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  1. Under his direction, the site grew to become a credible video game streaming contender . Matt Salsamendi was just 18 years old when he co-founded Mixer, the site which has grown to be the third most popular video game streaming platform. Now, he's announced he is moving on from the company to take on new projects. The company was originally called Beam, and it was acquired by Microsoft in 2016. It was subsequently renamed as Mixer, where it succeeded in tempting over some high-profile Twitch users such as Fortnite star Ninja. Mixer remains a David next to Twitch's Goliath though, with a StreamElements report showing Twitch makes up 72.2 percent of time spent watching live streams and Mixer makes up just 3 percent. Mixer is continuing to grow, however, with a report from Streamlabs showing the number of gaming hours streamed on the platform has tripled in the third quarter of this year, likely due to the presence on Ninja on the platform. "During my time at Mixer, we made leaps in technology and community that changed the way people think about competition in the game streaming space," Salsamendi wrote in a statement posted to Twitter. Regarding the company's acquisition by Microsoft, he was positive: "The support we received from across Microsoft was humbling for me and the experience I've gained in the last three years is irreplaceable." Salsamendi is now moving into a different field, working on using lasers in music projects. He didn't give a lot of details on what his new project will be, but he said he has a passion for lighting at EDM festivals and tours and will be pursuing that. Source
  2. Satellites play chase to measure gravity, achieve picometer accuracy Satellites tracked to the picometer, test tech for gravitational wave detector. Enlarge NASA/JPL-Caltech The spinoffs from gravitational wave detectors are not just new scientific discoveries. The technology also has other uses. A good example of this is the gravity-measuring mission, GRACE Follow On, which was launched last year. The first reports on its laser rangefinder's performance have been released, and it makes for impressive reading. Gravitational wave detectors work by measuring tiny changes in the distance between two mirrors. Ripples in space-time cause a tiny oscillation in that distance, which is then detected by comparing the phase shift between light that has traveled between the two mirrors and light that has traveled along a path that was unaffected by the gravitational wave. To put it in perspective, a gravitational wave detector measures changes that are far smaller than the diameter of an atom and are more like the diameter of a single proton. The gravity of GRACE Similar technology found its way into space to increase the sensitivity of Earth-monitoring instruments. On Earth, we have stationary detectors that wait for gravitational waves to pass through them. In orbit, the detector is moving and can measure subtle changes in the Earth's gravitational field. That brings us to GRACE—a backronym for gravity recovery and climate experiment—a pair of satellites that orbited the Earth at a fixed distance from each other. Or they would be fixed if the Earth’s gravity didn’t change in time and space. GRACE used a radar system to measure the distance between the two satellites to track those changes, providing information about the gravitational field it was traveling through. Changes in that distance could be translated into local measurements of the acceleration due to gravity. This, in turn, is used to measure things like the volume of water in aquifers. GRACE turned out to be hugely useful but, like all satellite missions, eventually died. In this case, the battery on GRACE-2 failed, and the pair was cremated in the Earth’s atmosphere. The follow-up to GRACE, called GRACE-FO (follow on), was launched in 2018. GRACE-FO is mostly a copy of GRACE, but scientists took the opportunity to include a new distance-measuring tool that would outperform the old GRACE radar system. This, if successful, would mean that the measurement data would not put a limit on how we interpreted the data. Instead, models of the tides would need to be improved. It also just happens that the technology required to do this sort of station-keeping measurement is exactly the technology required for LISA (a proposed space-based gravitational wave observatory). The LISA pathfinder mission was hugely successful but, being a single satellite, could not test station-keeping technologies. So, in many ways, the GRACE-FO satellites are also a lightweight LISA pathfinder mission. Smooth running Since June 14, when contact was established with the satellites, scientists have been testing the laser range-finder system. And, to put it simply, it absolutely smashes the design specifications. Over a time period between 5 and 1,000 seconds, the system should be able to detect distance changes of 2 to 40 billionths of a meter between two satellites that are separated by 220km. However, the team reports sensitivity as low as 300 trillionths of a meter. To put this in perspective, the radar system on the original GRACE was sensitive to changes at about the 10 micrometer level. How do you achieve this sort of accuracy? In short, with lasers. More seriously, a laser beam on the master satellite is stabilized to have a very precise frequency. That laser is shot at the slave satellite. This in itself is an achievement because the laser has to be continuously aimed in the right direction (the radar system manages this with a fixed antenna). The slave satellite uses the incoming light (all 25nW of it) to do two things. First it uses a tiny amount to check that the laser is pointing in the right direction. The remainder of the light is used to set the phase of its own laser, which is sent back to the master satellite—the received laser light is too weak to just be reflected back. The light that is received at the master acquires a phase shift relative to the transmitted light that is proportional to the distance between the two satellites. Since the distance is continuously changing, this is measured as an additional frequency in the received laser spectrum. Hence, a frequency measurement of the incoming laser spectrum becomes a measurement of distance, which, in turn, becomes a measurement of acceleration due to gravity. In the short term, this means that GRACE-FO data will be even better than expected, and the modelers are going to have to get back to work. In the long term, it means that more of the technology for LISA will be validated with the additional benefit of a long-term robustness study. In the very short term, it gave me some good weekend reading. Source: Satellites play chase to measure gravity, achieve picometer accuracy (Ars Technica)
  3. NASA’s Lunar Laser Communication Demonstration (LLCD) has made history using a pulsed laser beam to transmit data over the 239,000 miles between the moon and Earth at a record-breaking download rate of 622 megabits per second (Mbps). LLCD is NASA’s first system for two-way communication using a laser instead of radio waves. It also has demonstrated an error-free data upload rate of 20 Mbps transmitted from the primary ground station in New Mexico to the spacecraft currently orbiting the moon. “LLCD is the first step on our roadmap toward building the next generation of space communication capability,” said Badri Younes, NASA’s deputy associate administrator for space communications and navigation (SCaN) in Washington. “We are encouraged by the results of the demonstration to this point, and we are confident we are on the right path to introduce this new capability into operational service soon.” Since NASA first ventured into space, it has relied on radio frequency (RF) communication. However, RF is reaching its limit as demand for more data capacity continues to increase. The development and deployment of laser communications will enable NASA to extend communication capabilities such as increased image resolution and 3-D video transmission from deep space. “The goal of LLCD is to validate and build confidence in this technology so that future missions will consider using it,” said Don Cornwell, LLCD manager at NASA’s Goddard Space Flight Center in Greenbelt, Md. “This unique ability developed by the Massachusetts Institute of Technology’s Lincoln Laboratory has incredible application possibilities.” LLCD is a short-duration experiment and the precursor to NASA’s long-duration demonstration, the Laser Communications Relay Demonstration (LCRD). LCRD is a part of the agency’s Technology Demonstration Missions Program, which is working to develop crosscutting technology capable of operating in the rigors of space. It is scheduled to launch in 2017. LLCD is hosted aboard NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE), launched in September from NASA’s Wallops Flight Facility on Wallops Island, Va. LADEE is a 100-day robotic mission operated by the agency’s Ames Research Center at Moffett Field, Calif. LADEE’s mission is to provide data that will help NASA determine whether dust caused the mysterious glow astronauts observed on the lunar horizon during several Apollo missions. It also will explore the moon’s atmosphere. Ames designed, developed, built, integrated and tested LADEE, and manages overall operations of the spacecraft. NASA’s Science Mission Directorate in Washington funds the LADEE mission. The LLCD system, flight terminal and primary ground terminal at NASA’s White Sands Test Facility in Las Cruces, N.M., were developed by the Lincoln Laboratory at MIT. The Table Mountain Optical Communications Technology Laboratory operated by NASA’s Jet Propulsion Laboratory in Pasadena, Calif., is participating in the demonstration. A third ground station operated by the European Space Agency on Tenerife in the Canary Islands also will be participating in the demonstration. Original Article
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