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By NASA
NASA Goddard MODIS Rapid Response Team During the morning of March 20, 2015, a total solar eclipse was visible from parts of Europe, and a partial solar eclipse from northern Africa and northern Asia. NASA’s Terra satellite passed over the Arctic Ocean on March 20 at 10:45 UTC (6:45 a.m. EDT) and captured the eclipse’s shadow over the clouds in the Arctic Ocean.
Terra launched 25 years ago on Dec. 18, 1999. Approximately the size of a small school bus, the Terra satellite carries five instruments that take coincident measurements of the Earth system: Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Clouds and Earth’s Radiant Energy System (CERES), Multi-angle Imaging Spectroradiometer (MISR), Measurements of Pollution in the Troposphere (MOPITT), and Moderate Resolution Imaging Spectroradiometer (MODIS).
On Nov. 28, 2024, one of Terra’s power-transmitting shunt units failed. A response team reviewed Terra’s status and discussed potential impacts and options. Consequently, the team placed ASTER into Safe Mode. As a result, ASTER data are not currently being collected. All other instruments continue uninterrupted.
Image Credit: NASA Goddard MODIS Rapid Response Team
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By NASA
1 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
The Airspace Operations and Safety Program (AOSP) enables safe, sustainable, and efficient aviation transportation operations to benefit the flying public and ensure the global competitiveness of the U.S. aviation industry. We are transforming the future of aviation into a digital, federated, and service-oriented architecture that fosters the growth of safe airspace for all users.
By partnering with FAA, academia, safety experts, operators, manufacturers, municipalities, and other government agencies, we facilitate the integration of new aviation technologies, ensure airspace access for new entrants, and champion the success of increasingly autonomous operations. At AOSP, safety is at the heart of everything we do. We stand firm in our unwavering commitment to the safe integration of these vehicles.
AOSP Approach:
Efficient, Sustainable Aviation Operations Seamless Integration of Heterogeneous and Emergent Aviation Prognostic In-Time Aviation Safety Management System of Future Operations System Level Autonomy for Aviation Operations, Vehicle Command and Control Systems, and Safety Meet the diversity, density, and complexity challenges of future aviation AOSP Projects
Advanced Capabilities for Emergency Response Operations Project
Air Mobility Pathfinders
Air Traffic Management—Exploration (ATM-X)
System-Wide Safety (SWS)
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Last Updated Dec 17, 2024 EditorLillian GipsonContactJim Bankejim.banke@nasa.gov Related Terms
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By NASA
This article is from the 2024 Technical Update.
Multiple human spaceflight programs are underway at NASA including Orion, Space Launch System, Gateway, Human Landing System, and EVA and Lunar Surface Mobility programs. Achieving success in these programs requires NASA to collaborate with a variety of commercial partners, including both new spaceflight companies and robotic spaceflight companies pursuing crewed spaceflight for the first time. It is not always clear to these organizations how to show their systems are safe for human spaceflight. This is particularly true for avionics systems, which are responsible for performing some of a crewed spacecraft’s most critical functions. NASA recently published guidance describing how to show the design of an avionic system meets safety requirements for crewed missions.
Background
The avionics in a crewed spacecraft perform many safety critical functions, including controlling the position and attitude of the spacecraft, activating onboard abort systems, and firing pyrotechnics. The incorrect operation of any of these functions can be catastrophic, causing loss of the crew. NASA’s human rating requirements describe the need for “additional rigor and scrutiny” when designing safety-critical systems beyond that done
for uncrewed spacecraft [2]. Unfortunately, it is not always clear how to interpret this guidance and show an avionics architecture is sufficiently safe. To address this problem, NASA recently published NASA/TM−20240009366 [1]. It outlines best practices for designing safety-critical avionics, as well as describes key artifacts or evidence NASA needs to assess the safety of an avionics architecture.
Failure Hypothesis
One of the most important steps to designing an avionics architecture for crewed spacecraft is specification of the failure hypothesis (FH). In short, the FH summarizes any assumptions the designers make about the type, number, and persistence of component failures (e.g., of onboard computers, network switches). It divides the space of all possible failures into two parts – failures the system is designed to tolerate and failures it is not.
One key part of the FH is a description of failure modes the system can tolerate – i.e., the behavior exhibited by a failed component. Failure modes are categorized using a failure model. A typical failure model for avionics splits failures into two broad categories:
Value failures, where data produced by a component is missing (i.e., an omissive failure) or incorrect (i.e., a transmissive failure). Timing failures, where data is produced by a component at the wrong time.
Timing failures can be further divided into many sub-categories, including:
Inadvertent activation, where data is produced by a component without the necessary preconditions. Out-of-order failures, where data is produced by a component in an incorrect sequence. Marginal timing failures, where data is produced by a component slightly too early or late.
In addition to occurring when data is produced by a component, these failure modes can also occur when data enters a component. (e.g., a faulty component can corrupt a message it receives). Moreover, all failure modes can manifest in one of two ways:
Symmetrically, where all observers see the same faulty behavior. Asymmetrically, where some observers see different faulty behavior.
Importantly, NASA’s human-rating process requires that each of these failure modes be mitigated if it can result in catastrophic effects [2]. Any exceptions must be explicitly documented and strongly justified. In addition to specifying the failure modes a system can tolerate, the FH must specify any limiting assumptions about the relative arrival times of permanent failures and radiation-induced upsets/ errors or the ability for ground operator to intervene to safe the system or take recovery actions. For more information on specifying a FH and other artifacts needed to evaluate the safety of an avionics architecture for human spaceflight, see the full report [1].
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By NASA
5 Min Read Scientists Share Early Results from NASA’s Solar Eclipse Experiments
On April 8, 2024, a total solar eclipse swept across a narrow portion of the North American continent from Mexico’s Pacific coast to the Atlantic coast of Newfoundland, Canada. This photo was taken from Dallas, Texas. Credits:
NASA/Keegan Barber On April 8, 2024, a total solar eclipse swept across North America, from the western shores of Mexico, through the United States, and into northeastern Canada. For the eclipse, NASA helped fund numerous research projects and called upon citizen scientists in support of NASA’s goal to understand how our home planet is affected by the Sun – including, for example, how our star interacts with Earth’s atmosphere and affects radio communications.
At a press briefing on Tuesday, Dec. 10, scientists attending the annual meeting of the American Geophysical Union in Washington, D.C., reported some early results from a few of these eclipse experiments.
“Scientists and tens of thousands of volunteer observers were stationed throughout the Moon’s shadow,” said Kelly Korreck, eclipse program manager at NASA Headquarters in Washington. “Their efforts were a crucial part of the Heliophysics Big Year – helping us to learn more about the Sun and how it affects Earth’s atmosphere when our star’s light temporarily disappears from view.”
Changes in the Corona
On April 8, the Citizen CATE 2024 (Continental-America Telescopic Eclipse) project stationed 35 observing teams from local communities from Texas to Maine to capture images of the Sun’s outer atmosphere, or corona, during totality. Their goal is to see how the corona changed as totality swept across the continent.
On Dec. 10, Sarah Kovac, the CATE project manager at the Southwest Research Institute in Boulder, Colorado, reported that, while a few teams were stymied by clouds, most observed totality successfully — collecting over 47,000 images in all.
These images were taken in polarized light, or light oriented in different directions, to help scientists better understand the processes that shape the corona.
This preliminary movie from the Citizen CATE 2024 project stitches together polarized images of the solar corona taken from different sites during the total solar eclipse on April 8, 2024. SwRI/Citizen CATE 2024/Dan Seaton/Derek Lamb Kovac shared the first cut of a movie created from these images. The project is still stitching together all the images into the final, hour-long movie, for release at a later time.
“The beauty of CATE 2024 is that we blend cutting-edge professional science with community participants from all walks of life,” Kovac said. “The dedication of every participant made this project possible.”
Meanwhile, 50,000 feet above the ground, two NASA WB-57 aircraft chased the eclipse shadow as it raced across the continent, observing above the clouds and extending their time in totality to approximately 6 minutes and 20 seconds.
On board were cameras and spectrometers (instruments that analyze different wavelengths of light) built by multiple research teams to study the corona.
This image of the total solar eclipse is a combination of 30 50-millisecond exposures taken with a camera mounted on one of NASA’s WB-57 aircraft on April 8, 2024. It was captured in a wavelength of light emitted by ionized iron atoms called Fe XIV. This emission highlights electrified gas, called plasma, at a specific temperature (around 3.2 million degrees Fahrenheit) that often reveals arch-like structures in the corona. B. Justen, O. Mayer, M. Justen, S. Habbal, and M. Druckmuller On Dec. 10, Shadia Habbal of the University of Hawaii, who led one of the teams, reported that their instruments collected valuable data, despite one challenge. Cameras they had mounted on the aircraft’s wings experienced unexpected vibrations, which caused some of the images to be slightly blurred.
However, all the cameras captured detailed images of the corona, and the spectrometers, which were located in the nose of the aircraft, were not affected. The results were so successful, scientists are already planning to fly similar experiments on the aircraft again.
“The WB-57 is a remarkable platform for eclipse observations that we will try to capitalize on for future eclipses,” Habbal said.
Affecting the Atmosphere
On April 8, amateur or “ham” radio operators sent and received signals to one another before, during, and after the eclipse as part of the Ham Radio Science Citizen Investigation (HamSCI) Festivals of Eclipse Ionospheric Science. More than 6,350 amateur radio operators generated over 52 million data points to observe how the sudden loss of sunlight during totality affects their radio signals and the ionosphere, an electrified region of Earth’s upper atmosphere.
Students from Case Western Reserve University operate radios during the 2024 total solar eclipse. HamSCI/Case Western Reserve University Radio communications inside and outside the path of totality improved at some frequencies (from 1-7 MHz), showing there was a reduction in ionospheric absorption. At higher frequencies (10 MHz and above), communications worsened.
Results using another technique, which bounced high-frequency radio waves (3-30 MHz) off the ionosphere, suggests that the ionosphere ascended in altitude during the eclipse and then descended to its normal height afterward.
“The project brings ham radio operators into the science community,” said Nathaniel Frissell, a professor at the University of Scranton in Pennsylvania and lead of HamSCI. “Their dedication to their craft made this research possible.”
Also looking at the atmosphere, the Nationwide Eclipse Ballooning Project organized student groups across the U.S. to launch balloons into the shadow of the Moon as it crossed the country in April 2024 and during a solar eclipse in October 2023. Teams flew weather sensors and other instruments to study the atmospheric response to the cold, dark shadow.
The eclipse’s shadow was captured from a camera aboard Virginia Tech’s balloon as part of the Nationwide Eclipse Ballooning Project on April 8, 2024. Nationwide Eclipse Ballooning Project/Virginia Tech This research, conducted by over 800 students, confirmed that eclipses can generate ripples in Earth’s atmosphere called atmospheric gravity waves. Just as waves form in a lake when water is disturbed, these waves also form in the atmosphere when air is disturbed. This project, led by Angela Des Jardins of Montana State University in Bozeman, also confirmed the presence of these waves during previous solar eclipses. Scientists think the trigger for these waves is a “hiccup” in the tropopause, a layer in Earth’s atmosphere, similar to an atmospheric effect that is observed during sunset.
“Half of the teams had little to no experience ballooning before the project,” said Jie Gong, a team science expert and atmospheric scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But their hard work and research was vital in this finding.”
By Abbey Interrante and Vanessa Thomas
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Dec 10, 2024 Related Terms
2024 Solar Eclipse Citizen Science Goddard Space Flight Center Heliophysics Solar Eclipses The Sun Uncategorized Explore More
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By European Space Agency
A pair of spacecraft were launched together today from India with the potential to change the nature of future space missions. ESA’s twin Proba-3 platforms will perform precise formation flying down to a single millimetre, as if they were one single giant spacecraft. To demonstrate their degree of control, the pair will produce artificial solar eclipses in orbit, giving prolonged views of the Sun’s ghostly surrounding atmosphere, the corona.
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