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25 votes

How would blockchain be integrated into spaceflight? Have any methods been proposed yet?

Blockchain is a very poor solution to a specific problem: achieving ledger consensus among a large number of agents when there is substantial incentive to corrupt the record, and the entries in the ...
Russell Borogove's user avatar
18 votes

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

SGP4 is the standard procedure that TLEs are intended to work with. All of the following are extremely helpful, but the most important point would be use a standard, recent SGP4 package that is ...
uhoh's user avatar
  • 148k
17 votes
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How to get semi-major axis from TLE?

The TLE gives mean motion ($n$) in $\frac{rev}{day}$. This needs to be converted to $\frac{rad}{s}$ which can be accomplished by multiplying the $n$ TLE value by $\frac{2\pi}{86400}$. Therefore, to go ...
amkas90's user avatar
  • 456
17 votes
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How (the heck) are military satellites with (apparently) classified TLEs still showing up on sat map websites?

There is an international network of observers of classified satellites, organized around the Seesat-L mailing list: http://www.satobs.org/seesat/seesatindex.html They typically look for satellite ...
gosnold's user avatar
  • 1,308
13 votes
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Is SGP4 propagation necessarily more accurate near the epoch chosen for TLE generation?

It's somewhat an issue of the cart driving the horse -- TLEs are generated explicitly for the purpose of being an input into the SGP4 propagator. The data used to generate them often comes from ...
Tristan's user avatar
  • 17.3k
12 votes
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Has NORAD ever experienced a catastrophic event and "lost track of" a bunch of objects?

Yes, during the geomagnetic storm of March 1989, NORAD lost track of thousands of objects: During the great geomagnetic storm of 13-14 March 1989, tracking of thousands of space objects was lost ...
called2voyage's user avatar
  • 23.8k
11 votes
Accepted

What was the first proper Two Line Element to be generated?

This is more of a really-long comment than an answer, sorry, as it just narrows it down a bit. But I wanted to include links and quotes, so I put it in Answer form. First, it's not clear that what we ...
Bob Jacobsen's user avatar
  • 12.8k
11 votes
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Obtain archived TLE data

Celestrak For some selected groups of satellites, Celestrak has already-built group definitions of satellite archives at https://celestrak.org/NORAD/elements/ Space-Track Another option is to ...
uhoh's user avatar
  • 148k
10 votes
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How does the SpaceBEEs' experimental passive radar reflector work?

The original 4 satellites were 0.25U cubesats (as shown in the picture in the question) while the newer ones are 1U (cubical). The larger size of the newer sats provides space for Van Atta reflectors ...
Alex Hajnal's user avatar
  • 1,981
9 votes
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Determine orbit type from TLE

According to Wikipedia, field 8 of TLE line 2 is the "mean motion in revolutions per day"; you can determine the orbital period from this. For geosynchronous orbit, you should expect 1.0 ...
Russell Borogove's user avatar
9 votes
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How to generate TLE file?

In fact, your question is quite important. I will disagree with my colleagues who discourage the generation of custom TLEs. There are plenty of reasons to do so, mostly linked to the fact that most ...
Gustavo Boado's user avatar
9 votes

How would blockchain be integrated into spaceflight? Have any methods been proposed yet?

In space bandwidth is a premium commodity. The blockchain technology treats bandwidth worse than dirt. EVERYONE receives a complete copy of the entire blockchain whether they need it or not - and ...
SF.'s user avatar
  • 55.1k
9 votes

Will the new "TLE format" be orbitally-mechanically better than traditional TLEs?

Skimming CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES, it looks to me like three different message types are defined: Orbit Parameter Message (OPM), Orbit Mean Elements Message (OMM), and Orbit ...
Russell Borogove's user avatar
9 votes
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Tutorial for orbits from TLE data

You can get much of the software you would need from the same place you get TLEs. Go to https://www.space-track.org/documentation#/sgp4 , register for a free account, and download the file ...
Ryan C's user avatar
  • 8,047
8 votes

How (the heck) are military satellites with (apparently) classified TLEs still showing up on sat map websites?

There are a few ways. Visual tracking Tracking of it's RF emissions Radar tracking. I suspect it's the first two. If you know about where something is, you can see it visually, and track it's RF ...
PearsonArtPhoto's user avatar
  • 121k
8 votes
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How does the ISS Transit Finder website get the position of the ISS so accurately?

A typical TLE for a maintained satellite (as opposed to debris tracked via ground assets) has an error of only around 1 km at epoch (Vallado, et al, Appendix B), which grows at a rate of around 1-3 km ...
Tristan's user avatar
  • 17.3k
8 votes
Accepted

Is TESS really lost? What does Celestrak mean exactly?

You're right; these objects aren't lost. However, Space-Track doesn't actually track a lot of higher-orbiting objects. They just don't seem particularly interested in anything with a multi-day ...
Bill Gray's user avatar
  • 1,063
8 votes
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How to Update the Epoch in a Fake TLE While Maintaining Relative Position?

I believe the answer is "No, you won't get a same relative position to a point on the surface of the Earth using that method" for three reasons. Your orbit is non-circular (Eccentricity 0....
notovny's user avatar
  • 5,544
7 votes
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TLE and RINEX gps differences

They are in different reference frames. The TLE element set is defined relative to the True Equator, Mean Equinox (TEME) reference frame, and the elements in the RINEX Nav message are defined ...
DuffBeerBaron's user avatar
7 votes
Accepted

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

Satellites are routinely monitored by the likes of US, Russia and China. China for example is known to blind American spy satellites with lasers. The goal is to track the approx 23000 (sources vary ...
mike's user avatar
  • 1,646
7 votes
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Recreating the eccentricity value of TLE

Orbital values provided by TLEs are mean elements. They change through the orbit and propagation. Therefore, a direct calculation of eccentricity from position and velocity vectors would not produce ...
VolkanOzcan's user avatar
7 votes
Accepted

Which two satellites had a 44% probability of collision at 2017-01-07 21:53 UTC?

First of all, it was a miss. Whew! The close approach predicted at 21:53:00 UTC on 7 Jan 2017 has passed without incident. The JSpOC has confirmed that both satellites are being tracked as single ...
PearsonArtPhoto's user avatar
  • 121k
7 votes
Accepted

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

Code updated for python3* ...
Kwaku Amponsem's user avatar
7 votes

How to generate TLE file?

Do not make FAKE TLEs! Step 1: Read this answer. Step 2: Review all of the links in the answer. I'll repeat them here: Documentation webpage TLE format PDF Spacetrack report #3 PDF Revisiting ...
uhoh's user avatar
  • 148k
7 votes

Differences between SGP8 and the standard SGP4? Is it ever used in practice?

About fifteen years ago, I very carefully implemented SGP8 and SDP8 (and the 'original' SGP) into my software (see https://github.com/Bill-Gray/sat_code ). It is hard to prove a negative -- i.e., ...
Bill Gray's user avatar
  • 1,063
7 votes
Accepted

Why the PRN obtained from Android is different from calculated by TLE

It seems that latitude and longitude can (or must?) be provided to PyEphem as a string, using the degrees:minutes format i.e. Longitude: 116:17.75718, Latitude: 40:3.00174 See rhodesmill.org/pyephem/...
BlueCoder's user avatar
  • 2,113
7 votes
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Get dates when a satellite has performed maneuver from historical TLE data (python)?

For Python and TLE propagation using SGP4 one very handy option is https://rhodesmill.org/skyfield/ As you probably already know a TLE is a strange animal. It does not really contain proper orbital ...
uhoh's user avatar
  • 148k
7 votes
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Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4?

SDP4 has a lot of algorithmic nuances to handle objects in 12- and 24-hour orbits. You can get decent (km-level over a week or so) fits to the model. I see no evidence in the SDP4 algorithm that ...
Bill Gray's user avatar
  • 1,063
7 votes
Accepted

Will the new "TLE format" be orbitally-mechanically better than traditional TLEs?

Changes due to the new fence: The new space fence will most likely lead to better orbit estimates for most objects currently in the catalog, as they will be observed more often. It will also detect ...
Guest's user avatar
  • 86
7 votes

TLE on path to be deprecated - what is 9 digit?

You are mixing some topics. The TLE Format is not running out numbers (directly), the 5-digit NORAD ID is and the TLE-Format is not allowing more than 5 digits in the Satellite catalog number field (...
CallMeTom's user avatar
  • 3,316

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