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28

Spacecraft are placed into the orbits that they need to be in, given the objectives of the mission and the constraints during design. Nothing in space is arbitrary, since there is so much at stake if something goes wrong. In fact, GEO is not a particularly special place for a space telescope and several telescopes are placed (or are planned on being ...

27

Yes, GEO is a balance point for anchored to Earth space elevator. It has to be, to keep its rotation rate synchronized with Earth's own and keep tether stable. This necessarily means that at GEO altitude, the elevator rotates at GEO orbital speed. Stepping off it at that altitude then means you're in a stable equatorial geosynchronous orbit, or GEO (...

25

Orbits at the altitude of GEO are stable for very long times (millions of years). There is no significant decay of the orbital height due to some kind of drag, so the risk of these satellites interfering with working ones is close to zero. On the other hand, there are good reasons to store them above the belt and not below: The region below is used for ...

20

At the geostationary orbit, the growth (gradient) of tension will be practically zero, but the value will be far, far from zero. Actually, it will be the highest in the whole tether. After all, the whole length of the tether, that goes all the way down to Earth surface, is moving progressively slower than what orbital speed at corresponding altitude is - ...

20

You're asking about an idea that's been around for a long time: the Space Elevator or the Sky Hook. Konstantin Tsiolkovsky wrote about a similar concept in 1895, though his concept was for a standing building, a compression structure supported by a foundation on Earth. You can't just lower a cable from a geo bird. If you have a cable hanging from a geo ...

19

Altitude drops like that are common when the orbital stage has a high-efficiency, low-thrust engine. It takes a few minutes for the upper stage to bring the craft up to orbital speed. During that period, the craft is indeed starting to fall back towards Earth. The rocket's travel over the curvature of the Earth contributes an effective altitude gain that ...

19

Actually, it makes a lot of sense to raise the orbit of end-of-life geostationary satellites: Coming from Earth you have to cross through a lower orbit to transfer from low earth orbit to a geostationary orbit but you don't have to go farther out than that (some transfer orbits do, but it's not a requirement). That means that a higher orbit has less risk of ...

18

It wouldn't need to turn as fast to stay focused, maybe increasing the lifetime of its reaction wheels. On Earth when you "turn" a telescope, you are really keeping it pointed in one direction! It's the Earth that's turning, and you have to turn the telescope mount to keep the legs pointed at the ground. It's the same thing as having to move the antenna to ...

17

Such satellites are in a geosynchronous orbit (GSO), orbiting at an orbital altitude where orbital period matches Earth's rotation on its axis. Their orbital speed is roughly 3 km/s at mean orbital altitude of 35,786 km above the Earth's surface:    Orbital speeds ($v_o \approx \sqrt{\mu/r}$) at mean altitudes above the Earth's surface (blue) and ...

17

Theoretically, you can go anywhere in GEO for an arbitrarily small ∆v - you raise your apogee a little bit, which slows you down, wait until you've phased to your destination latitude, then re-circularize back into GEO. In practice, though, as @uhoh mentions in comments, there are stable longitudes in GEO that require more than an infinitesimal maneuver to ...

16

Regarding proximity, we'll need a good database first. For example, Eric Johnston publishes on a SatSig.net page a list of satellites in Geostationary Orbit (GEO) that was last updated on 21 Feb 2014, so fairly recent. I couldn't find more complete list, but this individual has been upkeeping the list for a fairly long time (some older pages where he ...

14

No, and the reason is simple enough. GEO is at an altitude of 35,786 kilometres (22,236 mi) above the Earth's equator and no satellites in geostationary or geosynchronous (GSO) orbit are large enough to reflect sufficient amounts of light towards the observer with their truss and solar panels to be visible to the naked eye on the surface of the Earth. They'...

14

Assuming orbital assembly (with separate launch vehicles, each delivering a portion of the total mass of the satellite), there is no real upper limit, short of technical limitations that we're currently struggling with. At least not until you orbit such a huge mass, that you literally start playing the game of pool with celestial bodies, permanently ...

14

It seems that the company ExoAnalytic Solutions regularly observes high- orbiting satellites (MEO, HEO, and GEO), using the data to provide tracking, ensure they are at the right spot, and provide data in the event of an emergency. They have 200 telescopes dedicated to the effort, which seems to indicate that they can't observe every satellite all the time, ...

12

We have a similar question in What is the current cost-per-pound to send something into LEO? While launching to a Low Earth Orbit (LEO) is of course expected to be a lot cheaper per kilogram than lifting same mass to a Geosynchronous Orbit (GSO) or a Geostationary Orbit (GEO), be it because of an individual GSO/GEO capable launcher's payload capacity to LEO ...

12

A Clarke style space elevator is a (very large) gravity gradient stabilized vertical tether. When in a rotating frame (as on a merry-go-round) you feel a tug. It's just inertia but feels like an acceleration. This so called acceleration is $\omega^2r$ where $\omega$ is angular velocity expressed in radians/time. Gravity's acceleration is $GM_{earth}/r^2$. ...

12

Geosynchronous orbit radius can be calculated imposing the orbital period to be equal to the Earth's rotational period, which results in: $R_{GEO}=\sqrt[3]{\frac{GM_ET_{rot}^2}{4\pi^2}}$ where $G = 6.673 \cdot 10^{-11} \frac{Nm^2}{kg^2}$ is the universal gravitational constant, $M_E = 5.97\cdot 10^{24} kg$ is the Earth Mass and $T_{rot} = 86164 s$ is the ...

12

tl;dr There are zero CubeSats in GEO The Union of Concerned Scientists has a great database of satellites orbiting the Earth, the smallest satellite that they have in GEO orbit is the S5 smallsat launched by the ARFL, it has a launch weight of 60kg definitely in the smallsat range but much bigger than the largest CubeSats. Bonus! Here are some histograms ...

11

I think the question is asking what the release altitude from a space elevator would result in an orbit with a perigee of $R_E + 500 km$ ($R_E$ is the earth radius — 6378.135 km) The velocity of the space elevator varies linearly along its length, with the velocity at GEO altitude ($R_{GEO}$) equal to GEO orbital velocity ($V_{GEO} = \sqrt{\mu/R_g}$). ...

11

Generally, the GEO satellites are to keep their desired position above ground within +/- 0.05 deg (both N and E) which translates into a 70 km 2D projection corridor at GEO altitude. The laser pointer case, is dependent on the beam width. A laser pointer of the kind you get in stores has beamwidth of 1-3 milliradian, i.e. about 0.05 to 0.17 deg. This ...

10

No, altitude is not the hardest thing about getting to space, it's getting enough lateral velocity so that you literally miss the earth as you fall. A weather balloon would get you to 23 miles (37 kilometres). Geostationary orbit is 22,000 miles (35,000 km), almost one thousand times that. In fact no balloon could get you that high since the earth's ...

10

It really depends on what stage the satellite is in. If the satellite still functions at a reduced capacity, then likely everything except the batteries, and fuel, is salvageable. Some of the transmitters, instruments, etc could also work, although it really depends on why the satellite failed. If the satellite isn't functioning, then some components may ...

10

When I was a bit more active supporting GTO launches, 15 years ago, the following constraints helped shape the launch window (not in any order and I may have forgotten some important points completely): Sensor viewing angle to ensure attitude acquisition coming off the launch vehicle (Sun and Earth sensors, may have been superseded by direct use of a star-...

10

Are there any satellites in geosynchronous but not geostationary orbits? Yep, lots! Apparently there are various advantages to being synchronous even when oscillating wildly in position above/below the Earth's equator (up to +/- 60 degrees!) You can still communicate with them continuously using a single ground station, if it is somewhat near the equator. ...

9

I can't imagine such a system would make any sense to build. At it's heart you have a space elevator--something we don't have the materials to build on Earth yet. A pipe full of fuel hanging on that elevator will be HEAVY--meaning a lot more elevator. Not to mention the weight of all the fuel in it. The pressure requirements won't be a big deal--use ...

9

In theory, GEO locations are subdivided into fixed "slots" of 2 degrees longitude (or 1470km of orbital extent per slot). Within a slot, the individual satellite must confine itself to a "box" of 0.1 degrees longitude (or something like 70km). Naturally, this is not always a case in reality. Satellites do drift across slot boundaries every now and then. ...

9

In theory, the shortest practical time from spacecraft separation would be about five and a quarter hours, which is half of a geosynchronous transfer orbit. At apogee, which is carefully placed to occur over the equator, a single burn raises the perigee and changes the inclination of the orbit, and you're there. All early GEO birds used this approach, and ...

9

Yes. The elevator stop at GEO will itself be in orbit at GEO. Thus with a minimal delta-v away from it, you will also be in GEO orbit, at GEO orbital velocity.

9

This is a difficult question to answer, so I'm going to take a stab based off of a few assumptions. GEO satellites are ones with a period between 1430-1450 minutes (Standard definition from NORAD) I have no knowledge of classified satellites, those will not be included. I'm going to assume you mean GSO satellites (Geostationary). Active GEO satellites have ...

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