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VLA Low Band Ionospheric and Transient Experiment (VLITE)

VLITE is a commensal system capable of continuously accessing
64 MHz from the new 236-492 MHz Low Band system deployed on the VLA.

Radio (VLITE 90 cm and WSRT 50 cm) and optical (DSS) image of the giant radio galaxy DA 240. The VLITE data were fully processed through the VLITE pipeline. (Credit: Radio (blue) from VLA Low-band Ionosphere and Transient Experiment and (magenta and red) from the Westerbork Synthesis Radio Telescope. Optical (green) from the Digital Sky Survey 2. U.S. Naval Research Laboratory/ Dr. Simona Giacintucci).

Example of antenna-based TEC gradients from November 11, 2014 observation of the Galaxy cluster Abell 2052 (A2052). The north-south and east-west components of the gradient are shown for antennas V1 and V4.

Mollweide projection in Galactic coordinates showing the distribution of the VLITE pointings over a 30-month interval. Fields are colored by their total integration time across all images. This is an updated figure from Polisensky et al. (2016).

The U.S. Naval Research Laboratory (NRL) and NRAO have successfully collaborated to develop the VLA Low-band Ionosphere and Transient Experiment (VLITE). The VLITE backend includes dedicated samplers, fiber optics, and a DiFX-based real-time software correlator.

VLITE first fringes were obtained on July 17, 2014. Science operations with VLITE commensed November 25, 2014. During the initial phase of operation, VLITE correlated 10 antennas and, in the first year of science operation, VLITE acquired over 6300 hours of data. By harvesting data from the VLA's prime focus, VLITE effectively makes the VLA "two telescopes in one". A 2015 NRL press release describes the instrument and shows sources in a galaxy cluster that were in the VLITE field-of-view from observations of an unrelated low redshift galaxy.

In 2016, VLITE's DiFX correlator was modified to allow data recording during on-the-fly (OTF) mapping to provide support to the Very Large Array Sky Survey (VLASS), which commenced in September 2017. Also in 2017, VLITE was expanded 16 VLA antennas, more than doubling the number of baselines. The on-going VLITE expansion was discussd in an NRL press release on radio mini-halos. Another VLITE capability currently in development is a fast-transient GPU-based processing system, which is nearing completion.

VLITE Data Products

VLITE data are processed using two separate pipelines:

Astrophysics and Transients pipeline:
features automated calibration and imaging of the data and operates with a 48 hour delay following data acquisition. Initial processing is concentrated on generating Stokes I images; however, all polarization products are correlated. Future processing will include full polarization capabilities and a near real-time transient pipeline.
Ionosphere pipeline

features automated calibration of the data and operates in near real-time. The pipeline generates time series and corresponding fluctuation spectra to characterize Total Electron Content (TEC) gradient fluctuations.

Currently, VLITE raw data and calibration products are archived at NRL and distributed to the community upon request.

Data Rights and Archiving

VLITE obsrvations are recorded simultaneously with all VLA observing, with the following exceptions:

All NRAO TAC-approved P-band observations
Moving source observations (e.g. planets and the Sun)
On-The-Fly Mosaicing (OTFM) initially was not supported but has been included to support the VLASS

While VLITE data are proprietary, NRL invites Universities and others in the community to approach us for access to the data through collaboration. Only by tapping the potential of a wider community can we realize the full scientific value of VLITE and stimulate its expansion to a full broadband LOw Band Observatory (LOBO).

Contact Information

If you are interested in learning more about VLITE including inquiries about collaborations, please contact us directly as follows:

For general information concerning VLITE: Namir Kassim
For astronomical imaging, source catalogs, and technical questions: VLITE Project Scientist Tracy Clarke
For slow radio transients: Emil Polisensky
For fast radio transients or pulsar-related phenomena: Paul Ray
For ionospheric science: Joseph Helmboldt

Acknowledgements

Basic research in radio astronomy at the U.S. Naval Research Laboratory is supported by 6.1 Base Funding. Construction and installation of VLITE was supported by the NRL Sustainment Restoration and Maintenance fund. The VLA is operated by the National Radio Astronomy Observatory (NRAO). Special thanks are due to Summer Drew (Oviedo HS, FL) for her contributions to this website. Sliders were made using Jssor.