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(23 July 2020 – ESA) On the morning of 23 June 2020, a strong earthquake struck the southern state of Oaxaca, Mexico.

The 7.4- magnitude earthquake prompted evacuations in the region, triggered a tsunami warning and damaged thousands of houses. Satellite radar data, from the Copernicus Sentinel-1 mission, are being used to analyse the effects of the earthquake on land.

Mexico is one of the world’s most seismically active regions, sitting on top of three of Earth’s largest tectonic plates – the North American, Cocos and Pacific. Near Mexico’s southern region, the North American plate collides with the Cocos plate, which is forced underground in a subduction zone. This geological process is associated with many of the damaging earthquakes on the Pacific coast of Mexico – including the most recent on 23 June.

The earthquake reported in the Oaxaca region occurred at 10:29 local time – with its epicentre located around 12 km southwest of Santa María Zapotitlán. Several powerful aftershocks were registered the same day, with five more recorded in the following 24 hours.

While there is currently no way to predict when earthquakes will occur, radar imagery from satellites allow for the effects of earthquakes to be observed. Since its launch, the Copernicus Sentinel-1 mission has proven a magnificent system to measure the surface deformation caused by tectonics, volcanic eruptions and land subsidence.

Data from the Sentinel-1A and Sentinel-1B satellite, acquired shortly before and after the earthquake, have been combined to measure the coseismic surface displacement, or changes on the ground, that occurred between the two acquisition dates. This leads to the colourful interference (or fringe) pattern known as an ‘interferogram’, which enables scientists to quantify the surface displacement.

Oaxaca interferogram (modified Copernicus Sentinel data (2020), processed by ESA)

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Surface deformation (modified Copernicus Sentinel data (2020), processed by ESA)

Ramón Torres, Copernicus Sentinel-1 Project Manager, explains, “The interferogram represents surface displacement in the radar line of sight, i.e. half of the radar wavelength. The distance between the interference cycle, from yellow to yellow, corresponds to 28 mm deformation in the radar line of sight. For example, a blue-green-red colour cycle represents a relative movement towards the radar, while a red-green-blue colour cycle means a deformation away from the radar.”

“The fringes can be unwrapped to allow the conversion into metres. The result, referred to as the surface displacement map, shows the relative deformation caused by the earthquake.”

In the Oaxaca images, ground deformation of up to 0.45 m was observed in the coastal city of La Crucecita – where the epicentre was located.

With its 250 km-wide swath over land surfaces, the Copernicus Sentinel-1 mission gives scientists a broad view of the displacement, allowing them to examine the ground displacement and further develop the scientific knowledge of quakes.

By benefitting from the availability of both Sentinel-1A and Sentinel-1B imagery, scientists are able to quantify the ground movement in both vertical and east-west directions by combing the radar scans obtained as the satellites flew both south to north and north to south.

While current radar missions are limited in measuring the east-west component of surface displacement, the proposed Earth Explorer candidate mission, Harmony, will augment the capabilities by adding additional ‘lines of sight’ to the Sentinel-1 mission.

In areas where the displacement is predominantly in the north-south direction, Harmony will have the ability to systematically and accurately measure an additional dimension of displacement. This will help resolve ambiguities in the underlying geophysical processes that lead to earthquakes, landslides and volcanism.

Looking to the future, the upcoming six high-priority candidate missions will expand the current capabilities of the Sentinel missions, one of them being the L-band Synthetic Aperture Radar, ROSE-L, mission, which will also augment the current capabilities of Sentinel-1. The mission will allow scientists to further improve the mapping of earthquakes over the next decade.

Ramón Torres says, “The Sentinel-1 services are very well guaranteed for decades to come. The upcoming Sentinel-1C and Sentinel-1D are in the process of being completed, and the design of the next generation of satellites will begin later this year.”

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NRAO joins space mission to the far side of the Moon to explore the early universe

NRAO joins space mission to the far side of the

(22 September 2020 – NRAO) The National Radio Astronomy Observatory (NRAO) has joined a new NASA space mission to the far side of the Moon to investigate when the first stars began to form in the early universe.

Artist illustration of the Dark Ages Polarimetry Pathfinder (DAPPER), which will look for faint radio signals from the early universe while operating in a low lunar orbit. Its specialized radio receiver and high-frequency antenna are currently being developed by NRAO. (courtesy: NRAO/AUI/NSF, Sophia Dagnello)

The universe was dark and foggy during its “dark ages,” just 380 thousand years after the Big Bang. There were no light-producing structures yet like stars and galaxies, only large clouds of hydrogen gas. As the universe expanded and started to cool down, gravity drove the formation of the stars and black holes, which ended the dark ages and initiated the “cosmic dawn,” tens of millions of years later.

To learn more about that dark period of the cosmos and understand how and when the first stars began to form, astronomers are trying to catch energy produced by these hydrogen clouds in the form of radio waves, via the so-called 21-centimeter line.

But picking up signals from the early universe is extremely challenging. They are mostly blocked by the Earth’s atmosphere, or drowned out by human-generated radio transmissions. That’s why a team of scientists and engineers have decided to send a small spacecraft to lunar orbit and measure this signal while traversing the far side of the Moon, which is radio-quiet.

The spacecraft, called the Dark Ages Polarimetry Pathfinder (DAPPER), will be designed to look for faint radio signals from the early universe while operating in a low lunar orbit. Its specialized radio receiver and high-frequency antenna are currently being developed by a team at the NRAO’s Central Development Laboratory (CDL) in Charlottesville, Virginia, led by senior research engineer Richard Bradley.

“No radio telescope on Earth is currently able to definitively measure and confirm the very faint neutral hydrogen signal from the early universe, because there are so many other signals that are much brighter,” said Bradley. “At CDL we are developing specialized techniques that enhance the measurement process used by DAPPER to help us separate the faint signal from all the noise.” This project builds upon the work of Marian Pospieszalski who developed flight-ready low noise amplifiers at the CDL in the 1990s for the highly-successful Wilkinson Microwave Anisotropy Probe (WMAP), a spacecraft that gave the most precise figure yet for the age of the universe.

DAPPER will be part of the NASA Artemis program with the goal of landing “the first woman and the next man” on the Moon by 2024. It will likely be launched from the vicinity of the Lunar Gateway, the planned space station in lunar orbit intended to serve as a communication hub and science laboratory. Because it is able to piggy-back off of the surging interest in sending humans to lunar soil, DAPPER will be much cheaper to build and more compact than a full-scale NASA mission.

NRAO will spend the coming two years designing and developing a prototype for the DAPPER receiver, after which it will go to the Space Sciences Laboratory at UC Berkeley for space environmental testing.

“NRAO is very pleased to be working on this important initiative,” said Tony Beasley, director of the NRAO and Associated Universities Inc. vice president for Radio Astronomy Operations. “DAPPER’s contributions to the success of NASA’s ARTEMIS mission will build on the rapid growth of space-based radio astronomy research we’ve seen over the past decade. As the leading radio astronomy organization in the world, NRAO always looks for new horizons, and DAPPER is the start of an exciting field.”

DAPPER is a collaboration between the universities of Colorado-Boulder and California-Berkeley, the National Radio Astronomy Observatory, Bradford Space Inc., and the NASA Ames Research Center. Jack Burns of the University of Colorado Boulder is Principal Investigator and Science Team Chair. Project website for DAPPER.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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JPL meets unique challenge, delivers radar hardware for Jupiter mission

JPL meets unique challenge delivers radar hardware for Jupiter mission

(21 September 2020 – JPL) Engineers at NASA’s Jet Propulsion Laboratory met a significant milestone recently by delivering key elements of an ice-penetrating radar instrument for an ESA (European Space Agency) mission to explore Jupiter and its three large icy moons.

While following the laboratory’s stringent COVID-19 Safe-at-Work precautions, JPL teams managed to build and ship the receiver, transmitter, and electronics necessary to complete the radar instrument for the Jupiter Icy Moons Explorer (JUICE) mission.

NASA’s Jet Propulsion Laboratory built and shipped the receiver, transmitter, and electronics necessary to complete the radar instrument for JUICE, the ESA (European Space Agency) mission to explore Jupiter and its three large icy moons. Here the transmitter undergoes vibration testing at JPL. (courtesy: NASA/JPL-Caltech)

Set to launch in 2022, JUICE will orbit Jupiter for three years, perform multiple flybys of moons Callisto and Europa, then orbit Ganymede. The spacecraft will observe Jupiter’s atmosphere up close as well as analyze the surfaces and interiors of the three moons, which are believed to harbor liquid water under their icy crusts.

One of 10 instruments, the radar is key to exploring those moons. Called Radar for Icy Moon Exploration, or RIME, it sends out radio waves that can penetrate the surface up to 6 or 7 miles (10 kilometers) and collects data on how the waves bounce back. Some of the waves penetrate the crust and reflect off subsurface features – and the watery interiors – enabling scientists to “see” underneath.

In the case of Europa, which is believed to have a global ocean beneath its crust, the radar data will help gauge the thickness of the ice. NASA’s Europa Clipper mission, set to launch in the mid-2020s, will arrive around the same time as JUICE and collect complementary science as it performs multiple flybys of Europa.

Building RIME During a Pandemic

A collaboration between JPL in Southern California and the Italian Space Agency (ASI), JUICE’s RIME is led by Principal Investigator Lorenzo Bruzzone of the University of Trento in Italy. JPL’s responsibility was to make and deliver the transmitter and receiver – the pieces that send out and pull in radio signals – as well as the electronics that help those pieces communicate with RIME’s antenna. Now that the components have been delivered to ASI in Rome, the next steps are to test and integrate them before assembling the instrument.

“I’m really impressed that the engineers working on this project were able to pull this off,” said JPL’s Jeffrey Plaut, co-principal investigator of RIME. “We are so proud of them, because it was incredibly challenging. We had a commitment to our partners overseas, and we met that – which is very gratifying.”

In mid-March, engineers had just finished building the transmitter and its corresponding set of electronics. They were about to run an exhaustive regimen of tests to ensure the equipment would survive deep space – including vibration, shock, and thermal vacuum testing, which simulates the vacuum and extreme temperatures of space.

Then the coronavirus pandemic forced most JPL’s employees to work remotely. The tests would have to wait.

About a month later, RIME engineers and technicians came back on-site after JPL put in place its Safe-at-Work protocols, including – among other measures – social distancing, mask-wearing, and frequent hand-washing. Now the team had a schedule crunch, plus other new challenges. As one of the first teams to re-enter JPL (most employees continue to work remotely), they needed to figure out new ways to do things that used to be easy. Just finding screws and other fasteners, when the usual supply shop wasn’t open, became a puzzle to solve.

Project Manager Don Heyer had new human challenges as well.

“We needed to keep people not just safe – but comfortable being there,” Heyer said. “That was important, because otherwise they wouldn’t be able to do the job successfully.”

The key to moving forward was clearly defining next steps, he said. At the same time, they needed to make safety requirements thorough, but not too much of an additional burden for the staff. It was a learning experience, he said.

“But we got there pretty quickly.”

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SwRI instruments aboard Rosetta help detect unexpected ultraviolet aurora at a comet

SwRI instruments aboard Rosetta help detect unexpected ultraviolet aurora at

(21 September 2020 – SwRI) Data from Southwest Research Institute-led instruments aboard ESA’s Rosetta spacecraft have helped reveal auroral emissions in the far ultraviolet around a comet for the first time.

At Earth, auroras are formed when charged particles from the Sun follow our planet’s magnetic field lines to the north and south poles. There, solar particles strike atoms and molecules in Earth’s atmosphere, creating shimmering curtains of colorful light in high-latitude skies. Similar phenomena have been seen at various planets and moons in our solar system and even around a distant star. SwRI’s instruments, the Alice far-ultraviolet (FUV) spectrograph and the Ion and Electron Sensor (IES), aided in detecting these novel phenomena at comet 67P/Churyumov-Gerasimenko (67P/C-G).

Data from Southwest Research Institute-led instruments aboard ESA’s Rosetta spacecraft helped reveal unique ultraviolet auroral emissions around irregularly shaped Comet 67P. Although these auroras are outside the visible spectra, other auroras have been seen at various planets and moons in our solar system and even around a distant star. (courtesy: ESA/Rosetta/NAVCAM)

“Charged particles from the Sun streaming towards the comet in the solar wind interact with the gas surrounding the comet’s icy, dusty nucleus and create the auroras,” said SwRI Vice President Dr. Jim Burch who leads IES. “The IES instrument detected the electrons that caused the aurora.”

The envelope of gas around 67P/C-G, called the “coma,” becomes excited by the solar particles and glows in ultraviolet light, an interaction detected by the Alice FUV instrument.

“Initially, we thought the ultraviolet emissions at comet 67P were phenomena known as ‘dayglow,’ a process caused by solar photons interacting with cometary gas,” said SwRI’s Dr. Joel Parker who leads the Alice spectrograph. “We were amazed to discover that the UV emissions are aurora, driven not by photons, but by electrons in the solar wind that break apart water and other molecules in the coma and have been accelerated in the comet’s nearby environment. The resulting excited atoms make this distinctive light.”

Dr. Marina Galand of Imperial College London led a team that used a physics-based model to integrate measurements made by various instruments aboard Rosetta.

“By doing this, we didn’t have to rely upon just a single dataset from one instrument,” said Galand, who is the lead author of a Nature Astronomy paper outlining this discovery. “Instead, we could draw together a large, multi-instrument dataset to get a better picture of what was going on. This enabled us to unambiguously identify how 67P/C-G’s ultraviolet atomic emissions form, and to reveal their auroral nature.”

“I’ve been studying the Earth’s auroras for five decades,” Burch said. “Finding auroras around 67P, which lacks a magnetic field, is surprising and fascinating.”

Following its rendezvous with 67P/C-G in 2014 through 2016, Rosetta has provided a wealth of data revealing how the Sun and solar wind interact with comets. In addition to discovering these cometary auroras, the spacecraft was the first to orbit a comet’s nucleus, the first to fly alongside a comet as it travelled into the inner Solar System and the first to send a lander to a comet’s surface.

Additional instruments contributing to this research were Rosetta’s Langmuir Probe (LAP), the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA), the Microwave Instrument for the Rosetta Orbiter (MIRO) and the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS).

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI. Airbus Defense and Space built the Rosetta spacecraft. NASA’s Jet Propulsion Laboratory (JPL) manages the U.S. contribution of the Rosetta mission for NASA’s Science Mission Directorate in Washington, under a contract with the California Institute of Technology (Caltech). JPL also built the Microwave Instrument for the Rosetta Orbiter and hosts its principal investigator, Dr. Mark Hofstadter. SwRI (San Antonio and Boulder, Colorado) developed the Rosetta orbiter’s Ion and Electron Sensor and Alice instrument and hosts their principal investigators.

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