NASA's latest mission dedicated to observing Earth's oceans and atmosphere from space rocketed into orbit from Florida early Thursday on a SpaceX launch vehicle.
This mission will study phytoplankton, microscopic plants fundamental to the marine food chain, and tiny particles called aerosols that play a key role in cloud formation. These two constituents in the ocean and the atmosphere are important to scientists' understanding of climate change. The mission's acronym, PACE, stands for Plankton, Aerosol, Cloud, ocean Ecosystem.
Nestled in the nose cone of a Falcon 9 rocket, the PACE satellite took off from Cape Canaveral Space Force Station, Florida, at 1:33 am EST (06:33 UTC) Thursday after a two-day delay caused by poor weather.
Nine kerosene-fueled Merlin engines powered the Falcon 9 rocket southeast from the launch site, then the reusable booster stage separated to begin maneuvers to return back to Cape Canaveral for landing. Falcon 9's upper stage engine steered the rocket and the PACE satellite on a southerly trajectory along Florida's east coast.
Around 12 minutes after liftoff, NASA's nearly 2-ton PACE satellite deployed from the Falcon 9 rocket into an on-target polar orbit at an altitude of roughly 420 miles (676 kilometers). This was the first launch of a NASA satellite into polar orbit from the Florida spaceport in more than 60 years. These types of missions flying on north-south orbital tracks have typically launched from California, but SpaceX reopened the polar orbit corridor from Cape Canaveral for commercial missions beginning in 2020.
Saved from the chopping block
NASA authorized development of the PACE mission nine years ago, but the climate research satellite became a target for the Trump administration. During each of Trump's four years in the White House, the administration's annual budget request called for zeroing-out funding for PACE, along with other Earth science missions and NASA's education office.
Each year, Congress preserved funding for PACE to keep the mission on track. Lawmakers representing districts and states with strong interests in the PACE mission helped lead the charge to keep the mission alive. A groundswell of support from scientists also helped persuade Congress to maintain funding for PACE.
The American Geophysical Union, which promotes research in Earth and space sciences, in 2018 called the Trump administration's efforts to slash funding for PACE and other climate research programs "shortsighted." Chris McEntee, the AGU's chief executive at the time, vowed to make the case for the programs earmarked for cancellation by the Trump White House. "We expect Congress to be far more realistic and strategic in providing the funding that will allow the nation’s scientific enterprise to thrive," she wrote at the time.
"It has been a long, strange trip," said Jeremy Werdell, PACE project scientist at NASA's Goddard Space Flight Center in Maryland. "We were as confident as one can be that we would find ways to persevere... We've kept our morale high."
Scientists say PACE will try to fill in some gaps in their understanding of climate change. Phytoplankton, the minuscule marine organisms, absorb carbon dioxide from the atmosphere, helping scrub the air of the greenhouse gas most responsible for our planet's rising temperatures. However, each type of plankton processes carbon dioxide differently, and phytoplankton concentrations move in response to the changing climate. To sum it up, the plankton is both an influencer of, and is influenced by, climate change.
"Right now we’re somewhat blind to it from space, and where PACE comes in is to answer those questions on daily global scales," Werdell said.
Aerosols in the atmosphere—particles from things like dust, smoke, sea spray, and industrial activity—reflect sunlight and drive the formation of clouds, which can also temper global warming.
Karen St. Germain, who oversees all of NASA's Earth science missions, said the influence of aerosols is the "biggest source of natural uncertainty in predicting climate change." Last year was the hottest year on record, scientists announced last month. Data from PACE could close gaps in this area.
"In addition to the information PACE will provide that helps us understand long-term climate, PACE will also give us information about oceans and air quality that can help people today," said Kate Calvin, NASA's chief scientist and senior climate adviser.
For example, aside from PACE's importance for climate research, the mission will monitor harmful algae blooms, such as red tides, and track concentrations of plankton feeding large fish populations. The mission could produce insights into how clouds form and the role this plays in sparking severe weather or hurricanes.
"I would think about it in a couple of different dimensions," Calvin said of the PACE mission. "One is what it will observe both in ocean and atmosphere. There, in both cases, we’re looking at tiny things, so microscopic life in the oceans and tiny particles in the atmosphere.”
The second dimension is time, she said, with PACE capable of addressing day-to-day questions about phytoplankton and tiny aerosol particles in the atmosphere, while simultaneously monitoring how these factors change over several years.
St. Germain said the support of the broader science community was instrumental in saving PACE from the budget ax. "To maintain support for missions like PACE, that really depends on us getting the story out there about the kind of science we do and why that’s so important to communities at home and around the world," she said.
The entire PACE mission is budgeted for $964 million, including the cost of the spacecraft, science instruments, the launch, and operating the satellite in orbit, St. Germain said.
Rainbow glasses
Previous space missions have done a decent job of measuring the amount of phytoplankton in the sea and the total accumulation of aerosols in the air. What scientists need now is a better way of identifying what kinds of ocean algae and phytoplankton are present in a given part of the sea, and the different kinds of aerosols suspended in the atmosphere.
This is where PACE steps in.
The PACE spacecraft and its primary sensor, the Ocean Color Instrument, were built at NASA's Goddard Space Flight Center. The Ocean Color Instrument is hyperspectral, meaning it is highly sensitive to small changes in color. While a traditional ocean imaging instrument might be able to distinguish between eight colors, PACE's main instrument is sensitive to more than 200 colors across a broad spectrum in the sunlight reflected off of phytoplankton in the ocean and aerosols in the atmosphere.
The color signatures of different species of phytoplankton are slightly different. PACE's Ocean Color Instrument is capable of detecting the difference from an altitude of more than 400 miles.
It's a similar story with measuring cloud-seeding particles in the atmosphere.
Two polarimeter instruments on the PACE spacecraft will measure the characteristics of aerosols, helping distinguish between, for example, a particle from Saharan dust blown over the ocean or smoke from a wildfire.
"Cloud droplets tend to condense around aerosols," said Andy Sayer, a PACE atmospheric scientist for NASA. "We call them cloud condensation nuclei for that reason, and how efficient an aerosol is at doing this depends on what it’s made of.
"So knowing exactly what types of aerosols we’ve got, where they are, where they’re coming (from), that’s going to help us better understand where clouds are forming, how long is it going to be before they rain, how high are they going to get," Sayer said.
PACE is designed to operate for at least three years, but it has enough fuel to maintain its orbit for more than a decade. Ground controllers will put the spacecraft and its instruments through a 60-day commissioning period to verify everything is performing normally, then data from PACE will start flowing to scientists around the world.
“PACE’s data will be open source and available no later than 60 days after launch," Calvin said.
