For The Public

Overview / HLIS at a Glance

Roman: The Nancy Grace Roman Space Telescope, projected to launch by May 2027, is NASA’s next groundbreaking instrument for learning about the cosmos. With a field of view 100 times larger than the Hubble Space Telescope and the ability to observe the sky 1,000 times faster, the science made possible by the Roman Space Telescope will completely change how we understand our universe.  Roman’s central goals include learning about dark matter, directly observing planets orbiting other stars, and answering questions about the mysterious dark energy that makes up most of the universe.  

HLIS: Roman’s science  goals will be accomplished through several major surveys. The High Latitude Imaging Survey (HLIS)  is Roman’s primary cosmology survey, and will advance our understanding of the origins and expansion history of the universe. In the HLIS Project Infrastructure Team (PIT), we develop the architecture to ensure that the HLIS can achieve its full potential, measuring the properties of the universe using Roman’s Wide Field Instrument  with maximal precision. 

Interested in learning more about Roman and the HLIS? Check out the following links for more information on a variety of Roman-related topics:

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FAQ: Physics background

What is cosmology?

Cosmology is the study of the universe's origin, structure, and evolution. It seeks to answer fundamental questions about how the universe began, what it’s made of, and how it changes over time. Using advanced instruments like the Roman Space Telescope, scientists can explore dark matter, dark energy, and the large-scale structure of the cosmos, helping us understand the forces shaping the universe and its ultimate fate.

What are dark matter and dark energy?

While we can directly observe stars, galaxies, and other visible objects in the universe, a significant portion of the cosmos is made up of something we cannot see: dark matter. This mysterious substance doesn’t emit or interact with light, making it invisible to our telescopes. However, we know it exists because of its gravitational effects, such as the way it holds galaxies together and distorts light. Dark matter acts like a cosmic scaffolding, shaping the formation of galaxies and galaxy clusters. 

On an even grander scale, the universe’s expansion is being driven by another unknown force: dark energy. Unlike dark matter, which pulls objects together through gravity, dark energy pushes the universe apart, making it expand faster over time. This mysterious force makes up nearly 70% of the energy content of the universe, yet its nature remains one of the biggest puzzles in cosmology. By studying how galaxies are distributed and how they move, we can gather clues about both dark matter and dark energy. The Roman Space Telescope will help us unlock these mysteries by providing precise measurements that can test our theories about the invisible forces that shape the universe.

What is gravitational lensing? 

Imagine holding a candle behind the curved bottom of a wine glass, like in Figure 1. The glass bends the light, creating distorted and sometimes magnified patterns. In space, a similar phenomenon happens when light from distant galaxies passes near massive objects (called “lensing objects”), such as galaxies or galaxy clusters. This process is called gravitational lensing, and it provides two key types of information: strong lensing (SL) and weak lensing (WL).

niko_stronglensing_demonstration

Figure 1: Strong lensing demonstration. The light from our source (candle) is distorted due to the lensing effect (the bottom of the wine glass acts like a lens). The same phenomenon occurs when the light source is a galaxy and the lens is a large mass between us and the source. Photo credit: N. Šarčević

Strong lensing occurs when the alignment between a distant galaxy, the lensing object, and the observer is just right. The immense gravitational field of the intervening object distorts the light so dramatically that we can see multiple images, arcs, or even full "Einstein rings" (Figure 2) of the background galaxy. By studying these distortions, we can measure the mass of the lensing object very accurately. Strong lensing offers a direct way to "weigh" galaxies and clusters of galaxies, including the invisible dark matter that surrounds them.

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Figure 2: Einstein ring/Horseshoe galaxy. Credit: NASA/Public domain.

In contrast, weak lensing is subtler. Rather than producing visible distortions in individual galaxies, it slightly stretches and shears the shapes of millions of galaxies. The distortions are too small to be noticed in one galaxy, but when we study the shapes of thousands or even millions of galaxies, we can detect patterns that reveal the large-scale structure of the universe. Weak lensing allows us to map the distribution of both visible and dark matter across cosmic scales.

How will Roman use these tools to understand the mysteries of the cosmos?

The upcoming Roman Space Telescope will be a powerful tool for both strong and weak lensing studies. Its high-resolution images of large sections of the sky will allow scientists to use these lensing effects to investigate the distribution of mass in the universe. By carefully measuring how galaxies are distorted, we can learn not only where matter is but also how it has evolved over time.

Here’s what each lensing effect helps us uncover:

  • Strong Lensing: Helps us directly measure the mass of galaxies and galaxy clusters, including the hidden dark matter. It also allows us to study distant galaxies magnified by the lensing effect, offering a window into the early universe.

  • Weak Lensing: Maps out the large-scale structure of the universe, giving us insight into how matter, both normal and dark, is distributed. By comparing weak lensing data over time, we can track how cosmic structures have grown and evolved.

Together, these lensing techniques will help the Roman Space Telescope provide critical clues about the universe’s composition and structure. Strong lensing gives us precise measurements of individual massive objects, while weak lensing reveals the broader distribution of matter, offering a powerful combination of tools to investigate some of the universe’s most profound mysteries.

FAQ: Roman HLIS

Who / what is the PIT?

The HLIS Project Infrastructure Team (PIT) is a  collaboration of ~90 people across 25 Institutions in 12 states and 3 countries.  Our team consists of scientists and engineers at all stages in their careers, from undergraduate and graduate students to leading researchers in cosmology and people who have worked on Roman since its conception as an idea.

We work together to plan all components of the High Latitude Imagine Survey (HLIS). This includes working to control sources of error on the telescope and its detectors, writing the software infrastructure for science analysis, and forecasting our ability to execute Roman science at the highest precision possible. We also plan the basic aspects of the survey, such as where and how it will take place, based on our own team’s expertise and consultation with the broader Roman and astronomy community as a whole.  In addition to laying the foundations for Roman to achieve its cosmological science goals, we are also planning for future collaborations and joint analyses between Roman and other current and upcoming astrophysics observatories including DESI, LSST, JWST, and more. 

The HLIS PIT is just one of five Project Infrastructure Teams working hard to construct Roman missions that will achieve unprecedented goals in astrophysics research.  To learn more about the other PITs, visit some of the links to their sites below.


More about the PITs: