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(27 August 2020 – STScI) In a landmark study, scientists using NASA’s Hubble Space Telescope have mapped the immense envelope of gas, called a halo, surrounding the Andromeda galaxy, our nearest large galactic neighbor.

Scientists were surprised to find that this tenuous, nearly invisible halo of diffuse plasma extends 1.3 million light-years from the galaxy—about halfway to our Milky Way—and as far as 2 million light-years in some directions. This means that Andromeda’s halo is already bumping into the halo of our own galaxy.

They also found that the halo has a layered structure, with two main nested and distinct shells of gas. This is the most comprehensive study of a halo surrounding a galaxy.

Halo around the Andromeda Galaxy illustration (courtesy: NASA, ESA, and E. Wheatley (STScI))

“Understanding the huge halos of gas surrounding galaxies is immensely important,” explained co-investigator Samantha Berek of Yale University in New Haven, Connecticut. “This reservoir of gas contains fuel for future star formation within the galaxy, as well as outflows from events such as supernovae. It’s full of clues regarding the past and future evolution of the galaxy, and we’re finally able to study it in great detail in our closest galactic neighbor.”

“We find the inner shell that extends to about a half million light-years is far more complex and dynamic,” explained study leader Nicolas Lehner of the University of Notre Dame in Indiana. “The outer shell is smoother and hotter. This difference is a likely result from the impact of supernova activity in the galaxy’s disk more directly affecting the inner halo.”

A signature of this activity is the team’s discovery of a large amount of heavy elements in the gaseous halo of Andromeda. Heavier elements are cooked up in the interiors of stars and then ejected into space—sometimes violently as a star dies. The halo is then contaminated with this material from stellar explosions.

The Andromeda galaxy, also known as M31, is a majestic spiral of perhaps as many as 1 trillion stars and comparable in size to our Milky Way. At a distance of 2.5 million light-years, it is so close to us that the galaxy appears as a cigar-shaped smudge of light high in the autumn sky. If its gaseous halo could be viewed with the naked eye, it would be about three times the width of the Big Dipper. This would easily be the biggest feature on the nighttime sky.

Through a program called Project AMIGA (Absorption Map of Ionized Gas in Andromeda), the study examined the light from 43 quasars—the very distant, brilliant cores of active galaxies powered by black holes—located far beyond Andromeda. The quasars are scattered behind the halo, allowing scientists to probe multiple regions. Looking through the halo at the quasars’ light, the team observed how this light is absorbed by the Andromeda halo and how that absorption changes in different regions. The immense Andromeda halo is made of very rarified and ionized gas that doesn’t emit radiation that is easily detectable. Therefore, tracing the absorption of light coming from a background source is a better way to probe this material.

The researchers used the unique capability of Hubble’s Cosmic Origins Spectrograph (COS) to study the ultraviolet light from the quasars. Ultraviolet light is absorbed by Earth’s atmosphere, which makes it impossible to observe with ground-based telescopes. The team used COS to detect ionized gas from carbon, silicon and oxygen. An atom becomes ionized when radiation strips one or more electrons from it.

Andromeda’s halo has been probed before by Lehner’s team. In 2015, they discovered that the Andromeda halo is large and massive. But there was little hint of its complexity; now, it’s mapped out in more detail, leading to its size and mass being far more accurately determined.

“Previously, there was very little information—only six quasars—within 1 million light-years of the galaxy. This new program provides much more information on this inner region of Andromeda’s halo,” explained co-investigator J. Christopher Howk, also of Notre Dame. “Probing gas within this radius is important, as it represents something of a gravitational sphere of influence for Andromeda.”

Because we live inside the Milky Way, scientists cannot easily interpret the signature of our own galaxy’s halo. However, they believe the halos of Andromeda and the Milky Way must be very similar since these two galaxies are quite similar. The two galaxies are on a collision course, and will merge to form a giant elliptical galaxy beginning about 4 billion years from now.

Scientists have studied gaseous halos of more distant galaxies, but those galaxies are much smaller on the sky, meaning the number of bright enough background quasars to probe their halo is usually only one per galaxy. Spatial information is therefore essentially lost. With its close proximity to Earth, the gaseous halo of Andromeda looms large on the sky, allowing for a far more extensive sampling.

“This is truly a unique experiment because only with Andromeda do we have information on its halo along not only one or two sightlines, but over 40,” explained Lehner. “This is groundbreaking for capturing the complexity of a galaxy halo beyond our own Milky Way.”

In fact, Andromeda is the only galaxy in the universe for which this experiment can be done now, and only with Hubble. Only with an ultraviolet-sensitive future space telescope will scientists be able to routinely undertake this type of experiment beyond the approximately 30 galaxies comprising the Local Group.

“So Project AMIGA has also given us a glimpse of the future,” said Lehner.

The team’s findings appear in the August 27 edition of The Astrophysical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

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OSIRIS-REx spacecraft goes for early stow of asteroid sample

OSIRIS REx spacecraft goes for early stow of asteroid sample

(26 October 2020 – NASA) NASA’s OSIRIS-REx mission is ready to perform an early stow on Tuesday, Oct. 27, of the large sample it collected last week from the surface of the asteroid Bennu to protect and return as much of the sample as possible.

On Oct. 22, the OSIRIS-REx mission team received images that showed the spacecraft’s collector head overflowing with material collected from Bennu’s surface – well over the two-ounce (60-gram) mission requirement – and that some of these particles appeared to be slowly escaping from the collection head, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM).

A mylar flap on the TAGSAM allows material to easily enter the collector head, and should seal shut once the particles pass through. However, larger rocks that didn’t fully pass through the flap into the TAGSAM appear to have wedged this flap open, allowing bits of the sample to leak out.

Because the first sample collection event was so successful, NASA’s Science Mission Directorate has given the mission team the go-ahead to expedite sample stowage, originally scheduled for Nov. 2, in the spacecraft’s Sample Return Capsule (SRC) to minimize further sample loss.

This illustration shows NASA’s OSIRIS-REx spacecraft stowing the sample it collected from asteroid Bennu on Oct. 20, 2020. The spacecraft will use its Touch-And-Go Sample Acquisition Mechanism (TAGSAM) arm to place the TAGSAM collector head into the Sample Return Capsule (SRC). (courtesy: NASA/University of Arizona, Tucson)

“The abundance of material we collected from Bennu made it possible to expedite our decision to stow,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “The team is now working around the clock to accelerate the stowage timeline, so that we can protect as much of this material as possible for return to Earth.”

Unlike other spacecraft operations where OSIRIS-REx autonomously runs through an entire sequence, stowing the sample is done in stages and requires the team’s oversight and input. The team will send the preliminary commands to the spacecraft to start the stow sequence and, once OSIRIS-REx completes each step in sequence, the spacecraft sends telemetry and images back to the team on Earth and waits for the team’s confirmation to proceed with the next step.

Signals currently take just over 18.5 minutes to travel between Earth and the spacecraft one-way, so each step of the sequence factors in about 37 minutes of communications transit time. Throughout the process, the mission team will continually assess the TAGSAM’s wrist alignment to ensure the collector head is properly placed in the SRC. A new imaging sequence also has been added to the process to observe the material escaping from the collector head and verify that no particles hinder the stowage process. The mission anticipates the entire stowage process will take multiple days, at the end of which the sample will be safely sealed in the SRC for the spacecraft’s journey back to Earth.

“I’m proud of the OSIRIS-REx team’s amazing work and success to this point,” said NASA’s Associate Administrator for Science Thomas Zurbuchen. “This mission is well positioned to return a historic and substantial sample of an asteroid to Earth, and they’ve been doing all the right things, on an expedited timetable, to protect that precious cargo.”

NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. The University of Arizona, Tucson leads the mission’s science observation planning and data processing. Lockheed Martin Space in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace, in Tempe, Arizona, are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.

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Refueling mission completes second set of robotic tool operations in space

Refueling mission completes second set of robotic tool operations in

(23 October 2020 – NASA Goddard) NASA’s Robotic Refueling Mission 3 (RRM3) has successfully completed its second set of robotic tool operations on the International Space Station, demonstrating key techniques for transferring cryogenic fluids, used as coolants, propellants, or for life support systems in orbit.

These technologies have applications for extending spacecraft life and facilitating exploration to the Moon and Mars.

Visual Inspection Poseable Invertebrate Robot 2 (VIPIR2) before launch (top left), and in space during operations (top middle, top right); and Cryogen Servicing Tool (CST) before launch (bottom left), and in space during operations (bottom middle, bottom right). (courtesy: NASA)

From October 19-22, RRM3 – with the help of the station’s Dextre robot – connected an 11-foot long hose to a designated cryogen port while simultaneously using an inspection tool to verify the hose connection. This marks the first time that Dextre has had tools in both arms completing RRM3 operations. RRM3 supplied the hose and robotic tools of a future servicer spacecraft, as well as a piping system representing that of a satellite in need of fueling.

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For the first time, Dextre simultaneously uses its two arms to wield robotic refueling tools. The right arm uses the Cryogen Servicing Tool to maneuver a cryogen hose, and the left uses Visual Inspection Poseable Invertebrate Robot 2, an inspection camera, to verify placement. (courtesy: NASA)

During the demonstration, Dextre simultaneously operated two RRM3 tools: the Cryogen Servicing Tool (CST) and the Visual Inspection Poseable Invertebrate Robot 2 (VIPIR2) tool. One of Dextre’s arms held the CST, which was needed to grab and guide the hose into the port. The second arm extended the snake-like VIPIR2 camera into the piping system to ensure the hose was inserted correctly.

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The Visual Inspection Poseable Invertebrate Robot 2 (VIPIR2), extends its snake-like borescope camera for free-space checkout, to later be inserted into the RRM3 module’s piping system to verify proper cryogen hose placement. (courtesy: NASA)

The mission launched in December 2018 and conducted its first set of robotic operations in August 2019, during which it demonstrated its Multi-Function Tool 2 and a robotic-friendly hose adapter system. This RRM3 demonstration added experience and information to NASA’s knowledge base on transferring cryogenic fuel in space.

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The Cryogen Servicing Tool allows Dextre to maneuver the 11-ft long cryogen hose to a port on the RRM3 module. (courtesy: NASA)

Prior to an April 2019 venting operation, RRM3 stored liquid methane for four months, the longest in-space storage of a cryogen without any loss of fluid. This record had been difficult to achieve previously because cryogens vaporize in a process called boil-off when not maintained at a low enough temperature.

RRM3 was developed and operated by NASA’s Exploration and In-space Services (NExIS) projects division (formerly known as the Satellite Servicing Projects Division) at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The demonstration was funded by the Space Technology Mission Directorate’s Technology Demonstration Missions program, which is located at Marshall Space Flight Center in Huntsville, Alabama.

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All solid motors for Vega-C complete qualification tests

All solid motors for Vega C complete qualification tests

(23 October 2020 – ESA) Europe’s new-generation Vega-C small launch vehicle developed by ESA will increase performance and extend current launch capabilities at Europe’s Spaceport.

The solid rocket motors built for Vega-C under contract to Avio have all completed the hot fire tests to qualify them for flight.

Industry cooperation to build Vega-C (courtesy: ESA)

The first stage P120C, second stage Zefiro-40 and the third stage Zefiro-9 are all fueled by solid propellant. These motors, together with the AVUM+ liquid propulsion upper module, will allow Vega-C to lift payloads of up to 2300 kg to a reference 700 km altitude in polar orbit.

The P120C first stage will burn for 130 s using 142 t of fuel to deliver a liftoff thrust of about 4500 kN. This will take Vega-C to an altitude of about 60 km in the first phase of flight before the second stage takes over.

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Hot firing of P120C solid rocket motor for Vega-C (courtesy: ESA)

Europropulsion, owned jointly by Avio and ArianeGroup, built three P120C models for test. One development and two qualification models have all been static fired successfully at Europe’s Spaceport.

The first qualification model, in the Vega-C configuration, was hot fired in January 2019. The second qualification model, in the Ariane 6 configuration, was hot fired on 7 October. Using the P120C on two launch vehicles has saved on development costs and benefitted economies of scale and created an opportunity for Europe to scale up production.

Vega-C’s second stage, powered by the new Zefiro-40 contains about 36 t of solid propellant.

The Zefiro-40, developed and manufactured by Avio in their Colleferro factory in Italy, was static fired on 8 March 2018 and then again on 10 May 2019 at test facilities in Sardinia.

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Zefiro-40 DM on test bench (courtesy: ESA)

During a burn time of 92 seconds the Zefiro-40 generates an average thrust of 1300 kN which is four times greater than that of an engine of a modern passenger aircraft. This propels Vega-C to an altitude of about 123 km.

The Zefiro-9 will power Vega-C’s third stage. It is an advanced version with a new igniter with respect to the one used on the Vega launch vehicle currently operating at Europe’s Spaceport.

On 1 October, the Zefiro-9 seated on the test bench in Cagliari, Sardinia performed its final qualification hot firing. It burned for 120 s using 10 t of solid propellant. The Zefiro-9 will take Vega-C to an altitude of about 190km.

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Zefiro-9 test fire (courtesy: Avio)

Participating States in Vega-C development are: Austria, Belgium, Czech Republic, France, Germany, Ireland, Italy, Netherlands, Norway, Romania, Spain, Sweden and Switzerland.

“Industry is working very hard and very closely with ESA to complete the end of the qualification programme for Vega-C. Together we are overcoming the obstacles caused by the COVID-19 pandemic and we are committed to complete all activities planned for the preparation of the Vega-C maiden flight,” commented Giorgio Tumino, Head of Vega-C development and Chief Technical Advisor for Space Transportation at ESA.

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