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  • richardmitnick 2:43 pm on June 20, 2017 Permalink | Reply
    Tags: , , , , , , ESA Gravitational Wave Mission Selected. Planet Hunting Mission Moves Forward, ESA Lisa Pathfinder, , ESA/Plato, ,   

    From ESA: “Gravitational Wave Mission Selected. Planet Hunting Mission Moves Forward” 

    ESA Space For Europe Banner

    European Space Agency

    1
    Merging black holes. No image credit

    20 June 2017
    ESA Media Relations Office

    Tel: + 33 1 53 69 72 99

    Email: media@esa.int

    The LISA trio of satellites to detect gravitational waves from space has been selected as the third large-class mission in ESA’s Science programme, while the Plato exoplanet hunter moves into development.

    ESA/eLISA the future of gravitational wave research

    These important milestones were decided upon during a meeting of ESA’s Science Programme Committee today, and ensure the continuation of ESA’s Cosmic Vision plan through the next two decades.

    The ‘gravitational universe’ was identified in 2013 as the theme for the third large-class mission, L3, searching for ripples in the fabric of spacetime created by celestial objects with very strong gravity, such as pairs of merging black holes.

    Predicted a century ago by Albert Einstein’s general theory of relativity, gravitational waves remained elusive until the first direct detection by the ground-based Laser Interferometer Gravitational-Wave Observatory in September 2015. That signal was triggered by the merging of two black holes some 1.3 billion light-years away. Since then, two more events have been detected.

    Furthermore, ESA’s LISA Pathfinder mission has also now demonstrated key technologies needed to detect gravitational waves from space.

    ESA/LISA Pathfinder

    This includes free-falling test masses linked by laser and isolated from all external and internal forces except gravity, a requirement to measure any possible distortion caused by a passing gravitational wave.

    The distortion affects the fabric of spacetime on the minuscule scale of a few millionths of a millionth of a metre over a distance of a million kilometres and so must be measured extremely precisely.

    LISA Pathfinder will conclude its pioneering mission at the end of this month, and LISA, the Laser Interferometer Space Antenna, also an international collaboration, will now enter a more detailed phase of study. Three craft, separated by 2.5 million km in a triangular formation, will follow Earth in its orbit around the Sun.

    Following selection, the mission design and costing can be completed. Then it will be proposed for ‘adoption’ before construction begins. Launch is expected in 2034.

    Planet-hunter adopted

    In the same meeting Plato – Planetary Transits and Oscillations of stars – has now been adopted in the Science Programme, following its selection in February 2014.

    ESA/PLATO

    This means it can move from a blueprint into construction. In the coming months industry will be asked to make bids to supply the spacecraft platform.

    Following its launch in 2026, Plato will monitor thousands of bright stars over a large area of the sky, searching for tiny, regular dips in brightness as their planets cross in front of them, temporarily blocking out a small fraction of the starlight.

    The mission will have a particular emphasis on discovering and characterising Earth-sized planets and super-Earths orbiting Sun-like stars in the habitable zone – the distance from the star where liquid surface water could exist.

    It will also investigate seismic activity in some of the host stars, and determine their masses, sizes and ages, helping to understand the entire exoplanet system.

    Plato will operate from the ‘L2’ virtual point in space 1.5 million km beyond Earth as seen from the Sun.

    LaGrange Points map. NASA

    Missions of opportunity

    3
    Proba-3. No image credit.

    The Science Programme Committee also agreed on participation in ESA’s Proba-3 technology mission, a pair of satellites that will fly in formation just 150 m apart, with one acting as a blocking disc in front of the Sun, allowing the other to observe the Sun’s faint outer atmosphere in more detail than ever before.

    ESA will also participate in Japan’s X-ray Astronomy Recovery Mission (XARM), designed to recover the science of the Hitomi satellite that was lost shortly after launch last year.

    JAXA/Hitomi telescope lost

    4
    LAXA/NASA XARM future satellite

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 3:28 pm on April 17, 2017 Permalink | Reply
    Tags: ESA Lisa Pathfinder, , NASA Team Explores Using LISA Pathfinder as 'Comet Crumb' Detector   

    From Goddard: “NASA Team Explores Using LISA Pathfinder as ‘Comet Crumb’ Detector” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    April 17, 2017
    Francis Reddy
    francis.j.reddy@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    ESA/LISA Pathfinder

    LISA Pathfinder, a mission led by ESA (the European Space Agency) with contributions from NASA, has successfully demonstrated critical technologies needed to build a space-based observatory for detecting ripples in space-time called gravitational waves.

    ESA/eLISA

    Now a team of NASA scientists hopes to take advantage of the [Pathfinder] spacecraft’s record-breaking sensitivity to map out the distribution of tiny dust particles shed by asteroids and comets far from Earth.

    Most of these particles have masses measured in micrograms, similar to a small grain of sand. But with speeds greater than 22,000 mph (36,000 kph), even micrometeoroids pack a punch. The new measurements could help refine dust models used by researchers in a variety of studies, from understanding the physics of planet formation to estimating impact risks for current and future spacecraft.


    In a proof-of-concept study, NASA scientists are exploring using ESA’s (the European Space Agency) LISA Pathfinder spacecraft as a micrometeoroid detector. When tiny particles shed by asteroids and comets impact LISA Pathfinder, its thrusters work to quickly counteract any change in the spacecraft’s motion. Researchers are monitoring these signals to learn more about the impacting particles.
    Credits: NASA’s Goddard Space Flight Center

    “We’ve shown we have a novel technique and that it works,” said Ira Thorpe, who leads the team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The next step is to carefully apply this technique to our whole data set and interpret the results.”

    The mission’s primary goal was to test how well the spacecraft could fly in formation with an identical pair of 1.8-inch (46 millimeter) gold-platinum cubes floating inside it. The cubes are test masses intended to be in free fall and responding only to gravity.

    The spacecraft serves as a shield to protect the test masses from external forces. When LISA Pathfinder responds to pressure from sunlight and microscopic dust impacts, the spacecraft automatically compensates by firing tiny bursts from its micronewton thrusters to prevent the test masses from being disturbed.

    Scientists call this drag-free flight. In its first two months of operations in early 2016, LISA Pathfinder demonstrated the process with a precision some five times better than its mission requirements, making it the most sensitive instrument for measuring acceleration yet flown. It has now reached the sensitivity level needed to build a full multi-spacecraft gravitational wave observatory.

    “Every time microscopic dust strikes LISA Pathfinder, its thrusters null out the small amount of momentum transferred to the spacecraft,” said Goddard co-investigator Diego Janches. “We can turn that around and use the thruster firings to learn more about the impacting particles. One team’s noise becomes another team’s data.”

    Much of what we know about interplanetary dust is limited to Earth’s neighborhood, thanks in large part to NASA’s Long Duration Exposure Facility (LDEF).

    3
    The LDEF in Low Earth Orbit

    Launched into Earth orbit by the space shuttle Challenger in April 1984 and retrieved by the space shuttle Columbia in January 1990, LDEF hosted dozens of experiments, many of which were designed to better understand the meteoroid and orbital debris environment.

    The different compositions, orbits and histories of different asteroids and comets naturally produce dust with a range of masses and velocities. Scientists suspect the smallest and slowest particles are enhanced in Earth’s neighborhood, so the LDEF results are not representative of the wider solar system.

    “Small, slow particles near a planet are most susceptible to the planet’s gravitational pull, which we call gravitational focusing,” Janches said. This means the micrometeoroid flux near Earth should be much higher than that experienced by LISA Pathfinder, located about 930,000 miles (1.5 million kilometers) closer to the sun.

    To find the impacts, Tyson Littenberg at NASA’s Marshall Space Flight Center in Huntsville, Alabama, adapted an algorithm he originally developed to search for gravitational waves in data from the ground-based detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO), located in Livingston, Louisiana, and Hanford, Washington. In fact, it was one of many algorithms that played a role in the discovery of gravitational waves by LIGO, announced in February 2016.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    “The way it works is that we come up with a guess of what the signal might look like, then study how LIGO or LISA Pathfinder would react if this guess were true,” Littenberg explained. “For LIGO, we’re guessing about the waveform, the peaks and valleys of the gravitational wave. For LISA Pathfinder, we’re guessing about an impact.”

    To map out the probability of likely sources, the team generates millions of different scenarios describing what the source might be and compares them to what the spacecraft actually detects.

    In response to an impact, LISA Pathfinder fires its thrusters to counteract both the minute “push” from the strike and any change in the spacecraft’s spin. Together, these quantities allow the researchers to determine the impact’s location on the spacecraft and reconstruct the micrometeoroid’s original trajectory. This may allow the team to identify individual debris streams and perhaps relate them to known asteroids and comets.

    “This is a very nice collaboration,” said Paul McNamara, the LISA Pathfinder project scientist at ESA’s Directorate of Science in Noordwijk, the Netherlands. “This is data we use for doing our science measurements, and as an offshoot of that, Ira and his team can tell us about microparticles hitting the spacecraft.”

    Its distant location, sensitivity to low-mass particles, and ability to measure the size and direction of impacting particles make LISA Pathfinder a unique instrument for studying the population of micrometeoroids in the inner solar system. But it’s only the beginning.

    “This is a proof of concept, but we’d hope to repeat this technique with a full gravitational wave observatory that ESA and NASA are currently studying for the future,” said Thorpe. “With multiple spacecraft in different orbits and a much longer observing time, the quality of the data should really improve.”

    LISA Pathfinder is managed by ESA and includes contributions from NASA Goddard and NASA’s Jet Propulsion Laboratory in Pasadena, California. The mission launched on Dec. 3, 2015, and began orbiting a point called Earth-sun L1, roughly 930,000 miles (1.5 million km) from Earth in the sun’s direction, in late January 2016.

    LISA stands for Laser Interferometer Space Antenna, a space-based gravitational wave observatory concept that has been studied in great detail by both NASA and ESA. It is a concept being explored for the third large mission of ESA’s Cosmic Vision Plan, which seeks to launch a gravitational wave observatory in 2034.

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


    NASA/Goddard Campus

     
  • richardmitnick 3:59 pm on December 13, 2016 Permalink | Reply
    Tags: , , , ESA Lisa Pathfinder, ,   

    From ESA: “LISA Pathfinder’s pioneering mission continues” 

    ESA Space For Europe Banner

    European Space Agency

    13 December 2016
    Paul McNamara
    LISA Pathfinder Project Scientist
    European Space Agency
    Tel: +31 71 565 8239
    Email: paul.mcnamara@esa.int

    Oliver Jennrich
    LISA Pathfinder Deputy Mission Scientist
    L3 mission Study Scientist
    European Space Agency
    Tel: +31 71 565 6074
    Email: oliver.jennrich@esa.int

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder

    On 7 December, LISA Pathfinder started the extended phase of its mission, an additional six months during which scientists and engineers will push the experiment to its limits in preparation for ESA’s future space observatory of gravitational waves.

    LISA Pathfinder, a demonstration mission to validate important technologies to observe gravitational waves – fluctuations in the fabric of spacetime – from space, was launched just over a year ago, on 3 December 2015.

    After a six-week-long journey, the spacecraft reached its operational orbit around the first Sun-Earth Lagrange point, L1 – 1.5 million km away from Earth towards the Sun – at the end of January. There, following commissioning of the on board instrumentation, LISA Pathfinder started its science mission on 1 March.

    Much to the team’s surprise, it did not take as long as expected to achieve the mission’s goal: demonstrating that two test masses – a pair of identical gold-platinum cubes – can be placed in the most precise freefall ever performed. In fact, the desired level of precision was already obtained within the first day of LISA Pathfinder’s scientific operations.

    Over the following months, scientists and engineers kept improving the performance of the experiment. They described these first results, including an analysis of the residual sources of disturbance on the cubes’ almost perfect freefall motion, in a paper published at the beginning of June in Physical Review Letters.

    2
    LISA Pathfinder performance. Credit: spacecraft: ESA/ATG medialab; data: ESA/LISA Pathfinder Collaboration

    Then, on 25 June, the first operations phase, using the LISA Technology Package (LTP), was completed. The LTP is a European payload consisting of the test masses, inertial sensors, and laser interferometer, and uses a series of cold-gas micronewton thrusters to move the satellite and keep it centred on the cubes, in response to external and internal forces battering them around.

    Operations continued with NASA’s Disturbance Reduction System (DRS), an additional experiment which receives measurement input from the inertial sensors of the LTP but employs its own micronewton thrusters based on colloidal technology.

    Following completion of the DRS operations, the extended mission of LISA Pathfinder began on 7 December 2016, at 09:00 CET (08:00 UTC). It will last until 31 May 2017, making use of both the LTP and DRS payloads.

    “So far, we’ve been busy demonstrating the performance of LISA Pathfinder, which has been steadily improving as time went by,” says Paul McNamara, LISA Pathfinder Project Scientist at ESA, “but now we can spend the next six months learning everything we need to know to build and operate a gravitational-wave observatory in space.”

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    Artist’s impression of a pair of merging black holes, releasing gravitational waves. Credit: ESA–C.Carreau

    Last October, ESA issued a call inviting European scientists to propose concepts for the third large mission (L3) in its Cosmic Vision plan, which will be a space observatory to study the gravitational Universe. The selection is expected to take place in the first half of 2017, with a preliminary internal study phase planned for later in the year.

    The future observatory will detect gravitational waves with frequencies from 1 Hz down to 0.1 mHz. These are about a hundred to a million times lower than the frequencies of waves that can be measured with ground-based experiments like the Laser Interferometer Gravitational-Wave Observatory (LIGO), which obtained the first direct detection of gravitational waves in September 2015.

    LIGO bloc new
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib
    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    During the extended mission of LISA Pathfinder, the team will run a series of long duration experiments to better characterise the mission performance especially at the lowest frequencies that will be probed by the future observatory.

    “We are thrilled to be pushing the limits of LISA Pathfinder, a unique physics laboratory in space giving us confidence that we can definitely build a space-borne observatory of gravitational waves”, says Oliver Jennrich, LISA Pathfinder deputy mission scientist and L3 study scientist at ESA.

    One of the operations that will be attempted in the coming weeks concerns the station-keeping manoeuvres that mission operators have been regularly conducting to keep the satellite on its operational orbit.

    LISA Pathfinder orbits around L1, but if left unattended, it would slowly drift away from the Lagrangian point under the gravitational pull of Earth. To avoid that, it is sufficient to fire the micro-newton thrusters once every one to two weeks.

    Between 25 December and 14 January, however, the team decided to apply no correction manoeuvres. This will allow the scientists to run uninterrupted experiments for almost three weeks, exploring what happens in the range of very low frequencies that are of interest to detect gravitational wave from space.

    4
    The LISA Technology Package core assembly at the heart of LISA Pathfinder. Credit: ESA/ATG medialab

    Another experiment concerns slightly higher frequencies, around 1–60 mHz. At these frequencies, the main source of disturbance seems to be gas molecules that are present in the test mass enclosures and bouncing off the two cubes – an effect that has been reducing as more molecules are being vented into space.

    The team is now curious to see whether additional sources of noise are lurking underneath, something that will be important for the future L3 mission. One possible way of testing this entails simply waiting until most molecules are vented into space, but there is an alternative: to switch off many of the heaters on board, reducing the temperature by ten degrees, and thereby reducing the pressure inside the enclosure. The team will run this experiment in late January.

    These are some examples of the range of experiments that will be conducted during LISA Pathfinder’s extended mission. Eventually, at the end of the mission, the spacecraft will be gently pushed towards a heliocentric orbit.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 7:09 am on June 7, 2016 Permalink | Reply
    Tags: , , , ESA Lisa Pathfinder,   

    From APS Physics: “LISA Pathfinder Paves the Way for Space-Based Gravitational Wave Observatory” 

    AmericanPhysicalSociety

    American Physical Society

    June 7, 2016

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder

    A key component of a future gravitational wave observatory passed a series of tests with flying colors. The Laser Interferometer Space Antenna (LISA) Pathfinder mission is a European Space Agency (ESA) project that proves in principle that an orbiting formation of spacecraft will be able to function as a space-based gravitational wave observatory. A paper detailing the first results from the LISA Pathfinder mission appears in Physical Review Letters along with an accompanying Viewpoint commentary in Physics.

    At the heart of the experiment is a two-kilogram cube of a high-purity gold and platinum alloy, called a test mass. The cube is nestled inside the shell-like LISA Pathfinder spacecraft, and has been in orbit since February 2016. The researchers found the test mass could be sufficiently stable and isolated from outside forces to fly in space and detect a whole new range of violent events that create gravitational waves.

    The LISA Pathfinder spacecraft is equipped with electrodes adjacent to each side of the test mass cube to detect the relative position and orientation of the test mass with respect to the spacecraft. An array of tiny thrusters on the outside of the spacecraft compensates for forces that could affect the test mass orbit, chiefly including the pressure from the solar photon flux.

    The mission is a crucial test of systems that will be incorporated in three spacecraft that will comprise the Laser Interferometer Space Antenna (LISA) gravitational wave observatory scheduled to launch in 2034.

    ESA/eLISA
    ESA/eLISA

    The LISA observatory will follow a heliocentric orbit trailing fifty million kilometers behind the Earth. Each LISA spacecraft will contain two test masses like the one currently in the LISA Pathfinder spacecraft. The LISA Pathfinder mission’s success is a crucial step in developing the LISA observatory.

    In the LISA observatory mission planned for 2034, laser interferometers will measure the distances between test masses housed in spacecraft flying in a triangular configuration roughly a million kilometers on a side. The LISA Pathfinder spacecraft contains a second test mass to form a minuscule equivalent of one leg of the triangular LISA formation. The second Pathfinder mass is electrostatically manipulated to maintain its position relative to the free falling test mass. The masses are separated by only about a third of a meter, which is far too short for the detection of gravitational waves, but is vital for testing the systems that will eventually make up the LISA observatory.

    Researchers report that the system reduces acceleration noise between the test masses to less than 0.54 x 10-15 g/(Hz)^½ over a frequency range of 0.7 mHz to 20 mHz. The noise in this range is five times lower than the LISA Pathfinder design threshold, and within a factor of 1.25 of the LISA observatory requirements. Above 60 mHz, acceleration noise is two orders of magnitude better than design requirements. According to the researchers, the measured performance of the Pathfinder mission systems would allow gravitational wave observations close to the original plan for the LISA Observatory.

    See the full article here .

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    American Physical Society
    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries.

     
  • richardmitnick 4:25 pm on April 19, 2016 Permalink | Reply
    Tags: , , , ESA Lisa Pathfinder,   

    From BBC: “Gravitational wave mission passes ‘sanity check’ “ 

    BBC
    BBC

    18 April 2016
    Jonathan Amos

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder

    A European Space Agency [ESA] effort to try to detect gravitational waves in space is not only technically feasible but compelling, a new report finds.

    A panel of experts was asked to perform a “sanity check” on the endeavour, which is likely to cost well in excess of one billion euros.

    The Gravitational Observatory Advisory Team says it sees no showstoppers.

    It even suggests ESA try to accelerate the project from its current proposed launch date in 2034 to 2029.

    Whether that is possible is largely a question of funding. Space missions launch on a schedule that is determined by a programme’s budget.

    “But after submitting our report, ESA came back to us and asked what we thought might be technically possible, putting aside the money,” explained Goat chairman, Dr Michael Perryman.

    “We are in the process of finalising a note on that, which will suggest the third quarter of 2029. So, 13 years from now,” he told BBC News.

    The agency has stated its intention to build a mission that investigates the “gravitational Universe”, and is set to issue a call to the scientific community to submit a detailed proposal.

    Ripples in the fabric of space-time

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    Artwork: Advanced Ligo detected coalescing black holes more than a billion light-years from Earth. NSF

    Caltech/MIT Advanced aLigo detector in Livingston, Louisiana
    Caltech/MIT Advanced aLigo detector in Livingston, Louisiana

    Gravitational waves are a prediction of the Theory of General Relativity
    Their existence had been inferred by science but only recently directly detected
    They are ripples in the fabric of space and time produced by violent events
    Accelerating masses will produce waves that propagate at the speed of light
    Detectable sources ought to include merging black holes and neutron starsGravity mission passes ‘sanity check’
    Advanced Ligo fires lasers into long, L-shaped tunnels; the waves disturb the light
    Detecting the waves opens up the Universe to completely new investigations

    Gravitational waves – ripples in space-time – have become the big topic of conversation since their first detection last year by the ground-based Advanced LIGO facilities in the US.

    Using a technique known as laser interferometry, the labs sensed the fantastically small disturbance at Earth generated by the merger of two black holes more than a billion light-years away.

    The discovery opens up a completely new way to do astronomy, allowing scientists to probe previously impenetrable regions of the cosmos and to test some of the fundamental ideas behind general relativity – Einstein’s theory of gravity.

    The Goat says the stunning detection by aLIGO is a game-changer: “In a single step, gravitational wave astronomy has been placed on a secure observational footing, opening the panorama to the next robust steps in a space-based gravitational wave observatory.”

    That was not the case when the panel started its work. Then, there were many people who thought a detection might be beyond our measurement capability.

    The Goat believes that any space-borne observatory ESA might pursue should proceed using the same technical approach as aLigo – laser interferometry.

    2
    aLIGO employs laser interferometers – the technology suggested also for a space mission. LIGO

    The agency is currently doing experiments in orbit that will prove some of the equipment needed on a future gravitational wave observatory. But the Goat also identifies critical additional developments that must now be prioritised to take the laser approach into space.

    That said, there is also encouraging support in the report for an alternative detection concept called atom interferometry. This is too immature at the moment to be a contender, the Goat says, but it could benefit from a technology demonstration mission in the near future.

    Since the 1980s, scientists have been working on a system to detect gravitational waves from orbit called LISA – the Laser Interferometer Space Antenna.

    It would fly a network of satellites separated by a few million kilometres.

    Lasers fired between these spacecraft would sense ripples in space-time generated by much more massive objects than the black holes seen by LIGO. LISA’s targets would be the monster black holes, millions of times the mass of our Sun, that coalesce when galaxies collide, for example.

    Future LISA: How many lasers can you fly?

    ESA is set to fly a mission dedicated to gravitational astronomy in the 2030s

    3
    The available budget will determine the architecture of an operational Lisa mission. eLISA

    The current LISA design proposes a two-arm laser interferometer (left)
    But scientists would prefer to fly an architecture that has three arms (right)
    The latter could more easily locate gravitational wave sources in the sky
    Whether two or three arms are flown will depend on the available budget
    At present, ESA rules only permit a maximum 20% involvement from NASA
    But it may require a bigger US participation to get the full architecture

    LISA was previously proposed as a joint venture between Europe and the US.

    When the Americans then ran into funding difficulties and pulled out, scientists on the European side “de-scoped” the mission to try to make it fit within the financial envelope available at the time. Many commentators thought this revised design compromised the science to an unacceptable degree.

    Researchers on both sides of the Atlantic are now pushing hard to go back to the old arrangement.

    This potentially represents something of a headache for ESA’s hierarchy.

    Following the American withdrawal, the European Space Agency instigated a “rule” that foreign contributions to its missions should in future represent no more than 20% of the overall cost.

    The restriction was designed to ensure that no mission could be scuppered by a sudden change of heart from an international partner.

    But this financial ceiling may have to be broken if the US is to come back onboard and participate in the type of space mission that gravitational wave scientists most want to see fly.

    The Goat “suggests that such a mission will be more robust, and provide a greater science return per euro, if the US could consider a larger contribution, including a re-establishment of a meaningful collaboration.”

    The call to formally propose a new mission and its architecture should go out within the next 12 months.

    “It is to be determined precisely when, but within the year,” confirmed Dr Fabio Favata, head of ESA’s Science Planning and Community Coordination Office.

    “The call will ask the community to define a realistic mission in detail. In the meantime, we are already in discussions with our member states and NASA about who could do what, at least in the study phase. The implementation phase would take more time, of course.”

    4
    ESA is already developing some technologies, but the Goat says others must now be prioritised. AIRBUS DS.

    See the full article here .

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  • richardmitnick 9:18 am on March 8, 2016 Permalink | Reply
    Tags: , , ESA Lisa Pathfinder,   

    From ESA: “A perfectly still laboratory in space” 

    ESA Space For Europe Banner

    European Space Agency

    8 March 2016
    Markus Bauer








    ESA Science Communication Officer









    Tel: +31 71 565 6799









    Mob: +31 61 594 3 954









    Email: markus.bauer@esa.int

    Paul McNamara
    LISA Pathfinder Project Scientist
    Scientific Support Office
    Directorate of Science
    European Space Agency
    Tel: +31 71 565 8239
    Email: paul.mcnamara@esa.int

    Stefano Vitale
    LISA Technology Package Principal Investigator
    University of Trento and INFN, Italy
    Tel: +39 046 128 1568
    Email: stefano.vitale@unitn.it

    Karsten Danzmann
    LISA Technology Package Co-Principal Investigator
    Max Planck Institute for Gravitational Physics
    and Institute for Gravitational Physics of Leibniz Universität Hannover
    Germany
    Tel: +49-511-762 2356
    Email: karsten.danzmann@aei.mpg.de

    Oliver Jennrich
    LISA Pathfinder Deputy Mission Scientist and L3 mission Study Scientist
    Scientific Support Office
    Directorate of Science
    European Space Agency
    Tel: +31 71 565 6074
    Email: oliver.jennrich@esa.int

    Elizabeth Landau
    DRS Media Relations Specialist
    NASA’s Jet Propulsion Laboratory
    Pasadena, CA, USA
    Tel: +1-818-354-6425
    Email: Elizabeth.Landau@jpl.nasa.gov

    ESA LISA Pathfinder
    ESA LISA Pathfinder

    Following a long series of tests, ESA’s LISA Pathfinder has started its science mission to prove key technologies and techniques needed to observe gravitational waves from space.

    Predicted by Albert Einstein a century ago, gravitational waves are fluctuations in the fabric of spacetime produced by exotic astronomical events such as supernova explosions or the merging of two black holes.

    Recently, the first direct detection of these waves inaugurated the era of gravitational astronomy.

    A future observatory in space, sensitive to gravitational waves with longer wavelengths than those detected on the ground, would be an essential tool to exploit this new field of study by probing some of the most massive and powerful objects in the Universe.

    With LISA Pathfinder, scientists and engineers are testing the technology needed to extend the quest for gravitational waves to space.

    ESA LISA Pathfinder technology package
    ESA LISA Pathfinder technology package

    n particular, LISA Pathfinder is designed to achieve the purest-known ‘freefall’, the extremely challenging condition necessary to build such an observatory. To do so, the team released two test masses – a pair of identical 2 kg gold–platinum cubes measuring 46 mm – inside the spacecraft and is now verifying that they are truly moving under the effect of gravity alone.

    This is by no means trivial: even in space, there are forces capable of disturbing the cubes, including the radiation and wind from the Sun, and they need be isolated from all of these non-gravitational influences. To do so, LISA Pathfinder continually measures their positions and manoeuvres around them with microthrusters to avoid ever touching them.

    “As they fall freely through space, the two test masses should be extraordinarily still, since no other force is perturbing their gravitational motion – only a gravitational wave could jiggle them around,” explains Stefano Vitale of University of Trento and INFN, Italy, Principal Investigator of the LISA Technology Package, the mission’s core payload.

    LISA Pathfinder, however, is not capable of detecting gravitational waves itself. For this crucial technology demonstration, the two freefalling cubes are only 38 cm apart – too close to record the minute wobbles in the fabric of spacetime.

    The variation in distance caused by a passing gravitational wave is so small that a full-scale space observatory will need test masses separated by roughly a million kilometres, and be able to detect changes in that separation of about one millionth of a millionth of a metre.

    “The precision we need to attain for future observations of gravitational waves from space is so high that it demands an unprecedented understanding of the physical forces at play on the test masses,” says Paul McNamara, ESA’s Project Scientist.


    Download mp4 video here.
    ESA’s LISA Pathfinder mission is a technology demonstrator that will pave the way for future spaceborne gravitational-wave observatories. It will operate about 1.5 million km from Earth towards the Sun, orbiting the first Sun–Earth ‘Lagrangian point’, L1.

    The animation of the spacecraft build-up begins with two freely falling test masses. Between them lies the central component of LISA Pathfinder’s payload: the 20 x 20 cm optical bench interferometer. A set of 22 mirrors and beam-splitters directs laser beams across the bench. There are two beams: one reflects off the two free-falling test masses while the other is confined to the bench. By comparing the length of the different paths covered by the beams, it is possible to monitor changes accurately in distance and orientation between the two test masses.

    A box surrounds the two masses without touching them, shielding them from outside influence and constantly applying tiny adjustments to its position. This internal payload is housed in a central cylinder, isolating the test masses from the other components of the science payload and spacecraft.

    The solar array provides power to the instrumentation and acts as a thermal shield. Microthrusters control the spacecraft to keep the master test mass centred in its housing, opposing the force of the solar radiation pressure – the main source of ‘noise’ – impinging on the solar array.

    Although LISA Pathfinder is not aimed at the detection of gravitational waves themselves, it will prove the innovative technologies needed to do so. It will demonstrate that the two independent masses can be monitored as they free-fall through space, reducing external and internal disturbances to the point where the relative test mass positions would be more stable than the expected change caused by a passing gravitational wave, equal to much less than the size of an atom.

    This is the essence of the LISA Pathfinder mission: after having released the cubes from their locking mechanisms and having made sure they are in the most precise freefall ever obtained, the scientists will now spend the next six months running experiments, ‘poking’ the masses to verify how still they really are.

    To interfere with their motion, the team will apply a number of different forces to them and study their reaction. One experiment will raise the temperature inside the high vacuum environment of their housing, heating the very few gas molecules that are left there, to measure if this has any effect on the cubes.

    Increasingly stronger magnetic and electric forces will also be applied to assess what amount of force is needed to divert them from freefall.

    “Our aim is not only to reduce the impact of forces that we already know are disturbing the cubes, but also to learn more about the remaining effects that are hidden in the noise,” says Karsten Danzmann, director at the Max Planck Institute for Gravitational Physics, director of the Institute for Gravitational Physics of Leibniz Universität Hannover, Germany, and Co-Principal Investigator of the LISA Technology Package.

    The scientific mission of LISA Pathfinder officially started on 1 March. Following a formal review of the commissioning period on 7 March, the mission was formally handed over from the ESA project and industrial teams that built it to the scientists who are now busy carrying out experiments on this unique gravity laboratory in space.

    These operations will take six months, split between 90 days for the LISA Technology Package and 90 days for the Disturbance Reduction System (DRS), an additional experiment including two extra sets of thrusters, provided by NASA’s Jet Propulsion Laboratory (JPL).

    “We are looking forward to demonstrating this thruster system and its ability to keep the two test masses extremely still,” says Charles Dunn, project technologist for the DRS at JPL.

    The results of LISA Pathfinder’s precision experiments will pave the way towards the L3 mission in ESA’s Cosmic Vision programme, a future project that will be dedicated to investigating the gravitational Universe by means of a large spaceborne observatory.

    “The mission is working exceptionally well, and with every measurement performed on the two freefalling cubes, we are gaining the confidence needed to eventually build the first gravitational wave observatory in space,” says Oliver Jennrich, LISA Pathfinder deputy mission scientist and L3 study scientist at ESA.

    Observations from space would widen the recently opened window on the gravitational Universe, being sensitive to fluctuations produced by supermassive black holes, with masses millions to billions of times larger than our Sun’s, which sit at the centre of most large galaxies. When galaxies collide and merge, so do eventually the cosmic monsters at their cores, releasing gravitational waves as they slowly coalesce.

    These data will provide unique clues about the build-up of structures across the Universe, and especially at early times in cosmic history, when the very first stars and galaxies were taking shape.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 1:11 pm on December 3, 2015 Permalink | Reply
    Tags: , , ESA Lisa Pathfinder,   

    From JPL-Caltech: “LISA Pathfinder Carries Advanced NASA Thruster Tech” 

    JPL-Caltech

    December 3, 2015
    Elizabeth Landau
    NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    Elizabeth.Landau@jpl.nasa.gov

    1
    This cluster of four colloid thrusters is part of the Disturbance Reduction System, developed by NASA-JPL, which will help keep ESA’s LISA Pathfinder spacecraft extremely stable. Credit: ESA/NASA/JPL-Caltech

    The LISA Pathfinder spacecraft is on its way to space, having successfully launched from Kourou, French Guiana (Dec. 3 local time/Dec. 2 PST).

    ESA LISA Pathfinder
    ESA/ LISA Pathfinder

    On board is the state-of-the-art Disturbance Reduction System (DRS), a thruster technology developed at NASA’s Jet Propulsion Laboratory, Pasadena, California.

    LISA Pathfinder, led by the European Space Agency (ESA), is designed to test technologies that could one day detect gravitational waves. Gravitational waves, predicted by Einstein’s theory of general relativity, are ripples in spacetime produced by any accelerating body. But the waves are so weak that Earth- or space-based observatories would likely only be able to directly detect such signals coming from massive astronomical systems, such as binary black holes or exploding stars. Detecting gravitational waves would be an important piece in the puzzle of how our universe began.

    The incredible faintness of gravitational waves makes it critical to keep a spacecraft stable enough to detect them. But there are obstacles to staying completely still, even in seemingly empty space. Most notably, solar radiation pressure — the force exerted by sunlight — pushes on the spacecraft ever so delicately. In fact, the force of solar radiation pressure on LISA Pathfinder is analogous to the weight of a grain of sand on earth.

    The Disturbance Reduction System uses colloid micronewton thrusters, the first of their kind, to keep the spacecraft as still as possible and compensate for solar pressure. These thrusters electrically charge small liquid droplets and accelerate them through an electric field in order to generate thrust. Developed by Busek Co., Natick, Massachusetts, with technical support from JPL, the thrusters will deliver 5 to 30 micronewtons of thrust (about the weight of a mosquito) continuously, with exquisite precision, to counteract the force of sunlight.

    The DRS microthrusters aim to control the spacecraft’s position to within a millionth of a millimeter, using software provided by NASA’s Goddard Spaceflight Center, Greenbelt, Maryland.

    “The DRS is one of the most precise thruster systems for a spacecraft ever qualified for use in space,” said Phil Barela, DRS project manager at JPL.

    To test the concept of gravitational-wave detection technology, LISA Pathfinder uses two cube-shaped test masses. These masses are objects designed to respond — to the greatest extent possible — only to gravity. They are made of a mixture of gold and platinum, which means they are very dense and also non-magnetic. Each weighs about 4 pounds (2 kilograms) and measures 1.8 inches (4.6 centimeters) on a side. The masses will float in separate vacuum chambers, 15 inches (38 centimeters) apart.

    The spacecraft’s position will be continuously adjusted using its ultra-precise thrusters to stay centered about these test masses. Using lasers, the position of the freely floating test masses will be measured, by an ESA-provided interferometer instrument, to an accuracy of 100,000th of the width of a human hair.

    LISA Pathfinder will not directly detect gravitational waves, but it will demonstrate technologies necessary to observe these mysterious phenomena. A full-scale observatory could use the same kind of sensors, but they would be housed in three individual spacecraft separated by about 600,000 miles (1 million kilometers). Scientists could then measure how gravitational waves change the distance between the test masses, which would be a difference on the scale of picometers (one picometer is one trillionth of a meter).

    “A system akin to the DRS could be used on a future gravitational-wave mission for stability,” said Charles Dunn, project technologist for the DRS at JPL.

    The DRS may also pave the way for similar advanced thruster systems like it to be used by other spacecraft. For example, a DRS-like system could be used to stabilize a future spacecraft that needs to be very still in order to detect exoplanets.

    DRS could also be used for formation flying. For example, a constellation of small satellites could incorporate the thrusters in order to be perfectly synchronous while flying together. Even a single satellite in Earth orbit could benefit from DRS, as the system would allow for fine control of its path.

    LISA Pathfinder launched on a Vega rocket and will take about seven weeks to reach its operational orbit. The spacecraft will orbit what is called the Lagrange Point L1, about 930,000 miles (1.5 million kilometers) from Earth in the direction of the sun.

    2
    Simplified version of Langrange contour plot.

    The spacecraft will then begin a six-week commissioning period followed by eight months of technology demonstration. ESA’s LISA Technology Package, with a different set of cold gas thrusters and separate software that controls them, will be demonstrated for the first four months. The DRS will be tested for about four months after that.

    LISA Pathfinder is managed by ESA. The spacecraft was built by Airbus Defence and Space, Ltd. (UK). Airbus Defence and Space, GmbH (Germany), is the payload architect for the LISA Technology Package. The DRS is managed by JPL. The California Institute of Technology manages JPL for NASA.

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 11:32 am on November 27, 2015 Permalink | Reply
    Tags: , , ESA Lisa Pathfinder,   

    From ESA: “Flight teams prepare for LISA Pathfinder liftoff” 

    ESASpaceForEuropeBanner
    European Space Agency

    27 November 2015

    ESA LISA Pathfinder

    Following months of intensive training, mission controllers for the LISA Pathfinder gravitational wave detection testbed will complete a final rehearsal tomorrow, ensuring that all is ready for the journey to space.

    Next week, a Vega rocket will lift LISA Pathfinder into space on a mission that will test-drive the hardware for detecting gravitational waves – ripples in spacetime, the very fabric of the Universe.

    Vega is expected to lift off at 04:15 GMT on 2 December from Europe’s Spaceport in Kourou, beginning a 105-minute ride to space.

    LISA Pathfinder will separate from the final stage at around 06:00 GMT, moments before transmitting its first signals to the ground.

    For engineers at ESA’s ESOC control centre in Darmstadt, Germany, separation is a crucial moment in the demanding first days in orbit.

    Teams will establish control, start switching on the control systems and begin taking the craft through a series of health checks.

    2
    LISA Pathfinder’s journey from launch to its final destination, around the L1 Sun–Earth Lagrangian point some 1.5 million km away from Earth towards the Sun

    Insert: LISA Pathfinder will be launched in December 2015 on a Vega rocket from Europe’s Spaceport in French Guiana. Vega will place LISA Pathfinder into an elliptical orbit, with a perigee (closest approach) of 200 km, apogee (furthest approach) of 1540 km, and inclination of about 6.5º. Then, when Vega’s final stage is jettisoned, LISA Pathfinder will continue under its own power, beginning a series of six apogee-raising manoeuvres. These manoeuvres will be completed two weeks after launch.

    After this, LISA Pathfinder will cruise towards its final orbiting location. A month after its final burn, it will jettison its propulsion module and continue its journey before settling into an orbit around the L1. The entire journey, from launch to arrival at the operational orbit around L1, will take about eight weeks.

    Experts spanning a range of specialities, including mission operations, flight dynamics, software and ground stations, will work 24 hours a day for the first dozen days to ensure LISA Pathfinder is operating as it should and to send it towards its final destination.

    It will conduct its mission circling the ‘L1 Lagrange point’, a virtual position in space some 1.5 million kilometres from Earth in the direction of the Sun.

    “LISA Pathfinder is a complex mission,” notes flight director Andreas Rudolph. “Even after we’re safely in space, we will have to make seven or eight thruster burns in the first 10 days to take it as safely as possible through Earth’s radiation belts and get it onto the correct trajectory.

    “We won’t arrive at around L1 until late in January, and until then teams will be working intensively to ensure that the thruster burns go as planned, that our navigation is correct and that we ensure the instruments and all flight systems are working normally.”

    LISA Pathfinder’s science mission is expected to last 180 days (updates and details on the science and technology objectives).

    3
    Team training

    By launch day, the 80-plus people on the mission teams will have completed many months of training, including a lengthy series of simulations using the Main Control Room at ESOC.

    “Throughout 2015, the mission team have spent many hours sitting ‘on console’, using simulation software and real flight hardware to practise all stages of the mission,” says spacecraft operations manager Ian Harrison.

    “We’ve practised routine situations as well as contingencies, so that everyone knows what to do if something goes wrong.”

    Several of the trainings were ‘live’, with mission control systems at ESOC connected to LISA Pathfinder as it was being completed at a test centre near Munich. Many simulations also included the science operations teams responsible for the instruments.

    The mission will initially be followed by ESA ground stations at Kourou in French Guiana, Perth in Australia, and Maspalomas in Spain, as well as by a dedicated antenna at Italy’s Malindi station in Kenya.

    4
    Kourou tracking station

    On launch day, grabbing the first signal from LISA Pathfinder will be particularly complicated because the spacecraft uses higher-frequency X-band radio signals for its communications. This produces a much narrower beam than the traditional lower-frequency S-band radio waves normally used for missions to low Earth orbit.

    “X-band is typical for a craft that will voyage 1.5 million kilometres from Earth,” says ground operations engineer Fabienne Delhaise, “but is not common for satellites in low orbit, which is where LISA Pathfinder starts out.”

    “This means our ground stations must point especially accurately and use a special adapter to catch signals just after separation, when the craft is still near Earth.”

    Later, once its orbit rises above about 45 000 km, mission controllers will use ESA’s powerful deep-space radio dishes in Australia, Spain and Argentina, which are designed just for such distant signalling.

    “Our mission teams are ready, the tracking stations are ready and our carefully developed ground systems are ready,” says Paolo Ferri, who heads ESA’s mission operations.

    “We’re excited about the technology on board and we’re looking forward to a smooth launch and an excellent start to this fantastic mission.”

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 12:51 pm on November 17, 2015 Permalink | Reply
    Tags: , ESA Lisa Pathfinder, ,   

    From Nature: “Freefall space cubes are test for gravitational wave spotter” 

    Nature Mag
    Nature

    17 November 2015
    Elizabeth Gibney

    There is a lot riding on the LISA Pathfinder mission, an ambitious effort to test whether intricate technology designed to detect ripples in space-time can be deployed in space.

    ESA LISA Pathfinder
    LISA

    Scheduled to launch on 2 December, the spacecraft is a long-awaited test-drive for a future €1-billion (US$1.1-billion) space observatory planned by the European Space Agency (ESA). The follow-up mission would track the largest objects in the Universe, including mergers between supermassive black holes and collisions between galaxies, by the space-time ripples that they create.

    First predicted by Albert Einstein almost exactly 100 years ago as part of his general theory of relativity (see nature.com/relativity100), such gravitational waves have never been observed directly — let alone used to study the cosmos. There are already Earth-based observatories hunting these waves, but a space-based one would search for waves at the opposite end of the spectrum.

    Advanced Ligo
    MIT/Caltech Advanced LIGO

    “It’s like having a radio telescope as well as an optical one,” says Karsten Danzmann, director of the Max Planck Institute for Gravitational Physics in Hanover, Germany, and co-principal investigator for the Pathfinder mission. “The part of the Universe you see is completely different.”

    The final space-based observatory will try to spot the stretching and compressing of space by bouncing laser beams between three masses floating in freefall, each separated from the others by some 5 million kilometres. Because the masses would be protected from all other external forces, only a gravitational wave should disrupt the synchrony of their falling motion — a disturbance that would affect laser frequency.

    The LISA Pathfinder (named after the Laser Interferometer Space Antenna, the concept behind the gravitational-wave observatory) is a smaller-scale test of this ultimate plan. With a pricetag of €400 million, it uses just two masses — each a 2-kilogram cube of gold and platinum — separated by a mere 38 centimetres, which allows them to fit inside the same spacecraft.

    Unlike that of the observatory that it is designed to test-drive, this set-up is not sensitive enough to detect gravitational waves — instead, its purpose is to show that the masses can be completely isolated, and that any deviations in their relative motion can be measured with picometre accuracy. “We’re missing out the 5 million kilometres, but so what?” says Paul McNamara, the mission’s project scientist. “Pretty much everything that could affect our ability to measure gravitational waves is here.”

    From the time of Pathfinder’s launch from ESA’s spaceport in Kourou, French Guiana, to the end of its subsequent eight-week journey, the masses will stay pinned to their housing deep inside the craft. But on arrival in orbit around a stable point between the Sun and Earth called Lagrange point 1, or L-1, about 1.5 million kilometres away, the cubes will be gently released to float within the spacecraft (see ‘Precision lab in space’).

    2

    Once in freefall, “the challenge is to isolate this little cube from everything around it, so the only thing it sees is space-time”, says McNamara. Expected disturbances are pressure from solar radiation and stray magnetic fields; the equipment is so precise that it should detect even a force equal to the weight of a small bacterium on Earth.

    As a high-precision laboratory in space, the LISA Pathfinder is unlike anything that ESA has done before, says Tim Sumner, an astrophysicist at Imperial College London who led the team that constructed one of the craft’s protection mechanisms.

    Another unusual element is that the major cargo — the cubes — will define the craft’s trajectory, rather than vice versa. As they orbit around L-1 and fall in microgravity, Pathfinder will deploy microthrusters that are so gentle, it would take around 1,000 to lift a piece of paper on Earth. The thrusters will monitor the cubes’ positions, ensuring that the craft hovers around the cubes without letting them touch its sides. Such a set-up required the teams who built the instruments and the engineers who made the craft to work together to an unprecedented degree, says Sumner.

    These complexities go a long way towards explaining why the launch has taken so long to orchestrate, says Stefano Vitale, a physicist at the University of Trento in Italy, and a principal investigator for the Pathfinder mission; Pathfinder was approved by ESA in 2000 and originally intended for launch in 2006. “Coarsely speaking, I think people underestimated the difficulty,” says Vitale. “But that’s why you have a Pathfinder.”

    The final step in the planned mission will test Pathfinder’s limits by instructing onboard instruments to tweak the internal temperature and magnetic and electrostatic fields to see how such changes affect the cubes. “We want to learn everything we can about the physics of a free-floating body, and everything we learn will feed back into design of the future mission,” says McNamara.

    However, some opportunistic ESA scientists are already thinking about how Pathfinder’s instruments could be used to inform other problems once its main mission, which could take up to a year, is complete. Measurement of the gravitational constant, known as Big G, for example, should fall naturally out of Pathfinder’s data, Sumner says. Because the true value of Big G is disputed, a fresh measurement from space would provide useful perspective.

    To get a higher precision measurement, ESA may also consider extending the mission — although Sumner says that scientists would only request this after Pathfinder has proved itself, a few months in. He and his colleagues have also discussed using the craft’s thrusters to send it to a spot known as a saddle point, where the gravitational pulls of Earth and the Sun cancel each other out. This could reveal how gravity behaves at its lowest level possible in the Solar System, with little extra cost. Few scientists doubt that Einstein’s theories hold, says Sumner, but it would be interesting to do the test nonetheless.

    Vitale, however, points out that it is important for researchers to stay focused on the mission’s immediate goal. “Our main objective is to demonstrate freefall,” he says, “and we don’t want to be distracted from that.”

    See the full article here .

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    Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public.

     
  • richardmitnick 1:40 pm on September 28, 2015 Permalink | Reply
    Tags: , , ESA Lisa Pathfinder,   

    From ESA: “If our eyes could see gravitational waves” 

    ESASpaceForEuropeBanner
    European Space Agency

    28/09/2015

    1
    This image is from a simulation of two black holes merging and the resulting emission of gravitational radiation, published by NASA in 2012.

    Picture the scene: two gigantic black holes, each one a good fraction of the size of our Solar System spiralling around each other. Closer and closer they draw until they touch and merge into a single, even more gigantic gravitational prison.

    But what would you actually see? For such a cataclysmic event, it might all take place with remarkable stealth because black holes by their very nature emit no light at all. Rather than light, it would be a different story if our eyes could see gravitational waves.

    This is what the merger of two black holes would look like. It is a computer simulation of the gravitational waves that would ripple away from the titanic collision, a bit like the ripples on a pond when a pebble drops into the water.

    In the case of gravitational waves, the disturbances are not in water but in the spacetime continuum. This is the mathematical ‘fabric’ of space and time that Albert Einstein used to explain gravity.

    Gravitational radiation has been indirectly observed but never seen directly. Its detection would open a whole new way of studying the Universe. As a result, astronomers are working on both ground-based and space-based detectors. And it is a real challenge.

    Gravitational radiation is incredibly difficult to measure. The ripples cause atoms to ‘bob’ about to just 1 part in 1000 000 000 000 000 000 000. Building a detector to notice this is like measuring the distance from Earth to the Sun to the accuracy of the size of a hydrogen atom.

    Following decades of technology development and experiments, detectors on the ground are nearing the required sensitivity. The first detections are expected in the next few years. But these detectors can see only half of the picture. The mass of the colliding black holes determines the frequency of the gravitational radiation.

    The merger of small black holes, each about a few times the mass of the Sun, will create high-frequency gravitational waves that could be seen from the ground. But the giant black holes that sit at the heart of galaxies with masses of a million times that of the Sun will generate gravitational waves of much lower frequency. These cannot be detected with ground-based systems because seismic interference and other noise will overwhelm the signals. Hence, spaceborne observatories are needed.

    ESA has selected the gravitational Universe as the focus for the third large mission in the Cosmic Vision plan, with a launch date of around 2034.

    Unlocking the gravitational Universe will require a highly ambitious mission. In preparation, ESA will launch LISA-Pathfinder this November to test some of the essential technologies needed to build confidence in future spaceborne gravitational wave observatories.

    ESA LISA Pathfinder
    LISA Pathfinder

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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