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By NASA
Download PDF: Statistical Analysis Using Random Forest Algorithm Provides Key Insights into Parachute Energy Modulator System
Energy modulators (EM), also known as energy absorbers, are safety-critical components that are used to control shocks and impulses in a load path. EMs are textile devices typically manufactured out of nylon, Kevlar® and other materials, and control loads by breaking rows of stitches that bind a strong base webbing together as shown in Figure 1. A familiar EM application is a fall-protection harness used by workers to prevent injury from shock loads when the harness arrests a fall. EMs are also widely used in parachute systems to control shock loads experienced during the various stages of parachute system deployment.
Random forest is an innovative algorithm for data classification used in statistics and machine learning. It is an easy to use and highly flexible ensemble learning method. The random forest algorithm is capable of modeling both categorical and continuous data and can handle large datasets, making it applicable in many situations. It also makes it easy to evaluate the relative importance of variables and maintains accuracy even when a dataset has missing values.
Random forests model the relationship between a response variable and a set of predictor or independent variables by creating a collection of decision trees. Each decision tree is built from a random sample of the data. The individual trees are then combined through methods such as averaging or voting to determine the final prediction (Figure 2). A decision tree is a non-parametric supervised learning algorithm that partitions the data using a series of branching binary decisions. Decision trees inherently identify key features of the data and provide a ranking of the contribution of each feature based on when it becomes relevant. This capability can be used to determine the relative importance of the input variables (Figure 3). Decision trees are useful for exploring relationships but can have poor accuracy unless they are combined into random forests or other tree-based models.
The performance of a random forest can be evaluated using out-of-bag error and cross-validation techniques. Random forests often use random sampling with replacement from the original dataset to create each decision tree. This is also known as bootstrap sampling and forms a bootstrap forest. The data included in the bootstrap sample are referred to as in-the-bag, while the data not selected are out-of-bag. Since the out-of-bag data were not used to generate the decision tree, they can be used as an internal measure of the accuracy of the model. Cross-validation can be used to assess how well the results of a random forest model will generalize to an independent dataset. In this approach, the data are split into a training dataset used to generate the decision trees and build the model and a validation dataset used to evaluate the model’s performance. Evaluating the model on the independent validation dataset provides an estimate of how accurately the model will perform in practice and helps avoid problems such as overfitting or sampling bias. A good model performs well on
both the training data and the validation data.
The complex nature of the EM system made it difficult for the team to identify how various parameters influenced EM behavior. A bootstrap forest analysis was applied to the test dataset and was able to identify five key variables associated with higher probability of damage and/or anomalous behavior. The identified key variables provided a basis for further testing and redesign of the EM system. These results also provided essential insight to the investigation and aided in development of flight rationale for future use cases.
For information, contact Dr. Sara R. Wilson. sara.r.wilson@nasa.gov
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By NASA
5 Min Read NASA DAVINCI Mission’s Many ‘Firsts’ to Unlock Venus’ Hidden Secrets
The surface of Venus is an inferno with temperatures hot enough to melt lead. This image is a composite of data from NASA’s Magellan spacecraft and Pioneer Venus Orbiter. Credits:
NASA/JPL-Caltech NASA’s DAVINCI — Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging — mission embodies the spirit of innovation and exploration that its namesake, Leonardo da Vinci, was famous for.
Scheduled to launch in the early 2030s, DAVINCI will explore Venus with both a spacecraft and a descent probe. DAVINCI’s probe will be the first in the 21st century to brave Venus’ atmosphere as it descends from above the planet’s clouds down to its surface. Two other missions, NASA’s VERITAS and ESA’s (European Space Agency) Envision, will also explore Venus in the 2030s from the planet’s orbit.
The DAVINCI spacecraft will study Venus’ clouds and highlands during two flybys. It also will release a spherical probe, about 3 feet wide, that will plunge through the planet’s thick atmosphere and corrosive clouds, taking measurements and capturing high-resolution images of the Venusian surface as it descends below the clouds.
Here are some of DAVINCI’s coming “firsts” in Venus exploration:
Exploring Solar System’s One-of-a-Kind Terrain
The DAVINCI mission will be the first to closely explore Alpha Regio, a region known as a “tessera.” So far found only on Venus, where they make up about 8% of the surface, tesserae are highland regions similar in appearance to rugged mountains on Earth. Previous missions discovered these features using radar instruments, but of the many international spacecraft that dove through Venus’ atmosphere between 1966 and 1985, none studied or photographed tesserae.
Thought to be ancient continents, tesserae like Alpha Regio may be among the oldest surfaces on the planet, offering scientists access to rocks that are billions of years old.
By studying these rocks from above Alpha Regio, DAVINCI scientists may learn whether ancient Venus had continents and oceans, and how water may have influenced the surface.
Photographing One of the Oldest Surfaces on Venus
The DAVINCI probe will capture the first close-up views of Alpha Regio with its infrared and optical cameras; these will also be the first photos of the planet’s surface taken in more than 40 years.
With surface temperatures reaching 900° F and air pressure 90 times that of Earth’s, Venus’ harsh environment makes exploration challenging, while its opaque atmosphere obscures direct views. Typically, scientists rely on radar instruments from Earth or Venus-orbiting spacecraft to study its terrain.
But DAVINCI’s probe will descend through the atmosphere and below the clouds for a clear view of the mountains and plains. It will capture images comparable to an airplane’s landing view of Earth’s surface. Scientists will use the photos to compile 3D maps of Alpha Regio that will provide more detail than ever of Venus’ terrain, helping them look for rocks that are usually only made in association with water.
Unveiling Secrets of Venus’ Mysterious Lower Atmosphere
The DAVINCI mission will be the first to analyze the chemical composition of Venus’ lower atmosphere through measurements taken at regular intervals, starting from approximately 90,000 feet above the surface and continuing until just before impact.
This region is critical because it contains gases and chemical compounds that may originate from Venus’ lower clouds, surface, or even subsurface.
For example, sulfur compounds detected here could indicate whether Venusian volcanoes are currently active or were active in the recent past. Noble gases (like helium or xenon), on the other hand, remain chemically inert and maintain stable concentrations, offering invaluable clues about Venus’ ancient history, such as the planet’s past water inventory.
By comparing Venus’ noble gas composition with that of Earth and Mars, scientists can better understand why these planets — despite forming from similar starting materials — evolved into dramatically different worlds.
Moreover, DAVINCI’s measurements of isotopes and trace gases in the lower atmosphere will shed light on Venus’ water history, from ancient times to the present, and the processes that triggered the planet’s extreme greenhouse effect.
State-of-the-Art Technology to Study Venus in Detail
Thanks to modern technology, the DAVINCI probe will be able to do things 1980s-era spacecraft couldn’t.
The descent probe will be better equipped than previous probes to protect the sensitive electronics inside of it, as it will be lined on the inside with high-temperature, multi-layer insulation — layers of advanced ceramic and silica fabrics separated by aluminum sheets.
Venus’ super thick atmosphere will slow the probe’s descent, but a parachute will also be released to slow it down further. Most Earth-friendly parachute fabrics, like nylon, would dissolve in Venus’ sulfuric acid clouds, so DAVINCI will have to use a different type of material than previous Venus missions did: one that’s resistant to acids and five times stronger than steel.
Read More: Old Data Yields New Secrets as NASA’s DAVINCI Preps for Venus Trip
By Lauren Colvin, with Lonnie Shekhtman
NASA’s Goddard Space Flight Center, Greenbelt, Md.
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is the principal investigator institution for DAVINCI and will perform project management for the mission, provide science instruments, as well as project systems engineering to develop the in-situ probe flight system that will enter the atmosphere of Venus. Goddard also leads the overall science for the mission with an external science team from across the United States. Lockheed Martin Space in Denver, Colorado, will build the carrier/relay spacecraft. DAVINCI is a mission within the Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.
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By European Space Agency
A multi-orbit constellation of about 300 satellites that will deliver resilient, secure and fast communications for EU governments, European companies and citizens will be put in orbit after two contracts were confirmed today in Brussels.
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By NASA
4 min read
NASA, JAXA XRISM Mission Looks Deeply Into ‘Hidden’ Stellar System
The Japan-led XRISM (X-ray Imaging and Spectroscopy Mission) observatory has captured the most detailed portrait yet of gases flowing within Cygnus X-3, one of the most studied sources in the X-ray sky.
Cygnus X-3 is a binary that pairs a rare type of high-mass star with a compact companion — likely a black hole.
Cygnus X-3 is a high-mass binary consisting of a compact object (likely a black hole) and a hot Wolf-Rayet star. This artist’s concept shows one interpretation of the system. High-resolution X-ray spectroscopy indicates two gas components: a heavy background outflow, or wind, emanating from the massive star and a turbulent structure — perhaps a wake carved into the wind — located close to the orbiting companion. As shown here, a black hole’s gravity captures some of the wind into an accretion disk around it, and the disk’s orbital motion sculpts a path (yellow arc) through the streaming gas. During strong outbursts, the companion emits jets of particles moving near the speed of light, seen here extending above and below the black hole. NASA’s Goddard Space Flight Center “The nature of the massive star is one factor that makes Cygnus X-3 so intriguing,” said Ralf Ballhausen, a postdoctoral associate at the University of Maryland, College Park, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s a Wolf-Rayet star, a type that has evolved to the point where strong outflows called stellar winds strip gas from the star’s surface and drive it outward. The compact object sweeps up and heats some of this gas, causing it to emit X-rays.”
A paper describing the findings, led by Ballhausen, will appear in a future edition of The Astrophysical Journal.
“For XRISM, Cygnus X-3 is a Goldilocks target — its brightness is ‘just right’ in the energy range where XRISM is especially sensitive,” said co-author Timothy Kallman, an astrophysicist at NASA Goddard. “This unusual source has been studied by every X-ray satellite ever flown, so observing it is a kind of rite of passage for new X-ray missions.”
XRISM (pronounced “crism”) is led by JAXA (Japan Aerospace Exploration Agency) in collaboration with NASA, along with contributions from ESA (European Space Agency). NASA and JAXA developed the mission’s microcalorimeter spectrometer instrument, named Resolve.
Observing Cygnus X-3 for 18 hours in late March, Resolve acquired a high-resolution spectrum that allows astronomers to better understand the complex gas dynamics operating there. These include outflowing gas produced by a hot, massive star, its interaction with the compact companion, and a turbulent region that may represent a wake produced by the companion as it orbits through the outrushing gas.
XRISM’s Resolve instrument has captured the most detailed X-ray spectrum yet acquired of Cygnus X-3. Peaks indicate X-rays emitted by ionized gases, and valleys form where the gases absorb X-rays; many lines are also shifted to both higher and lower energies by gas motions. Top: The full Resolve spectrum, from 2 to 8 keV (kiloelectron volts), tracks X-rays with thousands of times the energy of visible light. Some lines are labeled with the names of the elements that produced them, such as sulfur, argon, and calcium, along with Roman numerals that refer to the number of electrons these atoms have lost. Bottom: A zoom into a region of the spectrum often dominated by features produced by transitions in the innermost electron shell (K shell) of iron atoms. These features form when the atoms interact with high-energy X-rays or electrons and respond by emitting a photon at energies between 6.4 and 7 keV. These details, clearly visible for the first time with XRISM’s Resolve instrument, will help astronomers refine their understanding of this unusual system. JAXA/NASA/XRISM Collaboration In Cygnus X-3, the star and compact object are so close they complete an orbit in just 4.8 hours. The binary is thought to lie about 32,000 light-years away in the direction of the northern constellation Cygnus.
While thick dust clouds in our galaxy’s central plane obscure any visible light from Cygnus X-3, the binary has been studied in radio, infrared, and gamma-ray light, as well as in X-rays.
The system is immersed in the star’s streaming gas, which is illuminated and ionized by X-rays from the compact companion. The gas both emits and absorbs X-rays, and many of the spectrum’s prominent peaks and valleys incorporate both aspects. Yet a simple attempt at understanding the spectrum comes up short because some of the features appear to be in the wrong place.
That’s because the rapid motion of the gas displaces these features from their normal laboratory energies due to the Doppler effect. Absorption valleys typically shift up to higher energies, indicating gas moving toward us at speeds of up to 930,000 mph (1.5 million kph). Emission peaks shift down to lower energies, indicating gas moving away from us at slower speeds.
Some spectral features displayed much stronger absorption valleys than emission peaks. The reason for this imbalance, the team concludes, is that the dynamics of the stellar wind allow the moving gas to absorb a broader range of X-ray energies emitted by the companion. The detail of the XRISM spectrum, particularly at higher energies rich in features produced by ionized iron atoms, allowed the scientists to disentangle these effects.
“A key to acquiring this detail was XRISM’s ability to monitor the system over the course of several orbits,” said Brian Williams, NASA’s project scientist for the mission at Goddard. “There’s much more to explore in this spectrum, and ultimately we hope it will help us determine if Cygnus X-3’s compact object is indeed a black hole.”
XRISM is a collaborative mission between JAXA and NASA, with participation by ESA. NASA’s contribution includes science participation from CSA (Canadian Space Agency).
Download additional images from NASA’s Scientific Visualization Studio
By Francis Reddy
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact:
Claire Andreoli
301-286-1940
claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Nov 25, 2024 Related Terms
Black Holes Electromagnetic Spectrum Galaxies, Stars, & Black Holes Research Goddard Space Flight Center Stars Stellar-mass Black Holes The Universe X-ray Binaries XRISM (X-Ray Imaging and Spectroscopy Mission) Facebook logo @NASAUniverse @NASAUniverse Instagram logo @NASAUniverse Keep Exploring Discover Related Topics
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