vendredi 24 mars 2017

Extending Science in the Search for the Origin of the Cosmos












ISS - AMS-02 Mission patch.

March 24, 2017

Attached to the outside of the International Space Station, the Alpha Magnetic Spectrometer (AMS) is circling Earth and sifting through cosmic ray particles traveling in the universe. Hundreds of scientists from 16 countries are analyzing the data, hoping to determine what the universe is made of and how it began, looking for clues on the origin of dark matter, invisible matter that can't be directly detected but can be inferred, and the existence of antimatter, made of elementary particles with the opposite charge of ordinary matter, which scientists have rarely been able to observe.

AMS is composed of a magnet and several detectors that provide the scientists on the ground with information about the particles. The magnetic field produced by the magnet bends the trajectory of the electrically-charged cosmic ray particles already traveling in the space station’s path, thereby identifying the sign of the particle’s charge. AMS records the number of particles that pass through its detectors; the kinds of particles passing, characteristics such as particle charge, the sign of the charge (positive or negative), mass and velocity; and which direction they came from so that scientists can attempt to track down their source. All of the information is collected using 300,000 data channels in the nanoseconds it takes a particle to travel through AMS, and then sent down to scientists on the ground for analysis.

The more particles AMS is able collect, the more scientists will be able to strengthen their findings. Launched in 2011, AMS was originally designed to operate for the duration of a three year mission, and has already surpassed that expectation. With the extension of the station through 2024, engineers are currently assessing long-term plans to extend the life of AMS to collect data throughout the lifetime of the station.

 Alpha Magnetic Spectrometer (AMS) on International Space Station (ISS)

Having exceeded the original three-year lifespan, some components are beginning to show wear. In particular, the thermal control system for one of the detectors, called the Silicon Tracker, has shown degradation. The system includes four redundant cooling pumps, only one of which is required to operate at given time. One of the pumps stopped functioning in March 2014, and another pump was found to have degraded as well, leading engineers on the ground to switch to one of two remaining pumps by the end of 2014 to continue collecting science data. A thermal cover was added during a spacewalk in 2015, and engineers switched to the last fully functional pump in March 2017 after the third pump showed similar signs of degradation.

A functioning thermal control system is required to support the silicon tracker, and data from the silicon tracker is needed in combination with the data from the other trackers to support the AMS research. The other components of AMS appear to be in good shape, and long-term planning is underway to evaluate the potential to bypass the pumps and associated equipment for this tracker with an upgraded system put in place during a series of spacewalks.

Close to 100 billion cosmic rays with energies up to multi trillion electron volts have been analyzed by AMS. Results to date have already challenged our understanding of the origin of cosmic ray particles and how they travel through the universe. For example, researchers have found an excess of high-energy positron particles, which are the anti-particle opposite to the common electron. The excess of positrons might be from a source we are familiar with, such as a pulsar, but they could also be produced by collisions of particles of dark matter. With additional data, enabled by extending the life of AMS, scientist may be able to determine the rate at which they decrease, shedding light on a possible cause. To provide further insight, AMS scientists are also analyzing high-energy antiprotons, which pulsars do not produce and may be a unique signature of dark matter.

AMS is a joint effort between NASA and the Department of Energy’s Office of Science and is led by Principal Investigator Samuel Ting, a Nobel laureate from the Massachusetts Institute of Technology.  The AMS team includes some 600 physicists from 56 institutions in 16 countries from Europe, North America and Asia. The contributions from the various participants were integrated when the AMS was built at the European Organization for Nuclear Research (CERN) outside of Geneva, Switzerland.

Alpha Magnetic Spectrometer (AMS): https://ams.nasa.gov/

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

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

Image (mentioned), Text, Credits: NASA/Kathryn Hambleton.

Greetings, Orbiter.ch

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