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Results from a spectral scan survey of the central molecular zone of the nearby starburst galaxy NGC 253. This exploration was conducted as part of the ALMA Large Program, ALMA Comprehensive High-resolution Extragalactic Molecular Inventory, ALCHEMI, by S. Martin, N. Harada, and J. Mangum et al. (Harada et al. 2024, ApJSS, 271, 38)

Upcoming Events

American Astronomical Society 244
June 9 - 13, 2024 | Madison, WI

International Symposium on Molecular Spectroscopy
June 17 - 21, 2024 | Urbana-Champaign, IL

International Microwave Symposium
June 17 - 21, 2024 | Washington, DC

IAU General Assembly XXXII
August 6 - 15, 2024 | Cape Town, South Africa

NRAO Scientist Urvashi Rau delivers prestigious lecture at ISMRM conference

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NRAO Scientist Urvashi Rau and ETH Zurich Professor Klaas Pruessman co-presented a plenary lecture at the International Society for Magnetic Resonance in Medicine (ISMRM) 2024 Conference in Singapore. Their talk, entitled From Innerspace to Outer Space: How? A Point-Counterpoint Exchange and Discussion focused on the cross-section between radio astronomy and magnetic resonance imaging. The plenary session highlighted similarities, unique challenges, and solutions bridging medical and astronomical imaging. Leon Axel of the NYU Grossmann School of Medicine, whose own career has spanned both disciplines, introduced the session. A recording is available from the conference website (watch from 33:30 onwards).

Compressed sensing and parallel imaging have been two of the most impactful concepts in magnetic resonance imaging over the past two decades, enabling significant reductions in scan times while preserving imaging quality at clinically acceptable levels. These same concepts are fundamental to radio interferometric imaging as well, where the equivalent techniques of iterative deconvolution and mosaic imaging have been mainstream in our field for several decades. A particularly interesting synergy comes from considering how and when each field has approached the problem of undersampled indirect imaging, because at any given time an area of current research in one field could have effectively been a long-solved problem in the other. Looking forward, as both fields explore new frontiers, especially using artificial intelligence and high performance computing, there is considerable potential for sharing lessons learnt.

The International Society for Magnetic Resonance in Medicine is an international, nonprofit, scientific association whose purpose is to promote communication, research, development, and applications in the field of magnetic resonance in medicine and biology and other related topics and to develop and provide channels and facilities for continuing education in the field. Its multidisciplinary membership of over 8,000 consists of clinicians, physicists, engineers, biochemists, and technologists.

NRAO's Technology Transfer Office and Algorithm R&D Group have hosted the Cells to Galaxies initiative with conferences in 2019 and 2021, and an online lecture series in 2020 to collaborate on similarities in imaging techniques across the two fields. NRAO and NYU have since arranged cross-disciplinary educational presentations as part of the NRAO colloquium series, the i2i conference in 2023, and this year at the ISMRM. These events have helped develop a collective understanding of where the state of the art is in image reconstruction in both domains, highlighting areas of potential future collaboration.

Dr. Rau does algorithm research on wideband imaging and interference mitigation for radio interferometry. At NRAO, she leads the international team of scientists and software engineers who develop the Common Astronomy Software Applications (CASA) package used for data processing by the Atacama Large Millimeter/submillimeter Array and the Karl G. Jansky Very Large Array. Dr. Klaas Pruessmann is a Professor and head of the Institute of Biomedical Engineering at ETH Zurich, and is known for his pioneering work in parallel imaging in Magnetic Resonance Imaging. Dr. Leon Axel is a radiologist and scientist at the Center for Advanced Imaging Innovation and Research at NYU, known for his long track record of innovations in cardiac MRI. The ISMRM session was conceived and organized by Dr. Seena Dekharghani from Montefiore Medical Center and NYU.

The ALMA Wideband Sensitivity Upgrade (WSU)

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The ALMA Wideband Sensitivity Upgrade (WSU) is a major initiative to enhance ALMA science potential, instrumentation, and software systems for sustained, high-capability operations through the 2030s. The WSU will dramatically increase the observational capabilities of ALMA and translate to new opportunities across a range of scientific topics. The initiative is well underway, with planned completion of core elements by the end of this decade.

The ALMA 2030 Development Roadmap, a Board-approved vision for ALMA sustainability and enhancement, identified the WSU initiatives as top priority. The goals of the WSU include an increase in bandwidth by a factor of 2 (ultimately x4), as well as increased digital sensitivity and improved sensitivity of key receivers.

The initial and most critical stage of the WSU is the upgrade of the signal chain for increased bandwidth and improved digital efficiency. Future stages will implement receivers with broader bandwidth and higher sensitivity. Nearly every hardware component in the existing signal chain is being replaced in this first stage and includes the IF Switch, Digitizer, Data Transmission System, a new Fiber Optic Cable, and a major new digital correlator - the Advanced Technology ALMA Correlator (ATAC) and a new Total Power GPU Spectrometer (TPGS). ATAC will be located at the Operations Support Facility (OSF) at 3000 m elevation rather than the Array Operations Site at 5000 m where the current Baseline Correlator resides and will provide improved power efficiency and ease of support. The relocation requires creation of a new correlator room in the OSF. The WSU also includes a major upgrade of both online and offline software systems, including a new calibration and imaging pipeline and data processing system. The signal chain upgrade will include at least one new, high bandwidth receiver, Band 2. Additional high bandwidth receivers with improved sensitivity are expected to follow. The entire ALMA partnership is contributing to the success of the WSU; North American contributions to the new signal chain include ATAC, the new OSF Correlator Room, and collaboration on the Digital Transmission System (DTS) with East Asia. A project to develop a prototype of the Band 6v2 receiver is also in progress at NRAO.

An initial project review for the WSU is scheduled for July of this year and several subsystem preliminary design reviews will be held over the coming few months. Future NRAO Newsletter articles will highlight science capability enhancements and key milestones for the WSU.

ALMA Program News


Image Credit - Pablo Carrillo (ALMA)

ALMA Observing Status

The array continues Cycle 10 observations. ALMA is now in configuration C-5. Altiplanic skies have prevailed.


New science opportunities enabled by the ALMA Wideband Sensitivity Upgrade were discussed at the recent ISSTT Meeting in Charlottesville. The full program with slides and recordings will be opened to the public June 1, 2024. A meeting on Spatio-spectral Modeling of Interferometric Data: Preparing for the Wideband Era was held in Charlottesville at the end of May.

The ALMA Cycle 11 Call for Proposals closed on April 25, 2024, at 15:00 UT. Results will be communicated to PIs in August 2024. Results after closing the Cycle 11 Call for Proposals (CfP) show the community submitted 1,712 proposals to make observations with ALMA, marking a slight increase from the previous year's Cycle 10 (1,679). Each proposal will now go through an anonymous selection process to determine which projects will be observed in this cycle. The requested observing time for the 12-m array continues to increase steadily: 31,610 hours stands as the most time ever requested in a single cycle. The observing time requested is 7.4 times larger than the amount of time available. See the ALMA announcement.

AAS 244

NAASC staff will be attending the upcoming American Astronomical Society Meeting 244 in Madison, WI June 9-13. Please visit the NRAO exhibit booth to talk with staff and learn more about ALMA.

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Cool Stars 22

The conference series "Cool Stars, Stellar Systems and the Sun" (CS 22) will be held in a hybrid format in San Diego from June 24 to 28, 2024, 44 years after its first edition in Cambridge (USA), with partial North American ALMA Science Center support. Several hundred international experts in Low-Mass Stars, Solar Physics, and Exoplanets meet every other year to exchange ideas in a cross-disciplinary and friendly environment. Virtual registration is open until June 10, 2024.

Resources for Analysis and Interpretation of ALMA Data

The NAASC compiled a non-exhaustive list of available tools and codes which may be used for scientific analysis and interpretation of ALMA data. We encourage community members to contact us if they would like to suggest other resources to be included in the list.

Upcoming Meetings

NRAO Participates in Spectrum Week (May 13-17, 2024)

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The second annual NSF Spectrum Week was held in Arlington, VA from May 13-17, 2024, bringing together six major spectrum events. The week featured three programs funded through the NSF Spectrum Innovation Initiative (SII) program (NRDZ, SpectrumX, and SWIFT). NRAO has received grants from all three of these programs over the past four years. In addition, Spectrum Week was co-located with IEEE DySPAN 2024, the National Spectrum Management Association (NSMA) Annual Conference, and the Networking and Information Technology Research and Development (NITRD) Wireless Spectrum R&D Interagency Working Group (WSRD IWG). The week concluded on Friday with a workshop on the National Spectrum Strategy R&D Plan.

NRAO was involved in many aspects of Spectrum Week, starting with a poster session by Bang Nhan (RFI Scientist) on the Operation Data Sharing (ODS) system being built by NRAO. His poster, entitled "Operational Data Sharing (ODS) Framework - A coexistence strategy for radio observatories in the broadband era", described early experiments with SpaceX and how the ODS system will help NRAO telescopes to share spectrum with satellite operators. NRAO Office of Diversity and Inclusion (ODI) was represented with an informational table and a well-attended session on Broader Impacts ("Spectrum Education") featuring work by Valarie Bogan (Curriculum Specialist) and Anja Fourie (Broader Impacts Lead).

On Thursday, Chris De Pree (Deputy Spectrum Manager) was a panelist for a session entitled "NRDZ: Spectrum Sharing Field Experiments". In his comments, he described the relationship between NRAO and SpaceX as an example of trust-building and experimentation, and a model for spectrum coexistence.

The VLA Sky Survey (VLASS) Update

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Observing for VLASS3.2, the second half of the third epoch of VLASS, began on April 29th and will continue through to October 7th. Quick Look images are being made available as they pass quality assurance, typically 2-5 weeks after observation. These are the final observations of VLASS as originally planned; however, a community-led proposal for a 4th epoch has been received and will be reviewed in September 2024. The VLASS team has also begun to produce single epoch continuum images (SECIs), starting with VLASS2.1. These images are of substantially better quality than the Quick Look images released previously, with self-calibration applied, deeper cleaning and in-band spectral index information (see the SE Continuum User's Guide for details of the images and how to obtain them). About 10% of the sky has currently been reimaged in this way. Progress can be viewed on the HiPS viewer by clicking the VLASS2.1 SE button.

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Shown at left are normalized histograms of the spectral indices of the first 136,000 VLASS source components (blue) and the 2600 matches to the SDSS DR16 quasar catalog (Lyke et al. 2020) in red. As expected, the quasars have a flatter mean spectral index, showing that the VLASS in-band spectral indices can be usefully employed to help distinguish quasar cores from other types of radio source component.

24B Semester Proposals

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Image Credit - Bettymaya Foott

The NRAO has completed the Semester 2024B proposal review and time allocation process for the Very Large Array (VLA) and the Very Long Baseline Array (VLBA).

For the VLA, the A-configuration will be available in the 24B semester, and 201 new proposals were received by the 31 January 2024 submission deadline. These included four large and twenty-two time critical (triggered) proposals. The oversubscription rate (by proposal number) was 2.3 and the proposal pressure (hours requested over hours available) was 2.6, both of which are similar to recent semesters.

For the VLBA 65 new proposals were submitted. The oversubscription rate was 3.3 and the proposal pressure was 2.4, slightly higher than past semesters.

Proposals submitted to the GBO were assessed through the same process. Eighty-two proposals for the GBT were received for the 24B Semester. The oversubscription rate is 2.0 and the proposal pressure is 6.3, much higher than past semesters due to nine Large proposals. For information on proposals for GBT observations see the GBO website.

There were thirty-five joint proposals submitted that requested time with our partner observatories: ALMA, JWST, HST, Swift, Chandra, XMM-Newton, and NICER.

The proposals were reviewed for scientific merit by ten Science Review Panels (SRPs) and for technical feasibility by NRAO staff. These reviews were completed in February - March 2024 and then considered by the Time Allocation Committee (TAC) during a face-to-face meeting on 16-17 April 2024. The TAC - comprising the 10 SRP chairs - was charged with recommending a science program for Semester 2024B to the Observatory Director. The recommended program was reviewed and approved on 1 May 2024.

A disposition letter was sent to the Principal Investigator and Co-Investigators of each proposal on 10 May 2024 and a TAC report containing information for proposers and observers, including statistics and telescope pressure plots, was released the same day. The approved science program for the VLA and the VLBA has been posted to the NRAO science website. The authors, title, abstract, and scheduled hours for each approved proposal can be accessed from the Proposal Finder Tool. The NRAO welcomes community feedback on the proposal review and time allocation process. Please provide such feedback via the Proposal Review department of the NRAO Helpdesk.

ngVLA Project News

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Follow the Monarchs: A Journey to Explore the Cosmos at (Sub)milliarcsecond Scales with the ngVLA

This ngVLA international science conference will be held November 11-14 in person in the UNESCO World Heritage site of Morelia, Mexico. The conference will highlight and explore the novel scientific opportunities that will unfold with the unprecedented angular resolution and sensitivity capabilities offered by this new flagship facility. The conference will coincide with the Monarch butterflies completing their migration journey from Canada and the US to the mountains surrounding Morelia. Abstract submission for oral presentations closes July 8th, and early registration is available until September 1st. Both abstract submission and registration are now open.

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A Coherent View of Atomic and Molecular Gas from Infrared to Radio Wavelengths

Graphic by Jeff Hellerman

This IAU Focus Meeting 2 will be held August 6-7 in person in Cape Town, South Africa at the XXXII International Astronomical Union (IAU) General Assembly. The meeting will explore how the work taking place at existing facilities is shaping our understanding of the interstellar medium structure and feedback in our own Milky Way and external galaxies, and how this work is re-framing the science that will be addressed by the remarkable capabilities of future radio observatories. An exciting program of oral presentations has been announced.

ngVLA Science - Cold Molecular Gas in z > 6 QSO Hosts

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Above: VLA CO(2-1) detection of a z=6.9 QSO host after 30 hours. An ngVLA detection would take ~15 minutes. Right: z>~6 QSO hosts show significantly higher global gas excitation compared to local gas-rich QSO hosts. Credit: Kaasinen et al. (2024)

For the last two decades, luminous z>~6 QSOs have challenged our understanding of how supermassive black holes (SMBHs) grow and evolve together with their host galaxies (e.g., Fan et. al. 2023). To understand this coevolution, the hosts have been observed with ALMA and VLA, revealing higher SFRs and more compact cold gas reservoirs than for local gas-rich QSO hosts. Yet the conditions within these cold gas reservoirs remain uncertain. ALMA observations are now revealing the warm/dense molecular gas via high-J CO transitions (J>5), but the VLA still provides the best view of the cold, diffuse molecular gas via the low-J CO transitions.

In Kaasinen et al. (2024), we analyzed the three highest-z CO(2-1) observations to date. We detected CO(2-1) in the highest redshift QSO, J2348-3054 at z=6.9, revealing a molecular gas mass of ~10^10 Msun (see figure). For the other two QSO hosts, P036+03 and J0305-3150, we detected no significant CO(2-1) emission, implying that CO(2-1) is fainter than expected from the line ratios of previously observed z~6 QSO hosts. Combining our results with nine CO(2-1)-observed, z~6 QSOs in the literature, we find that these QSO hosts exhibit much higher line ratios (see figure) and harbor more massive gas reservoirs than even the most IR-luminous, gas-rich local galaxies. These differences, combined with the higher SFRs and smaller intrinsic sizes, imply that z>~6 QSO hosts contain denser and (likely) more turbulent molecular gas, illuminated by stronger interstellar radiation fields than found in nearby galaxies.

But the sparse coverage of molecular gas tracers at z > 6 still leaves open questions. How warm, dense, and turbulent is the molecular gas? To what extent are these conditions governed by the radiation from the SMBH versus newly formed stars? Answers require well-sampled CO excitation ladders and dust spectral energy distributions, for statistical samples of high-z QSO hosts.

Critically, the ngVLA will anchor their CO excitation via observations of the faint low-J CO emission. Taking our z=6.9 QSO host as an example, the ngVLA will detect the CO(1-0) and CO(2-1) emission in just ~1.5 hours and ~15 minutes, respectively, and resolve CO(2-1) at ~0.1" in 15-30 hours. Such ngVLA observations are crucial for revealing the impact of the central SMBH, constraining the turbulence of cold gas, and hence advancing our understanding of galaxy and SMBH growth.

Since 2015 the acronym ngVLA has appeared in 1100+ publications indexed in the SAO/NASA Astrophysics Data System. This article continues a regular feature intended to showcase some of those publications. We are especially interested in showcasing work done by early-career researchers. The collection of showcase articles can be viewed online. Anyone wishing to volunteer to author a feature should contact Joan Wrobel.

20th Synthesis Imaging Summer School Workshop

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Photo courtesy of Jeff Hellerman, NRAO/AUI/NSF

The Synthesis Imaging Summer School returned to Socorro, NM for an in-person workshop. The school took place on May 15-22, 2024. The school covered fundamental and advanced lectures on aperture synthesis theory and techniques, data calibration, imaging and analysis methods, along with 1.5 days of tutorials on handling VLA, VLBA, and ALMA data. Watch for future announcements in the Newsletter for opportunities on data reduction, workshops, and other topical meetings.

Users Committee Meets in Green Bank

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The NRAO/GBO Users Committee met in Green Bank during May 2024. The Users Committee (UC) is made up of users and potential users of NRAO and GBO facilities from throughout the scientific community. It advises the NRAO and GBO Directors and the Observatory staff on all aspects of Observatory activities that affect the users of the telescopes. This committee, which is appointed by the NRAO and GBO Directors, meets annually.

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The Users Committee welcomes feedback from the astronomical community via the available web form.

Left: Users Committee members tour the Robert C. Byrd Green Bank Telescope in West Virginia. Thanks to Sophie de St Georges, Brenne Gregory, Evan Smith, and Bryan Jenkins for their outstanding tour of the facilities and to the Green Bank staff for hosting the meeting.

Marian Pospieszalski to receive 2024 Microwave Theory and Technology Society Pioneer Award

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NRAO Scientist Marian Pospieszalski will be awarded the 2024 Microwave Pioneer Award at the International Microwave Symposium in Washington, D.C., June 2024. The award cites his 1989 paper on "Modeling of noise parameters of MESFETs and MODFETs and their frequency and temperature dependence" in IEEE transactions on microwave theory and techniques.

The Microwave Pioneer Award recognizes an individual or team for outstanding and pioneering technical contributions that advanced microwave theory and techniques. These must be described in an archival paper published at least 20 years prior to the year of the award.

Marian W. Pospieszalski was awarded the M.Sc. and D.Sc. degrees in electrical engineering from the Warsaw Institute of Technology, Warsaw, Poland, in 1967 and 1976, respectively.From 1967 to 1984 Dr. Pospieszalski was with the Institute of Electronics Fundamentals, Warsaw University of Technology (WUT), during which time he held visiting positions with the Electronics Research Laboratory, University of California at Berkeley (1977-1978), the National Radio Astronomy Observatory (NRAO), Charlottesville, VA (1978-1979), and the Department of Electrical Engineering, University of Virginia, Charlottesville VA (1982-1984). Since 1984, he has been with the NRAO Central Development Laboratory.

NRAO Remembers Mark Gordon (1937-2024)

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Mark A. Gordon, NRAO Emeritus Scientist and a pioneer of millimeter-wave astronomy, passed away on Saturday, April 27, 2024. Mark was the first Assistant Director of Tucson Operations during its most influential years and was a key contributor to the concepts for the Millimeter Array, the predecessor of ALMA.

Mark was born in 1937 and was a graduate of Yale University and the University of Colorado. He joined NRAO in 1969 and contributed to the development of the 140 Foot Telescope, including the design of the operator’s console that was in use for most of the life of the telescope. From 1973 to 1984, Mark was the first AD for Tucson Operations during the time that the 36 Foot Telescope essentially founded the field of millimeter-wave molecular spectroscopy. Mark is credited with establishing the 36-Foot as a reliable and highly productive NRAO user facility and originated the plan to upgrade the 12 Meter Telescope in 1984. This upgrade greatly improved the surface accuracy and thermal stability of the telescope and provided it with a standard focal ratio, which added many more years of high scientific productivity. Mark was also the project manager for the 25-meter Millimeter Wave Telescope proposed for Mauna Kea and was on the technical committee responsible for the design of the VLA antennas. In 1993, he became the first Division Head for Chile for the Millimeter Array (MMA), recommended that the array be sited in Chile, and developed an operations plan with estimated costs for a Chile-based facility, laying the foundation for the eventual Atacama Large Millimeter / submillimeter Array (ALMA).

Mark was an expert in radio recombination lines, and co-author with R. L. Sorochenko of Radio Recombination Lines, their Physics and Astronomical Applications. Mark also authored the book Recollections of Tucson Operations, The Millimeter-Wave Observatory of the National Radio Astronomy Observatory, which is one of the best accounts available of the early history of millimeter-wave astronomy.

Mark was a generous and prolific contributor to the NRAO Archives. The finding aid to his contributions may be found in the NRAO archives.

Mark was gracious with an excellent sense of humor. He will be missed as a colleague, member of the NRAO staff, and pioneer of millimeter-wave astronomy.

NRAO Remembers Campbell Wade (1930-2024)

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Campbell (Cam) M. Wade, Jr., former director of the Very Large Array, passed away in May 2024, in New Mexico.

Cam received his PhD from Harvard in 1958, where his thesis was entitled A 21-cm study of an expanded H-II region. He then spent a number of years as a postdoc at CSIRO (1957-1959), where he worked on Fornax A with the then new Parkes dish. He then came to NRAO Green Bank in 1960, serving as a mentor to young scientists in the 1960s, and working on the Green Bank Interferometer. He used the interferometer for observations of Cygnus A; Barry Clark and Dave Hogg worked on the astrometry.

Cam was involved with the VLA design team from its inception, and was heavily involved in the VLA site selection. When construction got underway, Cam was involved with the VLA post-processing group, and followed them to Socorro in 1976. There he did significant work on the reduction of polarization observations.

On the completion of VLA construction, Cam served as VLA director from 1978-1980, after which he continued as a staff scientist. He also played a major role in the selection of antenna sites for the Very Long Baseline Array, and wrote the first version of DOPSET, calculating the absolute (sky) frequencies given a position, an epoch, a rest frequency, and velocity information.

Cam's initial memo on the VLA, widely viewed as the real starting point for the VLA, is available. Interviews with Cam Wade can be found in the NRAO archives.

With contributions from Barry Clark, Paul Vanden Bout, Ellen Bouton, Ken Kellermann, and Rick Perley.

From the Archives

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About this month's photo: 2001 New Mexico summer students. Front row (left to right): Stacy Teng, Christina Murray, Katie Devine, Marjorie Frankel, Jennifer Donley, Bhasker Moorthy, Diane Wong. Back row (left to right): Matthew Kunz, Jason Adelstein, Daniel Perley, Michael Fine, Aaron Boley, James Anderson.

For over six decades, NRAO has welcomed summer students to our sites to work on a wide variety of research projects with NRAO staff mentors. Our 2024 class of 36 students will participate in a rich and unique research and professional development experience. The program kicked off with the "Radio Astronomy Bootcamp," a week-long workshop in Green Bank with lectures and hands-on observing. Students will work on their research in Green Bank, Charlottesville, and Socorro under the supervision of their mentors. Since its inception in 1959, the summer student program has engaged over 1,300 early career people in scientific research, and many NRAO summer students have gone on to distinguished careers in astronomy and other physical sciences.

From the Archives is an ongoing series illustrating NRAO and U.S. radio astronomy history via images selected from our collections of individuals' and institutional papers. If readers have images they believe would be of interest to the Archives, please contact Ellen Bouton.

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