SPACE
After 17 years away, NASA's sun-studying spacecraft will visit Earth on Aug. 12
Fri, August 11, 2023
An illustration shows NASA's STEREO-A probe making a close approach to Earth after 17 years.
A groundbreaking NASA spacecraft will return to Earth on Saturday (Aug. 12) after 17 years away from home.
One-half of the agency's STEREO (Solar Terrestrial Relations Observatory) mission, STEREO-A will fly close to our planet for the first time since its launch on Oct. 25, 2006, from the Cape Canaveral Air Force Station in Florida. STEREO-A will pass between Earth and the sun this weekend.
STEREO-A is the lead component of a dual-spacecraft mission, which also includes the STEREO-B spacecraft. This was the first mission to capture a multiple-perspective or "stereoscopic" view of the sun. The STEREO mission also made history in February of 2011, when the two spacecraft achieved a 180-degree separation in their orbital pathway, taking positions on opposite sides of the sun and offering humanity its first glimpse of our star as a complete sphere. Akin to their titles, STEREO-A's "A" stands for "ahead" and STEREO-B's "B" stands for "behind."
"Prior to that, we were 'tethered' to the sun-Earth line — we only saw one side of the sun at a time," STEREO program scientist, Lika Guhathakurta, said in a statement. "STEREO broke that tether and gave us a view of the sun as a three-dimensional object."
Related: Sun blasts out highest-energy radiation ever recorded, raising questions for solar physics
The STEREO mission had achieved a number of other scientific feats since leaving Earth 17 years ago, and both spacecraft were providing views of space until STEREO-B broke contact with mission control in 2014 after a planned reset (B's mission officially ended in 2018). STEREO-A, however, has remained in contact with Earth since the loss of its compatriot, and this brief return home won't see it rest on its laurels.
Instead, the spacecraft will team up with some newer NASA missions during its visit.
By synthesizing its view of the sun with the Solar and Heliospheric Observatory (SOHO) and NASA’s Solar Dynamics Observatory (SDO), STEREO-A will once again provide a stereoscopic 3D picture of our host star, just like it used to with STEREO-B. The fact that STEREO-A will be changing its distance from Earth during its visit also means it'll be able to offer views of solar features with differing sizes. This would be kind of like changing the focus of a telescope with a million-mile-wide field of view.
That should allow researchers to make vital solar measurements, identify active regions of the sun and even obtain 3D information about complex magnetic structures underlying sunspots. These structures are usually unavailable for study with 2D imagery.
Further, this visit by STEREO-A could help solar physicists decode some longstanding mysteries regarding the sun. "There is a recent idea that coronal loops might just be optical illusions," STEREO project scientist, Terry Kucera, said.
This refers to the fact that some scientists have suggested our limited viewing angles of massive bands of plasma emerging from the sun make them appear to have shapes they may not truly have. "If you look at them from multiple points of view, that should become more apparent," Kucera added.
A gif showing the trajectory of STEREO-A's flyby of Earth.
(Image credit: NASA's Goddard Space Flight Center/Scientific Visualization Studio/Tom Bridgman)
Star I used to know...
STEREO-A won't just be collecting visual data as it makes its flyby of Earth over the weekend. The spacecraft will also feel eruptions from our star, called coronal mass ejections (CMEs).
When blasted out into space, these massive plumes of charged particles can disrupt satellites orbiting Earth, interfere with radio signals across the planet and even damage power infrastructure. The influence of CMEs, in terms of whether they cause damage or disruption upon reaching Earth, is dictated by magnetic fields carried along with them. These fields can change dramatically as the charged particles cross the 93 million miles (150 million kilometers) of space between the sun and Earth.
A black and white video showing a CME, taken by STEREO-A.
This coronagraph image shows a coronal mass ejection escaping the Sun, which is occluded behind the black circle at the center of the image. STEREO-A imaged this Earth-directed CME eruption on July 17, 2023. (Image credit: NASA/STEREO-A/SECCHI)
Scientists can build models of CMEs and their magnetic fields, but these models are limited when observations come from a single spacecraft.
"It's like the parable about the blind men and the elephant — the one who feels the legs says 'it’s like a tree trunk,' and the one who feels the tail says 'it’s like a snake,'" University of New Hampshire professor and principal investigator for one of STEREO-A’s instruments, Toni Galvin, said. "That's what we're stuck with right now with CMEs, because we typically only have one or two spacecraft right next to each other measuring it."
In the months before it flies by our planet, STEREO-A has been collecting data about Earth-directed CMEs — and it will continue to do this for months after it leaves our planet's vicinity again. As it has been doing this, so have other near-Earth spacecraft. Put together, these datasets should give solar scientists different views of the same CMEs, revealing the ejections' magnetic innards.
A 3D view of the sun, spinning toward the right.
This composite view shows the Sun as it appeared on Jan. 31, 2011, with simultaneous views from both of NASA’s STEREO spacecraft and NASA’s Solar Dynamics Observatory. These three distinct viewpoints allowed scientists to capture almost the entire sun at once, with only a small gap in data. (Image credit: NASA/Goddard/STEREO)
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— Powerful sun storm knocks out radio transmissions across North America
It won't be all familiar territory when STEREO-A returns to Earth.
Last time the NASA craft was so close to our planet, in 2006, the sun was in a phase called "solar minimum." This means is was in a relatively quiet phase, with little activity and few sunspots.
By contrast, the sun STEREO-A will see this weekend is approaching a period of solar maximum in its roughly 11-year cycle, which should peak in 2025.
"The sun was so quiet at that point! I was looking back at the data, and I said, 'Oh yeah, I recognize that active region’ — there was one, and we studied it," Kucera said, "OK, it wasn’t quite that bad — but it was close."
That means that STEREO-A will experience a "fundamentally different" star than it did some 17 years ago. "There is so much knowledge to be gained from that," Guhathakurta concluded.
Course correction keeps Parker Solar Probe on track for Venus flyby
IMAGE: ARTIST’S CONCEPT OF PARKER SOLAR PROBE. view more
CREDIT: NASA’S GODDARD SPACE FLIGHT CENTER
NASA’s Parker Solar Probe executed a short maneuver on Aug. 3, 2023, that kept the spacecraft on track to hit the aim point for the mission’s sixth Venus flyby on Monday, Aug. 21, 2023.
Operating on preprogrammed commands from mission control at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, Parker fired its small thrusters for 4.5 seconds, enough to adjust its trajectory by 77 miles and speed up – by 1.4 seconds – its closest approach to Venus. The precise timing and position are critical to that flyby, the sixth of seven approaches in which Parker uses the planet’s gravity to tighten its orbit around the Sun.
“Parker’s velocity is about 8.7 miles per second, so in terms of changing the spacecraft’s speed and direction, this trajectory correction maneuver may seem insignificant,” said Yanping Guo, mission design and navigation manager at APL. “However, the maneuver is critical to get us the desired gravity assist at Venus, which will significantly change Parker’s speed and distance to the Sun”.
Parker Solar Probe will be moving 394,742 miles per hour when it comes within just 4.5 million miles from the Sun’s surface – breaking its own record for speed and solar distance – on Sept. 27, 2023. Follow the spacecraft’s journey through the inner solar system on the Parker Solar Probe website.
By Michael Buckley
Johns Hopkins Applied Physics Laboratory
Space weather and satellite security: Graz University of Technology and University of Graz supply new forecasting service for the ESA's Space Safety Programme
The effects of solar storms on the Earth's atmosphere can cause satellites to crash. To prevent this from happening, the European Space Agency (ESA) is now using SODA, a forecasting service developed in Graz
Business AnnouncementIMAGE: IMAGE OF THE SUN FROM THE ESA/NASA SOLAR ORBITER MISSION. THE DIAGRAM SHOWS THE DENSITY INCREASE IN THE ATMOSPHERE AND THE SUBSEQUENT LOSS OF ALTITUDE OF A SATELLITE AT 490 KM - BOTH CAUSED BY A CORONAL MASS EJECTION ON 21 NOVEMBER 2003. view more
CREDIT: IMAGE SOURCE: ESA & NASA/SOLAR ORBITER/EUI TEAM - DATA: TU GRAZ & UNI GRAZ
After a successful test phase, the Satellite Orbit DecAy (SODA) service, which was jointly developed by TU Graz and the University of Graz, officially became part of the ESA’s Space Safety Programme in mid-July. SODA provides accurate forecasts of the effects of solar storms on low Earth orbiting satellites. This makes TU Graz only the third Austrian institution contributing to this ESA programme. Seibersdorf Laboratories, and the University of Graz, through the Kanzelhöhe Observatory and the Institute of Physics, have previously already been involved in the agency’s work.
The new forecast service is freely available via the ESA Space Weather Service and offers a warning with a lead time of around 15 hours. The commissioning of SODA is of particular interest at this stage since the solar activity is expected to reach its maximum within the next two years. The extent to which solar storms can affect satellite orbits has already been demonstrated in SWEETS, a project funded by the Austrian Research Promotion Agency (FFG), on whose findings SODA is based. For the SWEETS project, atmospheric density data was combined with real-time measurements of solar wind plasma and the interplanetary magnetic field to calculate the effects of solar events. This research has shown that large coronal mass ejections have the capability to trigger satellite orbit decays of up to 40 metres for satellites at an altitude of 490 kilometres. In early February 2022, 38 Starlink satellites were even lost shortly after launch at an altitude of 210 kilometres due to a solar storm.
Solar activity reaches its maximum
Such losses of altitude largely occur because the charged plasma particles emitted by the Sun strike the Earth's magnetic field and cause a heating and expansion of the upper layers of the Earth's atmosphere. As a result, the atmospheric drag increases and subsequently causes satellites to lose speed and altitude. In light of the upcoming solar maximum, the ESA has already increased the altitude of some of its satellites by a few kilometres to get through this period safely. Accordingly, the predictions provided by SODA are intended to add an additional level of security. TU Graz contributed its expertise in the processing of satellite data available at the Institute of Geodesy, while the University of Graz’s involvement was based on its experience in the field of solar and heliospheric physics as well as interplanetary magnetic field observation.
The team led by Sandro Krauss from the Institute of Geodesy at TU Graz reviewed atmospheric densities over a 20-year period. For this purpose, they processed data from several low Earth orbit satellite missions, including CHAMP, GRACE, GRACE Follow-on and Swarm. At the University of Graz, a group led by Manuela Temmer from the Institute of Physics analysed around 300 solar storms catalogued between 2002 and 2017 based on measurements of the interplanetary magnetic field by probes at the L1 Lagrange point, which is about 1.5 million kilometres from the Earth in the direction of the Sun. TU Graz afterwards used the information to relate the atmospheric density variations to these solar storms. The forecasting model SODA was developed from the joint analysis of these interdisciplinary datasets.
Space research – highly valued in Austria
"I am very pleased that, through SODA, TU Graz, together with Uni Graz and Seibersdorf Laboratories, is now the third Austrian institution to contribute to ESA's Space Safety Programme," says Sandro Krauss from the Institute of Geodesy at TU Graz. "Of the five Expert Service Centres that constitute the ESA Space Weather Service Network, Austria is now represented in four, with only the United Kingdom involved in all five. This clearly underscores just how highly valued space research is in Austria. The partnership with the University of Graz on this project also provides proof of how valuable interdisciplinary research work is. And we are already working together to further improve SODA."
Manuela Temmer from the Institute of Physics at the University of Graz explained: “For Uni Graz and TU Graz, supplying ESA with this service is a welcome recognition of our work. I am also pleased that our partnership will continue as we work to improve SODA together within the framework of the FFG-funded project CASPER. It will help us to gain a better understanding of more complex solar storms, such as situations where two storms overlap on their way to Earth. We would also like to calculate the atmospheric density at altitudes of 450 and 400 kilometres – 490 kilometres is the lowest altitude we can calculate the density for so far. Since the field of solar storm forecasting is not yet very well researched, we are looking forward to some interesting insights."
Illustration of the ESA service SODA developed at TU Graz and Uni Graz. The grey area shows the prediction of the expected altitude loss for satellites at 490 km before the Starlink event in early February 2022.
CREDIT
Graz University of Technology & University of Graz
METHOD OF RESEARCH
Computational simulation/modeling
Direct evidence for modified gravity at low acceleration from Gaia observations of wide binary stars
Dawn of a new scientific revolution
Peer-Reviewed PublicationA new study reports conclusive evidence for the breakdown of standard gravity in the low acceleration limit from a verifiable analysis of the orbital motions of long-period, widely separated, binary stars, usually referred to as wide binaries in astronomy and astrophysics. The study carried out by Kyu-Hyun Chae, professor of physics and astronomy at Sejong University in Seoul, used up to 26,500 wide binaries within 650 light years (LY) observed by European Space Agency’s Gaia space telescope. Kareem El-Badry, then at Harvard and now a faculty at Caltech, helped Chae so that he could use the Gaia database.
For a key improvement over other studies Chae’s study focused on calculating gravitational accelerations experienced by binary stars as a function of their separation or, equivalently the orbital period, by a Monte Carlo deprojection of observed sky-projected motions to the three-dimensional space. Chae explains on this point, “From the start it seemed clear to me that gravity could be most directly and efficiently tested by calculating accelerations because gravitational field itself is an acceleration. My recent research experiences with galactic rotation curves led me to this idea. Galactic disks and wide binaries share some similarity in their orbits, though wide binaries follow highly elongated orbits while hydrogen gas particles in a galactic disk follow nearly circular orbits.” Also, unlike other studies Chae calibrated the occurrence rate of hidden nested inner binaries at a benchmark acceleration as shown in the Figure.
The study finds that when two stars orbit around with each other with accelerations lower than about one nanometer per second squared start to deviate from the prediction by Newton’s universal law of gravitation and Einstein’s general relativity. For accelerations lower than about 0.1 nanometer per second squared, the observed acceleration is about 30 to 40 percent higher than the Newton-Einstein prediction. The significance is very high meeting the conventional criteria of 5 sigma for a scientific discovery. In a sample of 20,000 wide binaries within a distance limit of 650 LY two independent acceleration bins respectively show deviations of over 5 sigma significance in the same direction.
Because the observed accelerations stronger than about 10 nanometer per second squared agree well with the Newton-Einstein prediction from the same analysis, the observed boost of accelerations at lower accelerations is a mystery. What is intriguing is that this breakdown of the Newton-Einstein theory at accelerations weaker than about one nanometer per second squared was suggested 40 years ago by theoretical physicist Mordehai Milgrom at the Weizmann Institute in Israel in a new theoretical framework called modified Newtonian dynamics (MOND) or Milgromian dynamics in current usage. Moreover, the boost factor of about 1.4 is correctly predicted by a MOND-type Lagrangian theory of gravity called AQUAL, proposed by Milgrom and the late physicist Jacob Bekenstein. What is remarkable is that the correct boost factor requires the external field effect from the Milky Way galaxy that is a unique prediction of MOND-type modified gravity. Thus, what the wide binary data show are not only the breakdown of Newtonian dynamics but also the manifestation of the external field effect of modified gravity.
On the results, Chae says, “It seems impossible that a conspiracy or unknown systematic can cause these acceleration-dependent breakdown of the standard gravity in agreement with AQUAL. I have examined all possible systematics as described in the rather long paper. The results are genuine. I foresee that the results will be confirmed and refined with better and larger data in the future. I have also released all my codes for the sake of transparency and to serve any interested researchers.”
Unlike galactic rotation curves in which the observed boosted accelerations can, in principle, be attributed to dark matter in the Newton-Einstein standard gravity, wide binary dynamics cannot be affected by it even if it existed. The standard gravity simply breaks down in the weak acceleration limit in accordance with the MOND framework.
Implications of wide binary dynamics are profound in astrophysics, theoretical physics, and cosmology. Anomalies in Mercury’s orbits observed in the nineteenth century eventually led to Einstein’s general relativity. Now anomalies in wide binaries require a new theory extending general relativity to the low acceleration MOND limit. Despite all the successes of Newton’s gravity, general relativity is needed for relativistic gravitational phenomena such as black holes and gravitational waves. Likewise, despite all the successes of general relativity, a new theory is needed for MOND phenomena in the weak acceleration limit. The weak-acceleration catastrophe of gravity may have some similarity to the ultraviolet catastrophe of classical electrodynamics that led to quantum physics.
Wide binary anomalies are a disaster to the standard gravity and cosmology that rely on dark matter and dark energy concepts. Because gravity follows MOND, a large amount of dark matter in galaxies (and even in the universe) are no longer needed. This is also a big surprise to Chae who, like typical scientists, “believed in” dark matter until a few years ago.
A new revolution in physics seems now under way. On the present results and the future prospects, Milgrom says, “Chae’s finding is a result of a very involved analysis of cutting-edge data, which, as far as I can judge, he has performed very meticulously and carefully. But for such a far-reaching finding -- and it is indeed very far reaching -- we require confirmation by independent analyses, preferably with better future data. If this anomaly is confirmed as a breakdown of Newtonian dynamics, and especially if it indeed agrees with the most straightforward predictions of MOND, it will have enormous implications for astrophysics, cosmology, and for fundamental physics at large.“
Xavier Hernandez, professor at UNAM in Mexico who first suggested wide binary tests of gravity a decade ago, says, “It is exciting that the departure from Newtonian gravity that my group has claimed for some time has now been independently confirmed, and impressive that this departure has for the first time been correctly identified as accurately corresponding to a detailed MOND model. The unprecedented accuracy of the Gaia satellite, the large and meticulously selected sample Chae uses and his detailed analysis, make his results sufficiently robust to qualify as a discovery.”
Pavel Kroupa, professor at Bonn University and at Charles University in Prague, has come to the same conclusions concerning the law of gravitation. He says, "With this test on wide binaries as well as our tests on open star clusters nearby the Sun, the data now compellingly imply that gravitation is Milgromian rather than Newtonian. The implications for all of astrophysics are immense."
The finding was published in the 1 August 2023 issue of the Astrophysical Journal.
Reference: https://iopscience.iop.org/article/10.3847/1538-4357/ace101 “Breakdown of the Newton–Einstein Standard Gravity at Low Acceleration in Internal Dynamics of Wide Binary Stars” (The Astrophysical Journal, 2023, Vol. 952, article ID 128)
JOURNAL
The Astrophysical Journal
METHOD OF RESEARCH
Data/statistical analysis
ARTICLE TITLE
Breakdown of the Newton–Einstein Standard Gravity at Low Acceleration in Internal Dynamics of Wide Binary Stars
SwRI micropatch algorithm improves ground-to-spacecraft software update efficiency
Team demonstrates novel software tool on International Space Station computer
IMAGE: SOUTHWEST RESEARCH INSTITUTE DEVELOPED THE MICROPATCHING ALGORITHM ILLUSTRATED HERE TO IMPROVE THE EFFICIENCY OF OVER-THE-AIR SPACECRAFT SOFTWARE UPDATES. THE TEAM SUCCESSFULLY TESTED SWRI’S MICROPATCHING SOFTWARE ON AN AXIOM SPACE-OPERATED COMPUTER ON THE ISS, UPLOADING THE PATCH VIA A TELEMETRY NETWORK. THE TOOL EFFICIENTLY FINDS AND PATCHES SOFTWARE ERRORS FROM FAILED UPDATES AND MALICIOUS ATTACKS INSTEAD OF REPLACING AN ENTIRE FILE OR OPERATING SYSTEM ON BANDWIDTH-LIMITED SPACE NETWORKS. view more
CREDIT: SOUTHWEST RESEARCH INSTITUTE
San Antonio – August 10, 2023 – Southwest Research Institute developed an algorithm to remotely update and repair spacecraft software using less time and data than conventional techniques.
The tool not only improves the overall efficiency of satellite software transmissions but also can recover data from failed over-the-air updates and malicious cyberattacks. It works by identifying missing bytes and other errors before deploying a custom “micropatch” to the damaged or missing software.
“Instead of updating an entire file or operating system, which is typically required with over-the-air satellite software updates, our tool can find and patch smaller errors,” said Henry Haswell, a research engineer in SwRI’s Intelligent Systems Division. Haswell will present a research paper titled “Secure Micropatching on the ISS” at DEF CON 31, August 10-13, in Las Vegas.
The researchers successfully deployed and tested the tool on the International Space Station (ISS) on June 25. SwRI worked with Axiom Space Inc. and Amazon Web Services (AWS) to upload and evaluate the micropatch technology on an Axiom Space-operated computer on the ISS. Axiom Space collaborated with AWS to bring this AWS Snowcone computer to the ISS as part of the Ax-1 mission.
“This real-world demonstration proved the advantages of using this powerful technology,” said Diego Alducin, an SwRI computer scientist. “You can test for months in a lab on Earth, simulating all kinds of scenarios, but the true test happens in the harsh conditions of space.
Updating satellite software through sluggish telemetry networks with limited bandwidth and intermittent contacts can interrupt updates and corrupt files in the process. When that occurs, the current standard is to resend the entire file over the network. However, that typically requires waiting for a window when a satellite is aligned with a ground station. This window can be as short as eight minutes and might only occur once every few days.
“We focused our research on reducing the size of data retransmissions because that is critical in reducing mission downtime,” Alducin said.
While other technologies address network interruptions, they can be cost-prohibitive. Some spacecraft use error detection and correction, or EDAC software, to correct transmission errors, but these applications are power-hungry and have a large memory footprint.
Prior to ISS testing, SwRI lab-tested five algorithms, simulating several corruption modes. The lab research identified a double breakpoint search (DBS) algorithm as the most promising solution for Earth-to-space deployment. A DBS patch addresses a variety of complex file errors such as insertion, modification and deletion, while legacy systems can only fix simple issues.
SwRI is planning the next phase of research to reduce the number of messages needed to update a file while maintaining the same error correction capabilities. Researchers also hope to enhance micropatching continuity, enabling seamless file transfers in the event of temporary connection loss.
The space micropatching research builds on an automotive cybersecurity tool that SwRI developed for securing over-the-air, or OTA, updates on cars and trucks. SwRI’s High Reliability Systems Department develops mission-critical systems for the aerospace, automotive, oil and gas, critical infrastructure and transportation industries. SwRI’s Intelligent Systems Division is a leader in development of software, cybersecurity, artificial intelligence, data analytics and systems engineering solutions.
For more information, visit https://www.swri.org/industries/cyber-security-services and https://www.swri.org/space-avionics-systems/.
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