Key Milestones for Tonight’s Launch

A SpaceX Falcon 9 rocket, carrying NASA’s SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) observatory and PUNCH (Polarimeter to Unify the Corona and Heliosphere) satellites, is vertical at Space Launch Complex 4 East from Vandenberg Space Force Base in California on Saturday March 8, 2025. SPHEREx will use its telescope to provide an all-sky spectral survey, creating a 3D map of the entire sky to help scientists investigate the origins of our universe. PUNCH will study origins of the Sun’s outflow of material, or the solar wind, capturing continuous 3D images of the Sun’s corona and the solar wind’s journey into the solar system.
A SpaceX Falcon 9 rocket, carrying NASA’s SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) observatory and PUNCH (Polarimeter to Unify the Corona and Heliosphere) satellites, is vertical at Space Launch Complex 4 East from Vandenberg Space Force Base in California on Saturday March 8, 2025. Photo credit: SpaceX

We’re about 90 minutes away from tonight’s launch of NASA’s SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) and PUNCH (Polarimeter to Unify the Corona and Heliosphere) missions aboard a SpaceX Falcon 9 rocket from Space Launch Complex 4 East at Vandenberg Space Force Base in California. Liftoff is targeted for 11:10 p.m. EDT (8:10 p.m. PDT).  

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

COUNTDOWN:
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    First stage liquid oxygen (LOX) loading begins
– 00:16:00    Second 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

LAUNCH, LANDING, AND SPACECRAFT DEPLOYMENT:
Hr/Min/Sec Event
00:00:00       Falcon 9 liftoff
00:01:08        Max Q (moment of peak mechanical stress on the rocket)
00:02:16        First stage main engine cutoff (MECO)
00:02:20       First and second stages separate
00:02:28       Second stage engine starts (SES-1)
00:02:33       Boostback burn starts
00:03:00      Fairing separation
00:03:28       Boostback burn ends
00:07:54       First stage landing
00:08:16       Second stage engine cutoff (SECO-1)
00:39:28      Second stage engine starts (SES-2)
00:40:10       Second stage engine cutoff (SECO-2)
00:41:56       SPHEREx separation
00:52:16       First set of PUNCH satellites separate
00:53:07      Second set of PUNCH satellites separate 

NASA’s live launch broadcast will begin at 10:15 p.m. EDT (7:15 p.m. PDT) and will air live on NASA+ and the agency’s website. 

Learn how to stream NASA content through a variety of platforms, including social media. You can also continue following along right here on the blog as we take you through the entire flight profile.