APOD: Earthset from Orion (2024 Nov 20)

[APOD Robot]

Earthset from Orion

Explanation: Eight billion people are about to disappear in this snapshot from space taken on 2022 November 21. On the sixth day of the Artemis I mission, their home world is setting behind the Moon's bright edge as viewed by an external camera on the outbound Orion spacecraft. Orion was headed for a powered flyby that took it to within 130 kilometers of the lunar surface. Velocity gained in the flyby maneuver was used to reach a distant retrograde orbit around the Moon. That orbit is considered distant because it's another 92,000 kilometers beyond the Moon, and retrograde because the spacecraft orbited in the opposite direction of the Moon's orbit around planet Earth. Orion entered its distant retrograde orbit on November 25. Swinging around the Moon, Orion reached a maximum distance (just over 400,000 kilometers) from Earth on November 28, exceeding a record set by Apollo 13 for most distant spacecraft designed for human space exploration. The Artemis II mission, carrying 4 astronauts around the moon and back again, is scheduled to launch no earlier than September 2025.

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[RocketRon]

Looks like a dime falling down out of reach !
An iconic pic for the future ?

I have always wondered how NASA organises the navigation for these events.
What do they do for reference points/waypoints for celestial navigation in 3-D. ??
Are there any online 3-D navigation explainers ?

Merely pointing the nose towards the Moon would not quite achieve what is required.
When the whole plot is swirling around, almost independently of each other.
Planning that 130 km flyover would require near pinpoint precision, all along the way..
Must require some serious computer time ?
Calculating rocket burn times must be a very precise business also.
(Ask that Tesla that missed Mars - by a long way !).
??

[raschumacher]

Why is the resolution of the Moon's surface much worse than the image of Orion? Something to do with the dynamic range of the camera?

[Ann]

Since I am the self-appointed Color Commentator, I note that the only spot of color in this image is the (rather pale) bluish color of the Earth.

Earthset from Orion. Image Credit: NASA, Artemis 1

---

I note that the sunlit face of the Moon is not very much darker than the sunlit face of the Earth. But parts of the Orion spacecraft are much brighter than the Moon (and the Earth). I guess it goes to show that the albedo (reflectivity) of the Earth is perhaps not as high as some of us might imagine. The Moon, of course, is really dark.

(Speaking of color, I think I remember that one of the astronauts that landed on the Moon found a spot on the Moon which was bright orange. I guess that must have been a rare outcrop of some sort of iron oxide compound, similar to whatever it is that gives Mars its reddish color.)

A final note: The Earth that we see in this APOD seems to present a gibbous phase to whoever took the picture that is today's APOD.

Ann

[johnnydeep]

Why is the resolution of the Moon's surface much worse than the image of Orion? Something to do with the dynamic range of the camera?

Not sure, but this image seems to be a still (or even a screen grab) from the first second of this video:

https://www.flickr.com/photos/nasa2expl ... 303788800/

[Guest]

Why is the resolution of the Moon's surface much worse than the image of Orion? Something to do with the dynamic range of the camera?

I think it’s because the shuttle is closer than the moon. Visually it looks like they’re the same distance but pretty sure the moon couldn’t fit in the frame like that if it was the same distance away as the ship

[RockatRon]

It sez the camera is externally on the Orion, so its definitely way closer than the moon. !

That is a strange contrast in colour and contrast....

[RocketRon]

No comments/knowledge/expertise on celestial navigation ??

[johnnydeep]

No comments/knowledge/expertise on celestial navigation ??

Well, celestial navigation is a large and complex subject. But someone here like Chris could probably do a good job of encapsulating the most important ideas in a digestible format.

Wikipedia's long article about it:

https://en.m.wikipedia.org/wiki/Celestial_navigation

[raschumacher]

Why is the resolution of the Moon's surface much worse than the image of Orion? Something to do with the dynamic range of the camera?

Not sure, but this image seems to be a still (or even a screen grab) from the first second of this video:

https://www.flickr.com/photos/nasa2expl ... 303788800/

A-ha! The *screen grabber* had the dynamic range problem. Resolution of the Moon is just fine in the original video. Thanks for the link.

[RocketRon]

Well, celestial navigation is a large and complex subject.

Thanks.
I guess I was hoping for the actual specifics, rather than the generalizations that seem to abound in such articles.

But maybe this is beyond the realm of any one persons knowledge ? And is a large collaborative group of expertises
Being able to program a 'puter to calculate intersecting tangents and arcs v's using radar(s) to establish speeds and
distances v's knowing the weights and thrusts of various rockets v's accurate time tracking are clearly unrelated and
totally separate skills and abilities.

The fact that various countries and organistions are successfully launching space missions these days means that such
knowledge bases are being established and spread.
Did Mr von Braun et al write a rocketeers navigational handbook, we wonder
SpaceX might suggest its a matter of trial & error ?
Boeing too...

[johnnydeep]

Well, celestial navigation is a large and complex subject.

Thanks.
I guess I was hoping for the actual specifics, rather than the generalizations that seem to abound in such articles.

But maybe this is beyond the realm of any one persons knowledge ? And is a large collaborative group of expertises
Being able to program a 'puter to calculate intersecting tangents and arcs v's using radar(s) to establish speeds and
distances v's knowing the weights and thrusts of various rockets v's accurate time tracking are clearly unrelated and
totally separate skills and abilities.

The fact that various countries and organistions are successfully launching space missions these days means that such
knowledge bases are being established and spread.
Did Mr von Braun et al write a rocketeers navigational handbook, we wonder
SpaceX might suggest its a matter of trial & error ?
Boeing too...

It can't be too hard. NASA was doing it in the 60s, with only pitifully powerful electronic computers, to successfully land men on the Moon!

[RocketRon]

They sent missions in advance, to try things out.
Lots of them !

I'd perhaps comment that back when I was a kid, there was a little basic computer program that tested
you putting the lunar lander down on the moon.
This was apparently not so different to what was actually employed.

Albeit with a keyboard, rather than controls to hand.
That fuel countdown was the ultimate test
Brave stuff ...

[Chris Peterson]

Well, celestial navigation is a large and complex subject.

Thanks.
I guess I was hoping for the actual specifics, rather than the generalizations that seem to abound in such articles.

But maybe this is beyond the realm of any one persons knowledge ? And is a large collaborative group of expertises
Being able to program a 'puter to calculate intersecting tangents and arcs v's using radar(s) to establish speeds and
distances v's knowing the weights and thrusts of various rockets v's accurate time tracking are clearly unrelated and
totally separate skills and abilities.

The fact that various countries and organistions are successfully launching space missions these days means that such
knowledge bases are being established and spread.
Did Mr von Braun et al write a rocketeers navigational handbook, we wonder
SpaceX might suggest its a matter of trial & error ?
Boeing too...

It can't be too hard. NASA was doing it in the 60s, with only pitifully powerful electronic computers, to successfully land men on the Moon!

Correct, it's not very difficult. We know where the Earth is, we know where the Moon is, and a spacecraft can be oriented extremely accurately by looking a a reference star (basically, like using a sextant). The engine burn is very well controlled, especially with modern instruments that can monitor acceleration with extreme precision. The math is straightforward, developed long before spaceflight. Final corrections can be made based on radar feedback from Earth, or comparing the position of stars to the lunar horizon (again, the sextant).

[RocketRon]

The math is straightforward, developed long before spaceflight.

Its difficult to find examples of that math spelled out, in anything but general terms !!
Artillery bombardment charts don't quite make the grade ?

Given that you are aiming for a moon which is nowhere near where you are going to intercept it,
this requires a great deal of forethought and planning.
Finding examples/equations where you can actually plug numbers into, and get meaningful or insightful
results is uncommon, to say the least. Or see the workings.

NASA has of recent times provided little charts of mission(s) progress/expected progress.
Seeing the workings of how they calculated those would appear to be in the 'classified" realm ?

[RocketRon]

It took the graphic artist weeks ? to prepare this.
And quite a bit of computational time beforehand.

artemis-1-update[1].jpg

https://appel.nasa.gov/wp-content/uploa ... update.jpg

Would be interesting being a fly on the wall for those planning sessions ?
The mathematics would fill several notebooks ...

[Chris Peterson]

The math is straightforward, developed long before spaceflight.

Its difficult to find examples of that math spelled out, in anything but general terms !!
Artillery bombardment charts don't quite make the grade ?

Given that you are aiming for a moon which is nowhere near where you are going to intercept it,
this requires a great deal of forethought and planning.
Finding examples/equations where you can actually plug numbers into, and get meaningful or insightful
results is uncommon, to say the least. Or see the workings.

NASA has of recent times provided little charts of mission(s) progress/expected progress.
Seeing the workings of how they calculated those would appear to be in the 'classified" realm ?

Basically, it's just the equations of Kepler and Newton. Really, the math is very straightforward, and can be done with paper and pencil (as much of the early Moon mission orbit planning was). Now, of course, with computers it's very easy to design very energy efficient transfer orbits, but the math is still that of Keplerian orbits. And the approach is largely the same: get into Earth orbit, at the right spot fire your engine to change the shape of your orbit (like placing an apogee near the Moon), fire again at the end.

[RocketRon]

So, can anyone point to actual worked examples or demonstrations of these ?
As navigating to the Moon would entail.

Beyond mere theory ...