Following a pair of 24-hour postponements, due to unfavorable weather conditions on the Space Coast and higher-than-allowable ground winds preventing critical pre-launch checkouts, NASA’s $805 million Plankton, Aerosol, Cloud, Ocean Ecosystem (PACE) mission is officially underway, having taken flight at 1:33:36 a.m. EST Thursday atop a SpaceX Falcon 9 booster from storied Space Launch Complex (SLC)-40 at Cape Canaveral Space Force Station, Fla. The spacecraft and its three scientific instruments—a first-of-its-kind optical spectrometer and a pair of multi-angle polarimeters—have been a decade in the making and will spend up to a decade in low-Earth orbit performing critical measurements of our planet’s atmosphere and oceans on a global scale.
“Congratulations to the PACE team on a successful launch,” said NASA Administrator Bill Nelson. “With this new addition to NASA’s fleet of Earth-observing satellites, PACE will help us learn, like never before, how particles in our atmosphere and our oceans can identify key factors impacting global warming. Missions like this are supporting the Biden-Harris Administration’s climate agenda and helping us answer urgent questions about our changing climate.”
Launching PACE was the four-times-flown B1081 booster core, which entered service last August to deliver Dragon Endurance and her Crew-7 quartet of NASA astronaut Jasmin Moghbeli, Denmark’s Andreas Mogensen of the European Space Agency (ESA), Satoshi Furukawa of the Japan Aerospace Exploration Agency (JAXA) and Russian cosmonaut Konstantin Borisov to the International Space Station (ISS), where they currently reside. Two additional launches of B1081 last November and December delivered SpaceX’s CRS-29 Cargo Dragon for a month-long research stay at the space station and a 23-strong batch of Starlink low-orbiting internet communications satellites.
Liftoff of PACE was originally scheduled for 1:33 a.m. EST Tuesday, but with weather hovering no higher than 50-50 favorability, NASA and SpaceX teams opted late Monday to call off the first launch attempt and refocus on Wednesday instead. SpaceX also tweeted on X that high winds at the Cape’s Landing Zone (LZ)-1, where B1081 was set to make a solid-ground touchdown, were also unfavorable.
This grim picture made it not unreasonable for teams to stand down well in advance of Tuesday’s launch attempt and refocus on Wednesday’s pre-dawn hours when the Probability of Go (PGo) was predicted to improve to 95 percent. Only a “very low risk” of a Cumulus Cloud Rule violation stood in PACE’s way for Wednesday.
But yesterday also proved not to be a good day, as the long-awaited launch was again called off due to higher-than-allowable ground winds that precluded several critical pre-flight checkouts of the vehicle. Although PACE’s prime T-0 point, which has sat at 1:33 a.m. EST each day this week, is not strictly “instantaneous”, it only offered a roughly 90-second period of time, with SpaceX and NASA teams aiming for the middle of the “launch window” in order to leave the second half available to accommodate potential Collision Avoidance (COLA) considerations.
By Thursday, however, the weather had begun to turn a corner and the high winds began to subside. “Winds will decrease and veer from the north to the northeast,” noted the 45th Weather Squadron in an update yesterday afternoon. “While a few low-topped coastal showers can’t be ruled out in the evening/overnight hours, dry mid-level air will cap off any significant vertical development.
“High pressure will remain in control and similar conditions will persist through the remainder of the week,” the 45th concluded. “For both the primary launch window early Thursday morning and backup window early Friday morning, weather looks very favorable with the only concern being the very low risk of a Cumulus Cloud Rule violation.”
Originally tracking a liftoff at 1:33:32 a.m. EST, the T-0 point slipped slightly by four seconds in response to an anticipated COLA conjunction. As the clock passed T-1 minute and the Falcon 9 flight computers transitioned to “Startup”, the excitement began to build as a mission that had been a decade in the making approached fruition.
“Many on the PACE Spacecraft Team now going outside to watch this launch,” reported NASA commentator Derrol Nail at T-45 seconds. “It should be a beauty.”
His words could not have been better chosen and B1081 roared aloft perfectly, kicking ofF SpaceX’s inaugural mission of February. “Liftoff of the Falcon 9 and PACE,” exulted Mr. Nail. “Helping “keep pace” with our ever-changing atmosphere and ocean.”
B1081 powered the 230-foot-tall (70-meter) stack uphill for opening 2.5 minutes of ascent, before separating and executing a picture-perfect descent to alight on solid ground at the Cape’s Landing Zone (LZ)-1 at T+7 minutes and 30 seconds. Meanwhile, the single Merlin 1D+ Vacuum engine of the Falcon 9’s second stage burned longer than normal on this mission—igniting at T+2 minutes and 30 seconds and running for almost eight full minutes—in what Mr. Nail described as a “direct-inject” to get PACE into its 420-mile-high (675-kilometer) polar orbit at 98 degrees of inclination.
Spacecraft separation occurred at 12 minutes and 22 seconds into the flight.
Weighing 3,750 pounds (1,700 kilograms), PACE is managed by NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Md. It will provide global views of microscopic algae concentrations, known as “phytoplankton”, which occupy the sunlit upper part of the oceans and produce at least half of Earth’s oxygen and forming the base of the marine food chain.
Quantifying phytoplankton levels, NASA noted, carries important implications for expanding human knowledge of the carbon cycle and tracking climatic variability and change over time. “Knowing more about global phytoplankton community composition will help us understand how living marine resources respond to a changing climate,” said Project Scientist Jeremy Werdell of GSFC. “With PACE, we will learn more about the role of marine phytoplankton in the global carbon cycle.”
In June 2016, PACE transitioned out of its preliminary design phase at Key Decision Point-A (KDP-A) and the following September NASA opted to build the spacecraft “in-house”. This decision enabled instrument designs and capabilities to mature as the mission developed, as well as affording improved flexibility to meet budgetary and schedule challenges and in recognition of the fact that all the requisite engineering facilities and core competencies were readily available at GSFC.
Passing Key Decision Point-B (KDP-B) in August 2017, the “pace” of PACE accelerated as the design of the spacecraft and its primary instrument, the GSFC-furnished Ocean Color Instrument (OCI) got underway. Described as a first-of-its-kind optical spectrometer in terms of capability, OCI will take hyperspectral measurements of the oceans, covering a broader swath of the electromagnetic spectrum than any of its predecessor missions.
“We’re going to look at everything in the range from ultraviolet all the way out to shortwave infrared,” said PACE Project Manager André Dress of GSFC. “Other missions have only taken slices, and while that gives you good data, it doesn’t give you all of the information about different types of phytoplankton life in the ocean.”
Also sharing payload space aboard PACE are a pair of multi-angle polarimeters: the Hyper-Angular Rainbow Polarimeter-2 (HARP-2)—a follow-on from HARP, an initial hyper-angular rainbow polarimeter deployed from the ISS as a CubeSat in February 2020—and the Spectropolarimeter for Planetary Exploration (SPEXone). Developed by the University of Maryland, Baltimore County (HARP-2) and the Netherlands Institute for Space Research (SRON) and Airbus Defence and Space Netherlands (SPEXone), these instruments will accurately characterize aerosol properties and particulate sizes and compositions with unprecedented levels of accuracy and detail.
Together, the data output from OCI, HARP-2 and SPEXone will enable better quantification of phytoplankton and aerosol-particle effects upon marine biology, ocean chemistry and the home planet’s energy budget and ecological forecasting. PACE will permit scientists to better monitor fisheries, identify harmful algal “blooms” and observe changes over time in marine resources.
“Observations and scientific research from PACE will profoundly advance our knowledge of the ocean’s role in the climate cycle,” said Karen St. Germain, director of the Earth Science Division within the Science Mission Directorate at NASA Headquarters in Washington. “As an open-source science mission with early adopters ready to use its research and data, PACE will accelerate our understanding of the Earth system and help NASA deliver actionable science, data, and practical applications to help our coastal communities and industries address rapidly evolving challenges.”
“It’s been an honor to work with the PACE team and witness firsthand their dedication and tenacity in overcoming challenges, including the global pandemic, to make this observatory a reality,” said Marjorie Haskell, PACE program executive at NASA Headquarters. “The passion and teamwork are matched only by the excitement of the science community for the data this new satellite will provide.”
Attention now turns to Vandenberg Space Force Base, Calif., where another Falcon 9 is gearing up for launch with a 22-strong batch of Starlink internet communications satellites later on Thursday. Postponed yesterday due to poor weather on the West Coast, the veteran B1071 booster is now targeted to rise from Space Launch Complex (SLC)-4E during a raft of T-0 points extending from 4:56 p.m. PST through 8:54 p.m. PST.