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Mission Overview

SKYSURF Drizzled Images and Object Catalogs (SKYSURF)

 

Primary Investigator:  Rogier A. Windhorst

HLSP Authors:  Delondrae D. Carter, Timothy Carleton, Daniel J. Henningsen, Rogier A. Windhorst, Seth H. Cohen, Scott A. Tompkins, Rosalia O’Brien, Anton M. Koekemoer, Juno Li, Zak Goisman, Simon P. Driver, Aaron S. G. Robotham, Rolf A. Jansen, Norman A. Grogin, Sabine Bellstedt, Haina Huang, Tejovrash Acharya, Jessica M. Berkheimer, Haley Abate, Connor Gelb, Isabela Huckabee, and John MacKenty

Released:  2026-05-15

Updated:  2026-05-15

Primary References:  Tompkins et al. 2026, Carter et al. 2026

DOI:  10.17909/ajha-4009

Citations:  See ADS Statistics

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SKYSURF Sky Coverage

Sky coverage of SKYSURF's 38,027 single-visit mosaics. This is an Aitoff Equatorial projection. Each black point, which are scattered throughout the diagram, represents the location of one single-visit mosaic. The regions shaded grey represent the areas filtered out of the multi-visit analysis. Visits excluded from the multi-visit analysis are indicated by colored points: purple points indicate that a visit was filtered out due to being too close to a known bright source, blue points indicate that a visit was filtered out due to its location relative to the Milky Way's disk, and orange points indicate that a visit was filtered out due to its location relative to the Milky Way's bulge.

Sky coverage of SKYSURF's 38,027 single-visit mosaics. This is an Aitoff Equatorial projection. Each black point represents the location of one single-visit mosaic. The regions shaded grey represent the areas filtered out of the multi-visit analysis. Visits excluded from the multi-visit analysis are indicated by colored points: purple points indicate that a visit was filtered out due to being too close to a known bright source, blue points indicate that a visit was filtered out due to its location relative to the Milky Way's disk, and orange points indicate that a visit was filtered out due to its location relative to the Milky Way's bulge.

SKYSURF Logo

Project SKYSURF's logo, which looks like a wave with galaxies interior to the wave, with the Hubble Space Telescope above

Project SKYSURF's logo

Overview

Welcome to the HLSP page for the Hubble Space Telescope Cycle 27–29 Archival Legacy project SKYSURF, the largest archival program ever approved for Hubble. SKYSURF aims to constrain the extragalactic background light using all 143,914 ACS/WFC, WFC3/UVIS, and WFC3/IR images taken since Hubble’s launch in 2002. This page provides the project’s high‑level science products, including the sky surface brightness measurements of O’Brien et al. (2023, SKYSURF‑4), the ProFound sky maps of Tompkins et al. (2026, SKYSURF‑9), and the drizzled mosaics and source catalogs of Carter et al. (2026, SKYSURF‑10). A detailed description of all included products is provided in the accompanying README.

The drizzled mosaics and source catalogs follow the methodology described in Carter et al. (2026, SKYSURF‑10). The mosaics were produced with a non‑standard drizzling pipeline designed to preserve the lowest sky level in each drizzle group, using the 2D sky-maps of Tompkins et al. (2026, SKYSURF‑9) and the sky‑surface background measurements of O’Brien et al. (2023, SKYSURF‑4). Combined source catalogs were generated from the individual drizzled mosaic catalogs and filtered using completeness estimates from the calculator of Goisman et al. (2025, SKYSURF‑8), retaining only fields ≥90% complete for a 0.1″, 25 mag object. Please cite SKYSURF‑10, SKYSURF‑9, and SKYSURF‑4 when using the drizzled products or individual catalogs, and additionally cite SKYSURF‑8 when using the combined catalogs or any catalogs derived from them.

Data Products

Science, weight, modified weight, and cosmic ray mask image naming convention:

hlsp_skysurf_hst_<instrument>_<sv-mv>-<visit-id>_<filter>_v1_drz-<data-file-type>.fits.gz

where:

  • <instrument> is the instrument + detector combination used; one of "acs-wfc", "wfc3-ir", or "wfc3-uvis"
  • <sv-mv> indicates whether the image is a single or multi-visit mosaic; one of "sv" or "mv"
  • <visit-id> represents the integer identifier given to that single or multi-visit mosaic

  • <filter> is the HST filter used for the image 

Data file types:

sci

The science images (drizzled mosaics) output by AstroDrizzle.

wht

The weight images output by AstroDrizzle.

modwht

The modified versions of the weight maps output by AstroDrizzle, as described in Section 3.1 of Carter et al. 2026.

ctx

The cosmic ray masks output by AstroDrizzle.

Source catalog naming convention:

hlsp_skysurf_hst_<instrument>_<sv-mv>-sources-<type>-<visit-id>_<filter>_v1_cat.csv

where:

  • <instrument> is the instrument + detector combination used; one of "acs-wfc", "wfc3-ir", or "wfc3-uvis"
  • <sv-mv> indicates whether the image is a single or multi-visit mosaic; one of "sv" or "mv"
  • <type> is one of "raw", "clean", or "all"
  • <visit-id> represents the integer identifier given to that single or multi-visit mosaic; not included in "all"-type catalogs

  • <filter> is the HST filter used for the catalog 

Data file types:

...raw...cat.csv

The original (raw) source catalogs produced by Source Extractor for each drizzled mosaic.
...clean...cat.csv

Cleaned versions of the Source Extractor source catalogs for each mosaic produced using the methods described in Section 3 of Carter et al. 2026.
...all...cat.csv

A collection of clean catalogs for a given filter merged into a single catalog, using additional filtering criteria described in Section 3.2.1 of Carter et al. 2026.

ProFound Sky-Map naming convention:

hlsp_skysurf_hst_<instrument>_<ipppssoot>_<filter>_v1_skymap.fits.gz

where:

  • <instrument> is the instrument + detector combination used; one of "acs-wfc", "wfc3-ir", or "wfc3-uvis"
  • <ippssoot> is the corresponding HST IPPPSSOOT for corresponding sky map

  • <filter> is the HST filter used for the sky map

Data file types:

skymap.fits.gz

The 2D sky-maps generated with ProFound.

Star-galaxy separation fitting parameters catalog naming convention:

hlsp_skysurf_hst_<instrument>_<sv-mv>-sgs-params_multi_v1_cat.csv

where:

  • <instrument> is the instrument + detector combination used; one of "acs-wfc", "wfc3-ir", or "wfc3-uvis"
  • <sv-mv> indicates whether the catalog is based on a single or multi-visit mosaic; one of "sv" or "mv"

Data file types:

cat.csv

The fitting parameters calculated for the various horizontal, vertical, and diagonal star-galaxy separation cuts for all SKYSURF filters.

Stellar locus polygon catalog naming convention:

hlsp_skysurf_hst_<instrument>_<sv-mv>-locus-polygon_<filter>_v1_cat.csv

where:

  • <instrument> is the instrument + detector combination used; one of "acs-wfc", "wfc3-ir", or "wfc3-uvis"
  • <sv-mv> indicates whether the catalog is based on a single or multi-visit mosaic; one of "sv" or "mv"
  • <filter> represents the HST filter used for the catalog

Data file types:

cat.csv

The x and y coordinates of the stellar locus polygon points.

IGL catalog naming convention:

hlsp_skysurf_hst_<instrument>_<sv-mv>-<type>-igl_multi_v1_cat.csv

where:

  • <instrument> is the instrument + detector combination used; one of "acs-wfc", "wfc3-ir", or "wfc3-uvis"
  • <sv-mv> indicates whether the catalog is based on a single or multi-visit mosaic; one of "sv" or "mv"

Data file types:

...partial...csv

The Carter et al. 2026 IGL fitting parameters and partial IGL measurements for all SKYSURF filters.
...extrapolated...csv The Carter et al. 2026 extrapolated IGL estimates for all SKYSURF filters (includes the partial and extrapolated IGL measurements of Tompkins et al. 2026).

Information catalog naming convention:

hlsp_skysurf_hst_<instrument>_<sv-mv>-<type>-info_<filter>_v1_cat.csv

where:

  • <instrument> is the instrument + detector combination used; one of "acs-wfc", "wfc3-ir", or "wfc3-uvis"
  • <sv-mv> indicates whether the catalog is based on a single or multi-visit mosaic; one of "sv", "mv", or left blank for input image information catalogs
  • <filter> represents the HST filter used for the catalog

Data file types:

...input-image...csv

FITS header info, sky surface brightness measurements, and other useful information for each of the 143,914 calibrated Hubble images in the SKYSURF database
...drizzled-mosaic...csv

FITS header info, completeness calculations, and other useful information for each of the 38,027 single-visit

mosaics and 7,893 multi-visit mosaics in the SKYSURF database.

Data Access

MAST Portal and Astroquery

The SKYSURF data products are available in the MAST Search Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write).

  • In the MAST Search Portal, set the Provenance Name filter to "skysurf" in an Advanced Search to find these data. The user guide for how to search and download products using the MAST Portal is available here.
  • For Astroquery, the following example code demonstrates how to search for and download these products. This code assumes that you want to download a subset of products from this HLSP (target name = 'mv-103'). You may want to change your search to include other products of interest, but we do not recommend searching for all products as this is a large HLSP (> 10 GB) with many individual files (> 10k). You can find more astroquery.mast tutorials here.
from astroquery.mast import Observations
# Search for all SKYSURF products with target_name = 'mv-103'
all_obs = Observations.query_criteria(provenance_name="skysurf",target_name='mv-103')
data_products = Observations.get_product_list(all_obs)
# Print the number of data products that would be downloaded
print(len(data_products))
# Download data
Observations.download_products(data_products)

  • MAST Portal

    Link to the MAST Portal Webpage
    A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory.
    Portal

  • MAST Astroquery

    Search for and download data products for this HLSP programmatically in Python.
    MAST Astroquery

Direct Download Scripts

Additional data for this HLSP are available for direct download using the scripts provided in the table below:

Script Description
hlsp_skysurf_hst_multi_igl-measurements_multi_v1_bulkdl.sh Bulk download cURL script for the Carter et al. 2026 IGL catalogs.
hlsp_skysurf_hst_multi_image-info_multi_v1_bulkdl.sh Bulk download cURL script for catalogs which contain image information for all images provided in this HLSP.
hlsp_skysurf_hst_multi_sky-maps_multi_v1_bulkdl.sh Bulk download cURL script for all 2D ProFound Sky-Maps contained in this HLSP.
hlsp_skysurf_hst_multi_source-catalogs_multi_v1_bulkdl.sh Bulk download cURL script for all source catalogs (raw, clean, all) contained in this HLSP.
hlsp_skysurf_hst_multi_star-galaxy-separation_multi_v1_bulkdl.sh Bulk download cURL script for the star-galaxy separation fitting parameter catalogs.

 

Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work. 

Note: These HLSP data products are licensed for use under CC BY 4.0.

References

refs-container

  • Carter et al. 2026

    SKYSURF. X. A Novel Method for Measuring Integrated Galaxy Light

  • Tompkins et al. 2026

    SKYSURF IX - The Cosmic Optical Background from Integrated Galaxy Light Measurements

  • O'Brien et al. 2023

    SKYSURF-4: Panchromatic Hubble Space Telescope All-Sky Surface-brightness Measurement Methods and Results

  • Goisman et al. 2025

    SKYSURF. VIII. Modeling SKYSURF Completeness Data for Comparison to the Hubble Space Telescope Exposure Time Calculator