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NASA's Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) mission, a collaborative effort led by the University of Iowa (UI) with substantial contributions from Southwest Research Institute (SwRI), has entered its final integration phase. NASA is set to launch TRACERS' two satellites into low Earth orbit on July 22nd from Vandenberg Space Force Base in California. The TRACERS mission will explore the dynamic interactions between the sun's and Earth's magnetic fields.

SwRI is providing comprehensive mission management and science to UI and has developed the Analyzer for Cusp Ions (ACI) instruments, which study how the magnetic fields of the sun and Earth interact by making novel measurements on the north polar cusp. In addition to managing the development of the two satellite bus platforms provided by Millennium Space Systems and supporting instrument integration and testing, SwRI will support science operations post launch.

"TRACERS has two identical satellites outfitted with five instruments, each to collect data from over 3,000 cusp crossings during its one-year primary mission," said SwRI's Mark Phillips, deputy project manager for TRACERS. "By observing from two points along the orbit, the mission offers a multidimensional view of these reconnection events, providing crucial insights into how solar wind conditions impact the magnetosphere. This information is vital to understanding space weather phenomena that can disrupt satellite operations, communications and power grids on Earth."

The spacecraft will observe particles and fields in Earth's northern magnetic cusp region, which encircles the North Pole where our planet's magnetic field lines curve down toward Earth. This unique vantage point allows researchers to study how magnetic reconnection—when field lines connect and explosively reconfigure—affects the space environment.

"TRACERS is an exciting mission," added SwRI's Dr. Stephen Fuselier, the mission's deputy principal investigator and lead of the ACI instruments. "We flew NASA's TRICE-2 rockets in 2018 as a part of the international, multimission Grand Challenge Initiative—Cusp observational campaign. The data from that single pass through the cusp was amazing. We can't wait to get the data from thousands of cusp passes."

TRACERS will provide important context for data from the SwRI-led Magnetospheric Multiscale (MMS) mission, launched in 2015. MMS characterized magnetic reconnection in Earth's magnetosphere on the microscale for the first time. Magnetic reconnection is responsible for explosive solar events, such as solar flares and coronal mass ejections, which drive disturbances in Earth's space environment.

Such disturbances produce spectacular auroras, while the high-energy electromagnetic radiation they send toward Earth can shut down electrical power grids and disrupt satellite-based communication and navigation systems.

"Based on a standard top-hat electrostatic analyzer design, the ACI sensor measures energy-angle distributions every 0.3 seconds with excellent energy resolution and high-cadence coverage," Fuselier explained.

"By measuring how energy disperses separately by both TRACERS spacecraft, we can determine the nature of reconnection variability. If the changes occur at the same latitude on both spacecraft, then reconnection is spatially variable. If the changes occur at different latitudes, then reconnection is temporally variable."

The ACI instruments have direct heritage from the TRICE-2 ion analyzers and the Hot Plasma Composition Analyzers on MMS.

TRACERS will be the first long-term space mission to explore this process at the Earth's cusp with two satellites. Their observations will help researchers understand how processes change over both space and time. The cusp vantage point permits simultaneous observations of reconnection throughout near-Earth space.

Additional science observations will be enabled by combining the TRACERS data with observations from the SwRI-led PUNCH mission. In this context, scientists will gain a more complete understanding of how energy from the sun's atmosphere flows from the sun and through Earth's magnetosphere and atmosphere.