OVRO-LWA Solar Data Products

Overview

The Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) provides continuous low-frequency radio observations of the Sun over a broad instantaneous bandwidth. The array produces both high-time-resolution beamformed dynamic spectra and interferometric spectral imaging observations, enabling studies of solar radio bursts, coronal plasma, particle acceleration, radio-wave propagation, and space-weather-related phenomena.

OVRO-LWA operates over 13.4–86.9 MHz and consists of 352 crossed-dipole antennas distributed across the Owens Valley Radio Observatory site. The array supports several observing modes that can operate simultaneously:

• Beamformed observations provide high-time-resolution measurements of the disk-integrated solar radio emission.
• Standard interferometric imaging uses the full 352-element array for high-fidelity spectral imaging.
• Fast interferometric imaging uses a 48-antenna subset to obtain substantially higher time resolution for rapidly varying solar radio bursts.

The public solar data archive contains processed science-ready products, including all-day FITS dynamic spectra and HDF5 spectral image cubes.

For most users, the easiest way to locate and download data is through the OVRO-LWA Solar Data Portal. The long-term public archive is also available through the Registry of Open Data on AWS.

Instrument Specifications

A more complete description of the instrument is available on the OVRO-LWA Instrumentation page.

Parameter	Specification
Frequency range	13.4–86.9 MHz
Instantaneous bandwidth	73.5 MHz
Number of antennas	352 crossed-dipole antennas
Maximum baseline	Approximately 1.5 km
Raw frequency resolution	24 kHz (3072 channels)
Polarization	Full Stokes (I, Q, U, V) capability; availability depends on data product
Beamformer	256 core antennas
Standard visibility mode	352 antennas, 3072 frequency channels, 10 s integration
Fast visibility mode	48 antennas, 768 frequency channels, 0.1 s time resolution
Public spectrogram format	FITS
Public spectral image format	HDF5
Typical solar observing condition	Solar elevation greater than approximately 15 degrees

Because OVRO-LWA is located in Owens Valley and is surrounded by mountains, useful solar observations are generally obtained when the solar elevation is greater than approximately 15 degrees. Depending on season, this corresponds to approximately 7–14 hours of solar observations per day.

Beamformed Solar Data

Beamformer Observing Mode

The OVRO-LWA beamformer uses the 256 antennas in the core region to form a synthesized beam toward the Sun. The beam tracks the Sun throughout the observing day and provides a continuous measurement of the total solar radio emission without spatial resolution.

The system is capable of:

• Frequency coverage: 13.4–86.9 MHz
• Raw spectral resolution: 24 kHz (3072 frequency channels)
• Minimum instrumental time resolution: 1 ms
• Regular raw solar recording: approximately 64 ms
• Level 1 public spectrogram resolution: 256 ms and 96 kHz

These observations are particularly useful for studying rapidly varying coherent solar radio emission, including Type II and Type III radio bursts and their fine time-frequency structures.

Level 1 Beamformed Spectrograms

The standard public beamformed product is an all-day dynamic spectrum in FITS format.

The Level 1 product contains calibrated solar dynamic-spectrum measurements together with the observing time and frequency axes and relevant metadata.

Typical Level 1 product characteristics are:

Property	Level 1 Beamformed Product
Frequency range	13.4–86.9 MHz
Spectral resolution	96 kHz
Time resolution	256 ms
Format	FITS
Primary science product	Solar dynamic spectrum

A representative filename follows the convention

ovro-lwa.lev1_bmf_256ms_96kHz.YYYY-MM-DD.dspec_I.fits

Level 1.5 Beamformed Spectrograms

Level 1.5 beamformed products include additional corrections intended to provide a better estimate of the intrinsic solar flux density.

The principal additional processing steps are:

1. Non-solar background subtraction – emission from the rest of the radio sky contributes to the measured beamformed signal because an individual OVRO-LWA dipole has a very wide response.
2. Primary-beam correction – the antenna response toward the Sun varies with observing direction, time, and frequency.

The Level 1.5 products therefore provide the preferred beamformed data when quantitative solar flux measurements are required and the corresponding Level 1.5 product is available.

A representative filename is

ovro-lwa.lev1.5_bmf_256ms_96kHz.YYYY-MM-DD.dspec_I.fits

Interferometric Solar Imaging Data

OVRO-LWA also produces interferometric observations that preserve spatial information and provide imaging spectroscopy of the Sun.

Two visibility modes are used for solar observations.

Standard Imaging / Slow Visibility Mode

The standard imaging mode correlates the full 352-element array.

Important instrumental characteristics are:

• 3072 frequency channels across 13.4–86.9 MHz
• 24 kHz native channel spacing
• 10 s visibility integration
• Maximum baseline of approximately 1.5 km
• High-fidelity snapshot imaging enabled by the dense instantaneous uv coverage

This observing mode is well suited for imaging relatively slowly evolving solar structures and radio sources, including active regions, the quiet Sun, coronal structures, and long-duration radio emission associated with eruptive events.

The raw interferometric measurements are recorded as CASA Measurement Sets. Because of their extremely large data volume, the primary publicly distributed science products are processed spectral image cubes rather than the complete raw visibility stream.

Fast Imaging / Fast Visibility Mode

The fast visibility mode uses a 48-antenna subset, selected primarily from the longer-baseline antennas.

Its principal characteristics are:

• 768 frequency channels
• 96 kHz spectral resolution
• 0.1 s time resolution

This mode is intended for rapidly varying coherent radio emission where high time resolution is more important than the imaging dynamic range obtainable from the full array.

Fast imaging is particularly useful for spatially resolving fine structures in Type II and Type III radio bursts and other short-duration solar radio phenomena.

Availability of processed fast-imaging products may differ from that of the standard imaging archive.

Standard Spectral Image Products

The standard imaging pipeline calibrates the interferometric observations and produces spectral image cubes in heliocentric solar coordinates.

The processing includes complex-gain calibration, bandpass calibration, absolute flux calibration, self-calibration, and synthesis imaging.

Two standard spectral image products are provided.

Fine-Channel Spectral Images

The fine-channel product provides relatively high spectral resolution across the principal solar imaging band.

Property	Fine-Channel Product
Approximate frequency coverage	32–87 MHz
Number of image channels	144
Effective spectral resolution	384 kHz
Integration time	10 s
Typical image cadence	Approximately 20–60 s, depending on observing period and processing
Format	HDF5

A representative filename is

ovro-lwa-352.lev1_fch_10s.YYYY-MM-DDTHHMMSSZ.image_I.hdf

Band-Averaged / MFS Spectral Images

For applications where smaller data volume and improved sensitivity are preferred over fine spectral resolution, the calibrated visibility data are also combined into broader frequency bands using multi-frequency synthesis (MFS).

The standard product contains 12 frequency bands centered approximately at:

34.1, 38.7, 43.2, 47.8, 52.4, 57.0,
61.6, 66.2, 70.8, 75.4, 80.0, 84.6 MHz

Property	Band-Averaged / MFS Product
Approximate frequency coverage	32–87 MHz
Number of image channels	12
Effective bandwidth per image	Approximately 4.6 MHz
Integration time	10 s
Typical cadence	Approximately 20–60 s
Format	HDF5

A representative filename is

ovro-lwa-352.lev1_mfs_10s.YYYY-MM-DDTHHMMSSZ.image_I.hdf

For many science applications, the MFS files are a convenient starting point because they are substantially smaller than the fine-channel image cubes while still sampling the frequency dependence of the solar radio emission.

Level 1.5 Spectral Images

Low-frequency radio observations are affected by propagation through the Earth's ionosphere. One important effect is an apparent frequency-dependent displacement of radio sources caused by ionospheric refraction.

For Level 1.5 spectral image products, an additional correction is applied when the quiet solar disk can be reliably identified. The measured frequency-dependent displacement is fitted using the expected approximately inverse-frequency-squared dependence and the resulting correction is applied to the spectral image cube.

Representative filenames are

ovro-lwa-352.lev1.5_fch_10s.YYYY-MM-DDTHHMMSSZ.image_I.hdf
ovro-lwa-352.lev1.5_mfs_10s.YYYY-MM-DDTHHMMSSZ.image_I.hdf

The refraction correction cannot always be robustly determined, particularly during periods containing strong broadband solar radio bursts. Therefore, Level 1.5 imaging products may not be available for every observing interval and should be used with awareness of the assumptions involved in the correction.

Finding and Downloading Data

OVRO-LWA Solar Data Portal

The recommended starting point for locating individual OVRO-LWA solar observations is the

OVRO-LWA Solar Data Portal.

The portal provides a convenient lookup interface for determining what OVRO-LWA solar data products are available for a selected observing date/time and provides links to the corresponding downloadable products.

Users interested in a particular solar radio burst or other event should generally:

1. Identify the event date and approximate UT time.
2. Use the OVRO-LWA Data Portal to inspect the available observations.
3. Select the desired beamformed or imaging data product.
4. Follow the provided download link to obtain the file.

For most interactive data searches, this is easier than manually navigating the underlying archive.

Public Archive on AWS

OVRO-LWA solar data products are also hosted as a public dataset in the Registry of Open Data on AWS:

OVRO LWA Solar Observation – AWS Open Data

The AWS archive is designed for long-term public access and programmatic analysis. It contains both spectral image products and all-day beamformed spectrogram products.

The public S3 bucket is

s3://ovro-lwa-solar/

No AWS account is required for unsigned public access.

The primary directory organization is

s3://ovro-lwa-solar/
    image_hdf/
        YYYY/
            MM/
                DD/
    spec_fits/
        YYYY/

where

• image_hdf/ contains spectral imaging products in HDF5 format.
• spec_fits/ contains all-day beamformed dynamic spectra in FITS format.

The AWS dataset is updated regularly as new observations are processed and released.

The dataset is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.

Access with the AWS CLI

The contents of the public bucket can be listed without AWS credentials:

aws s3 ls --no-sign-request s3://ovro-lwa-solar/

For example, imaging products for a particular date can be inspected with

aws s3 ls --no-sign-request \
    s3://ovro-lwa-solar/image_hdf/YYYY/MM/DD/

A selected file can be downloaded using

aws s3 cp --no-sign-request \
    s3://ovro-lwa-solar/path/to/file \
    .

For bulk processing, users may access the S3 archive directly from Python rather than downloading an entire observing day in advance.

Working with the Data

Google Colab Example

A Google Colab notebook demonstrating how to interact with OVRO-LWA solar data is available here:

OVRO-LWA Solar Data Example – Google Colab

This provides a convenient starting point for users who want to explore the data in Python without first configuring a local analysis environment.

Python Utilities

The lwa-solar-util package provides lightweight Python tools for working with OVRO-LWA solar products:

lwa-solar-util on GitHub

The package includes utilities for:

• querying available imaging products from the public OVRO-LWA S3 bucket;
• reading multi-dimensional solar FITS files;
• converting between the distributed HDF5 image format and FITS;
• plotting standard multi-frequency OVRO-LWA solar image products;
• reading and plotting dynamic-spectrum FITS files; and
• applying or examining the ionospheric refraction correction used for Level 1.5 imaging products.

It can be installed directly from GitHub:

pip install git+https://github.com/ovro-eovsa/lwa-solar-util.git

For S3 access, the AWS dependencies can also be installed as described in the repository documentation.

Data Product Summary

Observation	Public Product	Frequency Coverage	Spectral Resolution	Time Resolution / Integration	Format
Beamformed dynamic spectrum	Level 1	13.4–86.9 MHz	96 kHz	256 ms	FITS
Beamformed dynamic spectrum	Level 1.5	13.4–86.9 MHz	96 kHz	256 ms	FITS
Standard imaging, fine channel	Level 1 / 1.5	Approximately 32–87 MHz	384 kHz	10 s integration; typically 20–60 s cadence	HDF5
Standard imaging, band averaged / MFS	Level 1 / 1.5	Approximately 32–87 MHz	Approximately 4.6 MHz	10 s integration; typically 20–60 s cadence	HDF5
Fast interferometric observations	Event/processing dependent	Instrumental range	96 kHz	0.1 s	Product availability varies

Useful Links

• OVRO-LWA Instrument Specifications
• OVRO-LWA Solar Data Portal and Data Lookup
• OVRO-LWA Solar Observation on the Registry of Open Data on AWS
• OVRO-LWA Solar Data Google Colab Example
• OVRO-LWA Solar Data Utilities
• OVRO-LWA Solar Data Products Wiki

Citation and Data Use

When using the public AWS dataset, please acknowledge the OVRO-LWA solar data archive and cite the relevant OVRO-LWA instrument/data-product publications associated with the scientific analysis.

The AWS dataset entry can be cited following the instructions provided at:

Registry of Open Data on AWS – OVRO LWA Solar Observation

The public AWS archive is distributed under the CC BY 4.0 license.

Migrated from MediaWiki page OVRO-LWA Solar Data Products, latest revision 16177 (2026-08-10T05:53:31Z).