Dark Matter May be Smoother than Expected

ESO - European Southern Observatory logo.

7 December 2016

Careful study of large area of sky imaged by VST reveals intriguing result

Dark matter map of KiDS survey region (region G12)

Analysis of a giant new galaxy survey, made with ESO’s VLT Survey Telescope in Chile, suggests that dark matter may be less dense and more smoothly distributed throughout space than previously thought. An international team used data from the Kilo Degree Survey (KiDS) to study how the light from about 15 million distant galaxies was affected by the gravitational influence of matter on the largest scales in the Universe. The results appear to be in disagreement with earlier results from the Planck satellite.

Hendrik Hildebrandt from the Argelander-Institut für Astronomie in Bonn, Germany and Massimo Viola from the Leiden Observatory in the Netherlands led a team of astronomers [1] from institutions around the world who processed images from the Kilo Degree Survey (KiDS), which was made with ESO’s VLT Survey Telescope (VST) in Chile. For their analysis, they used images from the survey that covered five patches of the sky covering a total area of around 2200 times the size of the full Moon [2], and containing around 15 million galaxies.

By exploiting the exquisite image quality available to the VST at the Paranal site, and using innovative computer software, the team were able to carry out one of the most precise measurements ever made of an effect known as cosmic shear. This is a subtle variant of weak gravitational lensing, in which the light emitted from distant galaxies is slightly warped by the gravitational effect of large amounts of matter, such as galaxy clusters.

Dark matter map of KiDS survey region (region G9)

In cosmic shear, it is not galaxy clusters but large-scale structures in the Universe that warp the light, which produces an even smaller effect. Very wide and deep surveys, such as KiDS, are needed to ensure that the very weak cosmic shear signal is strong enough to be measured and can be used by astronomers to map the distribution of gravitating matter. This study takes in the largest total area of the sky to ever be mapped with this technique so far.

Intriguingly, the results of their analysis appear to be inconsistent with deductions from the results of the European Space Agency’s Planck satellite, the leading space mission probing the fundamental properties of the Universe. In particular, the KiDS team’s measurement of how clumpy matter is throughout the Universe — a key cosmological parameter — is significantly lower than the value derived from the Planck data [3].

Massimo Viola explains: “This latest result indicates that dark matter in the cosmic web, which accounts for about one-quarter of the content of the Universe, is less clumpy than we previously believed.”

Dark matter map of KiDS survey region (region G15)

Dark matter remains elusive to detection, its presence only inferred from its gravitational effects. Studies like these are the best current way to determine the shape, scale and distribution of this invisible material.

The surprise result of this study also has implications for our wider understanding of the Universe, and how it has evolved during its almost 14-billion-year history. Such an apparent disagreement with previously established results from Planck means that astronomers may now have to reformulate their understanding of some fundamental aspects of the development of the Universe.

Hendrik Hildebrandt comments: “Our findings will help to refine our theoretical models of how the Universe has grown from its inception up to the present day.”

The KiDS analysis of data from the VST is an important step but future telescopes are expected to take even wider and deeper surveys of the sky.

Zooming in on one of the KiDS survey regions

The co-leader of the study, Catherine Heymans of the University of Edinburgh in the UK adds: “Unravelling what has happened since the Big Bang is a complex challenge, but by continuing to study the distant skies, we can build a picture of how our modern Universe has evolved.”

“We see an intriguing discrepancy with Planck cosmology at the moment. Future missions such as the Euclid satellite and the Large Synoptic Survey Telescope will allow us to repeat these measurements and better understand what the Universe is really telling us,” concludes Konrad Kuijken (Leiden Observatory, the Netherlands), who is principal investigator of the KiDS survey.

Notes:

[1] The international KiDS team of researchers includes scientists from Germany, the Netherlands, the UK, Australia, Italy, Malta and Canada.

[2] This corresponds to about 450 square degrees, or a little more than 1% of the entire sky.

[3] The parameter measured is called S8. Its value is a combination of the size of density fluctuations in, and the average density of, a section of the Universe. Large fluctuations in lower density parts of the Universe have an effect similar to that of smaller amplitude fluctuations in denser regions and the two cannot be distinguished by observations of weak lensing. The 8 refers to a cell size of 8 megaparsecs, which is used by convention in such studies.

More information:

This research was presented in the paper entitled “KiDS-450: Cosmological parameter constraints from tomographic weak gravitational lensing”, by H. Hildebrandt et al., to appear in Monthly Notices of the Royal Astronomical Society.

The team is composed of H. Hildebrandt (Argelander-Institut für Astronomie, Bonn, Germany), M. Viola (Leiden Observatory, Leiden University, Leiden, the Netherlands), C. Heymans (Institute for Astronomy, University of Edinburgh, Edinburgh, UK), S. Joudaki (Centre for Astrophysics & Supercomputing, Swinburne University of Technology, Hawthorn, Australia), K. Kuijken (Leiden Observatory, Leiden University, Leiden, the Netherlands), C. Blake (Centre for Astrophysics & Supercomputing, Swinburne University of Technology, Hawthorn, Australia), T. Erben (Argelander-Institut für Astronomie, Bonn, Germany), B. Joachimi (University College London, London, UK), D Klaes (Argelander-Institut für Astronomie, Bonn, Germany), L. Miller (Department of Physics, University of Oxford, Oxford, UK), C.B. Morrison (Argelander-Institut für Astronomie, Bonn, Germany), R. Nakajima (Argelander-Institut für Astronomie, Bonn, Germany), G. Verdoes Kleijn (Kapteyn Astronomical Institute, University of Groningen, Groningen, the Netherlands), A. Amon (Institute for Astronomy, University of Edinburgh, Edinburgh, UK), A. Choi (Institute for Astronomy, University of Edinburgh, Edinburgh, UK), G. Covone (Department of Physics, University of Napoli Federico II, Napoli, Italy), J.T.A. de Jong (Leiden Observatory, Leiden University, Leiden, the Netherlands), A. Dvornik (Leiden Observatory, Leiden University, Leiden, the Netherlands), I. Fenech Conti (Institute of Space Sciences and Astronomy (ISSA), University of Malta, Msida, Malta; Department of Physics, University of Malta, Msida, Malta), A. Grado (INAF – Osservatorio Astronomico di Capodimonte, Napoli, Italy), J. Harnois-Déraps (Institute for Astronomy, University of Edinburgh, Edinburgh, UK; Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada), R. Herbonnet (Leiden Observatory, Leiden University, Leiden, the Netherlands), H. Hoekstra (Leiden Observatory, Leiden University, Leiden, the Netherlands), F. Köhlinger (Leiden Observatory, Leiden University, Leiden, the Netherlands), J. McFarland (Kapteyn Astronomical Institute, University of Groningen, Groningen, the Netherlands), A. Mead (Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada), J. Merten (Department of Physics, University of Oxford, Oxford, UK), N. Napolitano (INAF – Osservatorio Astronomico di Capodimonte, Napoli, Italy), J.A. Peacock (Institute for Astronomy, University of Edinburgh, Edinburgh, UK), M. Radovich (INAF – Osservatorio Astronomico di Padova, Padova, Italy), P. Schneider (Argelander-Institut für Astronomie, Bonn, Germany), P. Simon (Argelander-Institut für Astronomie, Bonn, Germany), E.A. Valentijn (Kapteyn Astronomical Institute, University of Groningen, Groningen, the Netherlands), J.L. van den Busch (Argelander-Institut für Astronomie, Bonn, Germany), E. van Uitert (University College London, London, UK) and L. van Waerbeke (Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Research paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1642/eso1642a.pdf

Photos of the VST: http://www.eso.org/public/images/archive/search/?adv=&subject_name=VLT%20Survey%20Telescope

Argelander-Institut für Astronomie: https://astro.uni-bonn.de/en

Kilo Degree Survey (KiDS): http://kids.strw.leidenuniv.nl/

ESO’s VLT Survey Telescope (VST): http://www.eso.org/public/teles-instr/surveytelescopes/vst/

European Space Agency’s Planck satellite: http://www.esa.int/ESA

Images, Text, Credits: ESO/Richard Hook/Leiden Observatory/Konrad Kuijken/Massimo Viola/Institute for Astronomy, University of Edinburgh/Catherine Heymans/Kilo-Degree Survey Collaboration/H. Hildebrandt & B. Giblin/ESO/Video: Kilo-Degree Survey Collaboration/H. Hildebrandt & B. Giblin/ESO/N. Risinger (skysurvey.org). Music: Konstantino Polizois (soundcloud.com/konstantino-polizois).

Best regards, Orbiter.ch

2016: an exceptional year for the LHC

CERN - European Organization for Nuclear Research logo.

6 Dec 2016

It's the particles’ last lap of the ring. On 5 December 2016, protons and lead ions circulated in the Large Hadron Collider (LHC) for the last time. At exactly 6.02am, the experiments recorded their last collisions (also known as 'events').

Image above: This proton-lead ion collision in the ATLAS detector produced a top quark – the heaviest quark – and its antiquark (Image: ATLAS).

When the machines are turned off, the LHC operators take stock, and the resulting figures are astonishing.

The number of collisions recorded by ATLAS and CMS during the proton run from April to the end of October was 60% higher than anticipated. Overall, all of the LHC experiments observed more than 6.5 million billion (6.5 x 10¹⁵) collisions, at an energy of 13 TeV. That equates to more data than had been collected in the previous three runs combined.

Image above: One of the first proton-lead ion collisions at 8.16 TeV recorded by the ALICE experiment. (Image: ALICE/CERN).

In technical terms, the integrated luminosity received by ATLAS and CMS reached 40 inverse femtobarns  (fb⁻¹), compared with the 25fb⁻¹ originally planned. Luminosity, which measures the number of potential collisions in a given time, is a crucial indicator of an accelerator’s performance.

“One of the key factors contributing to this success was the remarkable availability of the LHC and its injectors,” explains Mike Lamont, who leads the team that operates the accelerators. The LHC’s overall availability in 2016 was just shy of 50%, which means the accelerator was in 'collision mode' 50% of the time: a very impressive achievement for the operators. “It’s the result of an ongoing programme of work over the last few years to consolidate and upgrade the machines and procedures,” Lamont continues.

Image above: An event recorded by the CMS experiment during the LHC’s proton-lead ion run for which no fewer than 449 particles tracks were reconstructed. (Image: CMS/CERN).

For the last four weeks, the machine has turned to a different type of collision, where lead ions have been colliding with protons. “This is a new and complex operating mode, but the excellent functioning of the accelerators and the competence of the teams involved has allowed us to surpass our performance expectations,” says John Jowett, who is in charge of heavy-ion runs.

With the machine running at an energy of 8.16 TeV, a record for this assymetric type of collision, the experiments have recorded more than 380 billion collisions. The machine achieved a peak luminosity over seven times higher than initially expected, as well as exceptional beam lifetimes. The performance is even more remarkable considering that colliding protons with lead ions, which have a mass 206 times greater and a charge 82 times higher, requires numerous painstaking adjustments to the machine.

Image above: A proton-lead ion collision recorded by the LHCb experiment in the last few days of the LHC’s 2016 run. (Image: LHCb).

The physicists are now analysing the enormous amounts of data that have been collected, in preparation for presenting their results at the winter conferences.

Graphic above: The integrated luminosity of the LHC with proton-proton collisions in 2016 compared to previous years. Luminosity is a measure of a collider’s efficiency and is proportional to the number of collisions. The integrated luminosity achieved by the LHC in 2016 far surpassed expectations and is double that achieved at a lower energy in 2012. (Image : CERN).

Meanwhile, CERN’s accelerators will take a long break, called the Extended Year End Technical Stop (EYETS) until the end of March 2017. But, while the accelerators might be on holiday, the technical teams certainly aren’t. The winter stop is an opportunity to carry out maintenance on these extremely complex machines, which are made up of thousands of components. The annual stop for the LHC is being extended by two months in 2017 to allow more major renovation work on the accelerator complex and its 35 kilometres of machines to take place. Particles will return to the LHC in spring 2017.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

Large Hadron Collider (LHC): http://home.cern/topics/large-hadron-collider

ALICE experiments: http://home.web.cern.ch/about/experiments/alice

ATLAS experiments: http://home.web.cern.ch/about/experiments/atlas

CMS experiments: http://home.web.cern.ch/about/experiments/cms

LHCb experiments: http://home.web.cern.ch/about/experiments/lhcb

For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/

Images (mentioned), Graphic (mentioned), Text, Credits: CERN/Corinne Pralavorio.

Best regards, Orbiter.ch

Curiosity Rover Team Examining New Drill Hiatus

NASA - Mars Science Laboratory (MSL) patch.

Dec. 6, 2016

Mission Status Report

NASA's Curiosity Mars rover is studying its surroundings and monitoring the environment, rather than driving or using its arm for science, while the rover team diagnoses an issue with a motor that moves the rover's drill.

Image above: This Dec. 2, 2016, view from the Navigation Camera (Navcam) on the mast of NASA's Curiosity Mars Rover shows rocky ground within view while the rover was working at an intended drilling site called "Precipice" on lower Mount Sharp. Image Credits: NASA/JPL-Caltech.

Curiosity is at a site on lower Mount Sharp selected for what would be the mission's seventh sample-collection drilling of 2016. The rover team learned Dec. 1 that Curiosity did not complete the commands for drilling. The rover detected a fault in an early step in which the "drill feed" mechanism did not extend the drill to touch the rock target with the bit.

"We are in the process of defining a set of diagnostic tests to carefully assess the drill feed mechanism. We are using our test rover here on Earth to try out these tests before we run them on Mars," Curiosity Deputy Project Manager Steven Lee, at NASA's Jet Propulsion Laboratory in Pasadena, California, said Monday. "To be cautious, until we run the tests on Curiosity, we want to restrict any dynamic changes that could affect the diagnosis. That means not moving the arm and not driving, which could shake it."

Two among the set of possible causes being assessed are that a brake on the drill feed mechanism did not disengage fully or that an electronic encoder for the mechanism's motor did not function as expected. Lee said that workarounds may exist for both of those scenarios, but the first step is to identify why the motor did not operate properly last week.

The drill feed mechanism pushes the front of the drill outward from the turret of tools at the end of Curiosity's robotic arm. The drill collects powdered rock that is analyzed by laboratory instruments inside the rover. While arm movements and driving are on hold, the rover is using cameras and a spectrometer on its mast, and a suite of environmental monitoring capabilities.

At the rover's current location, it has driven 9.33 miles (15.01 kilometers) since landing inside Mars' Gale Crater in August 2012. That includes more than half a mile (more than 840 meters) since departing a cluster of scenic mesas and buttes -- called "Murray Buttes" -- in September 2016. Curiosity has climbed 541 feet (165 meters) in elevation since landing, including 144 feet (44 meters) since departing Murray Buttes.

The rover is climbing to sequentially higher and younger layers of lower Mount Sharp to investigate how the region's ancient climate changed, billions of years ago. Clues about environmental conditions are recorded in the rock layers. During its first year on Mars, the mission succeeded at its main goal by finding that the region once offered environmental conditions favorable for microbial life, if Mars has ever hosted life. The conditions in long-lived ancient freshwater Martian lake environments included all of the key chemical elements needed for life as we know it, plus a chemical source of energy that is used by many microbes on Earth.

Image above: The top of the rover's mast faces away in this May 11, 2016, self-portrait of NASA's Curiosity Mars rover, which shows the vehicle at the "Okoruso" drilling site on lower Mount Sharp. The scene is a mosaic of multiple images taken with the arm-mounted Mars Hands Lens Imager (MAHLI). Image Credits: NASA/JPL-Caltech/MSSS.

Curiosity's drill, as used at all 15 of the rock targets drilled so far, combines hammering action and rotating-bit action to penetrate the targets and collect sample material. The drilling attempt last week was planned as the mission's first using a non-percussion drilling method that relies only on the drill's rotary action. Short-circuiting in the percussion mechanism has occurred intermittently and unpredictably several times since first seen in February 2015.

"We still have percussion available, but we would like to be cautious and use it for targets where we really need it, and otherwise use rotary-only where that can give us a sample," said Curiosity Project Scientist Ashwin Vasavada at JPL.

JPL, a division of Caltech in Pasadena, California, manages NASA's Mars Science Laboratory Project for NASA's Science Mission Directorate, Washington, and built the project's rover, Curiosity. For more information about the mission, visit: http://mars.jpl.nasa.gov/msl/

Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Guy Webster.

Greetings, Orbiter.ch

ExoMars orbiter images Phobos

ESA & ROSCOSMOS - ExoMars Mission patch.

6 December 2016

The ExoMars Trace Gas Orbiter has imaged the martian moon Phobos as part of a second set of test science measurements made since it arrived at the Red Planet on 19 October.

The Trace Gas Orbiter (TGO), a joint endeavour between ESA and Roscosmos, made its first scientific calibration measurements during two orbits between 20 and 28 November.

ExoMars first colour image of Phobos

Example data from the first orbit were published last week, focusing on Mars itself. During the second orbit, the instruments made a number of measurements of Phobos, a 27×22×18 km moon that orbits Mars at a distance of only 6000 km.

The camera imaged the moon on 26 November from a distance of 7700 km, during the closest part of the spacecraft’s orbit around Mars. TGO’s elliptical orbit currently takes it to within 230–310 km of the surface at its closest point and around 98 000 km at its furthest every 4.2 days.

A colour composite has been created from several individual images taken through several filters. The camera’s filters are optimised to reveal differences in mineralogical composition, seen as ‘bluer’ or ‘redder’ colours in the processed image.

An anaglyph created from a stereo pair of images captured is also presented, and can be viewed using red–blue 3D glasses.

 Phobos in 3D

“Although higher-resolution images of Phobos have been returned by other missions, such as ESA’s Mars Express and NASA’s Mars Reconnaissance Orbiter, this provided a good test of what can be done with our data in a very short time,” says Nick Thomas, principal investigator of the CaSSIS camera team at the University of Bern.

“The images have given us a lot of useful information about the colour calibration of the camera and its internal timing.”

Two other instruments also made calibration measurements of Phobos, and the teams are analysing their data.

“We’re very happy with the results of both test science orbits and will be using these calibration data to improve our measurements once we begin the main science mission later next year,” adds Håkan Svedhem, ESA’s TGO Project Scientist.

 ExoMars science orbit 2

The focus of the mission now returns to preparations for aerobraking required to bring the spacecraft towards its near-circular science orbit by the end of 2017. More details on the upcoming operations will be provided soon.

TGO’s main scientific goal is to make a detailed inventory of rare gases that make up less than 1% of the atmosphere’s volume, including methane, water vapour, nitrogen dioxide and acetylene.

Of high interest is methane, which on Earth is produced primarily by biological activity, and to a smaller extent by geological processes such as some hydrothermal reactions.

The spacecraft will also seek out water or ice just below the surface, and will provide colour and stereo context images of surface features, including those that may be related to possible trace gas sources.

TGO will also act as a data relay for present and future landers and rovers on Mars, including the second ExoMars mission that will feature a rover and surface science platform, and which is scheduled for launch in 2020.

Related article:

First views of Mars show potential for ESA’s new orbiter
http://orbiterchspacenews.blogspot.ch/2016/11/first-views-of-mars-show-potential-for.html

Related links:

Robotic exploration of Mars: http://exploration.esa.int/

ExoMars Factsheet: http://www.esa.int/Our_Activities/Space_Science/ExoMars/ExoMars_Factsheet

ExoMars frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/ExoMars/ExoMars_frequently_asked_questions

ExoMars brochure: http://www.esa.int/About_Us/ESA_Publications/ESA_Publications_Brochures/ESA_BR-327_EXOMARS_2016

Roscosmos: http://en.federalspace.ru/

ExoMars at IKI: http://exomars.cosmos.ru/

Thales Alenia Space: https://www.thalesgroup.com/en/worldwide/space/space

NASA In 2016 ExoMars orbiter (Electra radio): http://mars.nasa.gov/programmissions/missions/future/exomarsorbiter2016/

Where on Mars?: http://whereonmars.co/

ExoMars for broadcasters: http://www.esa.int/esatv/Transmissions/2016/10/ExoMars_at_Mars_live_coverage

Images, Text, Credits: ESA/Markus Bauer/Håkan Svedhem/Center for Space and Habitability, University of Bern/Nicolas Thomas/Roscosmos/CaSSIS.

Best regards, Orbiter.ch

Chaos at Hyperion

NASA - Cassini International logo.

Dec. 5, 2016

The moon Hyperion tumbles as it orbits Saturn. Hyperion's (168 miles or 270 kilometers across) spin axis has a chaotic orientation in time, meaning that it is essentially impossible to predict how the moon will be spinning in the future. So far, scientists only know of a few bodies with such chaotic spins.

The image was taken in green light with the Cassini spacecraft narrow-angle camera on Aug. 22, 2016.

The view was acquired at a distance of approximately 203,000 miles (326,000 kilometers) from Hyperion and at a Sun-Hyperion-spacecraft, or phase, angle of 10 degrees. Image scale is 1 mile (2 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.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and ESA's website http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

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

Greetings, Orbiter.ch

Cassini Makes First Ring-Grazing Plunge

NASA - Cassini Mission to Saturn patch.

Dec. 5, 2016

NASA's Saturn-orbiting Cassini spacecraft has made its first close dive past the outer edges of Saturn's rings since beginning its penultimate mission phase on Nov. 30.

Cassini crossed through the plane of Saturn's rings on Dec. 4 at 5:09 a.m. PST  (8:09 a.m. EST) at a distance of approximately 57,000 miles (91,000 kilometers) above Saturn's cloud tops. This is the approximate location of a faint, dusty ring produced by the planet’s small moons Janus and Epimetheus, and just 6,800 miles (11,000 kilometers) from the center of Saturn's F ring.

Image above: This graphic shows the closest approaches of Cassini's final two orbital phases. Ring-grazing orbits are shown in gray (at left); Grand Finale orbits are shown in blue. The orange line shows the spacecraft's Sept. 2017 final plunge into Saturn. Image Credits: NASA/JPL-Caltech.

About an hour prior to the ring-plane crossing, the spacecraft performed a short burn of its main engine that lasted about six seconds. About 30 minutes later, as it approached the ring plane, Cassini closed its canopy-like engine cover as a protective measure.

"With this small adjustment to the the spacecraft's trajectory, we're in excellent shape to make the most of this new phase of the mission," said Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory, Pasadena, California.

A few hours after the ring-plane crossing, Cassini began a complete scan across the rings with its radio science experiment to study their structure in great detail.

Animation above: Cassini crosses Saturn's F ring once on each of its 20 Ring-Grazing Orbits, shown here in tan and lasting from late November 2016 to April 2017. Blue represents the extended solstice mission orbits, which precede the ring-grazing phase. Animation Credits: Credits: NASA/JPL-Caltech.

"It's taken years of planning, but now that we're finally here, the whole Cassini team is excited to begin studying the data that come from these ring-grazing orbits," said Linda Spilker, Cassini project scientist at JPL. "This is a remarkable time in what's already been a thrilling journey."

Cassini's imaging cameras obtained views of Saturn about two days before crossing through the ring plane, but not near the time of closest approach. The focus of this first close pass was the engine maneuver and observations by Cassini's other science instruments. Future dives past the rings will feature some of the mission's best views of the outer regions of the rings and small, nearby moons.

Each of Cassini's orbits for the remainder of the mission will last one week. The next pass by the rings' outer edges is planned for Dec. 11. The ring-grazing orbits -- 20 in all -- will continue until April 22, when the last close flyby of Saturn's moon Titan will reshape Cassini's flight path. With that encounter, Cassini will leap over the rings, making the first of 22 plunges through the 1,500-mile-wide (2,400-kilometer) gap between Saturn and its innermost ring on April 26.

Image above: Cassini mission controllers at NASA-JPL received signals from the spacecraft early Sunday morning (PST) that the maneuvers were completed successfully.
Image Credits: NASA/JPL-Caltech.

On Sept. 15, the mission will conclude with a final plunge into Saturn's atmosphere. During the plunge, Cassini will transmit data on the atmosphere's composition until its signal is lost.

Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004 for an up-close study of the planet, its rings and moons. During its journey, Cassini has made numerous dramatic discoveries, including a global ocean with indications of hydrothermal activity within the moon Enceladus, and liquid methane seas on another moon, Titan.

For details about Cassini's ring-grazing orbits, visit: https://saturn.jpl.nasa.gov/news/2966/ring-grazing-orbits

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and ESA's website http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Images (mentioned), Animation (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Preston Dyches.

Greetings, Orbiter.ch

Vega lofts Turkey’s Earth observation satellite

ARIANESPACE - Vega / Flight VV08 Mission poster.


5 December 2016

Vega lifts off

Arianespace today launched a Vega rocket on a commercial mission to deliver a Turkish Earth observation satellite into orbit.

Liftoff of Vega’s eighth flawless mission from Europe’s Spaceport in Kourou, French Guiana came at 13:51 GMT on 5 December (14:51 CET; 10:51 local time).

Arianespace Flight VV08: GÖKTÜRK-1

With a mass at liftoff of 1060 kg, Göktürk-1 was manoeuvred into its target Sun-synchronous orbit about 57 minutes into the mission after a series of burns of Vega’s upper stage.

Complying with debris regulations to help keep space clean, Vega’s upper stage fired a final time to burn up high in the atmosphere over the ocean.

Göktürk-1 satellite

Vega is a 30 m-high, four-stage vehicle designed to accommodate small scientific and Earth observation payloads of 300–2500 kg depending on the orbit.

Related links:

Vega rocket: http://www.esa.int/Our_Activities/Launchers/Launch_vehicles/Vega

Arianespace: http://www.arianespace.com/

Images, Video, Text, Credits: European Space Agency (ESA)/Arianespace/Telespazio/Thales Alenia.

Best regards, Orbiter.ch