Comb on a Chip...

Experimental setup to generate a set of stable frequencies in a cryogenically cooled laser microresonator frequency comb. The ring-shaped microresonator, small enough to fit on a microchip, operates at very low laser power and is made from the semiconductor aluminum gallium arsenide.

Topics: Applied Physics, Instrumentation, NIST, Nanotechnology, Semiconductor Technology

Just as a meter stick with hundreds of tick marks can be used to measure distances with great precision, a device known as a laser frequency comb, with its hundreds of evenly spaced, sharply defined frequencies, can be used to measure the colors of light waves with great precision.

Small enough to fit on a chip, miniature versions of these combs — so named because their set of uniformly spaced frequencies resembles the teeth of a comb — are making possible a new generation of atomic clocks, a great increase in the number of signals traveling through optical fibers, and the ability to discern tiny frequency shifts in starlight that hint at the presence of unseen planets. The newest version of these chip-based “microcombs,” created by researchers at the National Institute of Standards and Technology (NIST) and the University of California at Santa Barbara (UCSB), is poised to further advance time and frequency measurements by improving and extending the capabilities of these tiny devices.

Comb on a Chip: New Design for ‘Optical Ruler’ Could Revolutionize Clocks, Telescopes, Telecommunications, NIST

Paper: G. Moille, L. Chang, W. Xie, A. Rao, X. Lu, M. Davanco, J.E. Bowers and K. Srinivasan. Dissipative Kerr Solitons in a III-V Microresonator. Laser and Photonics Reviews. June 2020. DOI: 10.1002/lpor.202000022

TEPCE...

Image source: Futurism/Dan Robitzski

Topics: Astrophysics, Instrumentation, Space, Space Junk

A massive cloud of space junk—containing more than 23,000 pieces larger than 10 centimeters across—is currently zooming around Earth with an average speed of about 36,000 kilometers per hour. And as companies such as SpaceX and OneWeb plan to launch tens of thousands of new satellites over the next few years, this hazardous clutter will likely pose an increasing threat to space missions and astronauts. One possible solution may be an electrodynamic tether, a device that could help prevent future satellites from becoming abandoned wrecks. The U.S. Naval Research Laboratory plans to test this technology in the next few weeks.

In early November the Tether Electrodynamic Propulsion CubeSat Experiment (TEPCE), already in orbit, is set to make its move under the watchful gaze of telescopes on the Hawaiian island of Maui. The Earth-bound control team is waiting for an ideal 10-minute period at dawn or dusk, when the dim sunlight will offer the best possible view of the shoe box-size spacecraft involved. Once the crew triggers the process, TEPCE should separate into two identical minisatellites joined by a kilometer-long tether as thick as several strands of dental floss. If deployment goes smoothly, the mission can observe how the tether interacts with Earth’s magnetic field in the ionosphere (where much of the space junk orbits) to change the satellites’ velocity and orbit; the results could possibly enable future spacecraft to move around while orbiting Earth—without having to carry unwieldy chemical propellant.

“In other words, it is the sailing ship of space,” says Enrico Lorenzini, a professor of energy management engineering at the University of Padova in Italy, who is not involved in the TEPCE mission. But instead of wind, the electrodynamic tether technology moves thanks to the physical laws that govern electric and magnetic fields. A tether in Earth’s ionosphere—an upper atmospheric layer filled with charged particles such as free electrons and positive ions—can collect electrons at one end and emit them at the other, generating an electric current through itself. The electrified tether’s interactions with Earth’s magnetic field produce an impetus known as the Lorentz force, which pushes on the tether in a perpendicular direction.

Kilometer-Long Space Tether Tests Fuel-Free Propulsion
Jeremy Hsu, Scientific American

Atomically Precise Manufacturing...

Credit: University of Texas at Dallas

Topics: Instrumentation, Modern Physics, Nanotechnology, Quantum Mechanics, Scanning Tunneling Microscopy

A University of Texas at Dallas graduate student, his advisor and industry collaborators believe they have addressed a long-standing problem troubling scientists and engineers for more than 35 years: How to prevent the tip of a scanning tunneling microscope from crashing into the surface of a material during imaging or lithography.

Details of the group's solution appeared in the January issue of the journal Review of Scientific Instruments, which is published by the American Institute of Physics.

Scanning tunneling microscopes (STMs) operate in an ultra-high vacuum, bringing a fine-tipped probe with a single atom at its apex very close to the surface of a sample. When voltage is applied to the surface, electrons can jump or tunnel across the gap between the tip and sample.

"Think of it as a needle that is very sharp, atomically sharp," said Farid Tajaddodianfar, a mechanical engineering graduate student in the Erik Jonsson School of Engineering and Computer Science. "The microscope is like a robotic arm, able to reach atoms on the sample surface and manipulate them."

The problem is, sometimes the tungsten tip crashes into the sample. If it physically touches the sample surface, it may inadvertently rearrange the atoms or create a "crater," which could damage the sample. Such a "tip crash" often forces operators to replace the tip many times, forfeiting valuable time.

Dr. John Randall is an adjunct professor at UT Dallas and president of Zyvex Labs, a Richardson, Texas-based nanotechnology company specializing in developing tools and products that fabricate structures atom by atom. Zyvex reached out to Dr. Reza Moheimani, a professor of mechanical engineering, to help address STMs' tip crash problem. Moheimani's endowed chair was a gift from Zyvex founder James Von Ehr MS'81, who was honored as a distinguished UTD alumnus in 2004.

"What they're trying to do is help bring atomically precise manufacturing into reality," said Randall, who co-authored the article with Tajaddodianfar, Moheimani and Zyvex Labs' James Owens. "This is considered the future of nanotechnology, and it is extremely important work."

Microscopy breakthrough paves the way for atomically precise manufacturing, The University of Texas at Dallas

Starship GPS...

Pulsars spin rapidly while emitting powerful beams of radiation.Credit: Dana Berry/NASA

Topics: Astrophysics, Instrumentation, International Space Station, NASA, Space Exploration

NATIONAL HARBOR, Maryland

From its perch aboard the International Space Station, a NASA experiment has shown how future missions might navigate their way through deep space. Spacecraft could triangulate their location, in a sort of celestial Global Positioning System (GPS), using clockwork-like signals from distant dead stars.

Last November, the Neutron Star Interior Composition Explorer (NICER) spent a day and a half looking at a handful of pulsars — rapidly spinning stellar remnants that give off beams of powerful radiation as they rotate. By measuring tiny changes in the arrival time of the pulses, NICER could pinpoint its location to within 5 kilometres.

It is the first demonstration in space of the long-sought technology known as pulsar navigation. One day, the method could help spacecraft steer themselves without regular instructions from Earth.

NASA test proves pulsars can function as a celestial GPS, Alexandra Witze, Nature

Beyond LIGO...

LIGO has detected at least two black hole mergers, illustrated here. Image credit: LIGO/A. Simonet

Topics: Astrophysics, Black Holes, Education, General Relativity, Gravitational Waves, Instrumentation, STEM

Discovery is in direct proportion to the instrumentation we currently have to detect phenomena. Thus, as our equipment gets more sophisticated, like the initial detection of Exoplanets, we'll likely encounter at least dozens more merging black holes and gravitational waves. It's why encouraging critical thinking, rationality, and science literacy - not conspiracy provocateurs, pseudo-science-word-salad-babble, Young Earth lunacy at the K-12 and secondary levels - is vital to our continued prosperity. Without it, in an increasingly technological world, we will quickly find ourselves behind...and irrelevant.

The two LIGO gravitational wave detectors in Hanford Washington and Livingston Louisiana have caught a second robust signal from two black holes in their final orbits and then their coalescence into a single black hole. This event, dubbed GW151226, was seen on December 26th at 03:38:53 (in Universal Coordinated Time, also known as Greenwich Mean Time), near the end of LIGO's first observing period ("O1"), and was immediately nicknamed "the Boxing Day event".

Like LIGO's first detection, this event was identified within minutes of the gravitational wave's passing. Subsequent careful studies of the instruments and environments around the observatories showed that the signal seen in the two detectors was truly from distant black holes – some 1.4 billion light years away, coincidentally at about the same distance as the first signal ever detected. The Boxing Day event differed from the LIGO's first gravitational wave observation in some important ways, however. [1]

*          *          *          *          *

On 3 December 2015, when the European Space Agency’s (ESA’s) LISA Pathfinder spacecraft launched from French Guiana on a Vega rocket, some big questions were facing gravitational-wave astronomers. Researchers were about to find out whether getting free-falling cubes in space to stay in sync was practical. Even if the mission succeeded, no definitive proof yet existed (although the rumor mill was in full swing) that gravitational waves could be directly detected, whether in space or on the ground.

What a difference half a year makes.

Today researchers with the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced their second gravitational-wave detection, this time the result of a merger between two black holes with 14 and 8 times the mass of the Sun. These black holes are less massive but no less interesting than the already legendary black hole duo that, on 11 February, temporarily diverted the world’s attention from Donald Trump’s first presidential primary victory. [2]

1. LIGO Does It Again: A Second Robust Binary Black Hole Coalescence Observed
2. Physics Today: Looking beyond LIGO, Andrew Grant

Orbital WALL-E...

Image Source: Figure 3 Debris engine, see link below

Topics: Astrophysics, Instrumentation, Space, Space Junk, Taikonaut

I am always glad when good science is proposed and achieved. This is mostly a thorough application of Kepler and Newtonian physics as well as engineering rocketry. I give the poignant observation with some exception, this is happening LESS in the country of my birth, currently known for carnival barkers and xenophobes as presidential front runners, and some of my fellow citizens thinking "The Flintstones" instead of a parody of "The Honeymooners" was a documentary.

TECHNOLOGY REVIEW: At 16:56 UTC on August 29, 2009, an Iridium communications satellite suddenly fell silent. In the hours that followed, the U.S. Space Surveillance Network reported that it was tracking two large clouds of debris—one from the Iridium and another from a defunct Russian military satellite called Cosmos 2251.

The debris was the result of a high-speed collision, the first time this is known to have happened between orbiting satellites. The impact created over 1,000 fragments greater than 10 centimeters in size and a much larger number of smaller pieces. This debris spread out around the planet in a deadly cloud.

Space debris is a pressing problem for Earth-orbiting spacecraft, and it could get significantly worse. When the density of space debris reaches a certain threshold, analysts predict that the fragmentation caused by collisions will trigger a runaway chain reaction that will fill the skies with ever increasing numbers of fragments. By some estimates that process could already be underway.

An obvious solution is to find a way to remove this debris. One option is to zap the larger pieces with a laser, vaporizing them in parts and causing the leftovers to deorbit. However, smaller pieces of debris cannot be dealt with in this way because they are difficult to locate and track.

Another option is send up a spacecraft capable of mopping up debris with a net or some other capture process. But these missions are severely limited by the amount of fuel they can carry.

Today, Lei Lan and pals from Tsinghua University in Beijing, China, propose a different solution. Their idea is to build an engine that converts space debris into propellant and so can maneuver itself almost indefinitely as it mops up the junk.

Physics arXiv: Debris Engine: A Potential Thruster for Space Debris Removal
Lei Lan, Jingyang Li, Hexi Baoyin

#P4TC WALL-E mentions:
Predicted, but still kind of gross when you think of it...
NASA Going Green...

Light Sails Leakage...

Image Source: MIT Technology Review

Topics: Astronomy, Astrophysics, Instrumentation, Space Flight, SETI, Solar Sail

Please note the emoji: \\//_. That Trekkie cred set: It's probably going to be a lot easier to detect civilizations closer, but slightly past our stage of admitted technological adolescence, currently beset and hindered by fear of all things science and willful ignorance. With the noted exception of Star Trek, most of the science fiction I'm reading recently stay in the Einstein-relativistic-speeds range, along with the effects of time dilation to their plot twists. If an intelligence has begun to at least explore their own outer planets, maybe...just maybe there's hope that we'll survive our own hubris.

TECHNOLOGY REVIEW: Light sails are a promising way of exploring star systems. If other civilizations use them, these sails should be visible from Earth, say astrophysicists.

Abstract

The primary challenge of rocket propulsion is the burden of needing to accelerate the spacecraft's own fuel, resulting in only a logarithmic gain in maximum speed as propellant is added to the spacecraft. Light sails offer an attractive alternative in which fuel is not carried by the spacecraft, with acceleration being provided by an external source of light. By artificially illuminating the spacecraft with beamed radiation, speeds are only limited by the area of the sail, heat resistance of its material, and power use of the accelerating apparatus. In this paper, we show that leakage from a light sail propulsion apparatus in operation around a solar system analogue would be detectable. To demonstrate this, we model the launch and arrival of a microwave beam-driven light sail constructed for transit between planets in orbit around a single star, and find an optimal beam frequency on the order of tens of GHz. Leakage from these beams yields transients with flux densities of Jy and durations of tens of seconds at 100 pc. Because most travel within a planetary system would be conducted between the habitable worlds within that system, multiply-transiting exoplanetary systems offer the greatest chance of detection, especially when the planets are in projected conjunction as viewed from Earth. If interplanetary travel via beam-driven light sails is commonly employed in our galaxy, this activity could be revealed by radio follow-up of nearby transiting exoplanetary systems. The expected signal properties define a new strategy in the search for extraterrestrial intelligence (SETI).

Physics arXiv: SETI via Leakage from Light Sails in Exoplanetary Systems
James Guillochon (1), Abraham Loeb (1) ((1) Harvard ITC)