As teams work to bring Hubble back online, new science highlights missing dark matter in galaxy

Following an unexpected payload computer halt on June 13, Hubble teams are diligently working to… The post As teams work to bring Hubble back online, new science highlights missing dark matter in galaxy appeared first on NASASpaceFlight.com.

As teams work to bring Hubble back online, new science highlights missing dark matter in galaxy

Following an unexpected payload computer halt on June 13, Hubble teams are diligently working to bring the 31-year-old telescope back online. The halt, which has garnered news headlines throughout the past week, is proving to be quite the challenge for engineers to resolve.

Although this failure undoubtedly highlights Hubble’s growing age, scientists have continuously used the observatory for research. One team of researchers’ recently published research using Hubble highlights one of the universe’s most mysterious phenomena — dark matter.

Hubble payload computer failure

Shortly after 20:00 UTC on Sunday, June 13, 2021, Hubble’s main computer stopped receiving a “keep-alive” signal from the telescope’s payload computer. Once Hubble’s main computer recognized the payload computer halt, it immediately put the telescope into safe mode.

As with most spacecraft, Hubble’s main computer has a “safe mode” feature that will shut down all science instrumentation and only operate essential telescope systems (power, communications, etc.).

Hubble teams in the control center at the Goddard Space Flight Center in Maryland recognized that Hubble was in safe mode and later attempted to restart the telescope the following day.

However, the halt occurred yet again, and Hubble went back into safe mode.

Thankfully though, the payload computer to blame for this issue was built with redundancy. Thus, a second computer is available for use in orbit in the unlikely event a failure occurs.

The team switched to this backup computer on Wednesday, June 16, and attempted to run it for a day to see how it operated with the telescope. However, the command to start up and operate the backup computer was never fully completed. Other attempts to switch to the computer were performed the following day, but they too were all unsuccessful.

Hubble’s payload computer is tasked with coordinating and operating the many science instruments onboard the telescope. Currently, six instruments operate on Hubble.

Diagram of the Hubble Space Telescope’s instruments and spacecraft systems – via NASA

This payload computer is a 1980s NASA Standard Spacecraft Computer-1 (NSSC-1) system located in Hubble’s Science Instrument Command and Data Handling Unit. The NSSC-1 system features four memory modules containing 64K of Complementary Metal-Oxide Semiconductor (CMOS) memory.

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  • Following initial data analysis from the event, Hubble teams believed one of these memory modules was degrading, which would’ve caused the NSSC-1 system to halt.

    However, after running tests and collecting more data on certain telescope systems, Hubble teams now believe that either the Standard Interface (STINT) hardware or the Central Processing Module (CPM) is to blame for the halt, and that the memory failures are a side effect of the overall failure.

    If the payload computer issue can’t be fixed, the Hubble team is prepared to switch to the STINT and CPM hardware on the backup computer.

    Knowing this, Hubble teams plan to continue running tests on the telescope to gain data and hopefully identify a solution for the issue.

    Astronauts work to service Hubble in the payload bay of Space Shuttle Atlantis on STS-125 – via NASA

    Nonetheless, this failure once again highlights the growing age of the iconic telescope.

    STS-125, the final Hubble servicing mission of the Space Shuttle Program, concluded on May 24, 2009 — over 12 years ago.

    Without the ability to service the telescope and update its instruments, Hubble teams have had to work around Hubble’s various failures throughout the past 12 years. One of Hubble’s most recent failures occurred in March of this year.

    The amount of time Hubble has left is unknown, but failures like these show that we are slowly creeping closer to Hubble’s final days in orbit.

    Thankfully though, Hubble’s replacement, the James Webb Space Telescope, is currently set to launch in the fall of this year, pending the resolution of fairing issues on the Ariane 5 rocket.

    In the meantime, Hubble teams continue to work to bring the telescope out of safe mode and back into science operations, with updates being released every few days.

    The James Webb Space Telescope, successor to Hubble, is being prepared to launch later this year – via NASA

    Mysterious dark matter missing from galaxy

    72 million light-years away from our solar system, in the constellation Cetus, an ultra diffused galaxy named NGC 1052-DF2 (simply DF2) drifts through space.

    It has been the site of great mystery due to its lack of dark matter — a finding that challenges conventional theories.

    Current theories suggest that dark matter makes up a considerable amount of a galaxy’s mass. Dark matter in galaxies can be thought of as the scaffolding for their structures. Large amounts of dark matter dominate nearly all galaxies.

    Additionally, dark matter is thought to account for nearly 85% of the entire universe’s mass, and galaxies are even thought to form from large halos of dark matter throughout the universe.

    So, you can imagine that when a team of researchers announced in 2018 that they found DF2 to have little to no dark matter inside it, some were quick to become skeptical of the legitimacy of the findings.

    “We went out on a limb with our initial Hubble observations of this galaxy in 2018. I think people were right to question it because it’s such an unusual result,” said Pieter van Dokkum of Yale University, who led the 2018 research.

    Galaxy NGC 1052-DF2, imaged by the Hubble Space Telescope – via ESA

    Van Dokkum et al.’s 2018 findings were so shocking that they decided to perform a follow-up study on DF2 using Hubble. The 2021 results were recently published in The Astrophysical Journal Letters.

    To understand just how much dark matter is in DF2, we have to first measure how far away DF2 is from our solar system.

    To calculate how far away DF2 is, van Dokkum et al. had to observe the various movements of stars within DF2 due to star movements influenced by the galaxy’s gravitational pull.

    The team of researchers made estimates using information gathered throughout previous studies and observations. If DF2 were as distant as van Dokkum et al. suggested, the amount of total dark matter in the galaxy would be only a few percent.

    If DF2 were closer to Earth than van Dokkum et al.’s suggestions, the galaxy would need dark matter to compensate for the observed effects of the total mass because DH2 would be much smaller and less faint than it is.

    The results gathered using Hubble suggest that DF2 is located 72 million light-years away from Earth — much farther than other astronomers who suggested DF2 was only 42 million light-years away. In addition, the results were more distant than the original estimates made by the team in 2018 (65 million light-years).

    Van Dokkum et al. found that the total amount of stars accounts for the entire mass of the galaxy. Understanding this, the team found that with the number of stars in DF2, there isn’t much room for dark matter to be present in the galaxy.

    This suggests that there likely are very small amounts of dark matter present inside DF2.

    To measure DF2’s distance, Hubble’s Advanced Camera for Surveys instrument was used in observations. In the observations, the team observed aging red stars on the outskirts of DF2 to pinpoint the galaxy’s distance.

    But — why red stars?

    Hubble imagery showing the red stars used to determine the distance from Earth to DF2 – via NASA

    Red stars all reach the same peak brightness throughout their evolution, and using the intrinsic brightness of a star, astronomers can calculate intergalactic distances.

    “Studying the brightest red giants is a well-established distance indicator for nearby galaxies,” said van Dokkum et al. member Zili Shen from Yale University.

    Although the recently published results from van Dokkum et al. don’t explain exactly why DF2 is deficient in dark matter, knowing the galaxy’s distance and having accurate observation data bolsters the team’s initial results from 2018.

    However, DF2 is not the only galaxy in the universe lacking dark matter that we know of.

    Research published in 2020 led by Shany Danieli of the Institute for Advanced Study in Princeton, New Jersey, studied another galaxy similar in composition to DF2 — galaxy NGC 1052-DF4 (simply DF4).

    Both DF2 and DF4 are “ghostly galaxies” and “see-through galaxies” because of their massive size and faintness. DF2 is nearly as wide as the Milky Way.

    However, these galaxies only contain around 1/200th the number of stars in the Milky Way due to how spread out the stars in the galaxy are. The size, lack of stars, and distance between stars give these galaxies a “ghostly” or “cotton ball” look.

    According to Danieli et al.’s 2020 study, DF4 lacks dark matter like DF2. However, the way it lost its dark matter is likely a much different process.

    The research suggests a neighboring galaxy’s gravitational forces pulled the dark matter out of DF4, stripping the galaxy of all its dark matter.

    Theories suggest that DF2 and DF4 were once members of the same galaxy cluster. But, new Hubble observations show that the two galaxies are farther than astronomers thought and that DF2 has drifted away from the previous cluster.

    Furthermore, 19 dwarf galaxies deficient in dark matter were discovered in another 2020 study. So although we know of multiple galaxies lacking in dark matter, scientists say we will need to discover many more dark-matter deficient galaxies to truly uncover the mystery behind these mysterious galaxies.

    However, van Dokkum says that the discoveries of dark-matter deficient galaxies proves dark matter exists.

    “In our 2018 paper, we suggested that if you have a galaxy without dark matter, and other similar galaxies seem to have it, that means that dark matter is actually real and it exists,” van Dokkum said.

    (Lead photo via NASA)

    The post As teams work to bring Hubble back online, new science highlights missing dark matter in galaxy appeared first on NASASpaceFlight.com.

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    Orbital Demo the goal amid potential SN16 hypersonic test

    As the Launch Integration Tower at the Orbital Launch Site (OLS) continues to grow, Elon… The post Orbital Demo the goal amid potential SN16 hypersonic test appeared first on NASASpaceFlight.com.

    Orbital Demo the goal amid potential SN16 hypersonic test

    As the Launch Integration Tower at the Orbital Launch Site (OLS) continues to grow, Elon Musk has intimated a potential interim test with Starship SN16.

    As SN16 was rolled out of the High Bay towards the scrapyard, most believed that confirmed that the next vehicle to roll down Highway 4 to the launch site would be the Super Heavy and Starship tasked with the first orbital attempt. However, Musk soon tweeted SpaceX might use SN16 on a hypersonic flight test.

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  • Following the success of Starship SN15’s high altitude test, SN16 has been patiently sitting inside the High Bay.

    Complete with nosecone and aero surfaces, SN16 could have rolled to the suborbital site weeks ago had SN16 been required for a repeat of SN15’s test or to a higher altitude.

    However, with the focus firmly on uninterrupted work at the Orbital Launch Site (OLS) – which an SN16 test campaign would have impacted – the lack of SN16 movement pointed to the overall thinking that SpaceX was firmly focused on the full stack orbital test, currently set to involve “Booster 2” (which includes BN3 parts) and Starship SN20.

    With Booster 2 undergoing stacking operations inside the High Bay, SN16 was finally rolled out at the Production Facility and set on the road towards the scrapyard.

    Shortly after SN16 met up with the retired SN15, Musk reacted to Jack Beyer’s (@thejackbeyer) incredible photo of the duo, noting that SN16 may yet gain a reprieve.

    “We might use SN16 on a hypersonic flight test,” which came to the surprise of most of the community that was unaware such a test was under consideration.

    A hypersonic test would involve a fueled starship that accelerates too far greater speeds compared to the hop tests, which throttled down to the extent that Raptors were shut down in sequence ahead of the flip around.

    Such a test will be used to experience aerodynamic forces that the structure would have to endure during orbital launches and fly closer to the conditions of reentering from orbital speeds, providing vital data ahead of SN20’s orbital flight.

    This also beckons the question about the Thermal Protection System (TPS) tiles that will fly with SN16 should the hypersonic test become confirmed. SN16 has large patches of TPS, far more than SN15, although not yet enough for an orbital re-entry.

    With the fate of SN16 still in the air – and Musk tweeting of a Possible hypersonic test flight while SN16 appeared to be moving toward early retirement – all eyes will be on the FAA to see if any documentation points at a test that is being fully planned.

    All eyes will also be on Musk’s Twitter replies, as per usual.

    The Orbital Demonstration Flight

    For now, the official stance is focused on the progression from SN15’s success into the ambitious orbital demonstration flight.

    As previously documented to involve Super Heavy BN3 and Starship SN20, those vehicles are currently in the midst of being processed at the Production Site.

    BN3, since renamed “Booster 2” by Musk, is being stacked in the High Bay. The latest stacking operation involved the Aft Section, hoisted by the recently installed Bridge Crane.

    The Starship test plans are fluid and subject to change. More will be known once the vehicles take up their position at the OLS.

    Back at the launch site, the test article for Super Heavy boosters, called BN2.1, has been tested twice.

    During the tests, engineers filled the tank with liquid nitrogen and raised the pressure to verify the weld and structural integrity of the concept.

    It is not known at this point if the goal of the second attempt was a test to destruction or if they will do a third test to destruction, and SpaceX so far has not communicated the success or failure of these tests.

    Orbital Launch Site (OLS):

    The Orbital Demonstration flight will be the first launch from the OLS, converted from a spare plot of land next to the Suborbital Pad into a hive of construction activity.

    The centerpiece of the OLS is the Orbital Launch Tower, which continues to rise into the South Texas skyline with Sections 4 and 5 recently lifted and installed on the tower.

    The fast pace of construction has already seen section 6 rolled to the OLS and it is currently sitting next to the Tower, waiting to be lifted by the giant LR 11350 crane, nicknamed by the SpaceXers as “Frankencrane.”

    Section 7, which could be the last of the matched sections, is already under construction at the Propellant Production Site.

    However, Brady Kenniston spotted the initial construction of another section on Monday.

    Back at ground level, a giant winch – which was taken from Phobos, one of the SpaceX oil rigs being converted to be used as ocean spaceports – has been attached to the base of the tower and is most likely for the crane on top of the tower which will be used for Starship and Super Heavy stacking.

    This past week also marked the dismantling of one of the initial famed cranes at the launch site, with the LR1600 “Tankzilla” being prepared to depart, ahead of being replaced by the LR11000 for the construction of the OLS.

    As documented by Mary (@bocachicagal), SpaceX also received the delivery of a brand new wind radar earlier this month.

    It will further help SpaceX track the conditions and winds at higher altitudes in Boca Chica and find the right spots to launch Starship in the future, compared to the previously used method, which was using weather balloons on launch days. However, the installation of the radar so far has not taken place.

    This comes after SpaceX proposed to the FAA to change the wind model for future launch authorization, in the light of the investigation after the SN8 launch violation.

    Raptor Testing at McGregor:

    A key center for the future of Starship launch cadence is SpaceX’s Test Center at McGregor, Texas.

    Used for both Merlin and Raptor tests, photos from NSF’s Gary Blair in L2 McGregor showed SpaceX had prepared another Raptor engine with a vacuum nozzle extension on the horizontal test stand.

    NSF’s Gary Blair spots another RVac on the test stand at McGregor – via NSF/L2

    While no sea level Raptors were seen on the test stands during Saturday’s pass, SpaceX has shown rapid pace with sea level Raptor production in the past, which will be required for upcoming Super Heavy test flights.

    McGregor has already supplied engines up to SN74, with that engine seen arriving into Starbase along with SN72 last week.

    The Raptor Van is making almost daily trips on the Texas highways between the two sites, meaning the stock of Raptors already at Starbase could be in double digits.

    Near the Raptor test stands is a facility that SpaceX is currently using to test Starship and Super Heavy RCS thrusters.

    On his weekly flight, Gary Blair spotted the potential test stand for these hot gas thrusters used to steer the ship and booster to their destinations.

    The RCS Test Stand – via Gary Blair for NSF/L2

    As Elon Musk mentioned on Twitter, SpaceX currently aims to have the hot gas thrusters ready for the first orbital test flight.

    Photos and videos provided by Jack Beyer, Brady Kenniston, and Gary Blair. Additional information and article assistance provided by: Patrick Colquhoun, Evan Packer, Adrian Beil, Anthony Iemole, Leo Bruce, Justin Davenport, and Pierre Bou.

    For live updates, follow NASASpaceFlight’s Twitter account and the NSF Starship Forum Sections.

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