Mission Overview

Map of Observations

FIRST Footprint North

FIRST Footprint South

Wavelength Coverage

Radio continuum data in a single 42 MHz bandpass centered at 1.4 GHz (20 cm wavelength)

mission coverage

The  Faint Images of the Radio Sky at Twenty-cm (FIRST) project surveyed 10,575 square degrees of the North and South Galactic Caps at a frequency of 1.4 GHz using the NRAO Very Large Array (VLA).  An automated mapping pipeline was used to generate images with 1.8" pixels, a typical rms of 0.15 milliJansky (mJy), and a resolution of 5.4". At the 1 mJy source detection threshold, there are ~90 sources per square degree, ~35% of which have resolved structure on scales from 2–30". The survey covers approximately the same sky area as the Sloan Digital Sky Survey (SDSS), and 30% of the sources have optical counterparts in SDSS.

Active From

1993 - 2011


Source Position Accuracy - <1"

Imaging - 1.8" / pixel

Northern Beam, circular Gaussian FWHM - 5.4" 

Southern Beam, elliptical Gaussian FWHM - 6.4-6.8" x 5.4"


  • Point-source detection limit 1 mJy (deeper than any previous radio survey)
  • Resolution 5.4" FWHM (accurate enough to identify faint optical counterparts)
  • Images are available through MAST website
  • Catalogs are available through the FIRST survey website

On this Page

Search Tools

Featured Data Products

FIRST Source Catalog
FIRST Source Catalog
FIRST Image Cutouts
FIRST Image Cutouts
FIRST Full-Frame FITS Images
FIRST Full-Frame FITS Images

Primary Documents

Image Gallery

FIRST Survey logo

Faint Images of the Radio Sky in Twenty Centimeters (FIRST).  Survey Logo.

Sample FIRST Radio Image 1

Sample FIRST Radio Image 2

Sample FIRST Radio Image 3

Sample FIRST Radio Image 4

Sample FIRST Radio Image 5

Combined FIRST Radio / Optical Image Overlay

FIRST radio observations combined with POSS optical imaging data

External Links