Twice the charm: long-lived exotic particle discovered

 

CERN - European Organization for Nuclear Research logo.

July 31, 2021

Discovery of a new exotic hadron containing two charm quarks and an up and a down antiquark.

Image above: An artist’s impression of T_cc⁺, a tetraquark composed of two charm quarks and an up and a down antiquark (Image: CERN).

Today, the LHCb experiment at CERN is presenting a new discovery at the European Physical Society Conference on High Energy Physics (EPS-HEP). The new particle discovered by LHCb, labelled as T_cc⁺, is a tetraquark – an exotic hadron containing two quarks and two antiquarks. It is the longest-lived exotic matter particle ever discovered, and the first to contain two heavy quarks and two light antiquarks.

Quarks are the fundamental building blocks from which matter is constructed. They combine to form hadrons, namely baryons, such as the proton and the neutron, which consist of three quarks, and mesons, which are formed as quark-antiquark pairs. In recent years a number of so-called exotic hadrons – particles with four or five quarks, instead of the conventional two or three - have been found. Today’s discovery is of a particularly unique exotic hadron, an exotic exotic hadron if you like.

The new particle contains two charm quarks and an up and a down antiquark. Several tetraquarks have been discovered in recent years (including one with two charm quarks and two charm antiquarks), but this is the first one that contains two charm quarks, without charm antiquarks to balance them. Physicists call this “open charm” (in this case, “double open charm”). Particles containing a charm quark and a charm antiquark have “hidden charm” – the charm quantum number for the whole particle adds up to zero, just like a positive and a negative electrical charge would do. Here the charm quantum number adds up to two, so it has twice the charm!

The quark content of T_cc⁺ has other interesting features besides being open charm. It is the first particle to be found that belongs to a class of tetraquarks with two heavy quarks and two light antiquarks. Such particles decay by transforming into a pair of mesons, each formed by one of the heavy quarks and one of the light antiquarks. According to some theoretical predictions, the mass of tetraquarks of this type should be very close to the sum of masses of the two mesons. Such proximity in mass makes the decay “difficult”, resulting in a longer lifetime of the particle, and indeed T_cc⁺ is the longest-lived exotic hadron found to date.

The discovery paves the way for a search for heavier particles of the same type, with one or two charm quarks replaced by bottom quarks. The particle with two bottom quarks is especially interesting: according to calculations, its mass should be smaller than the sum of the masses of any pair of B mesons. This would make the decay not only unlikely, but actually forbidden: the particle would not be able to decay via the strong interaction and would have to do so via the weak interaction instead, which would make its lifetime several orders of magnitude longer than any previously observed exotic hadron.

The new T_cc⁺ tetraquark is an enticing target for further study. The particles that it decays into are all comparatively easy to detect and, in combination with the small amount of the available energy in the decay, this leads to an excellent precision on its mass and allows the study of the quantum numbers of this fascinating particle. This, in turn, can provide a stringent test for existing theoretical models and could even potentially allow previously unreachable effects to be probed.

Read more on the LHCb website and in the CERN Courier:

https://lhcb-public.web.cern.ch/Welcome.html#Tcc

https://cerncourier.com/a/new-tetraquark-a-whisker-away-from-stability/

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 23 Member States.

Related links:

LHCb experiment at CERN: https://home.cern/science/experiments/lhcb

European Physical Society Conference on High Energy Physics (EPS-HEP): https://indico.desy.de/event/28202/

For more information about European Organization for Nuclear Research (CERN), Visit: https://home.cern/

Image (mentioned), Text, Credit: European Organization for Nuclear Research (CERN).

Best regards, Orbiter.ch

Space Station Science Highlights: Week of July 26, 2021

 

ISS - Expedition 65 Mission patch.

July 30, 2021

Crew members aboard the International Space Station conducted scientific investigations during the week of July 26 that included studies of advanced materials, improving the food supply in space, and producing alloys without using a container.

Image above: This image shows Europe at night as the space station passes overhead. Image Credit: NASA.

The space station has been continuously inhabited by humans for 20 years, supporting many scientific breakthroughs. The orbiting lab provides a platform for long-duration research in microgravity and for learning to live and work in space, experience that supports Artemis, NASA’s program to go forward to the Moon and on to Mars.

Here are details on some of the microgravity investigations currently taking place:

Assembling advanced materials

Image above: Akihiko Hoshide of the Japan Aerospace Exploration Agency works on the InSPACE-4 investigation, which could advance next-generation materials for a variety of uses on Earth and in space. Image Credit: NASA.

InSPACE-4 studies using magnetic fields to assemble tiny structures from colloids, or particles suspended in a liquid. These structures affect the properties of assembled materials, such as mechanical response to or interaction with light and heat. Microgravity makes possible colloid assembly free from confining sample walls and sedimentation that occur on Earth. Results could lead to advanced materials for space applications such as better thermal shields, protection from micrometeorites, materials for energy production, energy-transfer devices, control systems, and new mechanical actuators and sensors for robotic and human missions. This investigation also helps advance next-generation nanomaterials for applications on Earth such as thermal shields, sound damping devices, shock absorbers, camouflage, medical diagnostic and environmental sensors, display technologies, and advanced coatings. The technology also is expanding into larger-scale applications such as building foundation stabilizers for areas prone to earthquakes. During the week, crew members set up and initiated multiple experiment runs.

The menu matters

An army marches on its stomach, the saying goes, and astronauts fly on theirs. The success of any mission relies on plentiful, nutritious, and enjoyable food. A growing body of research on the space station looks at ways to improve the food supply as missions increase in length. During this week, crew members worked on two current food-related investigations.

Image above: This image was taken during plant harvest from the Veggie production facility for the Veg-04A experiment, part of a series of fresh food experiments that includes HRF Veg. That investigation uses psychological surveys and crew evaluations of the flavor and appeal of plants grown on the space station. Image Credit: NASA.

HRF Veg is part of a fresh food analysis project that also includes Veg-04A, Veg-04B, and Veg-05. HRF Veg uses psychological surveys and crew evaluations of the flavor and appeal of plants grown on the space station for other investigations, focusing on the overall health benefits to crew members of having various plants and fresh food.

Food Acceptability looks at how the appeal of food changes during long-duration missions. Whether crew members like and actually eat foods directly affects their caloric intake and associated nutritional benefits. Crew members sometimes report that they tire of certain foods, which could lead to decreased acceptability of those foods and may contribute to the loss of body mass often experienced by crew members. This could become more of a problem as mission length increases, and the investigation supports developing strategies to improve the food system and better support crew health and performance.

Leveraging levitation

In order to produce glass, metal alloys, or other materials on Earth, a mixture of raw materials is melted in a container. But chemical reactions can occur between the materials and the container, causing imperfections and contaminations. The Japan Aerospace Exploration Agency (JAXA) developed the Electrostatic Levitation Furnace (ELF), an experimental facility that enables melting and solidifying materials without a container in order to reduce these imperfections, something possible only in microgravity. The JAXA-ELF Investigation uses ELF to observe the behavior of materials used for high-temperature manufacturing of oxides, semiconductors, insulators, and alloys. Results could contribute to the development of technology to process materials without containers, benefiting design of new materials. Crew members exchanged the sample holder assembly for this investigation during the week.

Other investigations on which the crew performed work:

- Cell Science-04 examines the genes involved in tardigrade adaptation and survival in high stress environments, both short-term and across multiple generations. The results could advance understanding of the stress factors affecting humans in space.
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7672

- GRIP, an ESA (European Space Agency) investigation, studies how spaceflight affects the grip force and movements that crew members use to manipulate objects. Results could identify potential hazards astronauts may face when they move between environments with different levels of gravity, such as landing on Mars after a lengthy voyage in space.
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1188

- Pilote, an investigation from ESA, tests the effectiveness of remote operation of robotic arms and space vehicles using virtual reality and haptics, or simulated touch and motion. Results may influence the design of workstations and interfaces for future spacecraft and space habitats.
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=8347

Image above: NASA astronaut Megan McArthur works on Plant Water Management, a series of investigations testing use of capillary fluidics to deliver adequate water and nutrients to plants. Image Credit: NASA.

- Plant Water Management is a series of investigations to test using concepts of capillary fluidics – such as surface tension, wetting, and geometry – to deliver adequate water and nutrients to plants.
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7884

- ACME includes six independent studies of flames that seek to improve fuel efficiency and reduce pollution from combustion on Earth and help prevent fires in spacecraft.
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1651

- Time Perception, an investigation from ESA, examines subjective changes in time perception that occur during and after long-duration exposure to microgravity. Astronauts need to accurately assess the passing of time in order to perform fine motor skills and control vehicles and other complex systems at a high level of cognitive function.
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7504

Space to Ground: Rosie the Rocketeer: 07/30/2021

Related links:

Expedition 65: https://www.nasa.gov/mission_pages/station/expeditions/expedition65/index.html

InSPACE-4: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7669

HRF Veg: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=8434

Veg-04A: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7896

Veg-04B: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7895

Food Acceptability: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7562

Electrostatic Levitation Furnace (ELF): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=1536

JAXA-ELF Investigation: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1738

ISS National Lab: https://www.issnationallab.org/

Spot the Station: https://spotthestation.nasa.gov/

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/overview.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Video (NASA), Text, Credits: NASA/Ana Guzman/John Love, ISS Research Planning Integration Scientist Expedition 65.

Best regards, Orbiter.ch

Earliest Launch Opportunity for NASA’s Boeing OFT-2 Mission is Aug. 3

 

Boeing / NASA - Starliner Orbital Flight Test-2 (OFT-2) patch.

July 30, 2021

NASA and Boeing have elected to stand down from Friday’s launch attempt of the agency’s second Orbital Flight Test (OFT-2) mission. Currently, the earliest available launch opportunity is 1:20 p.m. EDT Tuesday, Aug. 3. The International Space Station team will use the time to continue working checkouts of the newly arrived Roscosmos Nauka multipurpose laboratory module (MLM) and to ensure the station will be ready for Starliner’s arrival.

Launch preparations will resume following a final decision from the International Space Station and Commercial Crew Program teams for the next opportunity to send Starliner on its way to complete the OFT-2 mission, which will set the stage for the first Crew Flight Test.

Image above: On July 29, 2021, Boeing’s CST-100 Starliner spacecraft and the United Launch Alliance Atlas V rocket rolled out of the Vertical Integration Facility to the launch pad at Space Launch Complex-41 on Cape Canaveral Space Force Station in Florida. Photo credit: United Launch Alliance (ULA).

Earlier Thursday, Starliner atop its United Launch Alliance Atlas V rocket was moved to its seaside launch pad for standard launch preparations. Teams are assessing moving the vehicle back to its Vehicle Integration Facility to protect it from weather until launch preparations resume. Starliner and Atlas V are in a safe, flight-ready configuration and do not require any near-term servicing.

The Atlas V was assembled throughout July, which included the transfer of Starliner from Boeing’s spacecraft processing facility at NASA’s Kennedy Space Center in Florida to nearby Cape Canaveral Space Force Station Launch Complex 41 for mating atop the rocket.

Related articles:

Space Station Stable After Earlier Unplanned MLM Thruster Firing & Update OFT-2
https://orbiterchspacenews.blogspot.com/2021/07/space-station-stable-after-earlier.html

What You Need to Know about NASA’s Boeing Orbital Flight Test-2
https://orbiterchspacenews.blogspot.com/2021/07/what-you-need-to-know-about-nasas.html

Related links:

Commercial Crew Program: https://www.nasa.gov/exploration/commercial/crew/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Image (mentioned), Text, Credits: NASA/Amanda Griffin.

Greetings, Orbiter.ch

Hubble Spots Squabbling Galactic Siblings

 

NASA - Hubble Space Telescope patch.

July 30, 2021

A dramatic triplet of galaxies takes center stage in this image from the NASA/ESA Hubble Space Telescope, which captures a three-way gravitational tug-of-war between interacting galaxies. This system – known as Arp 195 – is featured in the Atlas of Peculiar Galaxies, a list which showcases some of the weirder and more wonderful galaxies in the universe.

Observing time with Hubble is extremely valuable, so astronomers don't want to waste a second. The schedule for Hubble observations is calculated using a computer algorithm which allows the spacecraft to occasionally gather bonus snapshots of data between longer observations. This image of the clashing triplet of galaxies in Arp 195 is one such snapshot. Extra observations such as these do more than provide spectacular images – they also help to identify promising targets to follow up with using telescopes such as the upcoming NASA/ESA/CSA James Webb Space Telescope.

Hubble Space Telescope (HST)

For more information about Hubble, visit:

http://hubblesite.org/

http://www.nasa.gov/hubble

http://www.spacetelescope.org/

Text Credits: European Space Agency (ESA)/NASA/Lynn Jenner/Image, Animation Credits: ESA/Hubble & NASA, J. Dalcanton.

Best regards, Orbiter.ch

ECOSTRESS Data Incorporated Into New Wildfire Response Tool

 

ISS - ECOSTRESS Mission logo.

July 30, 2021

The instrument on the International Space Station is uniquely positioned to provide wildfire responders with a high-resolution look at fire progression.

Video above: NASA’s ECOSTRESS instrument captured ground-surface temperature data over southern Oregon’s Bootleg Fire from July 7 to July 22. Areas in red – the hottest pixels detected – show the fire front, where resources are needed most. Video Credits: NASA/JPL-Caltech.

NASA’s ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) is aiding in the fight against fires in the Western U.S.

As of July 28, 2021, the size of the Bootleg Fire in southern Oregon was more than 410,000 acres, making it the largest wildfire currently burning in the U.S. So far, some 400 buildings and more than 340 vehicles have been destroyed. Wildfire responders have managed to contain about 53% of the fire, and new data from ECOSTRESS is helping.

NASA’s ECOSTRESS instrument on ISS. Image Credit: NASA

ECOSTRESS measures surface temperature from the vantage point of the International Space Station, and its ability to observe fires of the Northwest US often twice per day at a high spatial resolution (around 70 meters) makes it ideal for tracking fires. Researchers on the RADR-Fire team at Pacific Northwest National Laboratory have been experimenting with ECOSTRESS data as part of a new tool now being implemented for first responders like the U.S. Forest Service.

In the above visualization, ECOSTRESS is tracking the movement of the Bootleg Fire and identifying its proximity to critical infrastructure -- areas in red represent the hottest pixels ECOSTRESS detected. The extreme heat in those areas indicates the fire front, or where resources are most needed.

The capabilities of ECOSTRESS are unique. Satellites that acquire data more frequently don’t have high-enough resolution to track the fine line of the fire front, and satellites with higher resolution than ECOSTRESS cross over the same area much less frequently (every 5 to 16 days).

Dixie Fire

2021 Northern California Dixie Fire

Video above: NASA’s ECOSTRESS instrument captured ground-surface temperature data over northern California’s Dixie Fire from July 15 to July 24. Areas in red – the hottest pixels detected – show the fire front, where resources are needed most. Video Credit: NASA/JPL-Caltech.

ECOSTRESS also captured data over Northern California’s Dixie Fire, which has doubled in size to more than 220,000 acres over the last few days. In the Dixie Fire data visualization above, the red areas show the hottest pixels – and fire movement – from July 15 to July 24. The most heavily affected areas are south of Lake Almanor in Plumas County. As of July 27, the Dixie Fire was 23% contained.

More than 7,000 personnel are involved in the wildfire response to the two fires. Although they have many tools in their arsenal, the use of spaceborne data like that provided by ECOSTRESS is still relatively new – and also serves as a good example of the versatility and real-world impact satellite data can provide.

More information about ECOSTRESS can be found at: https://ecostress.jpl.nasa.gov/

Image (mentioned), Videos (mentioned), Text, Credits: JPL/Jane J. Lee/Ian J. O'Neill/Written by Esprit Smith, NASA’s Earth Science News Team.

Greetings, Orbiter.ch

Ariane 5 launches pioneering reprogrammable telecommunications satellite

 

ARIANESPACE - Ariane 5 Flight VA254 Mission patch.

July 30, 2021

Europe’s Ariane 5 has delivered two telecom satellites Star One D2 and Eutelsat Quantum into their planned transfer orbits.

Ariane 5 liftoff

Arianespace announced liftoff at 22:00 BST (23:00 CEST, 18:00 local time) this evening from Europe’s Spaceport in Kourou, French Guiana, for a mission lasting about 37 minutes.

Star One D2, with a launch mass of 6187 kg, in the upper berth of the fairing was released first.

Following a series of burns controlled by Ariane’s computer, the Sylda structure encasing the 3461 kg Eutelsat Quantum payload was then jettisoned before Eutelsat Quantum was released into its own geostationary transfer orbit.

Eutelsat Quantum Liftoff

Star One D2 is owned by Maxar and operated by Brazilian operator Embratel. It will deliver broadband coverage to regions in Central and South America. It has a design life of 15 years.

Eutelsat Quantum, developed under an ESA partnership project with satellite operator Eutelsat and prime manufacturer Airbus, is the first commercial fully flexible software-defined satellite in the world.

Eutelsat Quantum satellite

Because it can be reprogrammed in orbit, it can respond to changing demands for data transmission and secure communications during its 15-year lifetime. Its beams can be redirected to move in almost real time to provide information to passengers on board moving ships or planes. The beams also can be easily adjusted to deliver more data when demand surges. The satellite can detect and characterise any rogue emissions, enabling it to respond dynamically to accidental interference or intentional jamming.

“Every launch is exciting. Ariane 5 is the pride of Europe and continues to be the cornerstone of Europe’s access to space. Eutelsat Quantum, launched today, is the result of an ESA–industry partnership that brings a world first to telecommunications. I’m happy that Ariane 5 is also part of this achievement for Europe,” commented Daniel Neuenschwander, ESA Director of Space Transportation.

The performance requested for this Ariane launch was about 10 515 kg. The satellites totalled about 9647 kg, with payload adapters and carrying structures making up the rest.

Flight VA254 was the 110th Ariane 5 mission.

About Ariane 5

Ariane 5 is operated by Arianespace at Europe’s Spaceport. It is able to carry payloads weighing more than 10 tonnes to geostationary transfer orbit and over 20 tonnes into low-Earth orbit. Its performance perfectly complements that of Europe’s Vega light-lift launch vehicle, and Soyuz.

Europe’s next-generation Ariane 6 rocket will eventually replace Ariane 5. Available in two versions, it will be capable of a wide range of missions to any orbit.

Related links:

Eutelsat Quantum: https://www.esa.int/Applications/Telecommunications_Integrated_Applications/Eutelsat_Quantum

Ariane 5: http://www.esa.int/Enabling_Support/Space_Transportation/Ariane

ARIANESPACE:  https://www.arianespace.com/

Images, Video, Text, Credits: ESA/CNES/Arianespace/Eutelsat.

Greetings, Orbiter.ch

Russian module mishap destabilises International Space Station

 

ROSCOSMOS - Nauka (Science) Module patch.

July 30, 2021

The International Space Station (ISS) was destabilised after engines of a newly arrived Russian module inadvertently fired up.

"Mission control teams corrected the action and all systems are operating normally," US space agency Nasa said. This was done by activating thrusters on other modules of the ISS. An investigation is now under way. US and Russian officials stressed that the seven crew members aboard the space station were never in any danger.

Nauka (centre) joined the ISS high above the border between Mongolia and China

The malfunction happened three hours after the Nauka module docked with the ISS on Thursday, following an eight-day flight from Earth. Nasa officials said Nauka's jets started firing uncommanded at 12:34 EDT (16:45 GMT) "moving the station 45 degrees out of attitude". The Russian Zvezda segment and a Progress freighter then responded to push the station back into its correct pointing configuration. The incident was over by 13:29 EDT.

"What we saw today was just an awesome job by the mission control flight teams," said Joel Montalbano, Nasa's ISS programme manager. "Those guys were rock stars again and got us back in attitude control. That also shows you what a robust vehicle we have, and our ability to take these contingencies, recover from them and move on," he told reporters.

The unplanned firing of Nauka's thrusters

Communications with the ISS crew were lost for two periods, of four minutes and seven minutes, during the incident. However, the US agency said that the astronauts were safe. They "really didn't feel any movement", it added. The mishap forced Nasa and Boeing to push back Friday's uncrewed test flight of Boeing's Starliner capsule, a vehicle intended to carry astronauts in the future.

"We wanted to give the ISS programme time to assess what had happened today, to determine the cause and make sure that they were really ready to support the Starliner launch," explained Steve Stich, the manager of Nasa's commercial crew programme. "Right now the earliest opportunity would be Tuesday, 3 August, which would be a 13:20 EDT (17:20 GMT) launch.

Multipurpose Laboratory Module (MLM) or "Nauka" (Science) module docked to ISS

The 13m-long, 20-tonne Nauka was earlier attached to the rear of the orbiting platform, linking up with the other major Russian segments on the station. The module should have launched in 2007, but the vessel suffered repeated slips in schedule, in part because of budget difficulties but also because engineers encountered a raft of technical problems during development.

Even after it launched from the Baikonur Cosmodrome in Kazakhstan a week ago, it experienced propulsion issues that required workarounds from controllers in Moscow. In the end, however, it docked with the station on the planned date. The new module will result in a significant boost in habitable volume for the ISS, raising it by 70 cubic metres.

The delay for Nauka has also affected the European robotic arm

Cosmonauts will use the extra space to conduct experiments and to store cargo. They'll also use it as a rest area, and it has another toilet for crew to use on the station. In addition, the module carries with it a large robotic arm (ERA) supplied by the European Space Agency (ESA). This 11m-long device will be able to operate all around the Russian end of the ISS. With the aid of an "elbow" joint, it will shift position by moving hand over hand. Nauka's installation comes just as Russia has been questioning its future role in the ISS project.

Moscow officials recently warned about the more-than-20-year age of some of their on-orbit hardware and intimated the country could pull out of the station in 2025. And Russia has shown little interest in joining the US-led lunar platform, known as the Gateway, which will be assembled later this decade.

The hatches between the module "Science" and the ISS are open

On Thursday, July 29, 2021, at 16:29:06 Moscow time, the Nauka multipurpose laboratory module, launched on July 21, 2021 from the Baikonur cosmodrome, was docked to the International Space Station. Today at 20:47 Moscow time, Roscosmos cosmonauts Oleg Novitsky and Pyotr Dubrov opened the transfer hatches and boarded the new Russian module "Science".

Nauka hatch opening

After the completion of the docking operations of the multipurpose laboratory module with the nadir docking port of the Zvezda service module of the ISS Russian segment, specialists from the Moscow Region TsNIIMash Mission Control Center (part of the State Corporation Roscosmos), together with the crew of the ISS Russian segment, conducted a tightness control of the docking connections and analyzed telemetry information on the state of the module on-board systems. Then the Russian members of the ISS-65 Expedition Oleg Novitsky and Pyotr Dubrov opened the hatch of the transition compartment of the Zvezda module and a few minutes later entered the living area of ​​the instrument-hermetic compartment of the laboratory module. In accordance with today's work plan, on board the multipurpose laboratory module, Roskosmos cosmonauts will perform a control examination of the compartments, take air samples and install an atmosphere purification filter unit.

Internal Layout of "Nauka" (Science) Module (Click on the image for enlarge)

Nauka is a multipurpose laboratory module for the Russian segment of the International Space Station. It was created by a cooperation of enterprises with the leading role of the Rocket and Space Corporation Energia (Korolev, part of Roscosmos), as a module developer in order to implement a program of scientific experiments and expand the functionality of the Russian segment of the ISS. The module structure was manufactured by the State Space Research and Production Center named after M.V. Khrunicheva (Moscow, part of Roscosmos).

The multipurpose laboratory module "Science" is intended for the implementation of the Russian program of scientific and applied research and experiments. After its commissioning, the Russian segment of the station will receive additional volumes for the arrangement of workplaces and storage of goods, placement of equipment for the regeneration of water and oxygen. It consists of an instrument-hermetic compartment and a spherical pressurized adapter, separated by a sealed bulkhead with a hatch. It is also equipped with an airlock for carrying out scientific equipment outside the station and a European remote manipulator ERA (European Robotic Arm).

Multipurpose Laboratory Module (MLM) or "Nauka" (Science) module

In the new Russian module, it is planned to conduct 13 experiments in various directions, including Kaplya-2 (space technologies), Aseptic (space biology and physiology), Mirage, Vampire, Fullerene (space materials science ), "Vitacyc-T" (space biology and physiology), "Rakurs" (exploration of the Earth from space) and others. Flight tests of the "Science" module will be completed in about a year.

Related article:

Space Station Stable After Earlier Unplanned MLM Thruster Firing & Update OFT-2
https://orbiterchspacenews.blogspot.com/2021/07/space-station-stable-after-earlier.html

Related links:

TsNIIMash: https://www.roscosmos.ru/tag/cniimash/

ROSCOSMOS Press Release: https://www.roscosmos.ru/32037/

Expedition 65: https://www.nasa.gov/mission_pages/station/expeditions/expedition65/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images,  Animation, Videos, Text, Credits: BBC News/NASA/ESA/NASA TV/SciNews/ROSCOSMOS/Orbiter.ch Aerospace/Roland Berga.

Best regards, Orbiter.ch

Space Station Stable After Earlier Unplanned MLM Thruster Firing & Update OFT-2

 

ISS - Expedition 65 Mission patch.

July 29, 2021

Multipurpose Laboratory Module (MLM) "Nauka" arrival at ISS. Image Credit: ROSCOSMOS

Following the docking of the Multipurpose Laboratory Module (MLM), named Nauka, to the International Space Station at 9:29 am EDT, Russian cosmonauts aboard the space station conducted leak checks between Nauka and the service module. At 12:45 pm, the flight control team noticed the unplanned firing of MLM thrusters that caused the station to move out of orientation. Ground teams have regained attitude control and the motion of the space station is stable.

Image above: July 29, 2021: International Space Station Configuration. Three spaceships are docked at the space station including the SpaceX Crew Dragon and Russia’s Soyuz MS-18 crew ship and ISS Progress 78 resupply ship. The new Nauka Multipurpose Logistics Module (MLM) is now attached to the Zvezda service module’s Earth-facing port. Image Credit: NASA.

The crew was never and is not in any danger, and flight controllers in Mission Control Houston are monitoring the status of the space station. Teams are also monitoring the impact to tomorrow’s launch of the Boeing Starliner spacecraft.

Update on the Nauka module

Update to NASA’s Boeing Orbital Flight Test-2 Mission

Boeing CST-100 Starliner. Animation Credit: Boeing

NASA and Boeing have decided to stand down from Friday’s launch attempt of the agency’s Orbital Flight Test-2 mission. Currently, launch teams are assessing the next available opportunity. The move allows the International Space Station team time to continue working checkouts of the newly arrived Roscosmos’ Nauka module and to ensure the station will be ready for Starliner’s arrival.

Related article:

New Module Successfully Docks to Space Station
https://orbiterchspacenews.blogspot.com/2021/07/new-module-successfully-docks-to-space.html

Related links:

Expedition 65: https://www.nasa.gov/mission_pages/station/expeditions/expedition65/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Video, Text, Credits: NASA/Norah Moran/Dan Huot/NASA TV/SciNews.

Best regards, Orbiter.ch

Companies compete for payload to make air from moondust

 

ESA - European Space Agency patch.

July 29, 2021

ESA is challenging companies in its Member States to design a compact plant to demonstrate the manufacture of oxygen on the Moon. Industrial teams are competing this summer to propose and prove designs through testing, with the winner set to be declared in September. This small piece of technology will evaluate the prospect of building larger plants to produce propellant for spacecraft, air for astronauts and metallic raw materials for equipment.

ESA’s Directorate of Human and Robotic Exploration selected Airbus Defence and Space in Germany, OHB in Italy, Space Applications in Belgium and Thales Alenia Space in the UK as leaders of the competing teams during a summer-long study to develop payload concepts meeting stringent performance requirements.

Earth seen from the Moon

“We make high demands of our industrial companies”, says David Binns, Systems Engineer at ESA's Concurrent Design Facility. “We need a system which is small, doesn’t consume too much power and could fly on a number of different landers. It also needs to be available in the middle of this decade. With both ESA and NASA planning to return to the Moon with crewed missions, this time to stay, this technology needs to be ready.”

Giorgio Magistrati, Studies and Technologies Team Leader at ESA's ExPeRT (Exploration Preparation, Research and Technology) initative adds: “The system will represent the first step – a so called ‘demonstrator’ – in an In-Situ Resource Utilisation implementation strategy that foresees an ISRU plant in the early part of the next decade. It could potentially be deployed on the Moon's surface by the European Large Logistic Lander, EL3, a project currently in its preliminary design phase.”

Making oxygen out of moondust

The underlying concept has already been proven. Samples returned from the lunar surface confirm that lunar regolith is made up of 40–45% percent oxygen by weight, its single most abundant element. The difficulty is that this oxygen is bound up chemically as oxides in the form of minerals or glass, so is unavailable for immediate use.

However a prototype oxygen plant has been set up in the Materials and Electrical Components Laboratory of the European Space Research and Technology Centre, ESTEC, based in Noordwijk in the Netherlands.

Living on another world

This plant employs an electrolysis-based process to separate simulated lunar regolith into metals and oxygen, key basic resources for long-term sustainable space missions.

ESA space resources scientists Alexandre Meurisse comments: “Now we have the facility in operation we can help in designing a version of this system that could one day fly to the Moon to be operated there.”

Oxygen and metal from lunar regolith

But extracting oxygen from lunar rock in a laboratory setting is one thing; the real challenge is to design a system that will operate in the harsh lunar environment, within strict volume and power constraints.

ESA has set strict targets for the payload, proposed to be flown on a future lunar lander:

- Retrieve samples and extract 50-100g of oxygen
- Show that more than 70% of the available oxygen in a lunar rock sample can extracted
- Perform precision measurements of oxygen and metals production
- Do it all before the Sun goes down on the lunar surface (< 10 Earth days).

Having started work in June, the companies have had just three months to come up with working designs.

European Large Logistics Lander

“Our companies will need to decide the best way of extracting the oxygen,” adds David. ”This payload concept will need a method of acquiring the samples from the surface quickly, transferring them to a preparation area before finally loading the reactor which grabs the oxygen. And at each step of the way we need to measure and analyse what happens on the Moon.”

A panel will evaluate the concepts and the selected  winner will begin the work on the detailed design helping ESA prepare a proposal to build the payload, set to be presented for approval to space ministers of ESA Member States during the Agency’s Ministerial Council next year.

ESA's Concurrent Design Facility, used to evaluate design concepts

The aim is to produce autonomous, reliable, low maintenance, consumable free, and sustainable technology to utilise resources in space, and ‘live off the land’. Such efforts can deliver benefits on Earth too. Much water, energy and human effort is required to mine terrestrial raw metal oxides then remove unwanted oxygen to produce metals. A great deal of carbon dioxide can be produced in the process.

David concludes: “So by taking a risk in space to realise such technology, we could also improve the extraction of resources on Earth.”

Related links:

Airbus Defence and Space: https://www.airbus.com/space.html

OHB: https://www.ohb.de/

Space Applications: https://www.spaceapplications.com/

Thales Alenia Space: https://www.thalesgroup.com/en/global/activities/space

ESA's Concurrent Design Facility: https://www.esa.int/Enabling_Support/Space_Engineering_Technology/20_years_of_ESA_s_Concurrent_Design_Facility_an_oral_history

ESA's ExPeRT (Exploration Preparation, Research and Technology): https://www.esa.int/About_Us/Business_with_ESA/Business_Opportunities/ExPeRT_Exploration_Preparation_Research_and_Technology

European Large Logistic Lander (EL3): https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/European_Large_Logistics_Lander

European Space Research and Technology Centre (ESTEC): https://www.esa.int/About_Us/ESTEC

Images, Text, Credits: ESA/A. Conigili/G. Porter/JAXA/NHK/Beth Lomax - University of Glasgow.

Greetings, Orbiter.ch

New Module Successfully Docks to Space Station

 

ROSCOSMOS - Nauka (Science) Module patch.

July 29, 2021

Image above: Nauka approaches the space station, preparing to dock. Image Credit: NASA TV.

The uncrewed Multipurpose Laboratory Module (MLM), named Nauka, the Russian word for “science,” arrived at the International Space Station’s Poisk module on the space-facing side of the Russian segment at 9:29 a.m. EDT, eight days after lifting off from the Baikonur Cosmodrome in Kazakhstan.

Nauka docking to the International Space Station

Named Nauka, the Russian word for science, the 43-foot long, 23-ton module launched on July 21 and will serve as a new science facility, docking port, and spacewalk airlock for future operations. 

Related article:

Final correction of the orbit of the Nauka module before docking with the ISS
https://orbiterchspacenews.blogspot.com/2021/07/final-correction-of-orbit-of-nauka.html

Related link:

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Image (mentioned), Video, Text, Credits: NASA/Cballart/NASA TV/SciNews.

Best regards, Orbiter.ch

Clays, Not Water, Are Likely Source of Mars ‘Lakes’

 

NASA - Mars Reconnaissance Orbiter (MRO) patch.

July 29, 2021

Three studies published in the past month have cast doubt on the premise of subsurface lakes below the Martian south pole.

Image above: This image taken by NASA’s Mars Reconnaissance Orbiter shows ice sheets at Mars’ south pole. The spacecraft detected clays nearby this ice; scientists have proposed such clays are the source of radar reflections that have been previously interpreted as liquid water. Image Credits: NASA/JPL-Caltech/University of Arizona/JHU.

Where there’s water, there’s life. That’s the case on Earth, at least, and also why scientists remain tantalized by any evidence suggesting there’s liquid water on cold, dry Mars. The Red Planet is a difficult place to look for liquid water: While water ice is plentiful, any water warm enough to be liquid on the surface would last for only a few moments before turning into vapor in Mars’ wispy air.

Hence the interest generated in 2018, when a team led by Roberto Orosei of Italy’s Istituto Nazionale di Astrofisica announced they had found evidence of subsurface lakes deep below the ice cap at Mars’ south pole. The evidence they cited came from a radar instrument aboard the ESA (European Space Agency) Mars Express orbiter.

Image above: The colored dots represent sites where bright radar reflections have been spotted by ESA’s Mars Express orbiter at Mars’ south polar cap. Such reflections were previously interpreted as subsurface liquid water, but their prevalence and proximity to the frigid surface suggest they may be something else. Image Credits: ESA/NASA/JPL-Caltech.

Radar signals, which can penetrate rock and ice, change as they’re reflected off different materials. In this case, they produced especially bright signals beneath the polar cap that could be interpreted as liquid water. The possibility of a potentially habitable environment for microbes was exciting.

But after taking a closer look at the data, along with experiments in a cold laboratory here on Earth, some scientists now think clays, not water, might be creating the signals. In the past month, a trio of new papers have unraveled the mystery – and may have dried up the lakes hypothesis.

A Scientific Ecosystem

Martian polar scientists belong to a small, tight-knit community. Not long after the lakes paper was published, about 80 of those scientists met for the International Conference on Mars Polar Science and Exploration in Ushuaia, a seaside village at the southern tip of Argentina.

Gatherings like these provide an opportunity to test new theories and challenge each other’s perspectives. “Communities can generate their own little scientific ecosystems,” said Jeffrey Plaut of NASA’s Jet Propulsion Laboratory, one of the scientists who traveled to the conference. He’s also the co-principal investigator, along with Orosei, of the instrument behind the intriguing radar signals, called MARSIS, or the Mars Advanced Radar for Subsurface and Ionospheric Sounding. “These communities can be self-sustaining,” he continued, “because you bounce a question off someone and maybe a year or two later they help you figure out an answer.”

Lots of talk centered on the subsurface lakes. How much heat would it take to keep water liquid under all that ice? Could brine be lowering the freezing point of the water enough to keep it liquid?

Of course, it wouldn’t be the first time an exciting water-related hypothesis set off a flurry of investigations. In 2015, NASA’s Mars Reconnaissance Orbiter found what looked like streaks of damp sand running down slopes, a phenomenon called “recurring slope lineae.” But repeated observations using the spacecraft’s HiRISE – or High-Resolution Imaging Science Experiment – camera have since revealed this is more likely the result of sand flows. A paper released earlier this year found many recurring slope lineae after a global dust storm on Mars in 2018. The finding suggested that dust settling on slopes triggers sand flows, which, in turn, expose the darker subsurface materials that give the lineae their distinctive coloration.

As with the damp-sand hypothesis, several scientists began thinking up ways to test the subsurface-lakes hypothesis. “There was a feeling that we should try to address this,” said Isaac Smith of York University in Toronto, who organized the conference in Ushuaia and led the most recent study showing that clays can explain the observations.

Too Cold for Lakes

Among those scientists was Plaut. He and Aditya Khuller, an Arizona State University doctoral student who was interning at JPL, analyzed 44,000 radar echoes from the base of the polar cap across 15 years of MARSIS data. They turned up dozens more bright reflections like the ones in the 2018 study. But in their recent paper published in Geophysical Research Letters, they found many of these signals in areas close to the surface, where it should be too cold for water to remain liquid, even when mixed with perchlorates, a kind of salt commonly found on Mars that can lower the freezing temperature of water.

Two separate teams of scientists then analyzed the radar signals to determine whether anything else could be producing those signals.

Carver Bierson of ASU completed a theoretical study suggesting several possible materials that could cause the signals, including clays, metal-bearing minerals, and saline ice. But York University’s Isaac Smith, knowing that a group of clays called smectites were present all over Mars, went further in a separate, third paper: He measured smectite properties in a lab.

Image above: saac Smith of Toronto’s York University bundled up while working in a lab, freezing smectite clays with liquid nitrogen to test how they respond to radar signals. The results have challenged the hypothesis that subsurface lakes can be found at Mars’ south pole. Image Credits: York University/Craig Rezza.

Smectites look like ordinary rock but were formed by liquid water long ago. Smith put several smectite samples into a cylinder designed to measure how radar signals would interact with them. He also doused them with liquid nitrogen, freezing them to minus 58 degrees Fahrenheit (minus 50 degrees Celsius) – close to what they would be at the Martian south pole.

“The lab was cold,” Smith said. “It was winter in Canada at the time, and pumping liquid nitrogen into the room made it colder. I was bundled up in a hat, jacket, gloves, scarf, and a mask because of COVID-19. It was pretty uncomfortable.”

After freezing the clay samples, Smith found their response nearly perfectly matched the MARSIS radar observations. Then, he and his team checked for clays present on Mars near those radar observations. They relied on data from MRO, which carries a mineral mapper called the Compact Reconnaissance Imaging Spectrometer, or CRISM.

Mars Reconnaissance Orbiter (MRO). Image Credits: NASA/JPL-Caltech

Bingo. While CRISM can’t peer through ice, Smith found smectites scattered in the vicinity of the south pole’s ice cap. Smith’s team demonstrated that frozen smectite can make the reflections – no unusual amounts of salt or heat are required – and that they’re present at the south pole.

There’s no way to confirm what the bright radar signals are without landing at Mars’ south pole and digging through miles of ice. But the recent papers have offered plausible explanations that are more logical than liquid water.

“In planetary science, we often are just inching our way closer to the truth,” Plaut said. “The original paper didn’t prove it was water, and these new papers don’t prove it isn’t. But we try to narrow down the possibilities as much as possible in order to reach consensus.”

More About MRO:

To read more about the Mars Reconnaissance Orbiter, visit:

https://mars.nasa.gov/mro/

https://www.nasa.gov/mission_pages/MRO/main/index.html

JPL, a division of Caltech in Pasadena, California, manages the MRO mission for NASA's Science Mission Directorate in Washington. The University of Arizona, in Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, led the work to build the CRISM instrument and operates CRISM in coordination with an international team of researchers from universities, government and the private sector.

Related links:

Geophysical Research Letters: https://mars.nasa.gov/news/8972/study-looks-more-closely-at-mars-underground-water-signals/

Compact Reconnaissance Imaging Spectrometer, or CRISM: https://mars.nasa.gov/mro/mission/instruments/crism/

HiRISE – or High-Resolution Imaging Science Experiment: https://mars.nasa.gov/mro/mission/instruments/hirise/

International Conference on Mars Polar Science and Exploration: https://www.hou.usra.edu/meetings/marspolar2020/

Images (mentioned), Text, Credits: NASA/Tony Greicius/Karen Fox/Alana Johnson/JPL/Andrew Good.

Greetings, Orbiter.ch

Time Perception, Immersive Exercise, and Nanoparticles Rule the Day

 

ISS - Expedition 65 Mission patch.

July 28, 2021

Wednesday’s activities aboard the International Space Station remained focused on science and maintenance. In preparation of Russia’s Multipurpose Laboratory Module docking to the outpost the following day, July 29, Russian Cosmonaut Oleg Novitskiy located and gathered equipment to set up temporary ventilation for the 43-foot long, 23-ton module. Live coverage of tomorrow’s event begins at 8:30 a.m. EDT on NASA Television, the NASA app, and the agency’s website.

Commander Akihiko Hoshide of the Japan Aerospace Exploration Agency (JAXA) and ESA (European Space Agency) astronaut Thomas Pesquet took turns participating in a study that explores how astronauts perceive time in microgravity, which can impact physical and cognitive performance. Pesquet, along with NASA Flight Engineers Mark Vande Hei and Shane Kimbrough, continued operations for the Investigating the Structure of Paramagnetic Aggregates from Colloidal Ellipsoids, or InSPACE-4. This physics study investigates ways to produce high-quality protein crystals in microgravity to benefit pharmaceutical and biotechnology industries on Earth.

Image above: Expedition 65 Commander Akihiko Hoshide, pictured inside the Columbus laboratory module, wears virtual reality goggles for a time perception study. Image Credit: NASA.

Astronauts exercise two hours a day to help compensate for the loss of bone and muscle mass from living and working in weightlessness. However, their daily workout can quickly become repetitive in the closed and unchanging environment, leading to lack of motivation. The Immersive Exercise project aims to break the monotony with virtual reality (VR). In support of the first experiment session, Pesquet retrieved all the equipment and successfully completed the session by exercising on the bike with a VR headset.

Space gardening is key to sustaining human spaceflight as NASA and its international partners plan future missions to the Moon, Mars, and beyond. NASA Flight Engineer Megan McArthur and Kimbrough continued to work on the Plant Water Management study, an investigation that demonstrates how to operate hydroponics in microgravity. The duo conducted operations, set up, and configured hardware for the botany study that, eventually, may also improve watering systems on Earth.

International Space Station (ISS). Animation Credit: NASA

Meanwhile, two astronauts worked on maintenance activities. Hoshide replaced holder and installed cartridges on the Electrostatic Levitation Furnace (ELF) developed by JAXA. The ELF is a facility for materials science that melts levitating materials with a very high melting point, measures their properties, and solidifies them from a super-cooled state by taking advantage of the microgravity environment. In addition, Pesquet added ice bricks into the ESA-built Minus Eighty Laboratory Freezer, or MELFI, for the space station. The ice bricks provide cooling, or incubation, to the samples stored inside double-cold bags, which are insulated stowage bags used to transport samples to and from the orbiting laboratory.

Related article:

Final correction of the orbit of the Nauka module before docking with the ISS
https://orbiterchspacenews.blogspot.com/2021/07/final-correction-of-orbit-of-nauka.html

Related links:

NASA Television: https://www.nasa.gov/live

Expedition 65: https://www.nasa.gov/mission_pages/station/expeditions/expedition65/index.html

Perceive time in microgravity: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7504

InSPACE-4: https://iss-science.jsc.nasa.gov/details/7669

Loss of bone and muscle mass: https://www.nasa.gov/feature/astronauts-spines-under-scrutiny/

Immersive Exercise project: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=8370

Space gardening: https://www.nasa.gov/feature/can-space-gardening-help-astronauts-cope-with-isolation/

Plant Water Management: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=8191

Electrostatic Levitation Furnace (ELF): https://www.nasa.gov/mission_pages/station/research/news/b4h-3rd/it-levitating-without-container

Minus Eighty Laboratory Freezer: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=56

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/overview.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Image (mentioned), Animation (mentioned), Text, Credits: NASA/Deepthi Cauligi.

Best regards, Orbiter.ch

Final correction of the orbit of the Nauka module before docking with the ISS

 

ROSCOSMOS - Nauka (Science) Module patch.

July 28, 2021

On Wednesday, July 28, 2021, specialists of the flight control group of the multipurpose laboratory module "Nauka" at the Mission Control Center of TsNIIMash (part of the State Corporation Roscosmos) performed the final corrective maneuver of the module launched from the Baikonur cosmodrome a week ago in the normal mode.

The engines are switched on at 16:43:07 Moscow time. According to telemetry information, the propulsion system of the module worked normally. It is not planned to carry out new orbit corrections before the docking of the Nauka module with the Russian segment of the International Space Station, which is scheduled at 16:26 Moscow time on July 29, 2021. The live broadcast of the docking and docking will begin on the Roscosmos website and on the pages in the Roscosmos social networks from 15:40 Moscow time.

Nauka is a multipurpose laboratory module for the Russian segment of the International Space Station. It was created by the cooperation of enterprises in order to implement the program of scientific experiments and expand the functionality of the Russian segment of the ISS. After its commissioning, the Russian segment of the ISS will receive additional volumes for the arrangement of workplaces and storage of cargo, placement of equipment for the regeneration of water and oxygen.

Related articles:

ROSCOSMOS - MCC performed one more orbit correction of the "Nauka" module
https://orbiterchspacenews.blogspot.com/2021/07/roscosmos-mcc-performed-one-more-orbit.html

Module Pirs undocked from ISS & Pirs module and Progress MS-16 spacecraft completed flight
https://orbiterchspacenews.blogspot.com/2021/07/module-pirs-undocked-from-iss-pirs.html

ROSCOSMOS - MCC carried out two more orbit corrections of the Nauka module
https://orbiterchspacenews.blogspot.com/2021/07/roscosmos-mcc-carried-out-two-more.html

Related links:

ROSCOSMOS Press Release: https://www.roscosmos.ru/32022/

РКК Энергия / RSC Energia: https://www.roscosmos.ru/tag/rkk-ehnergija/

ЦНИИмаш / TsNIIMash: https://www.roscosmos.ru/tag/cniimash/

ЦУП / MCC (Flight Control Center): https://www.roscosmos.ru/tag/cup/

International Space Station (ISS): https://www.roscosmos.ru/tag/mks/

Images, Video, Text, Credits: ROSCOSMOS/MCC/Orbiter.ch Aerospace/Roland Berga.

Greetings, Orbiter.ch