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Questions tagged [artificial-satellite]

Questions about objects in orbit which are human made, such as communications and GPS satellites, orbital observatories and space stations, and other man-made object in permanent or semi-permanent orbits around the Earth, other celestial objects, aside from the Sun, or even other satellites. Not to be confused with non-orbited man-made objects in space, that are usually referred to as "probes", or simply "spacecraft".

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How do SDP4's "Deep space" corrections to SGP4 account for the Sun's and Moon's gravity?

The Simplified Perturbations model SGP4 is used to calculate Earth satellite state vectors (position and velocity) using standard ephemeris data encoded as TLEs (Two Line Elements). According to ...
uhoh's user avatar
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21 votes
3 answers
25k views

How can I plot a satellite's orbit in 3D from a TLE using Python and Skyfield?

I have obtained a Two Line Element (TLE) of a satellite in Earth orbit from Celestrak at https://celestrak.org/NORAD/elements/ and I would like to use it to calculate an orbit. How can I calculate the ...
uhoh's user avatar
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47 votes
8 answers
13k views

What would be the (most difficult) challenge to make a 10,000 year satellite?

Update: Bezos' recent Tweeted update on the 10,000 year clock. Also see The Verge's Construction begins on Jeff Bezos’ $42 million 10,000-year clock The discussions associated with the question Can ...
uhoh's user avatar
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20 votes
6 answers
13k views

What artificial satellite has the farthest orbit around the Earth?

What is the furthest Earth orbiting satellite? What is its speed and purpose?
Muze's user avatar
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5 votes
3 answers
837 views

Are there terms for Earth orbits with rational number multiples of 1 sidereal day?

An Earth orbit with a period of 1 sidereal day (and zero inclination) is a geosynchronous orbit, orbits slightly above and below that are supersynchronous and subsynchronous orbits, and a Molniya ...
uhoh's user avatar
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32 votes
4 answers
7k views

Is it possible to track an object as small as the Tesla Roadster around the Solar System

I have heard that we will soon lose track of the Tesla Roadster launched with the Falcon Heavy test launch. Yet, we know where Voyager is out beyond the Solar System and we followed other satellites ...
Dan Sorensen's user avatar
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18 votes
3 answers
2k views

What's the largest aperture telescope sent beyond the Earth-Moon system?

The question and answer about telescopes sent to different planets got me wondering. There are so many solar system bodies that have been photographed by deep space spacecraft, planets, dwarf planet(s?...
uhoh's user avatar
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17 votes
2 answers
6k views

WHY did Rosetta have to go into hibernation for 2.5 years?

It seems the Rosetta spacecraft was put (put itself) into hibernation 08-June-2011. It spun itself up to stabilize its attitude, then shut down navigation, attitude control, communication systems as ...
uhoh's user avatar
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11 votes
4 answers
2k views

Are large halo orbits around L₁'s and L₂'s preferred over small orbits for reasons other than geometry?

There have been many examples of the placement of satellites in orbits around Lagrange points, most have been sun-earth and earth-moon $L_1$ and $L_2$ due to their proximity to earth. In each case ...
uhoh's user avatar
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9 votes
2 answers
5k views

In "spacecraft talk" is nadir just a fancy word for "down"?

Assume the approximation that the Earth is spherically symmetric — without higher order gravitational multipoles, and other effects that might be related to gravity from other bodies or the ...
uhoh's user avatar
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6 votes
2 answers
867 views

The Orbital Mass Accelerator Engine Theory

Can 2 satellites equal in weight traveling on the same orbital path in the opposite directions intersect and propel each other to gain altitude in orbit? Can orbital perturbation be negated during ...
Muze's user avatar
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3 votes
1 answer
800 views

How will GOES-R simultaneously point some instruments down at Earth and others sunward?

GOES-R is scheduled to launch soon and put in geostationary orbit over North America for high bandwidth continuous monitoring of Earth, with only 120 minutes per year interruptions caused by ...
uhoh's user avatar
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17 votes
2 answers
11k views

What is the math behind Magnetorquers?

I'm trying to better understand the mathematics behind how torque rods work. I know that even if you have 3 axis of magnetic torquers, in effect there is only 2 axis of control, and I'm trying to ...
PearsonArtPhoto's user avatar
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14 votes
6 answers
4k views

Why do satellites appear to move faster when overhead and slower closer to the horizon?

I've been watching man-made satellites with the naked eye using the "Heavens Above" mobile app. They seem to move incredibly slowly near the horizon, but when they go overhead, they look like they ...
GlenPeterson's user avatar
10 votes
2 answers
1k views

Is this the longest that a spacecraft "went to sleep" and then woke up on schedule?

For various reasons, spacecraft are sometimes "put to sleep" for periods of time on long voyages. Many systems are shut down, and radio communications suspended. Tracking of spacecraft at very large ...
uhoh's user avatar
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4 votes
1 answer
699 views

What would be a "big picture" understanding of how the orbits of Earth satellites are monitored?

In preparation for another question, I typed "keeping track of satellites in orbit" into a search engine, and found a website called keeptrack.space which has a ...
uhoh's user avatar
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48 votes
1 answer
5k views

Are there any satellites in geosynchronous but not geostationary orbits?

I know there are a lot of geostationary satellites out there, but I'm wondering - are there any geosynchronous satellites that are not geostationary (ie - have a notable inclination to their orbit)?
ThePiachu's user avatar
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41 votes
6 answers
21k views

Does a satellite naturally turn in phase with its orbit, always facing Earth?

Assume you want a satellite to constantly point its radio dish towards Earth while orbiting it, or its solar panels towards the Sun if it is instead orbiting it. Is any of the following true about ...
LocalFluff's user avatar
25 votes
1 answer
5k views

What satellites did the Shuttle retrieve from orbit?

Hobbes wrote: The Shuttle was designed for things NASA rarely or never used: [...] The ability to retrieve satellites from orbit was used a few times, but not as often as envisioned. I wasn't ...
SF.'s user avatar
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11 votes
6 answers
3k views

Can a satellite work like a radiometer?

Like a Crookes Radiometer, could a satellite have a stiff vain to maneuver? With a white side to let light pass and the black side capture light radiation be enough provide radiation pressure to keep ...
Muze's user avatar
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9 votes
2 answers
3k views

Why do malfunctioning satellites come back to Earth?

In school, I learned that if a satellite moves at a speed $\sqrt{gR}$ (the square root of the product of the acceleration due to gravity and radius of the Earth), then it will remain in Earth's orbit. ...
SpringLearner's user avatar
6 votes
2 answers
1k views

Could a satellite in LEO "pump" or change mass distribution to gain forward momentum?

Similar to pumping your feet on a child's swing can a satellite run up and down a pole to produce a forward momentum? Red dots is the satellite's position running up and down the pole on an ...
Muze's user avatar
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6 votes
2 answers
745 views

Does Humanity Star have non-reflective triangular panels? If so, what are their characteristics?

Rocket Lab has successfully launched a rocket from New Zealand and placed several objects in orbit, see here for example. One payload is New Zealand's first satellite the Humanity Star, a reflective ...
uhoh's user avatar
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4 votes
2 answers
1k views

Has a TLE ever been issued for a spacecraft trajectory not bound to Earth orbit?

This excellent answer to the question Why has no TLE been published for the DSCOVR satellite and the Falcon 9 R/B? suggests that to the best of the writer's knowledge TLEs are only issued for ...
uhoh's user avatar
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4 votes
2 answers
485 views

Temperature of photovoltaic cells vs efficiency - is it ever actively controlled?

The efficiency of photovoltaic cells is surprisingly strong function of junction temperature. Hotter usually means lower efficiency. If one searches for example for images and sites tagged with "...
uhoh's user avatar
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42 votes
6 answers
56k views

How does GPS receiver synchronize time with GPS satellites?

GPS satellites transmit time values regularly, but if we put in consideration the time delay between the satellite and the receiver, the time value received wouldn't be accurate insofar as I know GPS ...
digiogi's user avatar
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19 votes
2 answers
8k views

What is the accuracy / uncertainty of Two Line Elements (TLEs)?

I use TLE sets supplied on this website to find the future position of satellites (well usually just the ISS) using the SGP4 propagation method implemented in C++. My question is: What is the ...
James C's user avatar
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14 votes
4 answers
34k views

Calculate Satellite Coordinates From TLE Data

I know it is not that hard for those familiar with the equations for it, but I am having trouble with the math. In order to fully understand the orbit elements of TLEs I read this which I found very ...
harryisaac's user avatar
14 votes
4 answers
21k views

How to obtain UTC of the epoch time in a satellite TLE (two line element)?

I want to convert the epoch time of a TLE to UTC. At this moment I am less interested in explanations and history - I just want to know quantitatively, with certainty, how to convert. I'm confused ...
uhoh's user avatar
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14 votes
1 answer
3k views

What are these air-vent-like structures on this satellite?

I struck out with my previous question so I'll try again. What are these large circular 4-vane structures on the sides of NOAA-19 - the satellite that "fell down"? They remind me of ...
uhoh's user avatar
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5 votes
1 answer
369 views

How could tiny Hagoromo have been seen visually from earth confirming its lunar orbit?

I saw the following sentence in The Space Review, and became intrigued: Japan’s Hagoromo lunar orbiter, deployed in 1990, reached orbit but ceased transmitting enroute. If it ceasted transmitting ...
uhoh's user avatar
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76 votes
3 answers
55k views

Was the NOAA-N Prime satellite really dropped on the floor?

Recently, Donald.McLean posted this image in The Pod Bay, the site chat room: It's a rather disturbing image once you think about it for more than about half a second. Did it really happen? What ...
user avatar
28 votes
3 answers
4k views

Why is the ribbon of decommissioned geosynchronous satellites skewed?

I was looking at this 3D map of satellites orbiting earth and noticed something interesting. Around the green ring of active geosynchronous satellites, there is a ribbon of what I assume are obsolete ...
EagleV_Attnam's user avatar
15 votes
6 answers
28k views

Can an artificial satellite stay in orbit forever?

If an artificial satellite is in orbit around the Earth, it collides with dust and gas and loses a very small amount of kinetic energy to these collisions, and eventually will spiral down towards ...
tlehman's user avatar
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13 votes
1 answer
851 views

Will Glonass, Galileo, or BeiDou-2 satellites provide better cis-lunar navigation than GPS?

My question is: Has there been any effort to improve or optimize the radiation patterns on the subsequent satellite navigation constellations (e.g. Glonass, Galileo, BeiDou-2) to facilitate trans-GEO ...
uhoh's user avatar
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11 votes
1 answer
1k views

Did Echo 2 remain spherical without requiring gas pressure? If so, how is this known to be true?

Echo 1 and Echo 2 (Project Echo) were giant balloons inflated in space after being launched into Earth orbit, and used to study both the bouncing of radar, TV, and radio signals from one Earth station ...
uhoh's user avatar
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8 votes
1 answer
713 views

Why is Nodal precession affected by the rotational period of the planet?

The $J_2$ term in Nodal Precession equation has the rotational period of the planet. I understand that the oblateness of the sphere with an equatorial bulge induces a torque on the orbit of a ...
karthikeyan's user avatar
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8 votes
6 answers
3k views

Could a spy satellite image another satellite?

Is it possible for one satellite to image another at high resolution? Would this information be useful from an intelligence perspective?
staticCommand's user avatar
7 votes
4 answers
1k views

Where is the best place to get a time history of launches and satellite numbers

There are a number of places you can find details about currently operational satellites, and a few sources for past values. Is there a reliable source that has the dates of each launch and how many ...
ThePlanMan's user avatar
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6 votes
2 answers
899 views

What actually happened here with a satellite, the ISS and the moon?

I can't follow exactly what happened from this string of tweets - I'm not really twitter-literate. It seems like there was a predicted conjunction of the ISS with the moon, and an actual video of what ...
uhoh's user avatar
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5 votes
1 answer
1k views

Can image-stacking allow this 0.25 m satellite telescope achieve 0.65m resolution?

The BBC News item UK satellite to make movies from space describes this newly deployed satellite: caption: Artwork: Manufacturer SSTL calls it Carbonite-2, but Earth-i refers to the satellite as ...
uhoh's user avatar
  • 149k
5 votes
1 answer
396 views

ISRO's PSLV-C37 with 104 satellites - after 56 hours only six TLEs, which factor is greatest challenge?

It's been 24 hours 56 hours since ISRO's PSLV-C37 launched from Satish Dhawan Space Centre (SRI) at 09:28 local time (03:58 UTC). I see satcat numbers and object names for 105 total objects; ...
uhoh's user avatar
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2 votes
1 answer
500 views

It's been over two weeks now, will the real Humanity Star please stand up?

edit: This must be some kind of record! (cf. ISRO's PSLV-C37 with 104 satellites - after 56 hours only six TLEs, which factor is greatest challenge? This time its only six total!) At the end of ...
uhoh's user avatar
  • 149k
43 votes
3 answers
28k views

Why are the GPS constellation satellites in such a high orbit?

Most satellites are in Low Earth Orbit. Some other satellites are in Geostationary Orbit because their function requires it. The GPS (and other GNSS, e.g. GLONASS) satellites are in a much higher ...
Max Q Lagrange's user avatar
30 votes
6 answers
4k views

What is the smallest operational artificial satellite?

Miniaturisation has many advantages, and in recent times, nanosatellites, picosatellites, and femosatellite concepts have emerged. The Wikipedia article on miniaturised satellite has some pointers. ...
gerrit's user avatar
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24 votes
4 answers
7k views

Is the Pi really fit for outer space?

Recently, there has been growing interest in using Raspberry Pis in CubeSats. NASA is even in on the trend. But, considering that outer space is pretty harsh on electronics (i.e. radiation and cosmic ...
Aloha's user avatar
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24 votes
1 answer
10k views

Which artificial satellites in lunar orbit are currently active?

Most of artificial satellites of the Moon has depleted their batteries, lost communication, been deorbited or impacted the surface after orbital decay. The list doesn't exactly make it clear which ...
SF.'s user avatar
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19 votes
6 answers
5k views

Can you make out the shape of the ISS with the unaided eye as it passes overhead?

Someone claimed to me that they could see the actual shape of the ISS as it passed overhead without use of any optical device. I would think this isn't possible since it is only about 100 meters wide ...
RossV's user avatar
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18 votes
3 answers
8k views

Are any geosynchronous satellites visible with the naked eye?

It is very easy to spot LEO satellites during dusk or dawn. I am wondering if satellites further out in a geosynchronous orbit are also visible. Of course, if even possible, these would appear more ...
Stu's user avatar
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17 votes
1 answer
4k views

Why did early satellites (e.g. China's Fanhui Shi Weixing) re-enter the atmosphere narrow end (nose)-first?

I was surprised to find out from @JohnnyRobinson's new answer that China's series of Fanhui Shi Weixing spacecraft (FSW) used impregnated oak heat shields. I found this in astronautix: The capsule ...
uhoh's user avatar
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