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TRACERS (Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites)

Key Milestones for Upcoming NASA’s TRACERS Mission

Image shows a SpaceX rocket at the launch pad
A SpaceX Falcon 9 rocket carrying NASA’s TRACERS (Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites) mission stands vertical Tuesday, July 22, 2025, at Space Launch Complex 4 East at Vandenberg Space Force Base in California. The TRACERS mission will study magnetic reconnection around Earth — a process in which electrically charged plasmas exchange energy in the atmosphere — to understand how the Sun’s solar wind interacts with the magnetosphere, Earth’s protective magnetic shield.
SpaceX

NASA’s TRACERS (Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites) mission is targeting 2:13 p.m. EDT (11:13 a.m. PDT) today for launch on a SpaceX Falcon 9 rocket from Space Launch Complex 4 East at Vandenberg Space Force Base in California. There is a 57-minute launch window for this mission. 

The TRACERS mission is a pair of twin satellites that will study how Earth’s magnetic shield — the magnetosphere — protects our planet from the supersonic stream of material from the Sun called solar wind. As they fly pole to pole in a Sun-synchronous orbit, the two TRACERS spacecraft will measure how magnetic explosions send these solar wind particles zooming down into Earth’s atmosphere — and how these explosions shape the space weather that impacts our satellites, technology, and astronauts. 

SpaceX will provide live coverage beginning about 15 minutes before launch on the company’s website and at @SpaceX on X.   

Here’s a closer look at countdown and ascent milestones (all times are approximate): 

Hr/Min/Sec Event 

00:38:00 SpaceX Launch Director verifies go for propellant load 

00:35:00 RP-1 (rocket grade kerosene) loading begins 

00:35:00 1st stage LOX (liquid oxygen) loading begins 

00:16:00 2nd stage LOX loading begins 

00:07:00 Falcon 9 begins engine chill prior to launch 

00:01:00 Command flight computer to begin final prelaunch checks 

00:01:00 Propellant tank pressurization to flight pressure begins 

00:00:45 SpaceX Launch Director verifies go for launch 

00:00:03 Engine controller commands engine ignition sequence to start 

00:00:00 Falcon 9 liftoff 

00:01:12 Max Q (moment of peak mechanical stress on the rocket) 

00:02:13 1st stage main engine cutoff (MECO) 

00:02:17 1st and 2nd stages separate 

00:02:21 Stage 1 flip 

00:02:24 2nd stage engine starts (SES-1) 

00:02:30 Boostback burn starts 

00:02:56 Fairing separation 

00:03:26 Boostback burn ends 

00:06:04 1st stage entry burn begins 

00:06:21 1st stage entry burn ends 

00:07:12 1st stage landing burn begins 

00:07:46 1st stage landing 

00:08:02 2nd stage engine cutoff (SECO-1) 

00:50:44 2nd stage engine starts (SES-2) 

00:50:47 2nd stage engine cutoff (SECO-2) 

00:54:30 Bard deploys 

00:54:50 REAL deploys 

01:05:40 2nd stage engine starts (SES-3) 

01:05:41 2nd stage engine cutoff (SECO-3) 

01:30:07 2nd stage engine starts (SES-4) 

01:30:08 2nd stage engine cutoff (SECO-4) 

01:34:26 First TRACERS satellite deploys 

01:40:41 Second TRACERS satellite deploys 

01:44:46 Epic Athena deploys 

01:45:06 LIDE deploys 

01:45:26 Skykraft 4 deploys  

Follow @NASAKennedy on X and Facebook for additional updates on the mission.