Radio Astronomy and Imaging

Radio Astronomy and Imaging

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So, I've been starting to investigate radio astronomy, and am wondering about if certain things are possible from an amateur standpoint. I was looking at this powerpoint(that discusses building a tiny radio telescope), .

On Slides 11, 12, and 13, it shows various radio emissions overlayed on the orion constellation. As well as Slide 17 and 18.

I'm wondering, is the data acquired in these images, doable from an amateur standpoint? From previous research I think I can build some detection devices for the Hydrogen Line emission(1420Mhz/21cm line), and that could lead to data(per my initial/basic understanding) that's shown in image 1. Am I right in that assumption, and are the other emissions or data doable from an amateur standpoint?

There are tons a amateur radio astronomy clubs and groups. Radio Astronomy was basically started by an amateur named Grote Reber, where he basically did the experiment that you are pondering to do in 1937 in his backyard in Wheaton, Illinois. You can visit that exact instrument at the NRAO facility in Green Bank, West Virginia. It was named a National Historic Landmark in 1989.

Just Google Amateur Radio Astronomy

Imaging the Milky Way in Neutral Hydrogen with an RTL-SDR

Over on Facebook Job Geheniau has recently been sharing how he's taken an image of our galaxy (the Milky Way) with a radio telescope consisting of a 1.5 meter dish, RTL-SDR and a few filters and LNAs. In the past we've posted several times about others observing the Hydrogen line with an RTL-SDR, and we have a tutorial here showing how to observe it on a budget.

In this case, Job went a step further than just a single measurement. He used a used a motorized dish and RTL-SDR to scan the entire Milky Way over one month, resulting in a full radio image of the galaxy. As his posts and pdf document are on Facebook and not visible to those without Facebook accounts, we asked for permission to reproduce some of them here for all to see. We have also mirrored his PDF file here, which contains more information about his radio telescope, results and setup.

To make a very long story short. After a month of angel patience (and that says something to me) I managed to take a 'picture' of our entire galaxy (galaxy) in neutral hydrogen! I attach some pictures. If you are more interested, please come after this and PDF with explanation. It was a hell of a job I can tell you. But here's the ' picture s' of the house (230 million light years wide) in which we live and in which we all have a big mouth.

For the Scientists among us. a beautiful plot of the Milky Way Graphically explained in neutral hydrogen. In short, summarized. if you look up on a beautiful summer evening you will see a beautiful galaxy, this is graphically the same but then on a different frequency than the eye can perceive. own dates of course.

A composite of Hydrogen Line readings at different points of the Milky Way produced by Job Geheniau An image of the Galactic Plane (longitude 20 to 240 steps of 5 degrees and latitude 0)

His setup consists of a 1.5m dish, extended to 1.9m with some mesh. A 1420 MHz tuned feed, Mini Circuits ZX6-P33ULN LNA, Bandpass Filter, NooElec SAWBird LNA, Bias-T, RTL-SDR V3, PST Rotator Dish Software, VIRGO software, SDR#, Cartes due Ciel sky chart and a home made netfilter.

He uses a modified version of the VIRGO software to read sky coordinates from a text file, and this points the telescope at each predefined coordinate. He then uses VIRGO to record data for 180 seconds before moving on to the next coordinate. The data is then plotted in Excel, and the highest peak is taken at each coordinate and put back into an 8x21 matrix in excel. Conditional formatting is then used to generate a color gradient resulting in a rough map. Then a Gaussian blur is applied, and it is projected over the Galaxy, resulting in the images above.

Job Geheniau's Radio Telescope Setup

In the past we've seen a very similar project performed by Marcus Leech from However, his measurements use 5 months of observations resulting in much higher resolution data.

The Hydrogen Line is an observable increase in RF power at 1420.4058 MHz created by Hydrogen atoms. It is most easily detected by pointing a directional antenna towards the Milky Way as there are many more hydrogen atoms in our own galaxy. This effect can be used to measure the shape and other properties of our own galaxy.

Radio Astronomy and Imaging - Astronomy

5G | Emerging Trends | Regulation | Satellite | Spectrum Management
November 13, 2019

Radio astronomy, spectrum management and WRC‑19

by Harvey Liszt, Spectrum Manager, National Radio Astronomy Observatory, (NRAO) and Chair, IUCAF

*This article was originally published in the recent ITU News Magazine edition “Managing spectrum for evolving technologies.” Any views expressed in this article do not necessarily reflect those of ITU.

Astronomy is the study of our place in the universe, and the radio astronomy service is responsible for many exciting discoveries in this grand endeavour. Whether imaging massive black holes in the centres of distant galaxies or watching new planetary systems form around nearby stars, radio astronomy’s success depends on the careful management of radio spectrum. Radio astronomy will be strongly affected by the outcomes of the World Radiocommunication Conference 2019 (WRC‑19), so it is a great privilege to contribute to this special edition of the ITU News Magazine.

The discovery of cosmic radio waves by Karl Jansky in 1932 and the discovery of radio emission from the primordial Big Bang by Penzias and Wilson in 1964 were by-products of measurements to determine the noise contributions to telecommunication systems.

Whether imaging massive black holes in the centres of distant galaxies or watching new planetary systems form around nearby stars, radio astronomy’s success depends on the careful management of radio spectrum.

But the meadow where Jansky worked isn’t used for radio astronomy now, as the need to avoid terrestrial interference has driven radio tele‑ scopes to remote sites that may also offer better high-frequency observing conditions. But the meaning of “remote” has changed: places that once seemed isolated are now merely suburban.

Truly remote areas range from the merely less-in‑ habited to the barely habitable, and the costs of operating there are considerable. In any case, new and old facilities alike require spectrum protection, and nowadays no site is hidden from high-altitude platforms, aircraft and satellites.

Some WRC‑19 agenda items stand out for their potential impact.

Studies done under agenda item 1.13 have showed that strict limits on unwanted emissions and the use of appropriate coordination distances are critical elements of compatibility between radio astronomy and terrestrial 5G wireless.

The high-altitude platform systems (HAPS) studied under agenda item 1.14 present unique challenges for radio astronomy. Circulating horizontally and moving vertically at nominal altitudes 20–26 km, HAPS platforms have service radii 50–70 km, but are visible above the horizon for 500 km or more.

Potential HAPS operators made substantial con‑ cessions in the levels of unwanted emissions at which they committed to illuminate radio tele‑ scopes, but the need for radio astronomy operators to avoid HAPS platforms’ strong downlink signals will nonetheless require modification of RAS operations.

Agenda item 1.6 touches on a subject of great concern — spectrum for use by large fixed-satellite service (FSS) constellations in low Earth orbit (LEO) at 37–42.5 and 47–51.4 GHz. Comparable FSS LEO systems operating at 10.7–12.75 GHz are already being launched and have been of recent concern for their impact on the visual appearance of the night sky and optical astronomy more generally. Radio astronomy use of its primary allocation at 42.5–43.5 GHz is protected by Footnotes No. 5.551H and 5.551I in the Radio Regulations (RR), but the FSS systems studied under agenda item 1.6 were never defined with sufficient precision to identify the specific measures that FSS operators would have to take to meet the protection thresholds.

Agenda item 1.15 addresses fixed service and land mobile service use of spectrum at 275–450 GHz, beyond the uppermost frequency allocations in Article 5.

Radio astronomy looks forward to working with other services to bring WRC‑19 to a successful and mutually satisfactory conclusion.

Until now, this frequency range has been the near-exclusive province of radio astronomy and the Earth exploration satellite service (passive), with spectrum bands identified for use by their applications in RR Footnote No. 5.565. At WRC‑19, a comparable footnote may be crafted identifying spectrum that can be used by the fixed and land mobile services, with consideration of compatibility but without regulatory constraints. Is this a step toward allocating spectrum above 275 GHz? Stay tuned.

Because it receives only cosmic radiation (or so we hope), radio astronomy has a somewhat unusual status in the ITU Radiocommunication Sector (ITU–R): it is a radio service but not a radiocommunication service. This could change if the radio search for extraterrestrial intelligence (SETI) succeeds and we begin to communicate with alien life forms in their protected frequency bands. In the meantime, RR No. 4.6 states “For the purpose of resolving cases of harmful interference, the radio astronomy service shall be treated as a radiocommunication service.” This is unambiguous and rendered comparably in French. But a second sentence addressing unwanted emissions differs in the French and English, and reconciling the difference will be discussed at WRC‑19 under agenda item 9. This arcane subject is of great interest to radio astronomy because it concerns some of the most basic aspects of its operation as a radio service.

Astronomy might seem to be way “out there,” but it is actually done “right here”, and a new generation of radio telescopes is being constructed on scales that were scarcely imaginable a few decades ago. The mm/sub‑mm ALMA array operating at 5000 m elevation was recently inaugurated in Northern Chile, the Square Kilometre Array is under development in Australia and South Africa, and planning for the next-generation VLA (ngVLA) is underway in the United States.

IUCAF’s world map of radio telescopes and quiet zones is available here. Operating such instruments in the terrestrial environment of an increasingly crowded sky and busy radio spectrum presents a variety of challenges, but underlying everything is access to the radio spectrum. Radio astronomy looks forward to working with other services to bring WRC‑19 to a successful and mutually satisfactory conclusion.

Radio Astronomy

Research interests

The University of Pretoria’s astrophysics research group was started in January 2018 with a primary focus in radio astronomy and major facilities such as MeerKAT, the Square Kilometre Array, and the Event Horizon Telescope. The group pursues science themes that cover a wide range of spatial and energy scales, with a particular focus on high angular resolution radio astronomy. A number of group members specialised in the technique of Very Long Baseline Interferometry (VLBI), which combines signals from radio antennas spread across to the globe to form a single, Earth-sized telescope.

UP astrophysics is particularly interested in supermassive black holes, when they come in pairs, how black holes and their host galaxies (co)evolve. For more detail on this, visit our research page. If you are interested in studying astrophysics at UP, look at our student opportunities or undergraduate programme pages.

Latest News

11-05-2020 - Solving the mystery of X-shaped radio sources with MeerKAT

10-04-2019 - Astronomers (including UP) capture first image of a black hole

Group Members

Group Leader

Prof Roger Deane
Associate Professor
Research interests: Binary supermassive black holes, strong gravitational lensing, wide-field VLBI surveys, black hole shadow imaging with the Event Horizon Telescope, radio interferometry techniques, high-redshift galaxies
Teaching: Observational astronomy (PHY 300) Computational Physics (Honours)
Location: 5-73, Natural Sciences I

Postdoctoral Researchers

Dr Kshitij Thorat
IDIA Postdoctoral Fellow
Research interests: My research revolves around extra-galactic radio sources: their life-cycles, morphology and their impact on their surroundings. I am involved in making fully automated data reduction, imaging and calibration pipelines for telescopes like MeerKAT! Finally, I am very interested in the application of Machine Learning techniques to solving problems in radio astronomy.
Teaching: Lecturer for PHY 210 Astronomy for physicists
Contact: thorat.k [at]
Location:: 5-70 Natural Sciences 1, University of Pretoria

Dr Jack Radcliffe
SARAO Postdoctoral Fellow
Other affiliations: University of Manchester
Research interests: Galaxy evolution as traced via radio surveys. AGN feedback and wide-field VLBI enthusiast. Also dabbles in radio interferometric calibration techniques
Teaching: Lecturer for PHY 700 Radio Astronomy and the Unit 4 of the Development in Africa with Radio Astronomy programme
Contact: jack.radcliffe [at] / jack.radcliffe [at]
Location: 5-70, Natural Sciences 1, University of Pretoria

Dr Iniyan Natarajan
Postdoctoral Fellow
Other affiliations: Rhodes University / SARAO
Research interests: High resolution (VLBI) observations of supermassive black holes and active galactic nuclei (AGNs), development of simulation and calibration algorithms for radio interferometry, and application of probability theory in novel ways to the analysis of astronomical data.
Contact: iniyannatarajan [at]
Location: Based at the Radio Astronomy Research Group (RARG) at the South African Radio Astronomy Observatory (SARAO) in Cape Town

Charissa Button
Advisor(s): Prof. Roger Deane
Research interests: galaxy clusters, particularly looking at neutral hydrogen and strong lensing models. Project title: MeerKAT galaxy cluster lens: Strong lensing magnification models and Omega HI constraints in a survey of galaxy clusters
Contact: charissa [at]
Location: 5-73 Natural Sciences 1, University of Pretoria

Tariq Blecher
Other affiliations: Rhodes University / SARAO
Advisor(s): Prof. Roger Deane
Research interests: I work in the overarching field of galaxy formation and evolution. My subfield is the study of neutral atomic hydrogen in galaxies using interferometric observations of the 21 cm emission line. My main focus is to investigate the feasibility of leveraging gravitational lensing to measure the neutral atomic hydrogen content of distant galaxies.
Contact: tariq.blecher [at]
Location: Based at the Radio Astronomy Research Group (RARG) at the South African Radio Astronomy Observatory (SARAO) in Cape Town


Thato Manamela
Advisor(s): Prof. Roger Deane
Research interests: Visibility stacking on realistic simulations mimicking MeerKAT's observations, trying to test how this technique is more effective compared to the traditional image stacking by performing a suite of visibility stacking experiments.
Contact: thatoeugine [at]
Location: 5-73, Natural Sciences 1, University of Pretoria

Shilpa Ranchod
Advisor(s): Prof. Roger Deane
Research interests: Aiming to detect neutral hydrogen (HI) emission of very distant galaxies that have been gravitationally lensed. I am searching for lensed HI in galaxy clusters, observed with MeerKAT-64
Contact: shilparanchod [at]
Location: -

Micaela Menegaldo
Advisor(s): Prof. Roger Deane, Prof. Heino Falcke (Radboud University) and Jordy Davelaar (Radboud University)
Research interests: Investigating the use of unsupervised learning algorithms, specifically self organising maps, in parameter analysis of GRMHD (general relativistic magneto hydro dynamic) simulations of black holes shadows. Currently focused on the supermassive black hole located in the centre of M87
Contact: micaelamenegaldo [at]
Location: Radboud University

Nkululeko Qwabe
Other affiliations: Hartebeeshoek Radio Astronomy Observatory (HartRAO) / SARAO
Advisor(s): Prof Roger Deane and Dr Jack Radcliffe
Research interests: I am working on developing a suite of simulations of the tied-array and interferometric performance of MeerKAT sub-arrays in order to systematically explore the scientific, technical, and processing trade-offs of MeerKAT sub-array and commensal observations, which is aimed at maximising the scientific utility of both MeerKAT and the VLBI networks it will participate in.
Contact: nkululekoqwb [at]
Location: 5-70 Natural Sciences 1, University of Pretoria (Fridays)

Karina Santana
Advisor(s): Prof Roger Deane
Research interests: HI distributions of nearby galaxy mergers
Teaching: Tutor and practical demonstrator for first year students in PHY 114 and PHY 124
Contact: u16283865 [at]
Location: 5-65 Natural Sciences 1, University of Pretoria

Leon Mtshweni
Advisor(s): Prof Roger Deane and Dr Kshitij Thorat
Research interests: MeerKAT observations of M87's radio halo and data calibration techniques involving machine learning.
Teaching: Tutor and practical demonstrator for PHY 114, 124, 131 and 255
Contact: u13371062 [at]
Location: 5-65, Natural Sciences 1, University of Pretoria

Issac Magolego
Advisor(s): Dr Kshitij Thorat and Prof Roger Deane
Research interests: Large-scale environments of the prototypical binary AGN systems. Currently, I am conducting spectral index studies of the X-shaped radio galaxies
Contact: isaacike07 [at]
Location: 5-73, Natural Sciences 1, University of Pretoria

Stefro Millard
Advisor(s): Prof Roger Deane and Dr Jack Radcliffe
Research interests: Binary supermassive blackholes and imaging techniques
Contact: stefromillard [at] / u16048327 [at]
Location: 5-73, Natural Sciences 1, University of Pretoria

Heinrich van Deventer
Advisor(s): Prof Roger Deane and Dr Iniyan Natarajan
Research interests: Bayesian parameter estimation for the Event Horizon Telescope, machine learning, and computational physics.
Teaching: Teaching assistant for PHY 114, 124, 263, 210 and 300
Contact: hpdeventer [at]
Location: 5-73, Natural Sciences 1, University of Pretoria

Jacques Smulders
Advisor(s): Prof Roger Deane and Dr Chris Cleghorn (CIRG)
Research interests: Applications of machine learning and optimisation in computational astronomy
Contact: jacqsmulders [at]
Location: 5-73, Natural Sciences 1, University of Pretoria

Fernando Ventura
Advisor(s): Prof Roger Deane and Dr Kshitij Thorat
Research interests: Finding and studying exotic radio galaxy morphologies with an interest in using machine learning to locate these unusual sources
Contact: u16000936 [at]
Location: 5-73, Natural Sciences 1, University of Pretoria

Paul Wilsenach
Advisor(s): Prof Roger Deane and Dr Jack Radcliffe
Research interests: TBA
Contact: wilsenach11 [at]
Location: 5-73, Natural Sciences 1, University of Pretoria


William Rasakanya
Advisor(s): Prof Roger Deane and Dr Kshitj Thorat
Research interests: Deep MeerKAT observation of an "X-shaped" source with a pair of black holes, galaxy NGC 326, and analysis of its jet morphology
Teaching: Tutor for PHY 114 and PHY 124 Contact: w.rasakanya [a]
Location: 5-65, Natural Sciences 1, University of Pretoria

Graham Lawrie
Advisor(s): Prof Roger Deane
Research interests: HI detections in Galaxy clusters
Contact: u17030394 [at]
Location: 5-65, Natural Sciences 1, University of Pretoria

Past Students


A Multiwavelength Analysis of the Faint Radio Sky (COSMOS-XS): the Nature of the Ultra-faint Radio Population
Algera, H. S. B., van der Vlugt, D., Hodge, J. A. et al. (including Radcliffe, J. ) 2020, ApJ, 903, 2, 139 (link)

MeerKAT's discovery of a radio relic in the bimodal merging cluster A2384
Parekh, V., Thorat, K. , Kale, R. et al. 2020, MNRAS, 499, 1, 404 (link)

Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope
Wielgus, Maciek, Akiyama, Kazunori, Blackburn, Lindy et al. (including Deane, R. and Natarajan, I. ) 2020, ApJ, 901, 1, 67 (link)

MeerKAT-16 HI observation of the dIrr galaxy WLM
Ianjamasimanana, R., Namumba, B., Ramaila, A. J. T. et al.(including Thorat, K. ) 2020, MNRAS, 497, 4, 4795 (link)

GASP XXVI. HI Gas in Jellyfish Galaxies: The case of JO201 and JO206
Ramatsoku, M., Serra, P., Poggianti, B. M. et al. (including Thorat, K. ) 2020, A&A 640, A22 (link)

MeerKATHI - an end-to-end data reduction pipeline for MeerKAT and other radio telescopes
Józsa, G. I. G., White, S. V., Thorat, K. et al. 2020, ADASS XXIX to appear in ASPC (link)

A probabilistic approach to phase calibration – I. Effects of source structure on fringe-fitting
Natarajan, I. , Deane, R. , van Bemmel, I. et al. 2020, MNRAS, 496, 801-813 (link)

The e-MERLIN Galaxy Evolution Survey (e-MERGE): Overview and Survey Description
Muxlow, T. W. B., Thomson, A. P., Radcliffe, J. F. et al. 2020, MNRAS, 495, 1, 1188 (link)

Hydrodynamical Backflow in X-shaped Radio Galaxy PKS 2014-55
Cotton, W. D., Thorat, K. , Condon, J. J. et al. (including Deane, R. ) 2020, MNRAS, 495, 1, 1271 (link)

Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
Kim, J-Y, Krichbaum, T. P., Broderick, A. E., et al. (including Deane, R. and Natarajan, I. ) 2020, A&A 640, A69 (link)

Verification of Radiative Transfer Schemes for the EHT
Gold, R,, Broderick, A. E., Younsi, Z. et al. (including Deane, R. and Natarajan, I. ) 2020, ApJ, 897, 2, 148 (link)

THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope
Broderick, A. E., Gold, R., Karami, M. et al. (including Deane, R. and Natarajan, I. ) 2020, ApJ, 897, 2, 139 (link)

Searching for obscured AGN in z

2 submillimetre galaxies
Chen, H., Garrett, M. A., Chi, S. (including Radcliffe, J. ) 2020, A&A, 638, A113 (link)

High-Resolution Radio Observations of Five Optically Selected Type 2 Quasars
Krezinger, M., Frey, S., Paragi, Z., and Deane, R. 2020, Symmetry, 12, 4, 527 (link)

SYMBA: An end-to-end VLBI synthetic data generation pipeline. Simulating Event Horizon Telescope observations of M 87
Roelofs, F., Janssen, M., Natarajan, I. et al. (including Deane, R. ) 2020, A&A, 636, A5 (link)

Collimated synchrotron threads linking the radio lobes of ESO 137-006
Ramatsoku, M., Murgia, M., Vacca, V. et al. (including Thorat, K. ) 2020, A&A, 636, L1 (link)

An insight into the extragalactic transient and variable microJy radio sky across multiple decades
Radcliffe, Jack F. , Beswick, Robert J., Thomson, A. P. et al. 2019, MNRAS, 490, 3, 4024 (link)

First M87 Event Horizon Telescope Results and the Role of ALMA
Event Horizon Telescope Collaboration, Goddi, C., Crew, G., Impellizzeri, V., et al. (including Deane, R. and Natarajan, I. ) 2019, The Messenger, 177, 25 (link)

Studying Black Holes on Horizon Scales with VLBI Ground Arrays
Doeleman, Sheperd, Blackburn, Lindy, Doeleman, Sheperd et al. (including Deane, R. ) 2019, Bulletin of the American Astronomical Society, 51, 7, 256 (link)

The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project
Porth, Oliver, Chatterjee, Koushik, Narayan, Ramesh et al. (including Deane, R. and Natarajan, I. ) 2019, ApJS, 243, 2, 26 (link)

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
Event Horizon Telescope Collaboration, Akiyama, Kazunori, Alberdi, Antxon et al. (including Deane, R. and Natarajan, I. ) 2019, ApJ, 875, 1, L1 (link)

First M87 Event Horizon Telescope Results. II. Array and Instrumentation
Event Horizon Telescope Collaboration, Akiyama, Kazunori, Alberdi, Antxon et al. (including Deane, R. and Natarajan, I. ) 2019, ApJ, 875, 1, L2 (link)

First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
Event Horizon Telescope Collaboration, Akiyama, Kazunori, Alberdi, Antxon et al. (including Deane, R. and Natarajan, I. ) 2019, ApJ, 875, 1, L3 (link)

First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
Event Horizon Telescope Collaboration, Akiyama, Kazunori, Alberdi, Antxon et al. (including Deane, R. and Natarajan, I. ) 2019, ApJ, 875, 1, L4 (link)

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
Event Horizon Telescope Collaboration, Akiyama, Kazunori, Alberdi, Antxon et al. (including Deane, R. and Natarajan, I. ) 2019, ApJ, 875, 1, L5 (link)

First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
Event Horizon Telescope Collaboration, Akiyama, Kazunori, Alberdi, Antxon et al. (including Deane, R. and Natarajan, I. ) 2019, ApJ, 875, 1, L6 (link)

Towards the first detection of strongly lensed H I emission
Blecher, Tariq, Deane, Roger , Heywood, Ian et al. 2019, MNRAS, 484, 3, 3681 (link)

The synergy between VLBI and Gaia astrometry
van Langevelde, H., Quiroga-Nuñez, L. H., Vlemmings, W., et al. (including Natarajan, I. and Deane, R. ) 2019, Proceedings of the 14th European VLBI Network Symposium (link)

Exploring Sub-Array Strategies for MeerKAT-VLBI
Qwabe, N. and Deane, R. 2019, Proceedings of the 14th European VLBI Network Symposium (link)

Initial progress toward planar integrate, low-cost water vapour radiometers
Stander, T., Cerfonteyn, W., Deane, R. et al. 2019, Proc. SPIE 11043, Fifth Conference on Sensors, MEMS, and Electro-Optic Systems, (link)

Phased array feed imaging system broadens vision for radio astronomy

The 19-element phased array feed developed by the NRAO CDL. Credit: NRAO/AUI/NSF

To accelerate the pace of discovery and exploration of the cosmos, a multi-institution team of astronomers and engineers has developed a new and improved version of an unconventional radio-astronomy imaging system known as a phased array feed (PAF). This remarkable instrument can survey vast swaths of the sky and generate multiple views of astronomical objects with unparalleled efficiency.

Looking nothing like a camera or other traditional imaging technologies such as CCDs in optical telescopes or single receivers in radio telescopes, this new PAF design resembles a forest of miniature tree-like antennas evenly arranged on a meter-wide metal plate. When mounted on a single-dish radio telescope, specialized computers and signal processors are able to combine the signals among the antennas to create a virtual multi-pixel camera.

This type of instrument is particularly useful in a number of important areas of astronomical research, including the study of hydrogen gas raining in on our galaxy and in searches for fast radio bursts.

Over the years, other radio astronomy research facilities have developed phased array receiver designs. Most, however, have not achieved the efficiency necessary to compete with classical radio receiver designs, which process one signal from one spot on the sky at a time. The value of the new PAF is that it can form multiple views (or "beams on the sky," in radio astronomy terms) with the same efficiency as a classical receiver, which can enable faster scans of multiple astronomical targets.

This newly developed system helps take PAF technology from a curious area of research to a highly efficient, multipurpose tool for exploring the universe.

Commissioning observations with the National Science Foundation's Green Bank Telescope (GBT) using this new design show that this instrument met and exceeded all testing goals. It also achieved the lowest operating noise temperature – a normally vexing problem for clear views of the sky—of any phased array receiver to date. This milestone is critical to move the technology from an experimental design to a fully fledged observing instrument.

The results are published in the Astronomical Journal.

Infographic demonstrating the layout of the newly designed Phased Array Feed receiver that was tested on the Green Bank Telescope. Credit: NRAO/AUI/NSF S. Dangello

"When looking at all phased array receiver technologies currently operating or in development, our new design clearly raises the bar and gives the astronomy community a new, more rapid way of conducting large-scale surveys," said Anish Roshi, an astronomer-engineer with the National Radio Astronomy Observatory (NRAO) and a member of the design team.

The new PAF was designed by a consortium of institutions: the NRAO's Central Development Laboratory, Green Bank Observatory, and Brigham Young University.

"The collaborative work that went into designing, building, and ultimately verifying this remarkable system is truly astounding," said NRAO Director Tony Beasley. "It highlights the fact that new and emerging radio astronomy technology can have an immense impact on research."

The new PAF design consists of 19 dipole antennas, radio receivers that resemble miniature umbrellas without a covering. A dipole, which simply means "two poles," is the most basic type of antenna. Its length determines the frequency—or wavelength of radio light—it is able to receive. In the PAF radio system, the strength of the signal can vary across the surface of the array. By calculating how the signal is received by each of the antennas, the system produces what is known as a "point-spread function" – essentially, a pattern of dots concentrated in one region.

The PAF's computer and signal processors can calculate up to seven point-spread functions at a time, enabling the receiver to synthesize seven individual beams on the sky. The new design also allows these regions to overlap, creating a more comprehensive view of the region of space being surveyed.

"This project brings together in one instrument a state-of-the-art, low-noise receiver design, next generation multi-channel digital radio technology, and advanced phased array modeling and beamforming," said Bill Shillue, PAF group lead at the NRAO's Central Development Laboratory.

The astronomical value of the receiver was demonstrated by GBT observations of the pulsar B0329+54 and the Rosette Nebula, a star-forming region of the Milky Way filled with ionized hydrogen gas.

Additional development and computing power could enable this same design to generated an even greater number of beams on the sky, greatly expanding its utility.

Figure 1 Angular resolution of radio telescopes versus time. Open symbols refer to instruments that were only capable of measuring the overall angular size. Closed symbols refer to imaging instruments. Filled aperture telescopes are shown in black connected element interferometers and arrays in green radio-linked interferometers in blue and independent-oscillator tape-recording interferometers in brown. Lunar occultations are in orange and estimates from ionospheric (○), interplanetary (□), or interstellar scintillations (Δ) are in red. In each case, the effective resolution is taken as λ/D for a two-element interferometer, 1.2 (λ/D) for a filled aperture telescope, and 0.7 (λ/D) for a multi-element array. Important performance factors ignored in this presentation include wavelength, collecting area, and sensitivity.

Figure 2 Illustration showing the improvement over the past half century in imaging the radio galaxy Cygnus A. (a) The intensity interferometer observations of Jennison & Das Gupta (1953). (b) Observations at 20 cm with the Cambridge 1-mile radio telescope (Ryle et al. 1965). (c) Observations with the 5-km radio telescope at 6 cm (Hargrave & Ryle 1974). (d) 6-cm VLA observations of Perley et al. (1984). (e) Same as in (d) but with CLEANing. (f) Same as (d) with CLEANing and self-calibration. (g) Self-calibrated CLEAN 6-cm image based on more extensive VLA observations by Carilli and Perley (see Carilli & Harris 1996). (h) Image of the nuclear region made with a 13-station global array working at 1.3 cm by Krichbaum et al. (1998). (i) The inner region of the nucleus imaged with a resolution of 0.00015 arcsec using an 8-station VLBI array at 7-mm wavelength (Krichbaum et al. 1998). The right hand panel of the figure was provided by T. Krichbaum.

Radio Astronomy and Imaging - Astronomy

Future Arrays for Radio Astronomy and Space Communications
<B>Sander Weinreb,</B> Principal Scientist, JPL, and Faculty Associate, Caltech EE Department

Much of radio astronomy has been performed with single-pixel telescopes that measure one point in the sky at a time. During the past 30 years arrays of telescopes such as the VLA and CARMA have been developed to provide many-pixel images. Future directions of array development to be introduced in this presentation are: 1) the Square KM Array (SKA) 2) combined use of future large arrays for radio astronomy and space communications 3) phased-array feeds for much larger field of view 4) wafer-scale integration for large format spectral imaging at millimeter and submillimeter wavelengths and 5) new transistors and integrated circuits to make this all affordable. The role of Caltech/JPL in these developments will be discussed.

CCAT - Cornell Caltech Atacama Telescope
<B>Steve Padin,</B> Senior Research Associate, Caltech

CCAT is a new, 25 m diameter, submillimeter wave telescope. It will be built on a high, dry site in the Atacama Desert. CCAT will probe the growth of structure over cosmic time, from the first galaxies to nearby star and planet forming regions. CCAT will be a powerful survey instrument, taking full advantage of recent advances in submillimeter detector arrays, particularly MKID arrays, CCAT's instrument suite will include 100k-pixel multi-band cameras, and multi-object spectrometers that can observe of order a hundred sources simultaneously.


By combining the already existing radio astronomy faculty of the University of Bonn led by Otto Hachenberg with the new Max Planck institute the Max Planck Institute for Radio Astronomy was formed. In 1972 the 100-m radio telescope in Effelsberg was opened. The institute building was enlarged in 1983 and 2002.

The southern wing of the whole complex is occupied by the Argelander Institute of Astronomy of the University of Bonn.

The Institute has three main research groups, each with its own Director

Departments Edit

Independent Research Groups Edit

The International Max Planck Research School (IMPRS) for Astronomy and Astrophysics is a highly competitive-entry graduate program offering a Ph.D. The school is run in cooperation with the University of Bonn and University of Cologne.

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Interferometry and Synthesis in Radio Astronomy

This book is open access under a CC BY-NC 4.0 license.

The third edition of this indispensable book in radio interferometry provides extensive updates to the second edition, including results and technical advances from the past decade discussion of arrays that now span the full range of the radio part of the electromagnetic spectrum observable from the ground, 10 MHz to 1 THz an analysis of factors that affect array speed and an expanded discussion of digital signal-processing techniques and of scintillation phenomena and the effects of atmospheric water vapor on image distortion, among many other topics.

With its comprehensiveness and detailed exposition of all aspects of the theory and practice of radio interferometry and synthesis imaging, this book has established itself as a standard reference in the field. It begins with an overview of the basic principles of radio astronomy, a short history of the development of radio interferometry, and an elementary discussion of the operation of an interferometer. From this foundation, it delves into the underlying relationships of interferometry, sets forth the coordinate systems and parameters to describe synthesis imaging, and examines configurations of antennas for multielement synthesis arrays. Various aspects of the design and response of receiving systems are discussed, as well as the special requirements of very-long-baseline interferometry (VLBI), image reconstruction, and recent developments in image enhancement techniques and astrometric observations. Also discussed are propagation effects in the media between the source and the observer, and radio interference, factors that limit performance. Related techniques are introduced, including intensity interferometry, optical interferometry, lunar occultations, tracking of satellites in Earth orbit, interferometry for remote Earth sensing, and holographic measurements of antenna surfaces.

This book will benefit anyone who is interested in radio interferometry techniques for astronomy, astrometry, geodesy, or electrical engineering.