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33 votes
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How is the altitude of a satellite defined, given that the Earth is not spherical?

update: 6378.137 km is what I use now. By convention the altitude of a spacecraft is the distance to the center of the Earth minus roughly 6378 kilometers, or some reference radius that is ...
uhoh's user avatar
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23 votes
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How does Ingenuity measure its altitude when flying?

From multiple sites, but for the following quote, ScienceMag.org references a laser altimeter: (emphasis mine) The data began to trickle in at 6:40 a.m. ET, relayed by the Perseverance rover to ...
fred_dot_u's user avatar
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20 votes

Did/does the US use statute or nautical miles to decide who gets astronaut wings?

According to an authoritative-sounding post on collectspace here, it's statute (which matches my recollection). Edit: OP @costrom found an FAA document Fact Sheet – Commercial Space Transportation ...
Organic Marble's user avatar
18 votes

Did/does the US use statute or nautical miles to decide who gets astronaut wings?

Are these statute miles (1609.344 m, 5280 ft) or nautical miles (1852 m, 6076-ish ft)? TL;DR Neither. Or rather, it is 50 statute miles, but a statute mile is not 1609.344 meters. That is the length ...
David Hammen's user avatar
  • 74.9k
13 votes

What is the deepest place on Mars? Do humans need pressurized suits there?

Is there any particular deep areas of Mars in which a person could survive with only an oxygen supply without a pressurized suit? No. Hellas Planitia is the lowest point on Mars, the basin floor is ...
Rob's user avatar
  • 3,276
13 votes
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At what minimum distance does the Earth appear star-like to the naked eye?

The visual acuity of a healthy human eye is about 1 arcminute (a full circle is 360°, 1 ° is divided into 60 arcminutes). A football with a diameter of 220 mm at a distance of about 775 m subtends an ...
Uwe's user avatar
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10 votes
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Why does a satellite with a higher mass fall slower?

That's a great software-based experiment! What is this about? It's about drag and Newton's 2nd law of motion! $$F = \frac{dp}{dt} = ma$$ but in the context of orbital mechanics. We can re-arrange ...
uhoh's user avatar
  • 149k
10 votes
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How do you find the propellant mass needed to reach an specified altitude? (altitude at end of burn plus altitude during coast)

How do you find the propellant mass needed to reach an inputted altitude?(altitude at end of burn plus altitude during coast) The first thing you should be considering for any rocket mission is the ...
A McKelvy's user avatar
  • 2,492
9 votes
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What is the deepest place on Mars? Do humans need pressurized suits there?

To Or how deep would one have to be in Mars not to need a pressurized suit? and starting with @Rob's values and Planetery-Science.org's scale height of about 10.8 km to at least roughly ballpark ...
uhoh's user avatar
  • 149k
9 votes

Why does a satellite with a higher mass fall slower?

From Force=Mass*Acceleration for a given starting drag force (from the constant drag area, altitude and velocity) increasing the mass will reduce the acceleration (deceleration in this case) slowing ...
GremlinWranger's user avatar
9 votes
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Is it wrong to say that the thrust increases with time?

It strictly depends on the context. Thrust increases with specific impulse, at sustained mass flow. Specific impulse increases with drop of atmospheric pressure. Atmospheric pressure drops with rising ...
SF.'s user avatar
  • 55k
8 votes
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Why isn't the Kármán line itself considered to be in outer space?

I do not think there is a useful distinction to make here. Any border you designate will be somewhat arbitrary. Any time you set one, someone else will argue. And setting the border to be exclusive or ...
Polygnome's user avatar
  • 6,956
8 votes

How is the altitude of a satellite defined, given that the Earth is not spherical?

In orbital mechanics, the position of a satellite can be defined using orbital elements (which have some advantages over other coordinate systems, for typical orbits). Orbital elements describe a ...
gerrit's user avatar
  • 11.7k
8 votes

How far do you have to be from Earth to be "in space"?

The beginning of outer space and spaceflight is something hard to classify because the boundary between an atmosphere and the vacuum of space is very fluid. A space border is to be defined according ...
LoveForChrist's user avatar
8 votes
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different ways to calculate satellite height

The first formula gives you the altitude at a particular point in the orbit, assuming that the position vector is the satellite's current position relative to the center of the Earth. The second ...
Russell Borogove's user avatar
8 votes

Using 2023 technology, how low can a satellite orbit earth?

About 180 kilometers. Give or take 20 or 30 km. This is actually one of those questions that lacks an unambiguous answer, because even the ISS, at around 400 km, requires periodic boosts to remain in ...
Mark Foskey's user avatar
7 votes

How is the altitude of a satellite defined, given that the Earth is not spherical?

To expand on the other answers, it really depends on what you want to use the altitude for. In the Shuttle Mission Simulator, we calculated the orbital altitude several different ways. Altitude ...
Organic Marble's user avatar
6 votes
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Have there ever been significant changes in the altitude of the ISS?

Yes, there have been changes of > 40 km, as shown in this graph. The X axis scale is not showing, but it is from Nov 1998 to July 2008. Reference Edit: I checked to make sure the graph is not just ...
Organic Marble's user avatar
6 votes

How is the altitude of a satellite defined, given that the Earth is not spherical?

Earth is approximated as a point-mass when doing this calculation. The oblatness of the planet and different gravity potentials can then be computed using spherical harmonics or "mascon" (short for ...
ChrisR's user avatar
  • 6,180
6 votes
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Is it possible for an asteroid to be captured by earth in such a way that it has minimal relative velocity?

The slowest you can have the asteroid enter Earth's atmosphere without active propulsion is LEO orbit velocity. It is indeed possible to have such an object enter the Earth-moon system, do a very ...
Tom Spilker's user avatar
  • 18.3k
6 votes
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Do astronauts set a pressure on the space craft altimeter before launch or zero it?

According to The Smithsonian, the pressure altimeter was intended primarily as a landing aid. In the event of an abort during takeoff, parachute deployment would be based on speed, not altitude. ...
HiddenWindshield's user avatar
5 votes
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What are the causes of these episodes of faster than average altitude loss by the ISS?

The following graphs show the ISS mean radius vector (or semi-major axis) minus 6371 km (just to show an approximate altitude) and the mean air density at the ISS position calculated with the NRLMSISE-...
Cristiano's user avatar
  • 1,750
5 votes
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Why is the LEO/MEO boundary at 2,000 km?

Indeed it was originally based on radiation dose rates. Hank Garrett told me years ago that it was considered the altitude above which satellites in relatively low-inclination orbits had to take ...
Tom Spilker's user avatar
  • 18.3k
5 votes

What is the Fischer 1960 Mercury Ellipsoid, and why is it called that?

The U.S. Department of Defense (DOD) 1960 World Geodetic System was produced by Irene Fischer and published in 1960. Today they are commonly known as 1960 Fisher Ellipsoids, as they are called today, ...
PearsonArtPhoto's user avatar
  • 121k
4 votes
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Satellite altitude as a function of time?

Approach 4 (Succesfull approach) At this point in time, I am not able to pursue the analytical approach any further, so I found a satellite (debris) via http://stuffin.space/?intldes=2012-008N that ...
a.t.'s user avatar
  • 549
4 votes

Is it possible to calculate Max-Q without having to input an altitude

I'm not sure I understand the question completely, but I'll work off of the comment Of course the faster you go, the faster you reach max-q. So you must be able to say "by going this fast, you will ...
uhoh's user avatar
  • 149k
3 votes
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How is stability of Geosynchronous Orbits (GSO) affected by Earth’s mass?

tl;dr: A satellite just above GEO would pass by all longitudes, and so the question asks if Earth's gravity deviations would lead to the GEO band being higher or lower in some places. Of course the ...
uhoh's user avatar
  • 149k
3 votes

Determining altitude of a cubesat/nanosat

To communicate with the cubesat from a ground station, it is necessary to know before the date and time interval and the direction of the antenna. If the altitude of the satellite is not known before, ...
Uwe's user avatar
  • 49k
3 votes

How far up have satellites used a GNSS for positioning, and how does the precision degrade with altitude?

Since the offer for the answer to be updated wasn't taken up I'll post it as a new answer. As of August 6, 2021 it's still 70,135 km above Earth from 2015 Sources: NASA.gov's NASA’s MMS Breaks ...
uhoh's user avatar
  • 149k

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