/Illustrations and composition: ESA / ATG medialab; data: ESA / XMM-Newton / F. Nicastro et al. 2018; cosmological simulation: R. Cen/courtesy of K. Dolag, Universitäts-Sternwarte München, Ludwig-Maximilians-Universität München, Germany.

Best regards, Orbiter.ch

mardi 19 juin 2018

Crew Packs Up on Science and Cleans Up After Spacewalk












ISS - Expedition 56 Mission patch.

June 19, 2018

The Expedition 56 crew‘s schedule is full of space science today as cleanup continues after last week’s spacewalk. The International Space Station’s three newest crew members also brushed up on their safety skills.


Image above: NASA astronaut Drew Feustel is pictured tethered to the International Space Station just outside of the Quest airlock during a spacewalk he conducted with fellow NASA astronaut Ricky Arnold (out of frame) on June 14, 2018. Image Credit: NASA.

Biology and physics were just part of the microgravity research taking place aboard the orbital laboratory today. NASA astronaut Serena Auñón-Chancellor started her day collecting blood and urine samples for a trio of ongoing human research studies. She then joined European Space Agency astronaut Alexander Gerst for the Myotone study observing how long-term space missions impact the biochemical properties of muscles. Gerst also researched ways to simplify and speed up procedures for astronauts for the Everywear experiment.

Auñón-Chancellor, Gerst and cosmonaut Sergey Prokopyev also gathered midday to review the location of safety gear throughout the space station. The trio also practiced emergency communication in the station’s Russian segment.

NASA astronaut Ricky Arnold spent the day cleaning soot created in a burner during a run of the Advanced Combustion Microgravity Experiment. That study is exploring ways to improve fuel efficiency, reduce pollution and prevent fires in space. Cosmonauts Oleg Artemyev and Prokopyev explored how living in microgravity affects their daily exercise regimen.


Image above: Sunrise over South Indonesia, seen by EarthCam on ISS, speed: 27'598 Km/h, altitude: 408,97 Km, image captured by Roland Berga (on Earth in Switzerland) from International Space Station (ISS) using ISS-HD Live application with EarthCam's from ISS on June 19, 2018 at 21:34 UTC. Image Credits: Orbiter.ch Aerospace/Roland Berga.

Commander Drew Feustel worked in the Quest airlock today continuing cleanup activities after Thursday’s six-hour, 49-minute spacewalk. Feustel scrubbed the U.S. spacesuit water loops then tested water samples for conductivity before wrapping up his day.

Related article:

Spacewalkers Complete HD Camera Installation Work
https://orbiterchspacenews.blogspot.com/2018/06/spacewalkers-complete-hd-camera.html

Related links:

Expedition 56: https://www.nasa.gov/mission_pages/station/expeditions/expedition56/index.html

Everywear: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=2041

Advanced Combustion Microgravity Experiment: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1651

Daily exercise regimen: https://www.energia.ru/en/iss/researches/human/26.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Text, Credits: NASA/Mark Garcia/Orbiter.ch Aerospace/Roland Berga.

Best regards, Orbiter.ch

Sentinel-3 flies tandem









ESA - Sentinel-3 Mission logo.

19 June 2018

The key to monitoring Earth’s changing environment and to guaranteeing a consistent stream of satellite data to improve our daily lives is to take the same measurements over the course of decades. But how do you know that measurements from successive satellites, even though identical in build, are like for like?

The answer, for the Copernicus Sentinel-3 mission, is to engage in some nifty orbital flying.

Tandem in images

Sentinel-3 is a two-satellite mission to supply the coverage and data delivery needed for Europe’s Copernicus environmental monitoring programme.

Launched in 2016, Sentinel-3A has been measuring our oceans, land, ice and atmosphere to monitor and understand large-scale global dynamics and to provide critical information for marine operations, and more.

Its twin, Sentinel-3B, was launched in April 2018 and is having its instruments calibrated and being commissioned for service. Once Sentinel-3B is operational, the two satellites will orbit Earth 140° apart.

Sentinel-3 spacecraft

Now, however, the satellites have been positioned much closer together, flying a mere 30 seconds apart. Travelling at 7.4 km per second, the separation equates to a distance of 223 km.

The reason for this is to see how their instruments compare.

Even though the two Sentinel-3 satellites are identical, each carrying a radar altimeter, a radiometer and an imaging spectrometer, there’s a chance that their instruments could behave slightly differently.

It is important that any differences are carefully accounted for otherwise the information they deliver could be misinterpreted as changes happening on Earth’s surface.

Given the satellites’ current brief separation, their measurements should be virtually the same.

Sentinel-3 going tandem

This tandem phase is also important for the future Sentinel-3 satellites.

ESA’s ocean scientist, Craig Donlon, explains, “Our Sentinel-3 ocean climate record will eventually be derived from four satellites because we will be launching two further Sentinel-3s in the future.

“We need to understand the small differences between each successive satellite instrument as these influence our ability to determine accurate climate trends.

“The four-month Sentinel-3 tandem phase is a fantastic opportunity to do this and will provide results so that climate scientists can use all Sentinel-3 data with confidence.”

ESA’s Sentinel-3 project manager, Bruno Berruti, said, “Following liftoff and the usual checks, the operations team has been expertly flying Sentinel-3B so that it gradually flies closer to Sentinel-3A.

Sentinel-3 comparison

“We recently reached the magic separation of 30 seconds and I am happy to say that we are now officially in the tandem phase.

“This will last around four months, after which the two satellites will be gently moved apart until they reach their operational separation of 140°. This is different to the other Sentinel missions, but for our mission it is better to measure ocean features such as eddies as accurately as possible.”

ESA’s Sentinel-3 mission manager, Susanne Mecklenburg, added, “So far, we are really happy with the results of the tandem phase. Measurements from the satellites’ instrument packages seem to be very much aligned, but we will be analysing the results very carefully over the next months to make sure we account for any minor differences.”

Related links:

Sentinel-3: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-3

Sentinel data access: https://scihub.copernicus.eu/

Images, Text, Credits: ESA/contains modified Copernicus Sentinel data (2018), processed by ESA/S3MPC/ACRI-ST/ESA, CC BY-SA 3.0 IGO.

Best regards, Orbiter.ch