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I'm not even going to name the object because there's been some variability and excitement in its identification (DSCOVR 2nd stage, no not DSCOVR, it's Chinese, no not that Chinse rocket body, this one, etc.)

I think it will hit the Moon this week circa March 3, 4, or 5 2022.

From Project Pluto's Corrected identification of object about to hit the moon:

Short version : back in March 2015, I (mis)identified this object as 2015-007B, the second stage of the DSCOVR spacecraft. We now have good evidence that it is actually 2014-065B, the booster for the Chang'e 5-T1 lunar mission. (It will, however, still hit the moon within a few kilometers of the predicted spot on 2022 March 4 at 12:25 UTC, within a few seconds of the predicted time. In fact, we've gotten more observations refining the impact point slightly.)

That post also includes a link to https://pastis.home.blog/2022/01/20/impact-lunaire-le-04-03-2022/ where photographs of the object show a "dotted line" because the object seems to be tumbling and oscillating dramatically in brightness (nominal ~ +16 mag)

Question: Can we watch the object hit the Moon this week at home? Will there be live telescope feeds just in case there's a plume?

I think it's going to hit the far side of the Moon so the chances of seeing anything thrown up by the impact are probably very low.

But it is an object tracked by reflected sunlight seen in optical telescopes, so it will be a star-like dot that moves towards the Moon and then disappear behind it.

Can we watch that at home somehow?

"bonus points:" Does anybody know how fast it will appear to move towards the Moon? 1 degree per second? Faster? Slower?

For reference see:

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    $\begingroup$ Should have made a tracking website for this... Oh well. It won't be particularly fast, of that I am sure. $\endgroup$
    – PearsonArtPhoto
    Mar 2 at 21:42
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    $\begingroup$ Highly related $\endgroup$ Mar 2 at 21:58
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    $\begingroup$ @BrendanLuke15 Excellent; ! I've added it to the post. $\endgroup$
    – uhoh
    Mar 2 at 22:00
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    $\begingroup$ From Horizons News: A trajectory for the object (discarded debris) expected to impact the lunar farside on March 4 is available as object "-78000" or "WE0913A". ssd.jpl.nasa.gov/api/… $\endgroup$
    – PM 2Ring
    Mar 3 at 11:27
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    $\begingroup$ Here's a dump of the distance & speed for the final day, using a 30 minute time step. ssd.jpl.nasa.gov/api/… I guess that means the impact speed is 4 km/s, but I don't know how trustworthy that final figure is. $\endgroup$
    – PM 2Ring
    Mar 3 at 12:44

2 Answers 2

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Big thanks to @PM2Ring for pointing us to the HORIZONS data!


Looking at the Earth referenced state vectors, the data is (relatively) low precision. The position resolution is in "steps" of 1000 km and the velocity resolution is in "steps" of 1 m/s. Though this directly says nothing about the data's accuracy, it may suggest (relatively) low confidence in its accuracy.

I used the HORIZONS data to create an animation of the objects trajectory to get a better sense of potential observation geometry:

The low solar phase angle leading up to and at impact makes observations difficult if not impossible due to the (relatively) bright twilight sky. This animation also shows that (from an Earth perspective) it is more so the Moon slamming into the impactor!

The angular separation rate is shown in this plot below (50 point smoothing):

ang. sep. rate

It looks ugly because of the aforementioned low resolution data causing the sort of "bounce" seen (note that this is reduced significantly in this plot because of the 50 point moving average used to smooth out the undesired "bounce").

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    $\begingroup$ Very nice! The only time I've seen Horizons output not be continuous and smooth is when they stitch solutions together (e.g. 1, 2) Do you know why this data is so weird and noisy when you look at angular rate? Are you calculating angular rate yourself or having Horizons output it? $\endgroup$
    – uhoh
    Mar 4 at 21:29
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    $\begingroup$ @uhoh self calculated, it's "noisy" because of the low precision state vectors and my finite difference rate representation (matlab fcn "diff"). The Earth relative XYZ values stick to multiples of 1000 (at first) then multiples of 100-500. Can HORIZONS output angular separation rate? $\endgroup$ Mar 4 at 22:08
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    $\begingroup$ @uhoh my guess is that the likely informal nature/source of the ephemeris data is the reason behind the low resolution. I checked output 25, and there is correspondingly low precision again, leading to the same issues. $\endgroup$ Mar 4 at 22:33
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    $\begingroup$ @uhoh it might actually be user (me) error! Excel likes to crunch down scientific notation resolution when saved as a CSV file. I'm too lazy to check atm though :) $\endgroup$ Mar 6 at 17:00
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    $\begingroup$ Ah! That could explain it, yes. $\endgroup$
    – uhoh
    Mar 6 at 17:03
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No

At least according to Jonathan McDowell's @planet4589 tweet:

A reminder that there is no live tracking of the impacting rocket stage. Based on observations made weeks ago, we're confident that it will hit Hertzprung crater at 1225 UTC Mar 4, because we trust Uncle Isaac - successfully predicting the trajectory of things in space since 1687

This is surprisingly misleading since a big factor limiting the accuracy of trajectory prediction for empty rocket bodies is that they are large, highly reflective, relatively low average density, and can tumble chaotically, so they get pushed around by solar photon pressure.

It's exactly the non- Newtonian forces that make cis-lunar and heliocentric rocket body trajectories so challenging in the first place!

Further reading:

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