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During May’s Solar Superstorm, the Little-Known Science of Heliophysics Kept Us Safe
NASA’s head of heliophysics explains how we weathered the worst solar storm of a generation—and discusses the challenges we face in preparing for the next one
NASA Welcomes Peru as 41st Artemis Accords Signatory
NASA Administrator Bill Nelson welcomed Peru as the newest nation to sign the Artemis Accords Thursday during a ceremony with the U.S. State Department at NASA Headquarters in Washington. Peru joins 40 other countries in a commitment to advancing principles for the safe, transparent, and responsible exploration of the Moon, Mars and beyond.
“NASA is proud to welcome Peru to the Artemis Accords family,” said Nelson. “This giant leap forward for our countries is a result of decades of work Peru has done to further its reach in the cosmos. We live in the golden era of space exploration. Together, we will continue to explore the cosmos openly, responsibly, as partners, for all.”
Javier González-Olaechea, foreign minister, signed the Artemis Accords on behalf of Peru. Alfredo Ferrero Diez Canseco, ambassador of Peru to the U.S. and Jennifer R. Littlejohn, acting assistant secretary, Bureau of Oceans and International Environmental and Scientific Affairs, Department of State, also participated in the signing ceremony.
“Peru, by joining the Artemis Accords, seeks not only to express a common vision with the other member countries but also to establish cooperation mechanisms with these countries, especially with the United States, to participate in activities of exploration and sustainable use of resources found in space, as well as to promote aerospace scientific development in our country,” said González-Olaechea.
The United States and seven other nations were the first to sign the Artemis Accords in 2020, which identified an early set of principles promoting the beneficial use of space for all humanity. The accords are grounded in the Outer Space Treaty and other agreements including the Registration Convention, the Rescue and Return Agreement, as well as best practices and norms of responsible behavior that NASA and its partners have supported, including the public release of scientific data. More countries are expected to sign the Artemis Accords in the months and years to come.
The commitments of the Artemis Accords, and efforts by the signatories to advance implementation of these principles, support NASA’s Artemis campaign with its partners, as well as for the success of the safe and sustainable exploration activities of the other accords signatories.
For more information about the Artemis Accords, visit:
https://www.nasa.gov/artemis-accords/
-end-
Faith McKie / Jennifer Dooren
Headquarters, Washington
202-358-1600
faith.d.mckie@nasa.gov / jennifer.m.dooren@nasa.gov
Travel
The NSSC provides travel reimbursement services for all authorized Agency travel including: domestic, foreign, local, ETDY, and Change of Station (COS).
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NSSC Travel now has another way that a transferee Traveler may submit his or her vouchers. Please see, submitting Change of Station Process Steps
If traveling CONUS, review: NASA’s Guide to a Successful Move (CONUS)
If traveling OCONUS, review: NASA’s Guide to a Successful Move (OCONUS)
Change of Station References
Change of Station Voucher Information And Samples
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SF 1038 Advance of Funds Application and Account
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Related Tax Information:
Check out the latest Taxability Change Notice for Change of Station travelers.
To learn more, see: Relocation Income Tax Allowance Information
POV Mileage for NASA Travelers
For Privately Owned Vehicle (POV) Mileage Reimbursement Rates for TDY and ETDY Travel please refer to the GSA Web site: http://www.gsa.gov/mileage
NASA Domestic Travel: Day that Travel Ends
For the day travel ends (the day a traveler returns to the PDS, home, or other authorized point), the per diem allowance is 75% of M&IE.
NASA Domestic Travel Rental Car Liability
When making a reservation for a rental car, please remember the Government is only responsible to pay for rental car charges for official travel time. If a traveler decides to take annual leave in conjunction with official travel and keeps the rental car during annual leave, the portion of the rental rate applicable to annual leave is the responsibility of the traveler. Please refer to 41 CFR 301-10.453
What is my liability for unauthorized use of a rental automobile obtained with Government funds?
You are responsible for any additional cost resulting from the unauthorized use of a commercial rental automobile for other than official travel-related purposes.
NASA Domestic Travel: Tax Exemption
Prior to traveling, refer to the GSA State Tax Information webpage: https://smartpay.gsa.gov/smarttax. Select your State/US territory of interest to see the exemption status and download the appropriate form, if required.
Extended Temporary Duty (ETDY)Reduced Per Diem rate
NASA’s standard reduced per diem rate for ETDY travel is 65 percent under the current policy as defined in the NASA Procedural Requirements (NPR) 9750.1-3.1.2.
a. Consistent with 41 CFR 301-11.200, an ETDY authorization can include reasonable further reductions from this standard rate or limitations on approved lodging for unique circumstances, to the extent it can be determined in advance that such will substantially lower costs without mission impact. For example, if lodging is obtained at 50 percent per diem, the ETDY authorization should be adjusted to authorize a lower rate.
b. The reduced rate of reimbursement begins on the first day of travel regardless of the mode of transportation, except as noted in 3.1.3. Allowances are covered by the reduced per diem rate; therefore, NASA will authorize the employee a per diem rate (up to 65 percent) to reasonably cover expenses for a one bedroom furnished apartment. For ETDY greater than 90 days, first consideration should be given to long-term lodging facilities. Long-term lodging facilities are available on the GSA schedule at http://www.gsa.gov. If a long-term facility is not selected, proper justification should be provided.
Find more about Allowable ETDY Expenses Included in Reduced Per Diem Rate, please see the following document:
Allowable ETDY Expenses Included in Reduced Per Diem Rate
GSA Long-term Lodging (Schedule 48)
GSA’s Schedule 48 is designed for lodging needs of 30 days or more. This program provides housing accommodations for temporary or permanent relocation. Typical facilities include apartment or condominium type properties that may be furnished with all the amenities of a regular home. The current list of vendors is available by clicking on the link above. Most of these properties will accommodate NASA Extended TDY travelers within the 65% reduce per diem rate and will allow use of the government charge card.
Foreign TravelPlease consult the Code of Federal Regulations (CFR), NPR 9710.1, and NPR 9750.1. Please call the NSSC Contact Center at 1-877-NSSC-123 (1-877-677-2123) for additional information.
Solar Orbiter traces solar wind back to its mysterious source for 1st time
Twin NASA Satellites Ready to Help Gauge Earth’s Energy Balance
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater) Earth’s polar regions radiates much of the heat initially absorbed at the tropics out to space, mostly in the form of far-infrared radiation. Clouds in the Arctic — like these seen over a Greenland glacier — and Antarctic can trap far-infrared radiation on Earth, increasing global temperatures.NASA/GSFC/Michael Studinger
Information from the PREFIRE mission will illuminate how clouds and water vapor in the Arctic and Antarctic influence the amount of heat the poles radiate into space.
A pair of new shoebox-size NASA satellites will help unravel an atmospheric mystery that’s bedeviled scientists for years: how the behavior of clouds and water vapor at Earth’s polar regions affects our planet’s climate.
The first CubeSat in NASA’s Polar Radiant Energy in the Far-InfraRed Experiment (PREFIRE) mission launched from New Zealand on Saturday, May 25. The second PREFIRE CubeSat is targeted to lift off on Saturday, June 1, with a launch window opening at 3 p.m. NZST (11 p.m. EDT, Friday, May 31).
The mission will measure the amount of heat Earth emits into space from the two coldest, most remote regions on the planet. Data from PREFIRE will improve computer models that researchers use to predict how Earth’s ice, seas, and weather will change in a warming world.
This video gives an overview of the PREFIRE mission, which aims to improve global climate change predictions by expanding scientists’ understanding of heat radiated from Earth at the polar regions. NASA/JPL-CaltechEarth absorbs a lot of the Sun’s energy in the tropics, and weather and ocean currents transport that heat toward the poles (which receive much less sunlight). Ice, snow, and clouds, among other parts of the polar environment, emit some of that heat into space, much of it in the form of far-infrared radiation. The difference between the amount of heat Earth absorbs at the tropics and that radiated out from the Arctic and Antarctic is a key influence on the planet’s temperature, helping to drive dynamic systems of climate and weather.
But far-infrared emissions at the poles have never been systematically measured. This is where PREFIRE comes in. The mission will help researchers gain a clearer understanding of when and where Earth’s polar regions emit far-infrared radiation to space, as well as how atmospheric water vapor and clouds influence the amount that escapes.
One of the two shoebox-size CubeSats that make up NASA’s PREFIRE mission sits on a table at Blue Canyon Technologies. The company built the satellite bus and integrated the JPL-provided thermal infrared spectrometer instrument.NASA/JPL-Caltech
Clouds and water vapor can trap far-infrared radiation on Earth, thereby increasing global temperatures — part of the greenhouse effect.
“It’s critical that we get the effects of clouds right if we want to accurately model Earth’s climate,” said Tristan L’Ecuyer, a professor at the University of Wisconsin-Madison and PREFIRE’s principal investigator.
Clouds in Climate ModelingClouds and water vapor at Earth’s poles act like windows on a summer day: A clear, relatively dry day in the Arctic is like opening a window to let heat out of a stuffy room. A cloudy, relatively humid day traps heat like a closed window.
The types of clouds — and the altitude at which they form — influence how much heat the polar atmosphere retains. Like a tinted window, low-altitude clouds, composed mainly of water droplets, tend to have a cooling effect. High-altitude clouds, made mainly of ice particles, more readily absorb heat, generating a warming effect. Because clouds at mid-altitudes can have varying water-droplet and ice-particle contents, they can have either a warming or cooling effect.
But clouds are notoriously difficult to study: They’re made up of microscopic particles that can move and change in a matter of seconds to hours. When it rains or snows, there’s a great reshuffling of water and energy that can alter the character of clouds entirely. These ever-changing factors complicate the task of realistically capturing cloud behavior in climate models, which try to project global climate scenarios.
Inconsistencies in how various climate models represent clouds can mean the difference between predicting 5 or 10 degrees Fahrenheit (3 or 6 degrees Celsius) of warming. The PREFIRE mission aims to reduce that uncertainty.
The thermal infrared spectrometer on each spacecraft will make crucial measurements of wavelengths of light in the far-infrared range. The instruments will be able to detect clouds largely invisible to other types of optical instruments. And PREFIRE’s instruments will be sensitive enough to detect the approximate size of particles to distinguish between liquid droplets and ice particles.
“PREFIRE will give us a new set of eyes on clouds,” said Brian Kahn, an atmospheric scientist at NASA’s Jet Propulsion Laboratory and a member of the PREFIRE science team. “We’re not quite sure what we’re going to see, and that’s really exciting.”
More About the MissionPREFIRE was jointly developed by NASA and the University of Wisconsin-Madison. A division of Caltech in Pasadena, California, JPL manages the mission for NASA’s Science Mission Directorate and provided the spectrometers. Blue Canyon Technologies built the CubeSats, and the University of Wisconsin-Madison will process and analyze the data the instruments collect.
NASA’s Launch Services Program selected Rocket Lab to launch both spacecraft as part of the agency’s Venture-class Acquisition of Dedicated and Rideshare (VADR) contract. CubeSats like PREFIRE serve as an ideal platform for technical and architecture innovation, contributing to NASA’s science research and technology development.
To learn more about PREFIRE, visit:
https://science.nasa.gov/mission/prefire/
5 Things to Know About NASA’s Tiny Twin Polar Satellites Get the PREFIRE fact sheet Meet NASA’s Twin Spacecraft Headed to the Ends of the Earth News Media ContactsJane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0307 / 626-379-6874
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
2024-076
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A New Telescope Can Observe Even in Broad Daylight
Astronomy is a profession that, so far, has only been done at night, at least on Earth. Light from the Sun overwhelms any light from other stars, making it impractical for both professional and amateur astronomers to look at the stars during daytime. There are several disadvantages to this, not the least of which is that many potentially exciting parts of the sky aren’t visible at all for large chunks of the year as they pass too close to the Sun. To solve this, a team from Macquarie University, led by graduate student Sarah Caddy, developed a multi-camera system for a local telescope that allows them to observe during daytime.
The University has a system known as the Huntsman Telescope, named after the famous Australian spider species. Its design was inspired by the Dragonfly Telescope Array, initially designed by researchers at the University of Toronto and Yale, among other institutions. Both telescopes feature an array of 10 telephoto lenses from Canon, the camera manufacturer, arranged in a honeycomb pattern.
Typically, the telescope is used for nighttime astronomy at the Siding Spring Observatory, about a seven-hour drive from Sydney. However, Ms. Caddy thought it could do better and potentially continue observations during the day.
An image of Betelgeuse during the day using the Huntsman Telescope.Credit – Macquarie University
They originally tested their ideas, which focused on a number of broadband filters and a single-lens test version of the Huntsman telescope. This allowed them to optimize things like exposure times and timing and show a proof of concept that they then wrote up in a paper in the Publications of the Astronomical Society of Australia.
In particular, Ms. Caddy and her colleagues are excited about several use cases. One is tracking particular stars that might soon undergo an exciting event. Betelgeuse comes to mind, as astronomers expect it to undergo a supernova sometime “soon,” though soon in astronomical terms could mean anywhere between tomorrow and 10 million years from now. If Betelgeuse happens to be on the other side of the Sun when it goes supernova, without daylight astronomy, there would be months of a gap where we would miss out on collecting data on the supernova that happened nearest to us in recorded history, and astronomers everywhere would be frustrated.
This is exactly why the Huntsman team used a daytime image of Betelgeuse as part of their proof of concept. While it might not look like a typical image of the star that is 650 light years away, the fact that it is visible at all during the daytime is striking.
Betelgeuse is one of the most interesting stars in the sky – a potential supernova that goes through occasional dimming periods, as Fraser explains.Another use case is the tracking of satellites. As the orbital space around Earth becomes increasingly crowded, there’s a higher likelihood that satellites will begin colliding, which could eventually result in something as severe as Kessler syndrome, which we’ve discussed before here at UT. Unfortunately, astronomers can only track satellites during the night, so if one of their orbits happens to shift for some reason during a day cycle, it would be impossible for them to suggest changes to the orbital paths of other satellites that are close by.
Unless you have daytime astronomy, which allows you to track satellites during the day, there’s a significantly decreased risk of two running into each other unexpectedly. This data can be combined with radar readings to help avoid catastrophic collisions, no matter how crowded orbital space gets.
This proof of concept is a step toward making those observations a reality. As it is more fully tested, the southern sky will become much more accessible, and it could pave the way for other daytime astronomy projects in other parts of the world.
Learn More:
Macquarie University – Stargazing in broad daylight: How a multi-lens telescope is changing astronomy
Caddy, Spitler & Ellis – An Optical Daytime Astronomy Pathfinder for the Huntsman Telescope
UT – Astro-Challenge: Adventures in Daytime Astronomy
UT – Why Can We See the Moon During the Day?
Lead Image:
Macquarie’s Huntsman Telescope can potentially observe space during the day.
Credit – Macquarie University
The post A New Telescope Can Observe Even in Broad Daylight appeared first on Universe Today.
Space debris from SpaceX Dragon capsule crashed in the North Carolina mountains. I had to go see it (video)
Our writers pick their favourite science fiction books of all time
Our writers pick their favourite science fiction books of all time
Volcanoes on Venus Might Be Erupting Right Now
Scientists have found signs of fresh flowing lava on Venus in decades-old data from NASA's Magellan spacecraft
The Sunspot Cluster behind the Recent Auroras Is Back!
The massive sunspot region that gave Earthlings stunning auroral displays earlier in May is back from its trip around the far side of the sun
Summary of the 2023 GRACE Follow-On Science Team Meeting
28 min read
Summary of the 2023 GRACE Follow-On Science Team MeetingFelix Landerer, NASA/Jet Propulsion Laboratory, felix.w.landerer@jpl.nasa.gov
Introduction
In October 2023, the annual gathering of the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On [G-FO] Science Team took place in Boulder, CO, hosted at University Corporation for Atmospheric Research’s (UCAR) Center Green campus. The event had 70 in-person participant and an additional 52 online participants – see Photo. G-FO is a U.S.–German collaboration between NASA and the Helmholtz Centre Potsdam GeoForschungsZentrum (GFZ) [German Research Centre for Geosciences].
Photo: Pictured here are the in-person attendees of the 2023 GRACE-FO Science Team. Another 52 people participated online. Image credit: Felix Landerer/JPL
The meeting agenda featured 15-minute presentations over three days, describing new findings from G-FO observations and the combined GRACE and GRACE-FO [G/G-FO] climate data record that now spans over 21 years (2002–2023).
The meeting began with the customary G-FO project status session, covering programmatic mission and flight segment technical updates, future mission plans, and descriptions of the latest data released from the GRACE Science Data System (SDS) centers. Subsequent sessions featured more than 53 contributed presentations covering analyses, algorithms, and science results by Science Team members and attendees, totaling 57 oral and 5 poster presentations. Many of the presentations are posted on the GRACE website. While this summary will cover all the content on the agenda of the meeting – it does do so in an exact linear fashion. It begins with a G-FO mission status update, followed by key highlights from the contributed analysis and science presentations.
Status of GRACE Follow-On
Since their launch on May 22, 2018, the twin G-FO satellites have been tracking Earth’s water movements and global surface mass changes that arise from climatic, anthropogenic, and tectonic changes. G-FO also enables new insights into variations of ice sheet and glacier mass, land water storage, as well as changes in sea level and ocean currents. These measurements have important applications and implications for everyday life. The impact of these data is underscored by the publication of over 6000 scientific papers – an average of 5 new publications per week – that have established G/G-FO as a leading Earth Science mission.
In May 2023, G-FO successfully completed its Prime Mission phase that lasted five years after launch. G-FO was among the missions that went through the 2023 NASA Earth Science Senior Review. The NASA project team submitted its response in spring of 2023 to extend mission operations through 2026. The proposal received overall Excellent score, highlighting the unique utility the data provide for Earth Science research and societal applications. However, the G-FO project’s NASA budget will be reduced (compared to the previous baseline) by 15% in fiscal year (FY) 2024 and 24% in FY 2025 and 2026 due to the overall budget constraints that NASA is facing. The G-FO team remains confident in its ability to continue delivering high-value and high-impact science data products – prioritizing science operations management and data latency over data reprocessing campaigns. Both NASA and GFZ had already formally committed to extending their collaboration on G-FO mission operations and data processing through the end of 2026 via a Memorandum of Understanding.
As of December 2023, the G-FO project team has processed and released 62 monthly gravity fields – the most recent being for October 2023 (at the time of this writing). The primary mission objective for G-FO is to provide continuity for the monthly GRACE mass-change observations (2002–2017) via its Microwave Interferometer (MWI) intersatellite range-change observations. G-FO also demonstrated a novel technology demonstration Laser-Ranging Interferometer (LRI) for more accurate satellite-to-satellite ranging observations for future GRACE-like missions. The LRI has been successfully operated in parallel with the MWI for most of the mission, delivering excellent quality data. LRI-based monthly gravity and mass change fields covering the period from mid-2018 to mid-2023 have been made available by the SDS teams for further analysis and study by the science community.
Programmatic, Mission, and Operations Updates
The meeting began with Frank Flechtner [GFZ–German G-FO Project Manager] and Felix Landerer [NASA/Jet Propulsion Laboratory (JPL)—U.S. G-FO Project Scientist] giving welcoming remarks, followed by detailed assessments of the G-FO mission and operations status from the core SDS centers and flight operations teams.
GRACE Follow-On Project Status
Felix Landerer gave an overview of the G-FO satellites and the science data system performance. He reported that G-FO continues to meet its goal of extending the GRACE mass-change and gravity data record at equivalent precision and spatiotemporal sampling.
Since the previous STM in October 2022, the overall G-FO science instrument performance has been stable, and the SDS team continued to deliver a gapless monthly data record to users ahead of schedule (on average, within 43 days instead of the 60-day requirement). Improving the data calibrations of the accelerometer measurements – which are noise contaminated on one of the two G-FO spacecraft – remains a core focus of the project SDS team. To this end, an improved calibration approach that reduced data errors by 10–20% has been developed and will be operationalized by the team in the coming months.
Landerer reported that, as forecasted, the current Solar Cycle 25 has gained in strength through 2023 and will continue to do so through 2024 before subsiding again. The resulting higher non-gravitational forces acting on the satellites need to be properly accounted for in the accelerometer data processing.
He also noted that small thruster leaks in the satellites cold gas propulsion system have been closely monitored since 2021. To ensure stable data collection and sufficient lifetime margin to achieve continuity with the proposed successor mission GRACE-Continuity, or GRACE-C (which is the new name for the Earth System Observatory Mass Change mission scheduled for launch no earlier than 2028), the G-FO project team, in conjunction with guidance from the satellite manufacturer Airbus and the German Space Operations Center, decided to adjust the operational data collection mode of G-FO to a wide pointing mode – which means that the two spacecraft are allowed to deviate from their relative line-of-sight pointing by up to 2°, whereas the previous pointing angles were 100 times smaller. This operational change necessitates fewer thruster firings, which in turn reduces leaks and improves accelerometer calibrations – and thus leads to better overall science data quality. Due to the wide pointing, the LRI intersatellite ranging data collection has been suspended in this operational mode. However, the LRI instruments are still activated and fully functional. Landerer emphasized that reducing the leak ensures that the GRACE-FO mission will have sufficient fuel to remain operational up until GRACE-C launches.
Despite these operational challenges, Landerer said that the science data delivered by G-FO continues to provide excellent utility and insights into a rapidly changing Earth system. He briefly highlighted a few scientific and decision-support contributions and achievements of G-FO over the last year. These included:
- Monitoring California Groundwater. G-FO recorded the largest seasonal total water storage gains over California after the multiple atmospheric rivers made landfall during the 2022/2023 winter. Yet, peak water storage in May was below values observed 15–20 years ago – due to long-term, sustained groundwater declines. Going forward, the data will be invaluable to assess groundwater recharge rates and processes.
- Observing Water Cycle Extremes: Droughts and Pluvials. The G-GFO 20-year data record has been analyzed to show the increasing intensity of wet and dry extremes of the global water cycle, which increased as global temperatures rose.
- Tracking Polar Ice Mass Loss. G/G-FO measured net ice mass gains over Antarctica that began around 2021 due to snow accumulation mainly in East Antarctica, which offset the unabated mass loss of the West Antarctic ice sheet.
Subsequent science presentations presented in-depth analyses of these and other findings in the dedicated science sessions, some of which are summarized below.
Landerer also highlighted the expanding portfolio of open science contributions that the project team is supporting: Jupyter notebooks are part of an expanding GRACE Open Science toolbox with the goal to expand this toolbox with input from the Science Team and user community in the coming years. In addition, easy-to-use browser data portals at JPL and GFZ have been key to expand the science and applications user community that increasingly use the Level-3 and higher data products in decision support contexts (e.g., for drought monitoring and water resources management).
A series of status reports on programmatic G-FO mission operations, science operations, and SDS processing followed the opening presentations. Krzysztof Snopek [GFZ] reported on the ground and mission operations at the German Space Operations Center (GSOC), which is responsible for G-FO spacecraft operations. All essential flight operations, software updates, and planned calibrations were successfully scheduled and carried out by GSOC. Himanshu Save [University of Texas, Center for Space Research (CSR)] provided the science operations assessment. He described the evolving Solar Cycle 25 and its influence on the G-FO spacecraft, the mission’s fuel budget, and adjusted operational procedures and modes (such as the already-mentioned ‘wide’ pointing mode). Christopher McCullough [JPL] reviewed the status of G/G-FO Level 1 processing at JPL, detailing additional improvements made in the accelerometer calibrations. The team is using the noisy accelerometer data on one satellite and retrieving improved science information from it.
A representative from each of the G-FO mission SDS centers – which includes JPL, GFZ, CSR, and GSFC – summarized the status of the latest gravity-field and mass change data products [RL06.X L2], including an overview of background dealiasing models and the GFZ GravIS portal, the updated JPL mascon data product, new data-processing strategies, e.g., via range acceleration [CSR], and the status of ancillary Satellite-Laser-Ranging (SLR) data processing and dedicated G/G-FO products [GSFC].
Following the project team’s status presentations, there was a 30-minute session to answer questions from the science community and discuss in more detail the mission performance, near-term operations and data processing plans, as well as to gather suggestions and feedback from the community.
Science Presentations
The remainder of the sessions in the meeting were open-submission science sessions, each of which centered around different thematic topics, including: G/G-FO analysis techniques and next generation gravity mission (NGGM) concept studies, and science analysis of mass-transport data in the fields of glaciology, oceanography, hydrology, and solid-Earth physics. As has been the case in previous years, the presenters underscored the value of interdisciplinary and multi-instrument analyses that utilize the unique complementary value of G/G-FO mass-change observations in combination with other remote sensing data (e.g., satellite altimetry or precipitation observations) and in situ data (e.g., surface deformation or ocean temperature profiles). Such hydrogeodetic combinations yield improved spatial and temporal resolutions that enable advances in Earth system process understanding, which increasingly advance societal applications of science results in support of NASA’s programmatic focus on Earth Science to Action, which seeks to “advance and integrate Earth science knowledge to empower humanity to create a more resilient world.”
Section A: GRACE and GRACE-FO Geodesy
The project status reports presented under the previous heading were part of the first section of the agenda (Session A1) as were two additional sessions: Analysis Techniques and Intercomparisons (Session A2) and NGGM and Bridging the Gap (Session A3), which focused on plans, concepts, and technologies being developed for future gravity missions. Highlights from each of these two sessions follow in the next two subsections.
Analysis Techniques and Inter-comparisons
This session featured 15 presentations by the SDS centers and ST members on progress in instrument data calibrations and novel data processing algorithms and methods, including data-fusion with other observations.
Representatives from G/G-FO processing centers presented updated gravity-field time-series data, which capitalize on improved parameterizations, better instrument error characterizations (e.g., from star cameras, accelerometers, or ranging instruments) and background models (e.g., for tides) for improved monthly mass change data and uncertainty quantification. The highly accurate LRI data provides further opportunities to identify and characterize measurement system errors, which can be exploited for G-FO data processing but is also informative in the development of the future GRACE-C mission. However, it was also shown that several metrics used in identifying gravitational errors are sensitive to the estimated satellite trajectory, and consequently a sufficient understanding of the orbital trajectory is necessary to make accurate adjustments to the gravity field based on satellite observations.
The G/G-FO data products make use of ground-based geodetic observations, such as satellite laser-ranging (SLR) to a network of dedicated SLR satellites, which can be used to extend the G/G-FO interannual data record back to ~1994 – albeit at a much-reduced spatial resolution. Additionally, SLR data provide an important validation and performance assessment opportunity for G/G-FO observations. In that regard one presenter showed results indicating the recent G-FO accelerometer updates have indeed resulted in better gravity and mass change fields. Other speakers discussed the value and potential for improvement that could be achieved by combining G-FO and SLR observations more formally to exploit the data strengths of the different observation types in an optimal way. Such approaches could reduce uncertainties in global ocean and land ice mass changes. Furthermore, deployment of stable, long-term ocean bottom pressure (OBP) recorders in the Arctic Ocean in 2022 has enabled progress on G/G-FO OBP data validation. The data from these OBP recorders are entirely independent of G/G-FO observations and are thus very valuable to assess the satellite data record. An initial comparison between 1.5 years of OBP data and various G-FO OBP products suggest excellent agreement.
The data collected from G/G-FO has a native resolution of about 300 km (~186 mi). By jointly analyzing these G/G-FO data with higher-resolution surface elevation changes from a multimission synthesis of radar and laser satellite altimeters, net mass changes can be effectively downscaled (within a Bayesian framework) to less than 20 km (~12 mi) resolution, which is sufficiently high resolution to resolve individual ice streams in Antarctica that cannot be separated using G/G-FO data alone.
NGGM and Bridging the Gap
The presenters in this session provided status-update on the GRACE-C mission, a joint project between NASA and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) [German Aerospace Center], as well as on future instrument developments and mission concepts.
The 2017 NASA Earth Science Decadal Survey Report highlighted mass-transport monitoring through gravity change as one of five designated observables (i.e., top priorities for study) in Earth observations for the next decade in collaboration with international partners. The GRACE-C project successfully passed the NASA/JPL Mission Concept Review in June 2022, and the NASA Key Decision Point B review in September 2023 and is currently in its Phase B project definition phase. GRACE-C will be a single satellite pair based on a fully redundant LRI (as demonstrated on GRACE-FO) in a polar orbit at 500 km (~311 mi) altitude. To avoid a data gap after GFO, a launch date of no later than 2028 is targeted for GRACE-C.
Similarly, GFZ has been conducting model simulation studies to determine the value of adding a second satellite pair, dubbed Next-Generation Gravity Mission (NGGM) in Europe. The experiments reveal that advanced parameterization techniques for improved de-aliasing of short-term mass variations can significantly reduce data errors and open the possibility for higher spatial and temporal resolution data products and science applications.
The technology demonstration LRI on G-FO has surpassed its performance requirements. With a LRI expected to be the primary instrument for the GRACE-C mission as well as other future GRACE-like missions, development of a new technique is required to provide long-term laser frequency knowledge to provide a scale correction factor to the geodesy measurement. The LRI-team presented updated results of a so-called scale factor measurement technique that allows the accurate determination of the laser frequency on-orbit that can meet the stringent GRACE-C mission requirements. This was achieved with a dual frequency modulation scheme, and a prototype electronics unit has been developed and tested, demonstrating performance better than the expected mission requirements.
There were also reports on progress in technology development of low-frequency optomechanical accelerometers for geodetic applications. These highly-sensitive, compact, portable – and cost-effective – optomechanical inertial sensors build upon recent advances in optomechanics to measure accelerations with small form factors. The development of a sensor with lower cost, size, weight, and power – yet with GRACE-like performance – is a major achievement as these could be integrated into cost-effective mission designs, spacecraft miniaturization, simplified architectures, as well as for the deployment of constellations of satellite pairs flying at lower altitudes.
Section B: Geophysics and Climate Science
There were five sessions included in this section of the agenda, which are summarized in the subsections below as follows: Hydrology (Session B4), Cryosphere (Session B2), Solid Earth Sciences (Session B1), Oceanography (Session B3), and Multidisciplinary Science (Session B5).
Hydrology
This session, with 12 presentations, highlighted advances in hydrology research and applications using G/G-FO data enabled by the unique value of long, uninterrupted mass change climate data record.
The topic of terrestrial water storage variations in California came up in several presentations, focusing on the see-saw swings between very wet and very dry years and the early impacts on groundwater recharge after the record-breaking snow accumulation during the 2022/2023 winter. The process of groundwater recharge – an important objective in the 2017 Earth Science Decadal Survey – is not well understood because of the challenges in observing infiltration of new water supply into the ground and the effects of rate of input, amount of input, and various aquifer characteristics. By combining observations of precipitation, snow water equivalent, surface water storage, ground surface deformation, and groundwater storage from G/G-FO, recharge behavior can be characterized in a natural experiment where source inputs are effectively not limited, but recharge capacity is limited. Results of studies shown during the meeting reveal that only a fraction of total available potential recharge can enter the aquifer, and that G/G-FO observations allow us to measure the effective aggregated recharge capacity and how it varies with several predictors. Another paper reported that subsurface water increases in California’s Sierra Nevada by 0.6 m (~2 ft) from October 2022 to June 2023, which represents 43% of the cumulative precipitation.
Several presenters reported on efforts to advance concepts to downscale G/G-FO data to bring the information closer to decision-making scales and expand water-related applications, as well as to fill gaps and expand the data record with multisensor observations. One presenter described a new spectral approach that employs wavelet multiresolution analysis to combine seasonal terrestrial water storage change data from G/G-FO with those from global navigation satellite system (GNSS) ground station networks to downscale the observations to smaller hydrological basins and to better separate processes over complex topographical terrain. This method can also be used by fusing G/G-FO and hydrological model data [e.g., from NASA’s Global Land Data Assimilation System (GLDAS) models at continental scales]. Importantly, the method yields trends and long-term signals that match G/G-FO observations – a strength of the observing system. Another approach used a statistical Bayesian framework to incorporate G/G-FO observations and Soil Moisture Change data from different available sources [e.g., NASA’s Soil Moisture Active Passive (SMAP) mission] to obtain nonparametric likelihood functions that allow for downscaling. A statistical technique called cyclostationary empirical orthogonal function (CSEOF) analysis – which is used to interpret space-time variability in a large dataset – allowed researchers to fill short data gaps (~1 year) in G/G-FO record (e.g., between 2017 and 2018 – the gap between GRACE and GRACE–FO) without having any additional data. With the support of physically-related data (e.g., precipitation and temperature), CSEOFs can be used to reconstruct water changes into the past or fill larger data gaps. Such datasets improve understanding of trends and natural variability and anticipate future trends in response to climatic changes.
Another presenter described a science study that found an apparent abrupt decline in temperate (non-ice) Terrestrial Water Storage (TWS) in 2015 to a new, lower regime that appears to be unique in the past 33 years. The triggering event for this new lower TWS regime appears to be the massive drought in Brazil in 2015. Subsequent droughts around the world (e.g., Europe, the western U.S., Canada, central Africa, and southern Brazil) have helped to keep TWS values depressed. Warm global sea surface temperatures, prevalent since 2015, have decreased rain accumulation over the continents, reducing TWS.
In the European Alps region, a G/G-FO data analysis found that glacier and ice changes are the major contributors to the observed signals. Overall, glaciers here have lost ice mass at rates between 1.4 to 2.2 Gt/year since 2002. Advances in spatial downscaling and data combinations are expected to allow for improved estimates and applications, including geological hazard monitoring.
In Northern Italy, accelerated groundwater loss has been detected using G/G-FO, well measurements, and vertical land motion observations. Since 2015, the groundwater loss has accelerated. Assuming a best-case scenario (conditions similar to 2007–2014), it could take 13–28 years for ground water storage to recover from recent long-term period of decline, thus setting the stage for prolonged drought conditions.
Since a pioneering study in 2014, it is well-established that G/G-FO observations of TWS are an effective means to estimate flood potential and flood risks due to water-saturated soil. Novel G/G-FO data processing schemes that exploit sub-monthly variations of total water storage enabled researchers to delineate basin-specific storage-discharge dynamics more accurately. They found that at submonthly timescales in many global basins, water storage (i.e., saturated soil) has more impact on whether a flood will occur than the amount of precipitation that falls.
Along the Nile River, G/G-FO data were used to monitor water changes in crucial artificial reservoirs. These data indicate that water losses through underground-seepage over the geologically highly fractured region via a complex network of shear systems, faults, and fractures, are significant and could impact the delicate water balance in the region. A separate study focusing on nearby Southern Arabia found that intense tropical cyclones (wind speeds > 64 kph or ~40 mph) have doubled in the past decade compared to the preceding two, which resulted in significant recharge of the aquifers in the study area. The findings demonstrate the ability of G/G-FO to capture recharge signals and monitor aquifer systems in poorly gauged basins and highlight the significant role of tropical cyclones in recharging aquifers in arid Arabia.
Cryosphere
The five contributions in this session reported on new ice mass balance results of the Earth’s land-ice, as well as on novel data-combinations approaches that can improve the spatial resolution over G/G-FO-only data.
The Antarctica Ice Sheet contributes to the largest sea level rise potential and remains as the largest uncertainty source in the prediction of future sea levels. Data from G-FO and the Ice, Clouds and land Elevation Satellite–2 (ICESat-2) mission have been used to track ice sheet mass and height changes in Greenland and Antarctica, respectively. By combining the strengths of G-FO (gravity or mass change) and ICESat-2, (laser altimetry) data, a more accurate and less uncertain estimate of ice sheet mass changes can be achieved. This combination has led to a proposal for an enhanced iterative algorithm for deriving Antarctic mass balance, incorporating key technologies such as altimetry, gravity measurements, Global Positioning System (GPS) satellite data, and surface mass balance models. The study utilizes an effective density map derived from ICESat-2 and tests the algorithm’s sensitivity and uncertainty with synthetic data, considering realistic physical processes and variability. This approach aims to address discrepancies in estimating ice mass loss in East Antarctica and provides important guidance for optimizing future ground measurements (i.e., GPS station positions). Another presentation focused on understanding the differences in mass change recovered by the G/G-FO and IceSat-2 missions – both in terms of spatial distributions and total magnitudes – to ultimately determine a best combined estimate of ice sheet mass change leveraging the strengths of each mission.
Temporal gravity field estimates from G/G-FO data reveal that the Antarctic ice sheet contributed approximately 6.1 mm (~0.2 in) to global sea level rise from 2002–2022, with a net loss of ~2150 GT of mass. While mass change accelerated during the GRACE era, it has decelerated during the GRACE-FO era – due to increased mass gain in East Antarctica. The deceleration is attributed to surface mass balance processes: annual precipitation and increased incidences of extreme weather events in East Antarctica, challenging predictions based on correlations with climate indices like Southern Annular Mode and El Niño Southern Oscillation.
A related study confirmed a pause in Antarctica’s mass loss, a non-accelerating mass loss in Greenland, and a steady loss from glaciers and ice caps away from the poles. The use of the LRI observations enabled novel submonthly analysis in key regions (including the Amundsen Sea Embayment of West Antarctica and the Pine Island/Thwaites basins) to gain more understanding of fast ice dynamics and their spatial extent.
While G/G-FO data span two decades, estimates of Earth’s oblateness from other satellite observations that date back to 1976 and provide a much longer data record – albeit at much coarser spatial resolution. This half-century long timeseries provides important constraints on ice mass change prior to the launch of GRACE in 2002. The data suggest that ice mass loss had already begun to accelerate by the 1990s. Recent progress in Earth system models, in conjunction with the long satellite data record, are being used to isolate trends in glacial isostatic adjustment (GIA) – which is the vertical movement of the Earth’s surface after the weight of glaciers is removed from them – and to improved estimates of ice mass loss prior to GRACE.
Solid Earth Sciences
Two presenters in this session described their efforts to evaluate signals in the G/G-FO data record associated with earthquakes. The G/G-FO data provide a unique opportunity to observe the Earth’s response to great earthquakes across diverse tectonic settings at time scales from days to decades. Using 13 earthquakes of magnitude (Mw)>8.0 over the last 20 years, it was found that elastic bulk modulus and viscosity govern large-scale coseismic and postseismic gravimetric changes, respectively. By constraining the solid Earth’s viscosity structure, improved physics-based models of long-term postseismic changes can be developed that incorporate observations from G/G-FO. The portion of the long-term gravity change signal that can be attributed to these earthquakes can then be removed from the G/G-FO data to better quantify processes related to ocean mass and hydrology changes. When physics-based models are not available, alternative statistic-based approaches can be used to remove the co- and post-seismic signature of large earthquakes (e.g., 2004 Andaman-Sumatra and 2011 Tohoku, Japan quakes) from the G/G-FO data.
As the G/G-FO data record extends into its third decade, the long time series of Earth gravity changes requires careful consideration of the solid-Earth response to contemporary surface mass changes. To isolate the gravity signature of any surface mass signal, it is becoming evident that simple elastic loading corrections are no longer sufficient. Recent advances in mantle rheology – describing and understanding the nature of Earth’s mantle – derived in mineral laboratory experiments, tidal modeling, and seismic imaging provide unequivocal evidence of anelastic contributions to solid-Earth deformation on time-scales ranging from hours to decades. New developments in the solid-Earth capabilities of JPL’s Ice-sheet and Sea-level System Model (ISSM) in the form of viscoelastic solvers for Love numbers and sea-level change was used to implement and explore the so-called Extended Burgers Material (EBM) and so resulting viscoelastic deformations between the seismic and GIA time scales. Preliminary testing with EBM rheology shows potential for a ~15–20% increase in mass change trends for some regions.
A subdecadal variation of large-scale (i.e., spanning over continental scales) gravity signals with a period of approximately six years has attracted intense interest in the geodesy and geodynamic communities. Earth’s fluid core motions, magnetic field, Earth rotation, and crustal deformations have been invoked as causes for this signal. An analysis of G/G-FO data showed that a significant part of the approximately six-year signals is in fact due to climate-related oscillation of ocean-atmosphere coupling in the Pacific and Atlantic and variations in the land water storage over Africa.
Oceanography
In the oceanography session, five presenters reported on the combination of G/G-FO, satellite altimeters (e.g., from the joint NASA–European Sentinel-6 Michael Freilich mission), and in situ ocean floats (e.g., Argo) to investigate variations in sea level and ocean circulations – e.g., see Figure 1. Other presenters discussed improvements in data processing by reducing errors in atmospheric tides that could lead to spurious trends or double-counting a subset of ocean tides and by incorporating new dedicated ocean data grids that remove geodetic signals not related to ocean dynamics (e.g., global ocean mass; large earthquake signals).
Figure 1. The top row of maps show estimates of individual components of the observed sea level trend in the northwestern Pacific from 2003 to 2016 including contributions from: land ice melt [top row, left], non-ice land water storage [top row, middle], and stereodynamic effects [top row right], which are estimated by directly combining in situ-based steric sea level (i.e., based on Argo ocean profiling floats) with the GRACE-derived ocean mass changes. The bottom row shows the sum of all of the components of sea level trend on the top two rows [bottom row, left], compared the same measurement using satellite-altimetry [bottom row, right]. These data clearly show the strong earthquake-related signature of ocean mass change east of Japan. Image credit: Felix Landerer/updated from a similar figure published in Nature’s Communications Earth & Environment.
Another presenter described how ocean mass redistribution and regional sea-level rise in the North-West Pacific marginal seas (i.e., around Japan and north of the Philippines) is impacted by seafloor deformation from earthquakes, which alter the ocean bathymetry. G/G-FO data are key to isolating these deformation effects, which in turn allows better sea level projections that can be used for planning purposes.
While long-term sea level trends are of major concern, the seasonal cycle is the dominating climate signal in ocean bottom pressure variability. Accurate representation of seasonal cycle is thus key to efforts to improve observations and models of ocean bottom pressure. Examining differences between models and observations elucidates remaining uncertainty in observations and missing physics in the models (e.g., lack of intrinsic variability due to coarse resolution, no accounting of gravitational and loading effects). This allows researchers to advance the quality of ocean mass change observations and unravel underlying dynamics.
Lastly, ocean bottom pressure observations from G/G-FO have been used to monitor transport variability of deep currents associated overturning circulation in the Northern Hemisphere (the Labrador Current) and Southern Hemisphere (Weddell Sea Bottom Water). This deepwater transport provides an important pathway for the sequestration of excess atmospheric heat and carbon from locations of water mass formation. Continuous observations of deep ocean currents provide valuable insight into Earth’s climate system. However, harsh conditions and complex recirculation transport pathways make in-situ observations of these deep flowing currents challenging.
Interdisciplinary Science
Six presenters contributed to this session. The first study revisited geodetic assumptions about measuring so-called Earth Center-of-Mass (CM) motions that can be traced to planetary-scale seasonal and long-term variations of water cycling between the land the oceans. Differences in SLR and G/G-FO estimates of CM estimates can be helpful to refining global circulation models. In a related study, G/G-FO and SLR data have been used to pin down the causes and origin of polar motion, particularly the mass component related to gravity changes. A novel hybrid SLR/GRACE time-variable gravity approach closely aligned well with the hydrological excitation in independently polar motion.
Errors in GIA corrections impact altimeter estimates of sea level and ocean mass estimates and the so-called sea level budget. Choices in modeling GIA, particularly based on paleoshoreline sites, affect Earth’s viscosity structure and GIA response, influencing global mean sea level (GMSL) budget closure. Even minor Earth model changes can have notable effects on the alignment of GMSL (altimetry), ocean mass (GRACE), and steric sea level change (Argo). Thus, future research needs to focus on accounting for the complex three-dimensional structure of the solid Earth to improve GIA corrections and more accurately isolate contemporary mass change in the G/G-FO data record.
Despite GIA uncertainties, G/G-FO, in combination with sea level measurements from altimetry, provide a unique capability to measure changes in ocean heat content. The ocean takes up nearly 90% of Earth’s current energy imbalance, signifying their important role in overall planetary heating. Two presenters reported consistent findings of ocean heat uptake rates of 0.9 W/m2 based on the indirect geodetic satellite measurements of sea level and ocean mass – a value that is entirely independent of other techniques and thus provides crucial validation – see Figure 2. In addition, the results indicated the overall heating rate over the last decade has increased, which means heat accumulation is accelerating.
Figure 2. This graph shows different estimates of ocean heat uptake (OHU), measured with in-situ ocean floats (orange curve), from top-of-the-atmosphere radiance satellite measurements of Earth energy imbalance (EEi) (black curve), and from geodetic satellites, i.e., G/G-FO and altimeters (blue curve). The satellite measurements agree well and show an increasing energy imbalance over the last 20 years. Image credit: Felix Landerer/originally in Geophysical Research Letters.
Summary
The hybrid 2023 G-FO STM brought together over 120 international participants and showcased a broad range of science results and applications that are supported and uniquely enabled by the satellite gravimetry-based mass change observations. The G-FO data now span nearly six years and continue to provide crucial insights into how Earth’s hydrosphere, including sea level, ocean currents, and water distribution over land, is changing. The G/G-FO data are extending important climate data records (e.g., the Greenland and Antarctic ice mass time-series, ocean mass sea level data, and TWS over land) into their third decade. The upcoming GRACE-C mission will build on and expand this mature data record, which is increasingly enabling important applications in support of water-related decision making and planning.
The G-FO project team remains focused on providing the mass-change data record at a level of performance consistent with that of GRACE. As the current Solar Cycle 25 increases towards its anticipated maximum in 2024, the team continues to improve the mission’s accelerometer data products in support of that goal. Corresponding data improvements in the monthly gravity and mass change products will be released early 2024.
The next G-FO STM will be held from October 8–10, 2024 in Potsdam, Germany, organized by GFZ. Check the GRACE website for specific details as the date gets closer.
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Webb finds most distant known galaxy
Using the NASA/ESA/CSA James Webb Space Telescope, scientists have found a record-breaking galaxy observed only 290 million years after the big bang.
Over the last two years, scientists have used the NASA/ESA/CSA James Webb Space Telescope to explore what astronomers refer to as Cosmic Dawn – the period in the first few hundred million years after the big bang where the first galaxies were born. These galaxies provide vital insight into the ways in which the gas, stars, and black holes were changing when the universe was very young. In October 2023 and January 2024, an international team of astronomers used Webb to observe galaxies as part of the JWST Advanced Deep Extragalactic Survey (JADES) programme. Using Webb’s NIRSpec (Near-Infrared Spectrograph), scientists obtained a spectrum of a record-breaking galaxy observed only two hundred and ninety million years after the big bang. This corresponds to a redshift of about 14, which is a measure of how much a galaxy’s light is stretched by the expansion of the Universe.
This infrared image from Webb’s NIRCam (Near-Infrared Camera) was captured as part of the JADES programme. The NIRCam data was used to determine which galaxies to study further with spectroscopic observations. One such galaxy, JADES-GS-z14-0 (shown in the pullout), was determined to be at a redshift of 14.32 (+0.08/-0.20), making it the current record-holder for the most distant known galaxy. This corresponds to a time less than 300 million years after the big bang.
In the background image, blue represents light at 0.9, 1.15, and 1.5 microns (filters F090W + F115W + F150W), green is 2.0 and 2.77 microns (F200W + F277W), and red is 3.56, 4.1, and 4.44 microns (F356W + F410M + F444W). The pullout image shows light at 0.9 and 1.15 microns (F090W + F115W) as blue, 1.5 and 2.0 microns (F150W + F200W) as green, and 2.77 microns (F277W) as red.
These results were captured as part of spectroscopic observations from the Guaranteed Time Observations (GTO) programme 1287, and the accompanying MIRI data as part of GTO programme 1180.
Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.
[Image description: A field of thousands of small galaxies of various shapes and colors on the black background of space. A bright, foreground star with diffraction spikes is at lower left. Near the image center, a tiny white box outlines a region and two diagonal lines lead to a box in the upper right. Within the box is a banana-shaped blob that is blueish-red in one half and distinctly red in the other half. An arrow points to the redder portion and is labeled “JADES GS z 14 – 0”.]
See the moon and Saturn meet in the night sky early on May 31
Next-Generation Radar Will Map Threatening Asteroids
When the Arecibo Observatory dish in Puerto Rico collapsed in 2020, astronomers lost a powerful radio telescope and a unique radar instrument to map the surfaces of asteroids and other planetary bodies. Fortunately, a new, next-generation radar system called ngRADAR is under development, to eventually be installed at the 100-meter (328 ft.) Green Bank Telescope (GBT) in West Virginia. It will be able to track and map asteroids, with the ability to observe 85% of the celestial sphere. It will also be able to study comets, moons and planets in our Solar System.
“Right now, there is only one facility that can conduct high-power planetary radar, the 70-meter (230-foot) Goldstone antenna that is part of NASA’s Deep Space network,” said Patrick Taylor, the project director for ngRADAR and the radar division head for the National Radio Astronomy Observatory. “We had begun this process of developing a next generation radar system several years ago, but with the loss of Arecibo, this becomes even more important.”
The iconic Arecibo Radio Telescope, before its collapse in 2020: Credit: UCFPlanetary radar can reveal incredibly detailed information about the surfaces and makeup of asteroids, comets, planets, and moons. The ngRADAR system could provide unprecedented data on these objects. In fact, a recent test with a low-power prototype of ngRADAR at the GBT produced some of the highest resolution planetary radar images ever captured from Earth. But the hallmark of the new system will be seeking out near Earth asteroids and comets to evaluate any hazard they might present to our planet.
“Radar is really powerful in determining the orbits of these asteroids and comets,” Taylor told Universe Today in an interview, “and the new system will deliver very precise data that will allow us to predict where these small bodies will be in the future. That will be one of the highest priority uses for the next generation radar system, where we can track and characterize near-Earth asteroids and comets to evaluate any hazard they might present to Earth in the future.”
A Radar FlashlightUsually, radio telescopes collect weak light in the form of radio waves from distant stars, galaxies, and other energetic astronomical objects – including black holes or cold, dark objects that emit no visible light. While radio telescopes don’t take pictures in the same way visible-light telescopes do, the radio signals detected are amplified and converted into data that can be analyzed and used to create images.
But radio telescopes can also be used to transmit and reflect radio light off planetary bodies in our Solar System. This is called planetary radar or Solar System radar.
This collage shows six planetary radar observations of 2011 AG5 a day after the asteroid made its close approach to Earth on Feb. 3, 2023. With dimensions comparable to the Empire State Building, 2011 AG5 is one of the most elongated asteroids to be observed by planetary radar to date. Credit: NASA/JPL-CaltechWhat is planetary radar and how does it work?
“Essentially we have a flashlight that works in radio waves,” Taylor explained. “Our narrow flashlight beam does not look at the whole sky, but we point it in a very precise location – the surface of an asteroid or moon. We know very well what our flashlight’s properties are, so we know exactly what we send out. When we receive the echo back from wherever we pointed our flashlight, we analyze that signal and see how it changed compared to what we transmitted.”
That’s what makes planetary radar so powerful and different from any other type of astronomy.
“When astronomers are studying light that is being made by a star, or galaxy, they’re trying to figure out its properties,” Taylor said. “But with radar, we already know what the properties of the signals are, and we leverage that to figure out the properties of whatever we bounced the signals off of. That allows us to characterize planetary bodies – like their shape, speed, and trajectory. That’s especially important for hazardous objects that might stray too close to Earth.”
In the past, planetary radar has been used to image asteroids, but also precisely measure the position and motion of the planets, allowing us to land spacecraft on Mars and to explore the outer Solar System. The technique has also made surprising discoveries, such as the finding the presence of water ice on Mercury.
The 70m telescope at the Goldstone Deep Space Communications Complex in California’s Mojave Desert. (NASA/JPL)Because radio waves are much longer than visible light waves, radio astronomy requires large antennas. The 70-meter Goldstone antenna located in California’s Mojave Desert, is primarily used to communicate with spacecraft as part of NASA’s Deep Space network. But it is also frequently used for planetary radar to study near Earth asteroids, and — as previously mentioned — is the only facility currently available to perform high-power planetary radar. (There are, however, are smaller facilities that can perform planetary radar, including smaller telescopes at the Goldstone site and a few in Australia, but they do not have the same scale of transmitter power as the Goldstone 70-meter dish.) Previously, the workhorse for planetary radar was the 1,000-foot-diameter (305 meters) Arecibo Observatory, which was about 20 times more sensitive and could detect asteroids about twice as far away than the Goldstone 70 meter.
However, because Arecibo’s dish was stationary and built inside a round sinkhole, it was fixed to the Earth and could only view whatever part of the sky happened to be straight overhead. That meant Arecibo’s dish could only see about one-third of the sky. Goldstone is fully steerable, can see about 80 percent of the sky, can track objects several times longer per day, and can image asteroids at finer spatial resolution.
ngRADARThe Robert C. Byrd Green Bank Telescope is the world’s largest fully steerable radio telescope. The maneuverability of its large 100-meter dish allows it to quickly track objects across its field of view, and see 85% of the sky.
The GBT’s new radar system will introduce a high-resolution tool that will be a vast upgrade, collecting data at higher resolutions and at wavelengths not previously available. Scientists at GBT and the National Radio Astronomy Observatory (NRAO) are also developing advanced data reduction and analysis tools that have not been available before, providing astronomers with unprecedented planetary radar capabilities.
To test out the proof of concept, Taylor and his team worked with the company Raytheon — a long-time developer of radar systems for both the military and science applications — to build a small version of the transmitter, with a lot less power.
“Our friends at Raytheon built a transmitter that could output 700 watts, so about half the power of a microwave oven,” Taylor said. “Ultimately, we want to build a system with 500 kilowatts, so up by a factor of a thousand. But even with 700 watts, we were able to do some really impressive observations.”
Radar image of the Apollo 15 landing site. Credit: Raytheon/NRAO.GBT’s planetary radar was aimed at the Moon, specifically at the Apollo 15 landing site in Hadley Rille, and at the giant Tycho Crater’s surface, and radar echoes were received with NRAO’s ten 25-meter VLBA antennas. At Tycho, the crater was captured with 5-meter resolution, showing unprecedented detail of the Moon’s surface from Earth. Taylor said the resolution with the ngRADAR prototype approached the optical resolution on Lunar Reconnaissance Orbiter, taking images with its high-resolution cameras from orbit around the Moon.
“The images of the crater floor were actually breathtaking,” Taylor said. “It’s pretty amazing what we’ve been able to capture so far, using less power than a common household appliance.”
A Synthetic Aperture Radar image of the Moon’s Tycho Crater, showing 5-meter resolution detail. Image credit Raytheon.Additionally, the prototype radar also detected a potentially hazardous asteroid named (231937) 2001 FO32, which happened to be flying past Earth at about six times more distant than the Moon during their radar pings. The asteroid is considered potentially hazardous because of its size, approximately 1 kilometer in diameter, along with how close it can get to Earth, at just over 2 million kilometers away during the observations in 2021. The asteroid’s detection appeared as a spike in their data.
“Just from the spike in our data, we can now figure out how fast this object is moving, determine its orbit, and figure out its trajectory in the future,” Taylor explained. “We can determine its impact risk and assess how much of a hazard it is, and even constrain its spin state, its size, its composition, its scattering properties, and so on. So, even though the data spike doesn’t look like much, that one little detection can tell you a lot of information about the asteroid.”
Radar signals transmitted by the GBT will reflect off astronomical objects, and those reflected signals will be received by the Very Long Baseline Array (VLBA), a network of ten observing stations located across the United States.
“The idea is for GBT is to do the transmitting almost constantly and the VLBA — either all ten of those or any subset of those telescopes — doing the receiving,” Taylor said. “This new system will allow us to characterize the surfaces of many different objects in a different frequency or wavelength that hasn’t been used before.”
Next: Part 2 of this series will look at the details of ngRADAR, the history of planetary radar, and take you up close to the GBT.
The post Next-Generation Radar Will Map Threatening Asteroids appeared first on Universe Today.
Astronaut's diary found among fallen Columbia space shuttle debris added to National Library of Israel
Removing Race from Lung Function Tests Could Benefit Millions of Black Americans
A new study shows that hundreds of thousands more Black people in the U.S. would qualify for a lung disease diagnosis and disability payments if lung-function measurements weren’t adjusted for race