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Early this morning we measured the brightness changes of a car tumbling in space! Credit to Erik Dennihy (@UNC), we can report that Tesla Roadster (Starman, 2018-017A) is rotating with a period of 4.7589 +/- 0.0060 minutes.pic.twitter.com/LA4YzdvjK9
You can see the car blinking in our time-lapse from the 4.1-m SOAR telescope in Chile, taken in twilight on 2018-02-10. The car is already more than 1 million km away, tens of thousands of times fainter than can be seen with the unaided eye.pic.twitter.com/WPHTPjps57
Considering the shape, I might think that the light curve is dominated by the harmonic, and the rotation period is 9.518 +/- 0.012 minutes? May depend on rotation axis and undercoating.
Yes, I reckon the peaks are the sides of the rocket 2nd stage, so two per rotation.
Is the car still attached to something? I thought it was detached from the 2nd stage bus. no?
SpaceX has confirmed that it's still attached to the second stage. Here is the car + stage adapter (plus mounts for the cameras).pic.twitter.com/DNEV5rDNYX
It's very hard to get a fixed reference point over a full cycle on their early videos, but the Earth comes into view on a period closer to 4.75 min than 9.5 min, for what it's worth:https://youtu.be/aBr2kKAHN6M?t=2h57m11s …
It's done a burn since then, and maybe dumped RCS propellant, so it could have changed. Clear though from that that it (at least was) rotating on the 2nd stage long axis.
Yep, third burn might have changed this. I wonder if @SpaceX even knows the rotation period.
Folding things on 9.518 min doesn't look particularly asymmetric, although there are only 3 points per bin. Any asteroid folks care to comment? cc: @erinleeryan @rszabo75pic.twitter.com/JN6DOD5K8C
I'd quite like to know if asteroid shape inference algorithms can retrieve a car! /cc @ChedyRaissi
Here is the reduced light curve for anyone who'd like to try to fit it: http://k2wd.org/share/roadster.dat …
and why do we care?
Observing something we know the shape of, calibrates the methods we use to measure unknown objects. And it's fun.
*Do* we know the shape of it? AIUI it's not just a roadster, there's the upper stage, there's the payload mount, there's whatever framework the cameras are on. Genuinely curious.
Yes, we know the shape of it. And if any astronomers aren’t sure they can check launch images or ask SpaceX when they analyze their data.
OK, cool. Can you link to a diagram of the whole object? (I doubt a photograph of it exists, given the circumstances of launch: when would it have been taken?)
A photo of the whole object probably doesn’t exist, but it could be pieced together from photos that do.
Here’s the image from the released animation. It doesn’t have dimensions, but I’m sure you could ask SpaceX if it’s for science.pic.twitter.com/aV8iqRGBtQ
Anyone that doesn't see the value of measuring a know object in space, or all the other things it's silliness has inspired & will teach, is polluting this blue ball and consuming valuable oxygen! (End rant) ION: I need an astro for dummies book so I can play with these formulas!
Plenty of relevant formulae on Wikipedia, and sufficiently well presented. If you mean that you need a training course in celestial mechanics, that's a different thing.
I will Google "space formulae" and see what I find! Thanks for the lesson. I wish we learned this in highschool physics. I loved Math when it was used to decode and understand natural systems. Regretful that I bought into the "girls aren't good at math" stigma :( Total BS
Lots of great women space engineers, and we sadly lost many more due to that BS. Suggest "astrodynamics" and "orbital mechanics" as good starting search terms.
Warmed my heart and fed my brain 
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