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By NASA
Figure 1. An artist’s concept of the Van Allen belts with a cutaway section of the giant donuts of radiation that surround Earth. Image Credit: NASA Goddard Space Flight Center/Scientific Visualization Studio A new instrument is using advanced detection techniques and leveraging an orbit with specific characteristics to increase our understanding of the Van Allen belts—regions surrounding Earth that contain energetic particles that can endanger both robotic and human space missions. Recently, the instrument provided a unique view of changes to this region that were brought on by an intense magnetic storm in May 2024.
The discovery of the Van Allen radiation belts by the U.S. Explorer 1 mission in 1958 marked a prominent milestone in space physics and demonstrated that Earth’s magnetosphere efficiently accelerates and traps energetic particles. The inner belt contains protons in the MeV (million electric volt) to GeV (109 electric volt) range, and even higher concentrations of energetic electrons of 100s of keV (1000 electric volt) to MeV are found in both the inner belt and the outer belt.
The energetic electrons in these belts—also referred to as “killer electrons”—can have detrimental effects on spacecraft subsystems and are harmful to astronauts performing extravehicular activities. Understanding the source, loss, and varying concentrations of these electrons has been a longstanding research objective. High-energy resolution and clean measurements of these energetic electrons in space are required to further our understanding of their properties and enable more reliable prediction of their intensity.
Overcoming the challenges of measuring relativistic electrons in the inner belt
Measuring energetic electrons cleanly and accurately has been a challenge, especially in the inner belt, where MeV to GeV energy protons also exist. NASA’s Van Allen Probes, which operated from 2012 to 2019 in low inclination, geo-transfer-like orbits, showed that instruments traversing the heart of the inner radiation belt are subject to penetration by the highly energetic protons located in that region. The Relativistic Electron Proton Telescope (REPT) and the Magnetic Electron and Ion Spectrometer (MagEIS) instruments onboard the Van Allen Probes were heavily shielded but were still subject to inner-belt proton contamination.
To attempt to minimize these negative effects, a University of Colorado Boulder team led by Dr. Xinlin Li, designed the Relativistic Electron Proton Telescope integrated little experiment (REPTile)—a simplified and miniaturized version of REPT—to fly onboard the Colorado Student Space Weather Experiment (CSSWE). An effort supported by the National Science Foundation, the 3-Unit CSSWE CubeSat operated in a highly inclined low Earth orbit (LEO) from 2012 to 2014. In this highly inclined orbit, the spacecraft and the instruments it carried were only exposed to the inner-belt protons in the South Atlantic Anomaly (SAA) region where the Earth’s magnetic field is weaker, which greatly reduced the time that protons impacted the measurement of electrons.
REPTile’s success motivated a team, also led by Dr. Xinlin Li, to design REPTile-2—an advanced version of REPTile—to be hosted on the Colorado Inner Radiation Belt Experiment (CIRBE) mission. Like CSSWE, CIRBE operates in a highly inclined low-Earth orbit to ensure the exposure to damaging inner-belt protons is minimized. The team based the REPTile-2 design on REPTile but incorporated two additional technologies—guard rings and Pulse Height Analysis—to enable clean, high-energy-resolution measurements of energetic electrons, especially in the inner belt.
Figure 2: PI observing two engineers testing the interface between the CIRBE bus and REPTile-2 on September 29, 2021. Image Credit: Xinlin Li, University of Colorado Boulder As shown on the left in Figure 3, the field of view (FOV) of REPTile-2 is 51o. Electrons and protons enter the FOV and are measured when they reach a stack of silicon detectors where they deposit their energies. However, very energetic protons (energy greater than 60 MeV) could penetrate through the instrument’s tungsten and aluminum shielding and masquerade as valid particles, thus contaminating the intended measurements. To mitigate this contamination, the team designed guard rings that surround each detector. These guard rings are electronically separated from the inner active area of each detector and are connected by a separate electric channel. When the guard rings are triggered (i.e., hit by particles coming outside of the FOV), the coincident measurements are considered invalid and are discarded. This anti-coincidence technique enables cleaner measurements of particles coming through the FOV.
Figure 3. Left (adapted from Figure 1 of Khoo et al., 2022): Illustration of REPTile-2 front end with key features labeled; Right: REPTile-2 front end integrated with electronic boards and structures, a computer-aided design (CAD) model, and a photo of integrated REPTile-2. Image Credit: Xinlin Li, University of Colorado Boulder To achieve high energy resolution, the team also applied full Pulse Height Analysis (PHA) on REPTile-2. In PHA, the magnitude of measured charge in the detector is directly proportional to the energy deposited from the incident electrons. Unlike REPTile, which employed a simpler energy threshold discrimination method yielding three channels for the electrons, REPTile-2 offers enhanced precision with 60 energy channels for electron energies ranging from 0.25 – 6 MeV. The REPT instrument onboard the Van Allen Probes also employed PHA but while REPT worked very well in the outer belt, yielding fine energy resolution, it did not function as well in the inner belt since the instrument was fully exposed to penetrating energetic protons because it did not have the guard rings implemented.
Figure 4: The CIRBE team after a successful “plugs-out” test of the CIRBE spacecraft on July 21, 2022. During this test the CIRBE spacecraft successfully received commands from ground stations and completed various performance tests, including data transmission back to ground stations at LASP. Image Credit: Xinlin Li, University of Colorado Boulder CIRBE and REPTile-2 Results
CIRBE’s launch, secured through the NASA CubeSat Launch Initiative (CSLI), took place aboard SpaceX’s Falcon 9 rocket as part of the Transporter-7 mission on April 15, 2023. REPTile-2, activated on April 19, 2023, has been performing well, delivering valuable data about Earth’s radiation belt electrons. Many features of the energetic electrons in the Van Allen belts have been revealed for the first time, thanks to the high-resolution energy and time measurements REPTile-2 has provided.
Figure 5 shows a sample of CIRBE/REPTile-2 measurements from April 2024, and illustrates the intricate drift echoes or “zebra stripes” of energetic electrons, swirling around Earth in distinct bunches. These observations span a vast range across the inner and outer belts, encompassing a wide spectrum of energies and electron fluxes extending over six orders of magnitude. By leveraging advanced guard rings, Pulse Height Analysis (PHA), and a highly inclined LEO orbit, REPTile-2 is delivering unprecedented observations of radiation belt electrons.
Figure 5: Color-coded electron fluxes detrended between REPTile-2 measurements for a pass over the South Atlantic Anomaly region on April 24, 2023, and their average, i.e., the smoothed electron fluxes using a moving average window of ±19% in energy; Black curves plotted on top of the color-coded electron fluxes are contours of electron drift period in hr. The second horizontal-axis, L, represents the magnetic field line, which CIRBE crosses. The two radiation belts and a slot region in between are indicated by the red lines and arrow, respectively. Image Credit: Xinlin Li, University of Colorado Boulder In fact, the team recently announced that measurements from CIRBE/REPTile-2 have revealed a new temporary third radiation belt composed of electrons and sandwiched between the two permanent belts. This belt formed during the magnetic storm in May 2024, which was the largest in two decades. While such temporary belts have been seen after big storms previously, the data from CIRBE/REPTile-2 are providing a new viewpoint with higher energy resolution data than before. Scientists are currently studying the data to better understand the belt and how long it might stick around — which could be many months.
PROJECT LEAD
Dr. Xinlin Li, University of Colorado Laboratory for Atmospheric and Space Physics and Department of Aerospace Engineering Sciences.
SPONSORING ORGANIZATIONS
Heliophysics Flight Opportunities for Research & Technology (H-FORT) program, National Science Foundation
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Last Updated Sep 17, 2024 Related Terms
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By NASA
On Sept. 10, 2009, the Japan Aerospace Exploration Agency (JAXA) launched its first cargo delivery spacecraft, the H-II Transfer Vehicle-1 (HTV-1), to the International Space Station. The HTV cargo vehicles, also called Kounotori, meaning white stork in Japanese, not only maintained the Japanese Experiment Module Kibo but also resupplied the space station in general with pressurized and unpressurized cargo and payloads. Following its rendezvous with the space station, Expedition 20 astronauts grappled and berthed HTV-1 on Sept. 17, and spent the next month transferring its 9,900 pounds of internal and external cargo to the space station and filling the HTV-1 with trash and unneeded equipment. They released the craft on Oct. 30 and ground controllers commanded it to a destructive reentry on Nov. 1.
Left and middle: Two views of the HTV-1 Kounotori cargo spacecraft during prelaunch processing at the Tanegashima Space Center in Japan. Right: Schematic illustration showing the HTV’s major components. Image credits: courtesy JAXA.
The HTV formed part of a fleet of cargo vehicles that at the time included NASA’s space shuttle until its retirement in 2011, Roscosmos’ Progress, and the European Space Agency’s (ESA) Automated Transfer Vehicle that flew five missions between 2008 and 2015. The SpaceX Cargo Dragon and Orbital (later Northrup Grumman) Cygnus commercial cargo vehicles supplemented the fleet starting in 2012 and 2013, respectively. The HTV weighed 23,000 pounds empty and could carry up to 13,000 pounds of cargo, although on this first flight carried only 9,900 pounds. The vehicle included both a pressurized and an unpressurized logistics carrier. Following its rendezvous with the space station, it approached to within 33 feet, at which point astronauts grappled it with the station’s robotic arm and berthed it to the Harmony Node 2 module’s Earth facing port. Space station managers added two flights to the originally planned seven, with the last HTV flying in 2020. An upgraded HTV-X vehicle will soon make its debut to carry cargo to the space station, incorporating the lessons learned from the nine-mission HTV program.
Left: Technicians place HTV-1 inside its launch protective shroud at the Tanegashima Space Center. Middle left: Workers truck the HTV-1 to Vehicle Assembly Building (VAB). Middle right: The HTV-1 atop its H-II rolls out of the VAB on its way to the launch pad. Right: The HTV-1 mission patch. Image credits: courtesy JAXA.
Prelaunch processing of HTV-1 took place at the Tanegashima Space Center, where engineers inspected and assembled the spacecraft’s components. Workers installed the internal cargo into the pressurized logistics carrier and external payloads onto the External Pallet that they installed into the unpressurized logistics carrier. HTV-1 carried two external payloads, the Japanese Superconducting submillimeter-wave Limb Emission Sounder (SMILES) and the U.S. Hyperspectral Imager for Coastal Ocean (HICO)-Remote Atmospheric and Ionospheric detection System (RAIDS) Experiment Payload (HREP). On Aug. 23, 2009, workers encapsulated the assembled HTV into its payload shroud and a week later moved it into the Vehicle Assembly Building (VAB), where they mounted it atop the H-IIB rocket. Rollout from the VAB to the pad took place on the day of launch.
Liftoff of HTV-1 from the Tanegashima Space Center in Japan. Image credit: courtesy JAXA.
Left: The launch control center at the Tanegahsima Space Center in Japan. Middle: The mission control room at the Tsukuba Space Center in Japan. Image credits: courtesy JAXA. Right: The HTV-1 control team in the Mission Control Center at NASA’s Johnson Space Center in Houston.
On Sept. 10 – Sept. 11 Japan time – HTV-1 lifted off its pad at Tanegashima on the maiden flight of the H-IIB rocket. Controllers in Tanegashima’s launch control center monitored the flight until HTV-1 separated from the booster’s second stage. At that point, HTV-1 automatically activated its systems and established communications with NASA’s Tracking and Data Relay Satellite System. Control of the flight shifted to the mission control room at the Tsukuba Space Center outside Tokyo. Controllers in the Mission Control Center at NASA’s Johnson Space Center in Houston also monitored the mission’s progress.
Left: HTV-1 approaches the space station. Middle: NASA astronaut Nicole P. Stott grapples HTV-1 with the station’s robotic arm and prepares to berth it to the Node 2 module. Right: European Space Agency astronaut Frank DeWinne, left, Stott, and Canadian Space Agency astronaut Robert Thirsk in the Destiny module following the robotic operations to capture and berth HTV-1.
Following several days of systems checks, HTV-1 approached the space station on Sept. 17. Members of Expedition 20 monitored its approach, as it stopped within 33 feet of the orbiting laboratory. Using the space station’s Canadarm2 robotic arm, Expedition 20 Flight Engineer and NASA astronaut Nicole P. Stott grappled HTV-1. Fellow crew member Canadian Space Agency astronaut Robert Thirsk berthed the vehicle on the Harmony Node 2 module’s Earth-facing port. The following day, the Expedition 20 crew opened the hatch to HTV-1 to begin the cargo transfers.
Left: Canadian Space Agency astronaut Robert Thirsk inside HTV-1. Middle: NASA astronaut Nicole P. Stott transferring cargo from HTV-1 to the space station. Right: Stott in HTV-1 after completion of much of the cargo transfer.
Over the next several weeks, the Expedition 20 and 21 crews transferred more than 7,900 pounds of cargo from the pressurized logistics carrier to the space station. The items included food, science experiments, robotic arm and other hardware for the Kibo module, crew supplies including clothing, toiletries, and personal items, fluorescent lights, and other supplies. They then loaded the module with trash and unneeded equipment, altogether weighing 3,580 pounds.
Left: The space station’s robotic arm grapples the Exposed Pallet (EP) to transfer it to the Japanese Experiment Module-Exposed Facility (JEM-EF). Right: Canadian Space Agency astronaut Robert Thirsk and NASA astronaut Nicole P. Stott operate the station’s robotic arm to temporarily transfer the EP and its payloads to the JEM-EF.
Left: The Japanese robotic arm grapples one of the payloads from the Exposed Pallet (EP) to transfer it to the Japanese Experiment Module-Exposed Facility (JEM-EF). Right: European Space Agency astronaut Frank DeWinne, left, and NASA astronaut Nicole P. Stott operate the Japanese robotic arm from inside the JEM.
Working as a team, NASA astronauts Stott and Michael R. Barratt along with Thirsk and ESA astronaut Frank DeWinne performed the transfer of the external payloads. On Sept. 23, using the station’s robotic arm, they grappled the Exposed Pallet (EP) and removed it from HTV-1’s unpressurized logistics carrier, handing it off to the Japanese remote manipulator system arm that temporarily stowed it on the JEM’s Exposed Facility (JEM-EF). The next day, using the Japanese arm, DeWinne and Stott transferred the SMILES and HREP experiments to their designated locations on the JEM-EF. On Sept. 25, they grappled the now empty EP and placed it back into HTV-1’s unpressurized logistics carrier.
Left: Astronauts transfer the empty Exposed Pallet back to HTV-1. Middle: NASA astronaut Nicole P. Stott poses in front of the now-closed hatch to HTV-1. Right: European Space Agency astronaut Frank DeWinne, left, and Stott operate the station’s robotic arm to grapple HTV-1 for release.
Left: The space station’s robotic arm grapples HTV-1 in preparation for its unberthing. Middle: The station’s robotic arm has unberthed HTV-1 in preparation for its release. Right: The arm has released HTV-1 and it begins its separation from the space station.
Following completion of all the transfers, Expedition 21 astronauts aboard the space station closed the hatch to HTV-1 on Oct. 29. The next day, Stott and DeWinne grappled the vehicle and unberthed it from Node 2. While passing over the Pacific Ocean, they released HTV-1 and it began its departure maneuvers from the station. On Nov. 1, the flight control team in Tsukuba sent commands to HTV-1 to execute three deorbit burns. The vehicle reentered the Earth’s atmosphere, burning up off the coast of New Zealand, having completed the highly successful 52-day first HTV resupply mission. Eight more HTV missions followed, all successful, with HTV-9 completing its mission in August 2020.
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By NASA
AMS-02 mounted on the outside of the space station.NASA Visible matter in the form of stars and planets adds up to about five percent of the total known mass of the Universe. The rest is either dark matter, antimatter, or dark energy. The exact nature of these substances is unknown, but the International Space Station’s Alpha-Magnetic Spectrometer or AMS-02 is helping to solve the mystery.
AMS-02 collects data on charged particles from cosmic ray events, which helps scientists understand the origin of those rays and could ultimately reveal whether dark matter and antimatter exist.
To date, the instrument has collected data on about 573 events per second on average – just over 18 billion per year. This high volume of data enables highly precise statistical analyses, and multiple groups of researchers independently process the raw data to ensure accurate results.
Learn more about astrophysics research on the space station.
This view shows the core of AMS-02, a massive magnet that bends particles from space to reveal whether their charge is positive or negative.NASA AMS-02 is the hexagonal shape visible on one of the space station’s trusses, just to the right of the center.NASA Keep Exploring Discover More Topics
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By European Space Agency
According to recent research, Europe’s net greenhouse gas emissions have decreased by around 25% since the 1990s. While this is good news, the study also revealed a weakening in the capacity of land and vegetation to absorb and store atmospheric carbon.
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
In a series of baseline flights beginning on June 24, 2024, the G-IV aircraft flew over the Antelope Valley to analyze aircraft performance. To accommodate a new radar instrument developed by JPL, NASA’s Airborne Science Program has selected the Gulfstream-IV aircraft to be modified and operated by Armstrong Flight Research Center in Edwards, California and will accommodate new instrumentation on board in support of the agency’s science mission directorate. Baseline flights began at NASA Armstrong in June 2024NASA/Carla Thomas In June 2024, a new tail number swept the sky above NASA’s Armstrong Flight Research Center in Edwards, California. Pilots conducted flights of a Gulfstream IV (G-IV) to evaluate its handling characteristics and to familiarize pilots with it before it begins structural modifications. The research plane is joining the center’s fleet serving NASA’s Airborne Science program.
The G-IV will carry the Next Generation Airborne Synthetic Aperture Radar (AIRSAR-NG), which sends and receives microwave signals to collect information about Earth’s topographic features and how they change over time. The goal for the team at NASA Armstrong is to modify the G-IV to accommodate three radars simultaneously.
“The AIRSAR-NG will be composed of three different Synthetic Aperture Radar antennas in one instrument to provide new insight into Earth’s surface more efficiently,” said Yunling Lou, principal investigator for the instrument at NASA’s Jet Propulsion Laboratory in Southern California. “The capabilities of this new instrument will facilitate new techniques, such as three-dimensional imaging, that will be useful for future space-borne missions.”
With those and other modifications being made, the G-IV will also be able to accommodate an increased load of science instruments, which could enable NASA to support more dynamic airborne science missions.
“This aircraft will aid Armstrong in continuing our long history of supporting airborne science for the agency and maintain the expertise in conducting successful science missions for years to come,” said Franzeska Becker, the G-IV project manager at NASA Armstrong.
Transferred in February from NASA’s Langley Research Center in Hampton, Virginia, the G-IV will undergo additional modifications overseen by NASA Armstrong’s team. Their goal is to enrich the agency’s airborne science program by outfitting the aircraft to function as a more capable and versatile research platform.
The knowledge and expertise of professionals at NASA centers like Armstrong (G-IV, ER-2, C-20) and Langley (777, G-III) will help enable the agency to produce a well-defined and airworthy platform for science instruments and airborne science missions.
Learn more about NASA’s Airborne Science program Learn more about NASA’s AirSar project Share
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Last Updated Aug 29, 2024 EditorDede DiniusContactErica HeimLocationArmstrong Flight Research Center Related Terms
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