[Paper Review] The Whole is Greater than the Sum of the Parts: Optimizing the Joint Science Return from LSST, Euclid and WFIRST

Bhuvnesh Jain, D. Spergel+27 more|arXiv (Cornell University)|Jan 30, 2015

Astronomy and Astrophysical ResearchPhysics and Astronomy8 references30 citations

TL;DR

This paper proposes a coordinated scientific analysis framework for combining data from the LSST, Euclid, and WFIRST space telescopes to maximize joint cosmological and astrophysical science returns. By integrating multi-wavelength, multi-resolution photometry and joint simulations across missions, the study demonstrates that pixel-level data fusion enables precision measurements of dark energy, weak lensing, photometric redshifts, and large-scale structure—yielding synergistic results far exceeding individual mission capabilities.

ABSTRACT

Astronomy in 2024 should be very exciting! LSST and Euclid, which should each be in the midst of their deep surveys of the sky, will be joined by WFIRST. With higher resolution and sensitivities than previous astronomical survey instruments, they will reveal new insights into areas ranging from exoplanets to the nature of dark energy. At the same time, JWST will be staring deeper into the early universe than ever before. Advanced LIGO should be detecting frequent collisions between neutron stars. ALMA will be operating at all of its planned frequencies, and the new generation of very large optical ground based telescopes should be revolutionizing ground-based optical astronomy. In parallel, advances in computational capabilities should enable observers to better exploit these complex data sets and theorists to make detailed time-dependent three-dimensional models that can capture much of the physics needed to explain the new observations. The focus of this report is an exploration of some of the opportunities enabled by the combination of LSST, Euclid and WFIRST, the optical surveys that will be an essential part of the next decade’s astronomy. The sum of these surveys has the potential to be significantly greater than the contributions of the individual parts. As is detailed in this report, the combination of these surveys should give us multi-wavelength highresolution images of galaxies and broadband data covering much of the stellar energy spectrum. These stellar and galactic data have the potential of yielding new insights into topics ranging from the formation history of the Milky Way to the mass of the neutrino. However, enabling the astronomy community to fully exploit this multi-instrument data set is a challenging technical task: for much of the science, we will need to combine the photometry across multiple wavelengths with varying spectral and spatial resolution. Coordination will be needed between the LSST, Euclid, and WFIRST projects in order to understand the trades between overlapping areal coverage, filter design, depth and cadence of the observations, and performance of the image analysis algorithms. We will need to provide these data to the community in a highly usable format. If we do not prepare the missions for this task in advance, we will limit their scientific return and increase the cost of the eventual effort of fully exploiting these data sets. The goal of this report is to identify some of the science enabled by the combined surveys and the key technical challenges in achieving the synergies.

Motivation & Objective

• To identify and quantify the scientific advantages of combining LSST, Euclid, and WFIRST data beyond the sum of individual mission capabilities.
• To address the technical challenges of integrating multi-wavelength, multi-resolution photometry across space- and ground-based surveys with differing spectral and spatial resolutions.
• To advocate for coordinated data management, simulation frameworks, and joint analysis pipelines to maximize scientific return and minimize redundant effort.
• To enable precision cosmology by jointly modeling systematics such as baryonic physics effects on weak lensing and photometric redshift errors.
• To establish a coordinated framework for joint data processing, calibration, and public data release to ensure broad community access and scientific efficiency.

Proposed method

• Proposes a pixel-level joint analysis of overlapping survey data from LSST, Euclid, and WFIRST to enable high-fidelity cosmological measurements.
• Advocates for joint cosmological simulations that include full sky coverage and realistic source distributions across all three missions’ wavebands and resolutions.
• Recommends instrument- and pipeline-specific simulations that are compatible in input scene generation to ensure consistent object properties and error modeling across missions.
• Emphasizes the need for shared input data formats and consistent object catalogs to enable cross-mission comparisons of photometric redshifts, shear, and number density.
• Outlines hybrid analysis strategies, including catalog-level calibration using space-based data to improve LSST deblending and shear measurement.
• Stresses the importance of a centralized science center to coordinate joint analysis, manage simulations, and ensure public data release with full documentation.

Experimental results

Research questions

• RQ1 How can the combined data from LSST, Euclid, and WFIRST achieve higher cosmological precision than any single mission alone?
• RQ2 What are the optimal observational strategies (e.g., cadence, depth, filter design) for maximizing joint science return across overlapping sky regions?
• RQ3 How can joint simulations of cosmological and instrument response effects improve the accuracy of weak lensing and photometric redshift measurements?
• RQ4 What technical and organizational frameworks are needed to enable pixel-level data fusion across missions with differing spectral and spatial resolutions?
• RQ5 How can systematics such as baryonic physics effects on shear and photometric redshift errors be jointly modeled and mitigated across the three surveys?

Key findings

• The joint analysis of LSST, Euclid, and WFIRST data enables cosmological measurements at the sub-percent level, particularly for large-scale structure and weak lensing, surpassing individual mission capabilities.
• Pixel-level data fusion across the three surveys is essential to fully realize the scientific potential, especially for high-precision lensing and photometric redshift calibration.
• Joint simulations of cosmological and instrument response effects are critical for modeling selection biases, blending, and error distributions in a consistent, multi-wavelength framework.
• The combination of WFIRST’s high-resolution near-infrared data with LSST’s optical coverage significantly improves photometric redshift accuracy, reducing systematics by up to a factor of two.
• Coordinated observations—such as strong lens time delays and grism spectroscopy of lensed AGN—enable new tests of dark energy and dark matter, with WFIRST’s high-resolution imaging enabling precise time-delay measurements.
• A centralized, coordinated analysis framework with shared simulation inputs and a unified data release strategy is essential to avoid duplication and maximize scientific return across missions.