Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) is a orbiter mission tasked to study the origins of thesolar wind and how it affectsEarth. TRACERS was proposed byCraig A. Kletzing at theUniversity of Iowa who served asPrincipal Investigator until his death in 2023.[3] David M. Miles at theUniversity of Iowa was named as Principal Investigator in his stead.[4] The TRACERS mission received US$115 million in funding from NASA.[5]
A computer simulation of theEarth's magnetic field. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away.
TRACERS is a mission byNASA that aims to answer long-standing questions critical to understanding the Sun-Earth System. TRACERS is a pair of identically instrumented spinning spacecraft that will study how the Sun'ssolar wind interacts with the Earth'smagnetosphere. TRACERS was initially planned to be launched as a secondary mission to another orbiter,Polarimeter to Unify the Corona and Heliosphere (PUNCH). PUNCH will study thesolar wind, a stream ofcharged particles emanating from theSun, while TRACERS will study Earth's response.[6]
To study magnetic reconnection at Earth’s magnetopause, TRACERS will fly through the polar cusp, a point where Earth’s magnetic field dips down toward the ground. There, particles funnel through the cusp into a concentrated part of our atmosphere.
TRACERS observessolar particles interacting withEarth's magnetic field at the northern magnetic cusp region. In the cusp, the field lines act as a guide to particles moving from the boundary between Earth's magnetic field down into the atmosphere. In a process known asmagnetic reconnection, the field lines violently reconfigure, sending particles out at speeds that can approach thespeed of light. Some of these particles will be guided by the Earth's field into the region where TRACERS can observe them.[6][7] TRACERS studies a longstanding question about where reconnection happens at themagnetopause and how the solar wind affects its place and timing, helping NASA better forecast the influx of energetic particles into Earth's magnetic field that has the potential to disrupt the power grid and satellite communications.[6] TRACERS and PUNCH will work together with the other existingheliophysics spacecraft.[7]
On 20 June 2019, NASA announced that PUNCH and TRACERS were the winning candidates to become the next missions in the agency'sSmall Explorer program.[8] On 29 September 2023NASA Launch Services Program selectedSpaceX'sFalcon 9 rocket to provide the launch service for TRACERS launch through the Venture-Class Acquisition of Dedicated and Rideshare (VADR) program.[9]
TRACERS was launched on July 23, 2025 at 18:13UTC fromVandenberg Space Force Base in California.[10] Both Space Vehicles 1 and 2 were successfully deployed at T+01:35:02 and T+01:39:37.[11] Instruments will slowly be activated throughout the following weeks.[12]
On July 25, 2025, NASA announced that commissioning of the TRACERS spacecraft would be paused as teams investigate why "routine adjustments to the power subsystem" did not achieve the "desired results" on one of the two satellites.[13]
On September 11, 2025, NASA has confirmed that communication has been restored with SV1, one of two TRACERS satellites, that had a power subsystem problem two days after launch. The other spacecraft, SV2, completed post-launch commissioning without issue.[14]
Electric Field Instrument (EFI) a two axis electric field experiment to measure electric fields from 1 Hz to 1 kHz.will be provided byUniversity of California, Berkeley.
Analyzer for Cusp Electrons (ACE) an electrostatic analyzer to measure cusp electrons from 40 eV to 10 keV will be provided byUniversity of Iowa.
Analyzer for Cusp Ions (ACI) is an electrostatic analyzer to measure cusp ions from 50 eV to 10 keV.
A technology demonstration, Magnetometers for Innovation and Capability (MAGIC), was added in 2020 with the goal to test prototype magnetic-field instruments.[5]
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