47 votes
Accepted

What impact will the deorbiting of thousands of satellites have on the atmosphere?

Not much research has been done on this question in recent years, but some researchers are worried enough to research into wooden satellites. The question on the environmental impact of deorbiting ...
gerrit's user avatar
  • 11.6k
34 votes

What impact will the deorbiting of thousands of satellites have on the atmosphere?

The mass of Earth's atmosphere is 5E+18 kg and the Troposphere alone has 3/4's of that. With an average height of 13 km that makes its volume $4 \pi r^2 h$ or about 6.6E+18 m^3. If we break up one ...
uhoh's user avatar
  • 149k
33 votes
Accepted

Is 75 meters an exceptionally close distance for two satellites to pass at >6,000 m/s?

No, 75 meters is not exceptionally close — several satellites show predicted passages that close or closer every single week of the year. But it is close enough to potentially appear in the top 10 ...
Brandon Rhodes's user avatar
28 votes

Is 75 meters an exceptionally close distance for two satellites to pass at >6,000 m/s?

Exceptionally rare? No. Uncommon, well, yes. From what I can recall, these happened about once every 10 years per satellite for the constellation of satellites I worked with, at least, prior to doing ...
PearsonArtPhoto's user avatar
  • 121k
28 votes
Accepted

SpaceX's 4,425 satellite constellation - what's the method to the madness?

Nodal precession doesn't matter for a plane of satellites like this, they will rotate around in unison, so the coverage will remain the same. Okay. So, why the unusual dual inclination constellation? ...
PearsonArtPhoto's user avatar
  • 121k
22 votes

How many SpaceX Starlink Internet-service satellites could be deployed in a single Falcon 9 launch? Falcon Heavy? BFR?

EDIT: With the third Starlink launch happening about right now, it's time to update this answer! We now know that each satellite has a weight of 260kg, and that they launch 60 satellites per mission. ...
gromain's user avatar
  • 766
22 votes
Accepted

Is it normal for the US Space Force to warn companies about a possible collision (conjunction)?

Space Fence is what our current tracking system is called. This article claims that some companies and countries have an arrangement to receive tracking data, but few details. It appears that this in ...
Harabeck's user avatar
  • 348
21 votes
Accepted

What is the largest number of identical satellites launched together?

88! PSLV-C37 launched 88 identical satellites into a sun-synchronous orbit. These satellites were for an imaging company called "Planet Labs". Technically the only ones that were identical were the ...
Magic Octopus Urn's user avatar
20 votes
Accepted

Why are there no LEO satellites in the earth's equatorial plane?

Uhoh touches one side of the problem: "Why" - the lower the orbit, the less of Earth is covered in a single pass, and the closer to equator the orbit, the less do the passes vary further narrowing the ...
SF.'s user avatar
  • 55k
18 votes
Accepted

Is the full GPS constellation a Walker Delta constellation?

I only had a quick look but the answer seems to be: do all GPS satellites have the same inclination? The intention is yes, the reality is no (small variations) And do they exist in a Walker Delta ...
blobbymcblobby's user avatar
17 votes

Is 75 meters an exceptionally close distance for two satellites to pass at >6,000 m/s?

75 meters isn't all that rare - for the full public catalog there are 75 meter predictions about 2-3 times per day. What you have to consider is the uncertainty in that number. For TLE data, that's ...
CoAstroGeek's user avatar
  • 1,919
16 votes
Accepted

What is this gap in the GNSS satellite trajectories?

GPS satellite orbits go up to only 55 degrees inclination, so there are regions over the poles that they do not fly directly over (they are high up enough that they give coverage in the polar regions)....
Dave's user avatar
  • 851
14 votes

What is the largest number of identical satellites launched together?

480,000,000!† †Depending on how you define satellite. I think Project West Ford is the current record holder, with 480,000,000 individual satellites. Well technically 480,000,000 copper dipole ...
DarcyThomas's user avatar
14 votes

Does SpaceX expect 1 collision involving one of their Starlink satellites every 2 years?

I think you've made a bit of a logical/statistical misstep. Primarily, the "1 in 100,000" figure is a bit misleading because it's not a statistic. It's an operational risk level threshold ...
Dragongeek's user avatar
  • 18.6k
13 votes

Is it normal for the US Space Force to warn companies about a possible collision (conjunction)?

It's routine, and done as a service for the space community at large. Companies doing official business with the U.S. Government can get access to a variety of additional services, but the basic ...
Ryan C's user avatar
  • 7,882
13 votes
Accepted

Which satellite constellations are already operational in LEO (Low Earth Orbit)?

Is there a webpage where I can see the list of LEO satellite constellations? Yes! Celestrak has several pre-arranged groups of satellites and many of those groups can be seen as constellations, and a ...
uhoh's user avatar
  • 149k
11 votes
Accepted

What is the biggest satellite constellation in space right now?

Since 'right now' applies whenever this question is read,) even four years after the question was asked, the answer has to be Starlink, which has 1700 satellites deployed in its constellation. ...
Pilothead's user avatar
  • 344
11 votes

Why are there no LEO satellites in the earth's equatorial plane?

Nothing physically prevents equatorial orbits at any altitude above the Kármán line. The question is really; what would be the point in flying over exactly the same equatorial band roughly every 90 ...
CBHacking's user avatar
  • 1,542
10 votes

Why is one Starlink satellite not following the adjacent one in this image?

Basically they are not quite in the same plane. As a satellite raises or lowers, not only does it change the relative position within an orbital plane, it also will slowly shift the longitude of the ...
PearsonArtPhoto's user avatar
  • 121k
10 votes

Something doesn't add up when calculating thrust for Starlink satellites

I see quite a couple of problems with this calculation, let me list them for further investigation: The difference between air drag at 550 km and 210 km seems to be off. Air density changes by a ...
asdfex's user avatar
  • 15k
9 votes

How does SpaceX plan to make money with StarLink Broadband?

I don't think anyone can give you a detailed answer on how they will make money, because their business plans are their own, and proprietary. But the premise of the question seems essentially flawed -...
Saiboogu's user avatar
  • 6,427
9 votes

How is a satellite constellation launched?

Does each satellite slightly raise or lower it's orbit to start spreading out compared to one reference satellite? Yes. So off the bat there's a deltaV penalty for distributing the ...
Russell Borogove's user avatar
8 votes

Why are there no LEO satellites in the earth's equatorial plane?

While there is a currently accepted answer explaining why there are "no LEO satellites in the earth's equatorial plane", I found two of them with inclinations currently less than 3 degrees! ...
uhoh's user avatar
  • 149k
8 votes

Is the full GPS constellation a Walker Delta constellation?

Partial answer only to address the apparent inclinations in the image (refer to @blobbymcblobby's thorough answer and others if posted for the rest) Through the extremely rigorous method1 of looking ...
uhoh's user avatar
  • 149k
7 votes
Accepted

Most challenging aspects of a reusable satellite scheme like this?

I imagine the most difficult hurdle to overcome in a satellite recovery program like you describe would be the financial one, as there is very little incentive for SpaceX (or any company) to do so. ...
Dragongeek's user avatar
  • 18.6k
7 votes

Revisit time estimation for a SAR constellation

One plane, no matter how many sensors you place in it, only observes part of the Earth at a time. The observed section is a band like a ribbon or a belt, covering the orbit's ground track and a bit ...
Ryan C's user avatar
  • 7,882
6 votes

What is this gap in the GNSS satellite trajectories?

Bart's correct. To elaborate, I was part the USAF team that tested the first DoD acquired GPS receivers. From what I remember, the GPS and common to all positioning systems, the orbital geometry was ...
JD Clayton's user avatar
6 votes
Accepted

Which satellites can hear emergency signals from Scott Kelley's watch?

The space segment of the Cospas-Sarsat system has two components, SAR signal repeaters (SARR) and SAR signal processors (SARP). The Sarsat instruments [...], receive these messages. They are ...
Polygnome's user avatar
  • 6,926
6 votes

Which satellites can hear emergency signals from Scott Kelley's watch?

The answer is given within the question, the emergency signals are received by the the International Cospas-Sarsat Programme satellites. From wikipedia: Space segment The Cospas-Sarsat system ...
Uwe's user avatar
  • 48.9k
6 votes

How are multiple low orbit communication satellites per launch distributed along an orbital plane for global coverage?

Your arithmetic getting to 50 birds per plane about 7° apart seems reasonable. I would be surprised if 50 satellites could be put on a single launch, if for no other reason that I don't think they'd ...
Adam Wuerl's user avatar
  • 3,889

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