Lunar surface impact from Falcon 9 creates rare observing opportunity

Most lunar impacts arrive without warning.

A small meteoroid strikes the Moon and produces a flash that may last less than a second. Unless a telescope and camera happen to be pointed at the right location at the right time, the moment is gone before anyone knows it happened.

The Falcon 9 upper stage expected to strike the lunar surface on August 5 is different. Astronomers have a predicted time, an estimated impact location, and useful information about the object's size, speed, and trajectory. That gives professional observatories and amateur astronomers a rare chance to prepare for an artificial impact before it happens.

The current prediction places the impact at approximately 06:35 UTC near Einstein Crater. For observers in Missouri and the central United States, that is around 1:35 a.m. CDT. The final time could still shift by a few seconds and the location by several kilometers as the orbit continues to be refined.

A rocket stage left behind after a lunar launch

The object is the spent upper stage from the Falcon 9 mission that launched Firefly Aerospace's Blue Ghost 1 and ispace's Hakuto-R Resilience lunar landers in January 2025.

After completing its job, the stage was left in a high Earth orbit that crossed the Moon's path. Its official designations are COSPAR 2025-010D and NORAD 62719. Continued observations showed that its evolving orbit would eventually end in a collision with the Moon.

The impact is expected near Einstein Crater on sunlit terrain close to the eastern lunar limb as seen from Earth. The Moon will be a little more than half illuminated, placing the impact point against a bright part of the lunar surface rather than the dark region where impact flashes are normally easier to detect.

That location creates both the opportunity and the problem. The site should be barely visible from Earth because of lunar libration, but any flash will have to compete with scattered light from the illuminated Moon.

What will hit the lunar surface

The research paper estimates that the empty upper stage has a mass of approximately 4,000 kilograms. It is expected to strike at about 2.43 kilometers per second and at an angle of roughly 34 degrees from vertical. The estimated kinetic energy is 11.8 gigajoules.

That is much more mass than the small natural objects usually responsible for detectable lunar flashes, but the rocket stage is moving far more slowly.

Natural meteoroids commonly hit the Moon at tens of kilometers per second. The Falcon 9 stage will arrive at only a fraction of that speed. Flash brightness does not scale evenly with mass, and slower impacts can be much dimmer than their size alone would suggest.

The surface material will also influence the result. An impact into loose lunar regolith could produce a brighter flash than a collision with exposed bedrock. The stage's orientation at impact is another unknown, making any prediction of visible brightness uncertain.

There is no guarantee observers will see anything obvious.

Three possible results to watch for

The research identifies three possible observables: the impact flash, the ejecta plume, and the final crater.

The flash would be created as part of the upper stage and lunar material are heated and vaporized. It is expected to last less than one second. Estimates range from approximately magnitude +3 under favorable conditions to fainter than magnitude +15 if the impact occurs in less favorable surface material.

No confirmed natural or artificial impact flash has been detected on the illuminated portion of the Moon. That makes this observation especially difficult because the impact will not occur against a dark background.

The ejecta plume may offer a second target.

Modeling in the original study suggests the impact could excavate roughly 1.1 to 1.2 million kilograms of lunar material. Larger particles resolved by the simulation reached around 1.5 kilometers above the surface, while smaller and faster material could travel higher and remain in flight for several minutes.

Because the site is close to the lunar limb, some of that material could rise above the Moon's edge rather than remaining completely hidden against the bright surface. It would still be a difficult observation, but the plume may last considerably longer than the initial flash.

The resulting crater is expected to measure approximately 20 to 30 meters across, with one estimate placing it near 27 meters wide and around 5 meters deep. It will be far too small to resolve from Earth, but NASA's Lunar Reconnaissance Orbiter and Korea's Pathfinder Lunar Orbiter are expected to collect follow-up observations.

Amateur astronomers have a real role

The research team specifically encourages amateur astronomers to attempt observations.

High-cadence video will be important because the flash may last less than one second. The paper recommends recording at 20 frames per second or faster when possible so the flash is not missed between frames. Lower frame rates may still be useful for tracking an ejecta plume that develops over a longer period.

The paper notes that previous lunar impact campaigns have used telescopes as small as 4 inches. NASA's Impact Flash citizen science project also recommends a telescope with an aperture of at least 4 inches and video-recording equipment for normal lunar impact monitoring.

A larger telescope and sensitive camera may improve the odds, but aperture alone does not guarantee a detection. Focus, exposure, frame rate, atmospheric conditions, timing accuracy, and careful framing will all play a role.

This is one of those observations where preparation may be more important than buying another piece of equipment.

Moon | 5s - 20 Frames - Dwarf Mini

Preparing to record the lunar surface impact

Anyone planning to attempt the observation should test the complete setup before the predicted time.

Focus should be locked down early. The recording software should be tested at the intended frame rate. Computer time should be synchronized accurately, and enough storage should be available for a recording that begins before the predicted impact and continues afterward.

The field of view needs to include the lunar limb near Einstein Crater without allowing the bright surface to overwhelm the camera. Since the predicted location could still shift slightly, framing too tightly may create more risk than benefit.

Recording should begin before 06:35 UTC and continue for several minutes after the expected impact. The flash may be over almost immediately, while the plume could take time to rise and become visible.

Raw video should be preserved.

A faint flash or plume may not be obvious during the live observation. It could require image subtraction, careful frame comparison, stacking, or coordinated analysis with recordings from other observers.

What useful observations could reveal

The most valuable measurements would include the location of the flash, accurate timing, changes in brightness, and the shape and duration of any ejecta plume.

Even a non-detection may be useful if the telescope, camera sensitivity, atmospheric conditions, exposure settings, and observing location are well documented. That information can help researchers understand how faint the event must have been.

Artificial impacts are useful because many of the source properties are known in advance. Researchers have estimates for the stage's mass, dimensions, speed, trajectory, and arrival time. That makes the collision closer to a controlled experiment than a random meteoroid impact.

The event could help improve models of slow artificial impacts, test methods for locating future impact sites, study ejecta behavior, and evaluate hazards created by artificial space debris near the Moon.

NASA's Impact Flash project already uses amateur video observations to study how often objects strike the Moon, what kinds of craters they create, and what those impacts may mean for future lunar activity.

Why this lunar surface impact is worth watching

No one can promise that an amateur telescope will capture anything.

The flash may be too dim. The plume may disappear into the glare of the sunlit lunar surface. Atmospheric conditions or clouds may decide the outcome before the recording even begins.

But the opportunity is real.

A known rocket stage is expected to strike a location that should be barely visible from Earth. We know roughly where to look and almost exactly when to begin recording. Professional observatories will be watching, and amateur astronomers have been invited to participate.

Even if the result is only a long video of an apparently unchanged Moon, taking part in a coordinated observation like this is one of the things that makes amateur astronomy special.

Sometimes we photograph a target because we already know what it looks like.

This time we are watching because no one knows exactly what we will see.