Orwell Astronomical Society (Ipswich)
Falcon 9 Carrying Four Probes, 28 February - 05 March 2025
At 00:17 on 27 Febuary 2025, a SpaceX Falcon 9 rocket blasted off from Kennedy Space Centre's Launch Complex 39A carrying four probes:
On 28 February, I attempted to image the craft (some or all of them!) The biggest challenge was caused by the poor viewing angle: all the craft were only some 40° distant from the Sun, visible after sunset.
The following image captures the second stage of the Falcon 9, at a magnitude of 15.5-16.0. The stage is white and measures 13.8 m long and 3.7 m in diameter. Athena is considerably smaller, some 4.7 m tall, and the other rideshares are much smaller still. The poor viewing angle meant that only the carrier stage was visible.
On 05 March, with an improved elongation from the Sun (~70°), I tried again to see the Falcon 9. ProjectPluto.com predicted a magnitude of 15.3, which should have been relatively easy to observe, even though motion of the stage would limit exposure times to 10 s. However, I could see nothing in individual images. Tracking and stacking revealed the Falcon 9, but it was very faint: see image below.
But how faint was it? Everything else in the above photo is a streak. However I can estimate the apparent "volume" of the Falcon 9 and compare that to stars of known brightness in another single frame. The composite frame can see about 6.5 magnitudes fainter (2.5*log10(408)) than a single frame. This gives an estimated magnitude of 17.8. If I had known in advance that the Falcon 9 was so faint, I'm not sure that I would have tried to image it! The following is a movie version: each frame is a sum of one hundred 10 s sub-frames.
Nigel Evans