If a space ship entered Earth orbit, how likely is it to be seen?Traffic in Space (a traffic controller for low earth orbit)How can a ship dock in space?Everyday tasks on a space shipSpace ship deceleration from speed of light
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If a space ship entered Earth orbit, how likely is it to be seen?
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If a space ship entered Earth orbit, how likely is it to be seen?
Traffic in Space (a traffic controller for low earth orbit)How can a ship dock in space?Everyday tasks on a space shipSpace ship deceleration from speed of light
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Mostly what it says on the tin. If a spaceship, let's say about 200 meters long and 100 meters wide (made of modern materials) was approaching Earth and slowing down (say from 100 km/s to 3km/s), how far out would it be noticed? How clear of a picture could something take of it? Is is possible it wouldn't be seen until it reached the atmosphere?
The ship in question is not announcing its presence, but it also isn't trying to hide (and has no means of stealth), so it can probably be treated similarly to an asteroid.
science-based spaceships detection
edited 7 hours ago
Cyn
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AetherfoxAetherfox
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add a comment
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$begingroup$
Mostly what it says on the tin. If a spaceship, let's say about 200 meters long and 100 meters wide (made of modern materials) was approaching Earth and slowing down (say from 100 km/s to 3km/s), how far out would it be noticed? How clear of a picture could something take of it? Is is possible it wouldn't be seen until it reached the atmosphere?
The ship in question is not announcing its presence, but it also isn't trying to hide (and has no means of stealth), so it can probably be treated similarly to an asteroid.
science-based spaceships detection
edited 7 hours ago
Cyn
19.1k2 gold badges37 silver badges86 bronze badges
asked 8 hours ago
AetherfoxAetherfox
1503 bronze badges
$endgroup$
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I'll throw it out there that the answer does depend a LITTLE bit on what you're thinking of by 'Earth Orbit'. Technically your ship could approach from the far side of the moon and slot into the L2 Lagrange point on the far side and still be in 'Earth Orbit' even though it's half a million miles away with the moon in between it and us. We've got satellites there too though, so we'd almost certainly still notice it.
$endgroup$
– Morris The Cat
6 hours ago
$begingroup$
The long version doesn't match the Title question. E.g. does it enter Earth orbit, or does it enter the atmosphere? E.g. is it seen while in orbit, or while slowing down?
$endgroup$
– Ray Butterworth
6 hours ago
$begingroup$
While this analysis of spacecraft detection analyses a stealth spacecraft, the hydrogen steamer, it has a lot of interesting explanations and useful equations.
$endgroup$
– TheDyingOfLight
3 hours ago
add a comment
|
$begingroup$
Mostly what it says on the tin. If a spaceship, let's say about 200 meters long and 100 meters wide (made of modern materials) was approaching Earth and slowing down (say from 100 km/s to 3km/s), how far out would it be noticed? How clear of a picture could something take of it? Is is possible it wouldn't be seen until it reached the atmosphere?
The ship in question is not announcing its presence, but it also isn't trying to hide (and has no means of stealth), so it can probably be treated similarly to an asteroid.
science-based spaceships detection
edited 7 hours ago
Cyn
19.1k2 gold badges37 silver badges86 bronze badges
asked 8 hours ago
AetherfoxAetherfox
1503 bronze badges
$endgroup$
Mostly what it says on the tin. If a spaceship, let's say about 200 meters long and 100 meters wide (made of modern materials) was approaching Earth and slowing down (say from 100 km/s to 3km/s), how far out would it be noticed? How clear of a picture could something take of it? Is is possible it wouldn't be seen until it reached the atmosphere?
The ship in question is not announcing its presence, but it also isn't trying to hide (and has no means of stealth), so it can probably be treated similarly to an asteroid.
science-based spaceships detection
science-based spaceships detection
edited 7 hours ago
Cyn
19.1k2 gold badges37 silver badges86 bronze badges
asked 8 hours ago
AetherfoxAetherfox
1503 bronze badges
edited 7 hours ago
Cyn
19.1k2 gold badges37 silver badges86 bronze badges
asked 8 hours ago
AetherfoxAetherfox
1503 bronze badges
edited 7 hours ago
Cyn
19.1k2 gold badges37 silver badges86 bronze badges
edited 7 hours ago
Cyn
19.1k2 gold badges37 silver badges86 bronze badges
edited 7 hours ago
Cyn
19.1k2 gold badges37 silver badges86 bronze badges
19.1k2 gold badges37 silver badges86 bronze badges
asked 8 hours ago
AetherfoxAetherfox
1503 bronze badges
asked 8 hours ago
AetherfoxAetherfox
1503 bronze badges
asked 8 hours ago
AetherfoxAetherfox
1503 bronze badges
1503 bronze badges
$begingroup$
I'll throw it out there that the answer does depend a LITTLE bit on what you're thinking of by 'Earth Orbit'. Technically your ship could approach from the far side of the moon and slot into the L2 Lagrange point on the far side and still be in 'Earth Orbit' even though it's half a million miles away with the moon in between it and us. We've got satellites there too though, so we'd almost certainly still notice it.
$endgroup$
– Morris The Cat
6 hours ago
$begingroup$
The long version doesn't match the Title question. E.g. does it enter Earth orbit, or does it enter the atmosphere? E.g. is it seen while in orbit, or while slowing down?
$endgroup$
– Ray Butterworth
6 hours ago
$begingroup$
While this analysis of spacecraft detection analyses a stealth spacecraft, the hydrogen steamer, it has a lot of interesting explanations and useful equations.
$endgroup$
– TheDyingOfLight
3 hours ago
add a comment
|
$begingroup$
I'll throw it out there that the answer does depend a LITTLE bit on what you're thinking of by 'Earth Orbit'. Technically your ship could approach from the far side of the moon and slot into the L2 Lagrange point on the far side and still be in 'Earth Orbit' even though it's half a million miles away with the moon in between it and us. We've got satellites there too though, so we'd almost certainly still notice it.
$endgroup$
– Morris The Cat
6 hours ago
$begingroup$
The long version doesn't match the Title question. E.g. does it enter Earth orbit, or does it enter the atmosphere? E.g. is it seen while in orbit, or while slowing down?
$endgroup$
– Ray Butterworth
6 hours ago
$begingroup$
While this analysis of spacecraft detection analyses a stealth spacecraft, the hydrogen steamer, it has a lot of interesting explanations and useful equations.
$endgroup$
– TheDyingOfLight
3 hours ago
$begingroup$
I'll throw it out there that the answer does depend a LITTLE bit on what you're thinking of by 'Earth Orbit'. Technically your ship could approach from the far side of the moon and slot into the L2 Lagrange point on the far side and still be in 'Earth Orbit' even though it's half a million miles away with the moon in between it and us. We've got satellites there too though, so we'd almost certainly still notice it.
$endgroup$
– Morris The Cat
6 hours ago
$begingroup$
I'll throw it out there that the answer does depend a LITTLE bit on what you're thinking of by 'Earth Orbit'. Technically your ship could approach from the far side of the moon and slot into the L2 Lagrange point on the far side and still be in 'Earth Orbit' even though it's half a million miles away with the moon in between it and us. We've got satellites there too though, so we'd almost certainly still notice it.
$endgroup$
– Morris The Cat
6 hours ago
$begingroup$
The long version doesn't match the Title question. E.g. does it enter Earth orbit, or does it enter the atmosphere? E.g. is it seen while in orbit, or while slowing down?
$endgroup$
– Ray Butterworth
6 hours ago
$begingroup$
The long version doesn't match the Title question. E.g. does it enter Earth orbit, or does it enter the atmosphere? E.g. is it seen while in orbit, or while slowing down?
$endgroup$
– Ray Butterworth
6 hours ago
$begingroup$
While this analysis of spacecraft detection analyses a stealth spacecraft, the hydrogen steamer, it has a lot of interesting explanations and useful equations.
$endgroup$
– TheDyingOfLight
3 hours ago
$begingroup$
While this analysis of spacecraft detection analyses a stealth spacecraft, the hydrogen steamer, it has a lot of interesting explanations and useful equations.
$endgroup$
– TheDyingOfLight
3 hours ago
add a comment
|
3 Answers
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Without any kind of stealth technology, it is 100% likely to be seen long before it gets anywhere close to Earth Orbit. This might give you some perspective:
A comet coming in unannounced from intersteller space, from outside of the ecliptic, was detected at 3au (three times as far from the sun as the earth is), by more than 20 different telescopes.
https://www.skyandtelescope.com/astronomy-news/possible-interstellar-comet-headed-our-way/
There are literally hundreds of organizations and thousands of amateur observers constantly looking for things like that.
An even better example might be Asteroid 2019_OK, which is just about the same size as what you're describing. It was moving about 25 times as fast as your example, and almost a worst case scenario in terms of where it was coming from in terms of being able to see it, and it was still detected about a million and a half km out, three times the distance to the moon.
Oh, and it looks like this is a duplicate too. So, my bad. =)
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
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Yet there are very large asteroids that we only ever learn about AFTER they've gone past the periapsis of their flyby.
$endgroup$
– Renan
8 hours ago
$begingroup$
@Renan those are moving much, much faster than the OPs example, and generally don't get nearly as close as 'earth orbit'. See en.wikipedia.org/wiki/2019_OK. It was almost a worst-case scenario in terms of difficulty of detection because of both speed and solar opposition, and it was still caught more than a million miles out.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
the sky and space still seems like a pretty vast expanse to claim 100% chance to spot it
$endgroup$
– BKlassen
7 hours ago
2
$begingroup$
@BKlassen sky and space generally, yes. The bit specifically between the earth and the Moon's orbit is really, really intensely observed. We track lost WRENCHES in earth orbit.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
@BKlassen: The ship is big, and it's coming close to Earth. We are really, really interested in biggish objects coming close to Earth.
$endgroup$
– AlexP
7 hours ago
add a comment
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$begingroup$
If the ship's orbit is perfectly circular and with a speed of 3km/s, it will be orbiting at an altitude of approximately 37,917 kilometers above sea level. That is just a very little bit above geosynchronous orbit.
This may be interesting for you: geosync altitude is kinda the sweet spot for communication satellites, so slots in it are in high demand. If you check the interactive graphic in this page, you will lots and lots of satellites there.
Then we have this article from Sky and Telescope:
Many geosynchronous satellites shine between magnitudes 10–12, so you can spot them in telescopes as small as 4 inches.
On top of that, being close to geosync altitude means that for an observer in the ground, the ship will be moving very slowly - so it will be easy to track once found.
How visible it will be, though, depends on its albedo. If it is completely dark, it will only be noticed if it passes in front of something - another planet, or the Moon. If however it is as shiny as a solar panel, lots of people stargazing will see it as a shiny dot. It might be visible by day, with the right angles and equipment.
If it has the albedo of the regular asteroid, it may probably be found before it settles into orbit. In 2018, 41.9% of the asteroids approaching Earth with a closest distance smaller than Lunar Distance were detected before closest approach.
The huge majority of those were in the 1 to 20 meters size range, so a much large ship might be easier to spot oncoming.
2019 is not over yet, but we seem to be doing slightly better at detecting things before they arrive. I'd give your ship's odds of coming in unexpected at around 50%. If it arrives without being detected, then once it settles in orbit it might be a matter of hours to days until it is seen.
P.s.: at a distance from the sun close to the Earth, the solar system's escape speed is around 42 km/s. The flight path of a 100km/s ship prior to decelleration would be a very broad, open curve entering the system at one side and exiting it again at the other side.
answered 7 hours ago
RenanRenan
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2
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Your graph tends to obscure the fact that the fast majority of those 'After closest approach' objects are quite small. The only things on that graph that got within 100,000km without being detected were less than 10m across. You're also not taking into account the fact that anything trying to insert into earth orbit would come into the range of the hundreds of radar stations that track earth's orbital space. Those systems are able resolve objects of 1m in Geosynchronous orbit, so I don't see how anything 200m across is going to arrive without being detected.
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– Morris The Cat
7 hours ago
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More important than the size of the object is its heat signature. Slowing down from 200 km/s to 3 km/s, without having the ship be 99.9% propellant, requires a LOT of energy, and that energy will show up as a bright heat signature even if the deceleration burn starts months in advance. It's my understanding that heat signatures in space are very, very easy to detect, to the point that a detector small enough to be put on a modern-day satellite could detect the exhaust plume of a space shuttle... from the orbit of Pluto, and that such a detector could scan the entire sky about once an hour. Granted, that last part is hearsay and I have no numbers to back it up; but if we have a heat detection system even 1% that effective, we'll spot this ship coming in from it's exhaust plume long, long before it gets into range of any radar or optical telescopes.
Assuming, of course, that it's not using a reactionless drive, but that's a whole other can of worms.
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
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3 Answers
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3 Answers
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$begingroup$
Without any kind of stealth technology, it is 100% likely to be seen long before it gets anywhere close to Earth Orbit. This might give you some perspective:
A comet coming in unannounced from intersteller space, from outside of the ecliptic, was detected at 3au (three times as far from the sun as the earth is), by more than 20 different telescopes.
https://www.skyandtelescope.com/astronomy-news/possible-interstellar-comet-headed-our-way/
There are literally hundreds of organizations and thousands of amateur observers constantly looking for things like that.
An even better example might be Asteroid 2019_OK, which is just about the same size as what you're describing. It was moving about 25 times as fast as your example, and almost a worst case scenario in terms of where it was coming from in terms of being able to see it, and it was still detected about a million and a half km out, three times the distance to the moon.
Oh, and it looks like this is a duplicate too. So, my bad. =)
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
$endgroup$
$begingroup$
Yet there are very large asteroids that we only ever learn about AFTER they've gone past the periapsis of their flyby.
$endgroup$
– Renan
8 hours ago
$begingroup$
@Renan those are moving much, much faster than the OPs example, and generally don't get nearly as close as 'earth orbit'. See en.wikipedia.org/wiki/2019_OK. It was almost a worst-case scenario in terms of difficulty of detection because of both speed and solar opposition, and it was still caught more than a million miles out.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
the sky and space still seems like a pretty vast expanse to claim 100% chance to spot it
$endgroup$
– BKlassen
7 hours ago
2
$begingroup$
@BKlassen sky and space generally, yes. The bit specifically between the earth and the Moon's orbit is really, really intensely observed. We track lost WRENCHES in earth orbit.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
@BKlassen: The ship is big, and it's coming close to Earth. We are really, really interested in biggish objects coming close to Earth.
$endgroup$
– AlexP
7 hours ago
add a comment
|
$begingroup$
Without any kind of stealth technology, it is 100% likely to be seen long before it gets anywhere close to Earth Orbit. This might give you some perspective:
A comet coming in unannounced from intersteller space, from outside of the ecliptic, was detected at 3au (three times as far from the sun as the earth is), by more than 20 different telescopes.
https://www.skyandtelescope.com/astronomy-news/possible-interstellar-comet-headed-our-way/
There are literally hundreds of organizations and thousands of amateur observers constantly looking for things like that.
An even better example might be Asteroid 2019_OK, which is just about the same size as what you're describing. It was moving about 25 times as fast as your example, and almost a worst case scenario in terms of where it was coming from in terms of being able to see it, and it was still detected about a million and a half km out, three times the distance to the moon.
Oh, and it looks like this is a duplicate too. So, my bad. =)
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
$endgroup$
$begingroup$
Yet there are very large asteroids that we only ever learn about AFTER they've gone past the periapsis of their flyby.
$endgroup$
– Renan
8 hours ago
$begingroup$
@Renan those are moving much, much faster than the OPs example, and generally don't get nearly as close as 'earth orbit'. See en.wikipedia.org/wiki/2019_OK. It was almost a worst-case scenario in terms of difficulty of detection because of both speed and solar opposition, and it was still caught more than a million miles out.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
the sky and space still seems like a pretty vast expanse to claim 100% chance to spot it
$endgroup$
– BKlassen
7 hours ago
2
$begingroup$
@BKlassen sky and space generally, yes. The bit specifically between the earth and the Moon's orbit is really, really intensely observed. We track lost WRENCHES in earth orbit.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
@BKlassen: The ship is big, and it's coming close to Earth. We are really, really interested in biggish objects coming close to Earth.
$endgroup$
– AlexP
7 hours ago
add a comment
|
$begingroup$
Without any kind of stealth technology, it is 100% likely to be seen long before it gets anywhere close to Earth Orbit. This might give you some perspective:
A comet coming in unannounced from intersteller space, from outside of the ecliptic, was detected at 3au (three times as far from the sun as the earth is), by more than 20 different telescopes.
https://www.skyandtelescope.com/astronomy-news/possible-interstellar-comet-headed-our-way/
There are literally hundreds of organizations and thousands of amateur observers constantly looking for things like that.
An even better example might be Asteroid 2019_OK, which is just about the same size as what you're describing. It was moving about 25 times as fast as your example, and almost a worst case scenario in terms of where it was coming from in terms of being able to see it, and it was still detected about a million and a half km out, three times the distance to the moon.
Oh, and it looks like this is a duplicate too. So, my bad. =)
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
$endgroup$
Without any kind of stealth technology, it is 100% likely to be seen long before it gets anywhere close to Earth Orbit. This might give you some perspective:
A comet coming in unannounced from intersteller space, from outside of the ecliptic, was detected at 3au (three times as far from the sun as the earth is), by more than 20 different telescopes.
https://www.skyandtelescope.com/astronomy-news/possible-interstellar-comet-headed-our-way/
There are literally hundreds of organizations and thousands of amateur observers constantly looking for things like that.
An even better example might be Asteroid 2019_OK, which is just about the same size as what you're describing. It was moving about 25 times as fast as your example, and almost a worst case scenario in terms of where it was coming from in terms of being able to see it, and it was still detected about a million and a half km out, three times the distance to the moon.
Oh, and it looks like this is a duplicate too. So, my bad. =)
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
edited 7 hours ago
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
answered 8 hours ago
Morris The CatMorris The Cat
8,6161 gold badge24 silver badges45 bronze badges
8,6161 gold badge24 silver badges45 bronze badges
$begingroup$
Yet there are very large asteroids that we only ever learn about AFTER they've gone past the periapsis of their flyby.
$endgroup$
– Renan
8 hours ago
$begingroup$
@Renan those are moving much, much faster than the OPs example, and generally don't get nearly as close as 'earth orbit'. See en.wikipedia.org/wiki/2019_OK. It was almost a worst-case scenario in terms of difficulty of detection because of both speed and solar opposition, and it was still caught more than a million miles out.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
the sky and space still seems like a pretty vast expanse to claim 100% chance to spot it
$endgroup$
– BKlassen
7 hours ago
2
$begingroup$
@BKlassen sky and space generally, yes. The bit specifically between the earth and the Moon's orbit is really, really intensely observed. We track lost WRENCHES in earth orbit.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
@BKlassen: The ship is big, and it's coming close to Earth. We are really, really interested in biggish objects coming close to Earth.
$endgroup$
– AlexP
7 hours ago
add a comment
|
$begingroup$
Yet there are very large asteroids that we only ever learn about AFTER they've gone past the periapsis of their flyby.
$endgroup$
– Renan
8 hours ago
$begingroup$
@Renan those are moving much, much faster than the OPs example, and generally don't get nearly as close as 'earth orbit'. See en.wikipedia.org/wiki/2019_OK. It was almost a worst-case scenario in terms of difficulty of detection because of both speed and solar opposition, and it was still caught more than a million miles out.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
the sky and space still seems like a pretty vast expanse to claim 100% chance to spot it
$endgroup$
– BKlassen
7 hours ago
2
$begingroup$
@BKlassen sky and space generally, yes. The bit specifically between the earth and the Moon's orbit is really, really intensely observed. We track lost WRENCHES in earth orbit.
$endgroup$
– Morris The Cat
7 hours ago
1
$begingroup$
@BKlassen: The ship is big, and it's coming close to Earth. We are really, really interested in biggish objects coming close to Earth.
$endgroup$
– AlexP
7 hours ago
$begingroup$
Yet there are very large asteroids that we only ever learn about AFTER they've gone past the periapsis of their flyby.
$endgroup$
– Renan
8 hours ago
$begingroup$
Yet there are very large asteroids that we only ever learn about AFTER they've gone past the periapsis of their flyby.
$endgroup$
– Renan
8 hours ago
$begingroup$
@Renan those are moving much, much faster than the OPs example, and generally don't get nearly as close as 'earth orbit'. See en.wikipedia.org/wiki/2019_OK. It was almost a worst-case scenario in terms of difficulty of detection because of both speed and solar opposition, and it was still caught more than a million miles out.
$endgroup$
– Morris The Cat
7 hours ago
$begingroup$
@Renan those are moving much, much faster than the OPs example, and generally don't get nearly as close as 'earth orbit'. See en.wikipedia.org/wiki/2019_OK. It was almost a worst-case scenario in terms of difficulty of detection because of both speed and solar opposition, and it was still caught more than a million miles out.
$endgroup$
– Morris The Cat
7 hours ago
1
1
$begingroup$
the sky and space still seems like a pretty vast expanse to claim 100% chance to spot it
$endgroup$
– BKlassen
7 hours ago
$begingroup$
the sky and space still seems like a pretty vast expanse to claim 100% chance to spot it
$endgroup$
– BKlassen
7 hours ago
2
2
$begingroup$
@BKlassen sky and space generally, yes. The bit specifically between the earth and the Moon's orbit is really, really intensely observed. We track lost WRENCHES in earth orbit.
$endgroup$
– Morris The Cat
7 hours ago
$begingroup$
@BKlassen sky and space generally, yes. The bit specifically between the earth and the Moon's orbit is really, really intensely observed. We track lost WRENCHES in earth orbit.
$endgroup$
– Morris The Cat
7 hours ago
1
1
$begingroup$
@BKlassen: The ship is big, and it's coming close to Earth. We are really, really interested in biggish objects coming close to Earth.
$endgroup$
– AlexP
7 hours ago
$begingroup$
@BKlassen: The ship is big, and it's coming close to Earth. We are really, really interested in biggish objects coming close to Earth.
$endgroup$
– AlexP
7 hours ago
add a comment
|
$begingroup$
If the ship's orbit is perfectly circular and with a speed of 3km/s, it will be orbiting at an altitude of approximately 37,917 kilometers above sea level. That is just a very little bit above geosynchronous orbit.
This may be interesting for you: geosync altitude is kinda the sweet spot for communication satellites, so slots in it are in high demand. If you check the interactive graphic in this page, you will lots and lots of satellites there.
Then we have this article from Sky and Telescope:
Many geosynchronous satellites shine between magnitudes 10–12, so you can spot them in telescopes as small as 4 inches.
On top of that, being close to geosync altitude means that for an observer in the ground, the ship will be moving very slowly - so it will be easy to track once found.
How visible it will be, though, depends on its albedo. If it is completely dark, it will only be noticed if it passes in front of something - another planet, or the Moon. If however it is as shiny as a solar panel, lots of people stargazing will see it as a shiny dot. It might be visible by day, with the right angles and equipment.
If it has the albedo of the regular asteroid, it may probably be found before it settles into orbit. In 2018, 41.9% of the asteroids approaching Earth with a closest distance smaller than Lunar Distance were detected before closest approach.
The huge majority of those were in the 1 to 20 meters size range, so a much large ship might be easier to spot oncoming.
2019 is not over yet, but we seem to be doing slightly better at detecting things before they arrive. I'd give your ship's odds of coming in unexpected at around 50%. If it arrives without being detected, then once it settles in orbit it might be a matter of hours to days until it is seen.
P.s.: at a distance from the sun close to the Earth, the solar system's escape speed is around 42 km/s. The flight path of a 100km/s ship prior to decelleration would be a very broad, open curve entering the system at one side and exiting it again at the other side.
answered 7 hours ago
RenanRenan
68.2k21 gold badges155 silver badges330 bronze badges
$endgroup$
2
$begingroup$
Your graph tends to obscure the fact that the fast majority of those 'After closest approach' objects are quite small. The only things on that graph that got within 100,000km without being detected were less than 10m across. You're also not taking into account the fact that anything trying to insert into earth orbit would come into the range of the hundreds of radar stations that track earth's orbital space. Those systems are able resolve objects of 1m in Geosynchronous orbit, so I don't see how anything 200m across is going to arrive without being detected.
$endgroup$
– Morris The Cat
7 hours ago
add a comment
|
$begingroup$
If the ship's orbit is perfectly circular and with a speed of 3km/s, it will be orbiting at an altitude of approximately 37,917 kilometers above sea level. That is just a very little bit above geosynchronous orbit.
This may be interesting for you: geosync altitude is kinda the sweet spot for communication satellites, so slots in it are in high demand. If you check the interactive graphic in this page, you will lots and lots of satellites there.
Then we have this article from Sky and Telescope:
Many geosynchronous satellites shine between magnitudes 10–12, so you can spot them in telescopes as small as 4 inches.
On top of that, being close to geosync altitude means that for an observer in the ground, the ship will be moving very slowly - so it will be easy to track once found.
How visible it will be, though, depends on its albedo. If it is completely dark, it will only be noticed if it passes in front of something - another planet, or the Moon. If however it is as shiny as a solar panel, lots of people stargazing will see it as a shiny dot. It might be visible by day, with the right angles and equipment.
If it has the albedo of the regular asteroid, it may probably be found before it settles into orbit. In 2018, 41.9% of the asteroids approaching Earth with a closest distance smaller than Lunar Distance were detected before closest approach.
The huge majority of those were in the 1 to 20 meters size range, so a much large ship might be easier to spot oncoming.
2019 is not over yet, but we seem to be doing slightly better at detecting things before they arrive. I'd give your ship's odds of coming in unexpected at around 50%. If it arrives without being detected, then once it settles in orbit it might be a matter of hours to days until it is seen.
P.s.: at a distance from the sun close to the Earth, the solar system's escape speed is around 42 km/s. The flight path of a 100km/s ship prior to decelleration would be a very broad, open curve entering the system at one side and exiting it again at the other side.
answered 7 hours ago
RenanRenan
68.2k21 gold badges155 silver badges330 bronze badges
$endgroup$
2
$begingroup$
Your graph tends to obscure the fact that the fast majority of those 'After closest approach' objects are quite small. The only things on that graph that got within 100,000km without being detected were less than 10m across. You're also not taking into account the fact that anything trying to insert into earth orbit would come into the range of the hundreds of radar stations that track earth's orbital space. Those systems are able resolve objects of 1m in Geosynchronous orbit, so I don't see how anything 200m across is going to arrive without being detected.
$endgroup$
– Morris The Cat
7 hours ago
add a comment
|
$begingroup$
If the ship's orbit is perfectly circular and with a speed of 3km/s, it will be orbiting at an altitude of approximately 37,917 kilometers above sea level. That is just a very little bit above geosynchronous orbit.
This may be interesting for you: geosync altitude is kinda the sweet spot for communication satellites, so slots in it are in high demand. If you check the interactive graphic in this page, you will lots and lots of satellites there.
Then we have this article from Sky and Telescope:
Many geosynchronous satellites shine between magnitudes 10–12, so you can spot them in telescopes as small as 4 inches.
On top of that, being close to geosync altitude means that for an observer in the ground, the ship will be moving very slowly - so it will be easy to track once found.
How visible it will be, though, depends on its albedo. If it is completely dark, it will only be noticed if it passes in front of something - another planet, or the Moon. If however it is as shiny as a solar panel, lots of people stargazing will see it as a shiny dot. It might be visible by day, with the right angles and equipment.
If it has the albedo of the regular asteroid, it may probably be found before it settles into orbit. In 2018, 41.9% of the asteroids approaching Earth with a closest distance smaller than Lunar Distance were detected before closest approach.
The huge majority of those were in the 1 to 20 meters size range, so a much large ship might be easier to spot oncoming.
2019 is not over yet, but we seem to be doing slightly better at detecting things before they arrive. I'd give your ship's odds of coming in unexpected at around 50%. If it arrives without being detected, then once it settles in orbit it might be a matter of hours to days until it is seen.
P.s.: at a distance from the sun close to the Earth, the solar system's escape speed is around 42 km/s. The flight path of a 100km/s ship prior to decelleration would be a very broad, open curve entering the system at one side and exiting it again at the other side.
answered 7 hours ago
RenanRenan
68.2k21 gold badges155 silver badges330 bronze badges
$endgroup$
If the ship's orbit is perfectly circular and with a speed of 3km/s, it will be orbiting at an altitude of approximately 37,917 kilometers above sea level. That is just a very little bit above geosynchronous orbit.
This may be interesting for you: geosync altitude is kinda the sweet spot for communication satellites, so slots in it are in high demand. If you check the interactive graphic in this page, you will lots and lots of satellites there.
Then we have this article from Sky and Telescope:
Many geosynchronous satellites shine between magnitudes 10–12, so you can spot them in telescopes as small as 4 inches.
On top of that, being close to geosync altitude means that for an observer in the ground, the ship will be moving very slowly - so it will be easy to track once found.
How visible it will be, though, depends on its albedo. If it is completely dark, it will only be noticed if it passes in front of something - another planet, or the Moon. If however it is as shiny as a solar panel, lots of people stargazing will see it as a shiny dot. It might be visible by day, with the right angles and equipment.
If it has the albedo of the regular asteroid, it may probably be found before it settles into orbit. In 2018, 41.9% of the asteroids approaching Earth with a closest distance smaller than Lunar Distance were detected before closest approach.
The huge majority of those were in the 1 to 20 meters size range, so a much large ship might be easier to spot oncoming.
2019 is not over yet, but we seem to be doing slightly better at detecting things before they arrive. I'd give your ship's odds of coming in unexpected at around 50%. If it arrives without being detected, then once it settles in orbit it might be a matter of hours to days until it is seen.
P.s.: at a distance from the sun close to the Earth, the solar system's escape speed is around 42 km/s. The flight path of a 100km/s ship prior to decelleration would be a very broad, open curve entering the system at one side and exiting it again at the other side.
answered 7 hours ago
RenanRenan
68.2k21 gold badges155 silver badges330 bronze badges
edited 7 hours ago
answered 7 hours ago
RenanRenan
68.2k21 gold badges155 silver badges330 bronze badges
answered 7 hours ago
RenanRenan
68.2k21 gold badges155 silver badges330 bronze badges
answered 7 hours ago
RenanRenan
68.2k21 gold badges155 silver badges330 bronze badges
68.2k21 gold badges155 silver badges330 bronze badges
2
$begingroup$
Your graph tends to obscure the fact that the fast majority of those 'After closest approach' objects are quite small. The only things on that graph that got within 100,000km without being detected were less than 10m across. You're also not taking into account the fact that anything trying to insert into earth orbit would come into the range of the hundreds of radar stations that track earth's orbital space. Those systems are able resolve objects of 1m in Geosynchronous orbit, so I don't see how anything 200m across is going to arrive without being detected.
$endgroup$
– Morris The Cat
7 hours ago
add a comment
|
2
$begingroup$
Your graph tends to obscure the fact that the fast majority of those 'After closest approach' objects are quite small. The only things on that graph that got within 100,000km without being detected were less than 10m across. You're also not taking into account the fact that anything trying to insert into earth orbit would come into the range of the hundreds of radar stations that track earth's orbital space. Those systems are able resolve objects of 1m in Geosynchronous orbit, so I don't see how anything 200m across is going to arrive without being detected.
$endgroup$
– Morris The Cat
7 hours ago
2
2
$begingroup$
Your graph tends to obscure the fact that the fast majority of those 'After closest approach' objects are quite small. The only things on that graph that got within 100,000km without being detected were less than 10m across. You're also not taking into account the fact that anything trying to insert into earth orbit would come into the range of the hundreds of radar stations that track earth's orbital space. Those systems are able resolve objects of 1m in Geosynchronous orbit, so I don't see how anything 200m across is going to arrive without being detected.
$endgroup$
– Morris The Cat
7 hours ago
$begingroup$
Your graph tends to obscure the fact that the fast majority of those 'After closest approach' objects are quite small. The only things on that graph that got within 100,000km without being detected were less than 10m across. You're also not taking into account the fact that anything trying to insert into earth orbit would come into the range of the hundreds of radar stations that track earth's orbital space. Those systems are able resolve objects of 1m in Geosynchronous orbit, so I don't see how anything 200m across is going to arrive without being detected.
$endgroup$
– Morris The Cat
7 hours ago
add a comment
|
$begingroup$
More important than the size of the object is its heat signature. Slowing down from 200 km/s to 3 km/s, without having the ship be 99.9% propellant, requires a LOT of energy, and that energy will show up as a bright heat signature even if the deceleration burn starts months in advance. It's my understanding that heat signatures in space are very, very easy to detect, to the point that a detector small enough to be put on a modern-day satellite could detect the exhaust plume of a space shuttle... from the orbit of Pluto, and that such a detector could scan the entire sky about once an hour. Granted, that last part is hearsay and I have no numbers to back it up; but if we have a heat detection system even 1% that effective, we'll spot this ship coming in from it's exhaust plume long, long before it gets into range of any radar or optical telescopes.
Assuming, of course, that it's not using a reactionless drive, but that's a whole other can of worms.
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
5141 gold badge2 silver badges11 bronze badges
$endgroup$
add a comment
|
$begingroup$
More important than the size of the object is its heat signature. Slowing down from 200 km/s to 3 km/s, without having the ship be 99.9% propellant, requires a LOT of energy, and that energy will show up as a bright heat signature even if the deceleration burn starts months in advance. It's my understanding that heat signatures in space are very, very easy to detect, to the point that a detector small enough to be put on a modern-day satellite could detect the exhaust plume of a space shuttle... from the orbit of Pluto, and that such a detector could scan the entire sky about once an hour. Granted, that last part is hearsay and I have no numbers to back it up; but if we have a heat detection system even 1% that effective, we'll spot this ship coming in from it's exhaust plume long, long before it gets into range of any radar or optical telescopes.
Assuming, of course, that it's not using a reactionless drive, but that's a whole other can of worms.
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
5141 gold badge2 silver badges11 bronze badges
$endgroup$
add a comment
|
$begingroup$
More important than the size of the object is its heat signature. Slowing down from 200 km/s to 3 km/s, without having the ship be 99.9% propellant, requires a LOT of energy, and that energy will show up as a bright heat signature even if the deceleration burn starts months in advance. It's my understanding that heat signatures in space are very, very easy to detect, to the point that a detector small enough to be put on a modern-day satellite could detect the exhaust plume of a space shuttle... from the orbit of Pluto, and that such a detector could scan the entire sky about once an hour. Granted, that last part is hearsay and I have no numbers to back it up; but if we have a heat detection system even 1% that effective, we'll spot this ship coming in from it's exhaust plume long, long before it gets into range of any radar or optical telescopes.
Assuming, of course, that it's not using a reactionless drive, but that's a whole other can of worms.
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
5141 gold badge2 silver badges11 bronze badges
$endgroup$
More important than the size of the object is its heat signature. Slowing down from 200 km/s to 3 km/s, without having the ship be 99.9% propellant, requires a LOT of energy, and that energy will show up as a bright heat signature even if the deceleration burn starts months in advance. It's my understanding that heat signatures in space are very, very easy to detect, to the point that a detector small enough to be put on a modern-day satellite could detect the exhaust plume of a space shuttle... from the orbit of Pluto, and that such a detector could scan the entire sky about once an hour. Granted, that last part is hearsay and I have no numbers to back it up; but if we have a heat detection system even 1% that effective, we'll spot this ship coming in from it's exhaust plume long, long before it gets into range of any radar or optical telescopes.
Assuming, of course, that it's not using a reactionless drive, but that's a whole other can of worms.
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
5141 gold badge2 silver badges11 bronze badges
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
5141 gold badge2 silver badges11 bronze badges
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
5141 gold badge2 silver badges11 bronze badges
answered 6 hours ago
FlyingLemmingSoupFlyingLemmingSoup
5141 gold badge2 silver badges11 bronze badges
5141 gold badge2 silver badges11 bronze badges
add a comment
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$begingroup$
I'll throw it out there that the answer does depend a LITTLE bit on what you're thinking of by 'Earth Orbit'. Technically your ship could approach from the far side of the moon and slot into the L2 Lagrange point on the far side and still be in 'Earth Orbit' even though it's half a million miles away with the moon in between it and us. We've got satellites there too though, so we'd almost certainly still notice it.
$endgroup$
– Morris The Cat
6 hours ago
$begingroup$
The long version doesn't match the Title question. E.g. does it enter Earth orbit, or does it enter the atmosphere? E.g. is it seen while in orbit, or while slowing down?
$endgroup$
– Ray Butterworth
6 hours ago
$begingroup$
While this analysis of spacecraft detection analyses a stealth spacecraft, the hydrogen steamer, it has a lot of interesting explanations and useful equations.
$endgroup$
– TheDyingOfLight
3 hours ago