Rovers Will Unroll a Telescope on the Moon’s Far Side

Astronomers need a quiet place to observe the cosmic dawn

2 min read
Illustration of a rover laying down flexible antenna on the lunar surface.
Illustration: Peter Sanitra

Illustration: Peter Sanitra

The far side of the moon offers a unique opportunity to radio astronomers: an observatory built there could peer into the early universe, shielded from electromagnetic interference from Earth.

For decades, astronomers have gazed up at the moon and dreamed about what they would do with its most unusual real estate. Because the moon is gravitationally locked to our planet, the same side of the moon always faces us. That means the lunar far side is the one place in the solar system where you can never see Earth—or, from a radio astronomer’s point of view, the one place where you can’t hear Earth. It may therefore be the ideal location for a radio telescope, as the receiver would be shielded by the bulk of the moon from both human-made electromagnetic noise and emissions from natural occurrences like Earth’s auroras.

Early plans for far-side radio observatories included telescopes that would use a wide range of frequencies and study many different phenomena. But as the years rolled by, ground- and satellite-based telescopes improved, and the scientific rationale for such lunar observatories weakened. With one exception: A far-side telescope would still be best for observing phenomena that can be detected only at low frequencies, which in the radio astronomy game means below 100 megahertz. Existing telescopes run into trouble below that threshold, when Earth’s ionosphere, radio interference, and ground effects begin to play havoc with observations; by 30 MHz, ground-based observations are precluded.

In recent years, scientific interest in those low frequencies has exploded. Understanding the very early universe could be the “killer app” for a far-side radio observatory, says Jack Burns, an astrophysics professor at the University of Colorado and the director of the NASA-funded Network for Exploration and Space Science. After the initial glow of the big bang faded, no new light came into the universe until the first stars formed. Studying this “cosmic dawn [PDF],” when the first stars, galaxies, and black holes formed, means looking at frequencies between 10 and 50 MHz, Burns says; this is where signature emissions from hydrogen are to be found, redshifted to low frequencies by the expansion of the universe.

With preliminary funding from NASA, Burns is developing a satellite mission that will orbit the moon and observe the early universe while it travels across the far side. But to take the next step scientifically requires a far larger array with thousands of antennas. That’s not practical in orbit, says Burns, but it is feasible on the far side. “The lunar surface is stable,” he says. “You just put these things down. They stay where they need to be.”

This article appears in the July 2019 print issue as “The View From the Far Side.”

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Q&A: Ghost Robotics CEO on Armed Robots for the U.S. Military

Jiren Parikh, the CEO of Ghost Robotics, on quadrupedal robots carrying weapons

6 min read
Ghost Robotics

Last week, the Association of the United States Army (AUSA) conference took place in Washington, D.C. One of the exhibitors was Ghost Robotics—we've previously covered their nimble and dynamic quadrupedal robots, which originated at the University of Pennsylvania with Minitaur in 2016. Since then, Ghost has developed larger, ruggedized "quadrupedal unmanned ground vehicles" (Q-UGVs) suitable for a variety of applications, one of which is military.

At AUSA, Ghost had a variety of its Vision 60 robots on display with a selection of defense-oriented payloads, including the system above, which is a remotely controlled rifle customized for the robot by a company called SWORD International.

The image of a futuristic-looking, potentially lethal weapon on a quadrupedal robot has generated some very strong reactions (the majority of them negative) in the media as well as on social media over the past few days. We recently spoke with Ghost Robotics' CEO Jiren Parikh to understand exactly what was being shown at AUSA, and to get his perspective on providing the military with armed autonomous robots.

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Biggest Tech Companies Now Building the Biggest Data Pipes

Facebook will lay a record-capacity submarine cable across the Atlantic

4 min read

Google's Grace Hopper subsea cable landing in the seaside town of Bude in England

Google

Old-fashioned telecommunication carriers are falling behind in the global bandwidth race as global giants of content and cloud computing are building their own global networks. Facebook has commissioned electronics and IT giant NEC Corporation to build the world's highest capacity submarine cable. When finished it will carry a staggering 500 terabits—some 4000 Blu-Ray discs of data—per second between North America and Europe on the world's busiest data highway.

For decades, transoceanic cables were laid by consortia of telecommunication carriers like AT&T and British Telecom. As cloud computing and data centers spread around the world, Google, Amazon, Facebook and Microsoft start joining cable consortia, and in the past few years Google began building its own cables. The new cable will give Facebook sole ownership of the world's biggest data pipeline.

Transoceanic fiber-optic cables are the backbones of the global telecommunications network, and their change in ownership reflects the rapid growth of data centers for cloud computing and content distribution. Google has 23 giant data centers around the globe, each one constantly updated to mirror the Google cloud for users in their region. Three years ago, flows between data centers accounted for 77 percent of transatlantic traffic and 60 percent of transpacific traffic, Alan Mauldin, research director at TeleGeography, a market-research unit of California-based PriMetrica, said at the time. Traffic between data centers is thought to be growing faster than the per-person data consumption, which Facebook says increases 20 to 30 percent a year.

Vying for maximum bandwidth at the intersection of Moore's Law and Shannon's limit

Fiber-optic developers have worked relentlessly to keep up with the demand for bandwidth. For decades, data capacity of a single fiber increased at a faster rate than the number of transistors squeezed onto a chip, the definition of Moore's Law. But in recent years that growth has slowed as data rates approached Shannon's limit, a point at which noise in the transmission system overwhelms the signal. In 2016 the maximum data rate per fiber pair (each fiber carrying a signal in one direction) was around 10 terabits per second, achieved by sending signals at 100 gigabits per second on 100 separate wavelengths through the same fiber.

Developing more sophisticated signal formats offered some improvement, but not enough to keep pace with the demand for bandwidth. The only way around Shannon's limit has been to open new paths for data delivery.

In 2018, Facebook and Google placed bets on broadening the transmission band of optical fibers by adding signals at a hundred new wavelengths to squeeze 24 terabits through a single fiber. Each bought one pair of fibers on the Pacific Light Cable stretching from Hong Kong to Los Angeles. The leader of the consortium, Pacific Light Data Communications, of Hong Kong, retained four other pairs in the six-pair cable. Although the cable was soon laid, the U.S. Federal Communications Commission has refused to license its connection to the U.S. network because of security concerns arising from its Chinese connections.

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Adhesives for Cryogenic Applications

Cryogenic Temperatures and the Role of Specialty Adhesives

1 min read

What are the challenges facing applications that operate at cryogenic temperatures? What effect do these low temperatures have on efforts to bond, seal, coat or encapsulate? In this paper, learn how specialized adhesives meet the performance requirements necessary to maintain the physical, thermal and electrical properties as temperatures approach absolute zero.

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