A Sea of Data with PACE

A trio of faint objects (circled) captured in the James Webb Space Telescope’s deep image of the galaxy cluster SMACS 0723 exhibit properties remarkably similar to rare, small galaxies called “green peas” found much closer to home. The cluster’s mass makes it a gravitational lens, which both magnifies and distorts the appearance of background galaxies. We view these early peas as they existed when the universe was about 5% its current age of 13.8 billion years. The farthest pea, at left, contains just 2% the oxygen abundance of a galaxy like our own and might be the most chemically primitive galaxy yet identified. Credit: NASA, ESA, CSA, and STScI Same as above, but the galaxies are labeled with their identifications and the green circles have been removed.Credit: NASA, ESA, CSA, and STScI Same as above but without text.Credit: NASA, ESA, CSA, and STScI A GIF sequence of the above.Credit: NASA, ESA, CSA, and STScI The James Webb Space Telescope’s Near-Infrared Spectrograph captured the chemical fingerprints of selected galaxies behind SMACS 0723, including three faint, distant objects. When corrected for the wavelength stretch caused by the expansion of space over billions of years, the spectra of these galaxies (shown in red) exhibit features emitted by oxygen, hydrogen, and neon that show a stunning resemblance to those seen from so-called green pea galaxies found nearby (in green). Additionally, the Webb observations made it possible to measure the amount of oxygen in these cosmic dawn galaxies for the first time. The spectral lines have been stretched vertically in order to clarify these relationships. Credit: NASA’s Goddard Space Flight Center/Rhoads et al. 2023 A green pea galaxy imaged by the Sloan Digital Sky Survey is shown alongside an infrared picture of an early pea captured by NASA’s James Webb Space Telescope. At left is J122051+491255, a green pea about 170 million light-years away that’s about 4,000 light-years across, a typical size. At right is an early pea known as 04590, whose light has taken 13.1 billion years to reach us. Compensating for the cluster’s gravitational lensing effect and the galaxy’s greater distance to us, 04590 is even more compact, comparable to the smallest nearby green peas.Credit: SDSS and NASA, ESA, CSA, and STScI Same as above but without text.Credit: SDSS and NASA, ESA, CSA, and STScI

PACE orbiting the Earth showing OCI, HARP2, and SPEXone instument fields of view followed by instrument ground swath patterns This visualization shows the planned orbit of NASA’s PACE mission (Plankton, Aerosol, Cloud, ocean Ecosystem). The visualization is organized into three sections.In the first section, PACE's orbit is shown from a global view. PACE will be in a 98-degree-inclination, sun-synchronous polar orbit with an equatorial crossing time of 1:00 pm local time. PACE's orbital period (i.e., the time it takes to complete one orbit) is 98.3 minutes at an altitude of 676.5 km.In second section, the camera zooms in to look at the fields of view of each of PACE's instruments:• The Ocean Color Instrument (OCI) viewing width is 113 degrees. During each orbit on the sunlit side of the Earth, OCI will change its pointing from 20 degrees behind the spacecraft (aft) when south of the Sun's latitude to 20 degrees ahead of the spacecraft (fore) when north. This is to avoid having the instrument’s field of view look into Sun glint. OCI will change its pointing back from fore to aft on the dark side of each orbit.• The Hyper Angular Research Polarimeter (HARP2) instrument has a viewing width of 94 degrees. HARP2 has 10 viewing angles along the orbit track for its blue, green, and near-infrared wavelength channels and 60 viewing angles for its red wavelength channel. These viewing angles vary along the direction of travel over a range of 114 degrees. The ground swath as viewed on Earth will vary in width with viewing angle.• The Spectro-polarimeter for Planetary Exploration (SPEXone) instrument's ground swath is about 100 km wide. SPEXone has 5 different viewing angles from -50 degrees (aft) to +50 degrees (fore). Like HARP2, the ground swath as viewed on Earth will vary in width with viewing angle.The third section shows example ground swaths for each instrument. SPEXone has a relatively narrow swath. HARP2 has a wider swath for its nadir (straight down) view. OCI has an even wider swath. At the end all 3 instruments swaths are shown at the same time.In terms of life on Earth, color describes more than simply how features look. In many cases color serves as a proxy for biological processes. When studying ocean biology, colors count in a big way.The PACE mission has been conceived principally as a way to measure ocean color for assessing large scale ocean health. These measurements will provide data to determine the distribution of phytoplankton, tiny plants and algae that sustain the marine food web. A simple way to think about this is the more “green” that’s visible from space, the more prevalent are plant cells containing chlorophyll, an essential green pigment responsible for energy-producing photosynthesis in plants. Phytoplankton populations are fundamental to understanding the overall health of the ocean food web, as well as a wide range of related processes.PACE will be able to see other colors too—a broad range of color, in fact, stretching beyond the bounds of visible light into both ultraviolet as well as infrared. PACE will also be able to make measurements of aerosols in the atmosphere, essential for scientists to improve our understanding of and our ability to forecast weather and climate.PACE continues a more than 20 year legacy of ocean color measurements, providing the scientific community with a long time series of data. That legacy enables better assessments of long term trends about complex processes on Earth.PACE will be able to see other colors too—a broad range of color, in fact, stretching beyond the bounds of visible light into both ultraviolet as well as infrared. PACE will also be able to make measurements of aerosols in the atmosphere, essential for scientists to improve our understanding of and our ability to forecast weather and climate.PACE continues a more than 20-year legacy of ocean color measurements, providing the scientific community with a long time series of data. That legacy enables better assessments of long-term trends about complex processes on Earth. Related pages