Questions tagged [two-line-elements]

Set of values carefully prepared to be used together with a simplified perturbations model (most often SGP4) to predict satellite positions with a moderate level of accuracy for times near the epoch contained within the TLE.

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

As I first noted in this comment I couldn't get TLEs for the recently launched OFEQ-11 spy satellites from space-track.com. When I looked at Search Resuls: OFEQ 11 Satellite details 2016-056A NORAD ...
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How to generate TLE file?

Subsequently to this answer: What is the way of generation of TLE file for a satellite? How to deal with BSTAR drag term, mean orbital elements, etc.? The generated TLE will be used as the input for ...
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Is SGP4 propagation necessarily more accurate near the epoch chosen for TLE generation?

This interesting answer includes a quote from Space-Track: From Space-Track.Org FAQ TLEs can contain future epochs. About 20 satellites are categorized as "multi-day objects" because ...
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How does the SpaceBEEs' experimental passive radar reflector work?

My Question: What is the nature of the "experimental passive radar reflector developed by the U.S. Navy’s Space and Naval Warfare Systems Command"? How does it work, and why does it work for ...
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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 ...
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How would blockchain be integrated into spaceflight? Have any methods been proposed yet?

Blockchain offers a way of keeping track of information such that its authenticity can be verified and it can not easily be falsified. In a space environment with an increasing number of both active ...
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Obtain archived TLE data

Now I'm achieving the up-to-date TLE from the celestrak.com and tle.info However, for some analysis in the past, I need old TLE files, to make my calculations more accurate. Is there a way to obtain ...
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Where to look for historical or reconstructed orbit data for early NASA missions - Mercury-Atlas 6 for example

After reading this answer to How many earth stations had astronauts on-site during John Glenn's orbit in Friendship-7? I decided that for my own use I'd like to plot the orbit of Mercury-Atlas 6, the ...
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Are SpaceBEEs actually hard to track?

The IEEE News article FCC Accuses Stealthy Startup of Launching Rogue Satellites focuses mostly on the intrigue addressed in the question What checks are supposed to be carried out to prevent illegal ...
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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 ...
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Failing at getting apogee and perigee from TLE

At Celestrak, the current orbit for ISS is currently listed as 423x417 km, but if I'm getting the TLE data from Celestrak and use orb.get_lonlatalt(now) from ...
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Has NORAD ever experienced a catastrophic event and "lost track of" a bunch of objects?

NORAD tracks satellites for several very important reasons. From time to time an object might become temporarily mis-identified or otherwise confused with another object, these things usually get ...
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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; ...
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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 ...
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Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4?

This fascinating answer to Why has no TLE been published for the DSCOVR satellite and the Falcon 9 R/B? presents links to custom-made TLEs for the Falcon 9 rocket body that put DSCOVR into orbit, and ...
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Will the new "TLE format" be orbitally-mechanically better than traditional TLEs?

Celetrak's A New Way to Obtain GP Data (aka TLEs) by Dr. T.S. Kelso 2020 May 27 explains the arrival a new infoblob format that in several ways is "better" than the ancient TLE, and contains ...
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How does the ISS Transit Finder website get the position of the ISS so accurately?

The recent Petapixel article How to Shoot the ISS Flying Across the Face of the Moon gives a lot of detailed, helpful advice for photographing transits of the ISS across the disk of the Moon. For ...
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How do cubesat owners first find out their cubesat's initial trajectory? How do they point antennas at it before official TLEs start to appear?

When cubesats are first deployed it can sometimes take several days before they start appearing in official TLE distributions, and even then if many were deployed it may take a lot more work to decide ...
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In a 3D space defined by semimajor axis, eccentricity and inclination, what would be the shape of the space where SDP4 works better than SGP4?

@BillGray's answer to Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4? is quite interesting and informative; I fail to do it justice by summarizing it as ...
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Suppose I wanted to compare TLEs to actual LEO satellite positions, what data is available? From which may it be easiest to extract X, Y, Z, T points?

Under @RyanC's answer to How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time? I wrote: I think that SGP4 + TLEs is so popular because the TLEs ...
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How to get semi-major axis from TLE?

This should be fairly straightforward, but, how do I get the semi-major axis (a) from at TLE. For example if I have the TLE: ...
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Differences between SGP8 and the standard SGP4? Is it ever used in practice?

The Wikipedia article Two Line Element Set says: The SGP4 model was later extended with corrections for deep space objects, creating SDP4, which used the same TLE input data. Over the years a number ...
uhoh's user avatar
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TLE and RINEX gps differences

I have TLE and RINEX navigation file for GPS satellite PRN 20, for 01.04.17r. 19:56:56 and 20:00:00 respectively. See also The Receiver Independent Exchange Format Version 3.03. It seems that the ...
kas's user avatar
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PSLV-C39/IRNSS-1H TLE accuracy

The TLEs accuracy for PSLV-C39/IRNSS-1H seems low when compared to that of the other LEO satellites (ISS, HST, Tiangong, Sfera 2, ...). Look, for example, at the following graph that shows the radius ...
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How to correctly make a fake, counter-propagating TLE?

In this answer I have said: Do not make FAKE TLEs! I would now like to make a fake TLE. Specifically I'd like to generate a counter-propagating "twin" of an orbit by flipping inclination by 180° ...
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2 votes
0 answers
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How can I "debounce" these TDRS satellite inclinations? (reconstruct the zero-crossings)

The plot below is from the question Why do the geosynchronous TDRS satellites have this distribution of inclinations?, and the explanation says Inclination and mean motion (rev/day) for TDRS ...
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Why did the frequency of TLEs for the Hubble Space Telescope drop by a factor of 3 in 2009?

I noticed that the TLEs for the Hubble Space Telescope (HST) are posted almost twice a day. Then I looked back in time and saw that this rate varies quite a lot! The plot shows the time interval ...
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9 votes
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Which two satellites had a 44% probability of collision at 2017-01-07 21:53 UTC?

I saw this message on space-track.org: The JSpOC has identified a close approach between two non-maneuverable satellites in a sun-synchronous orbit (approximately 800km altitude) with a time of ...
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Why is the NORAD Catalog number of SpaceX's Starlink's "Darksat" both 71130 and 44972?

@BowlOfRed's answer to Which of the recently launched Starlink satellites is the coated one? links to Celestrak's supplemental table for Starlink. https://celestrak.org/NORAD/elements/supplemental/...
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What is "OBJECT BS"?

I checked 2018-099 in Celestrak's satcat again for the question Where can I find the TLE of ExseedSat 1, India's first ever private LEO satellite? and noticed that ...
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Textbook or scholarly discussion of equations used by the SDP4 part of SGP4 TLE propagators beyond Space Track Report #1?

(the famous) Space Tract Report #3 discussed at length in Dr. T.S. Kelso's Revisiting Spacetrack Report #3, AIAA 2006-6753 Describes the "deep space" corrections to the original SGP4 known ...
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4 votes
2 answers
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What is/was legacy TLE ephemeris type 2? (TLE, line 1, column 63)

Wikipedia's Two-Line Element Set entry for line 1, column 63 (1.12) says: Ephemeris type (internal use only - always zero in distributed TLE data)13 13Celestrak Frequently Asked Questions: Two-Line ...
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How to find T₀ and other parameters from a TLE to calculate an approximate mean anomaly?

The equation for mean anomaly is $$M = \sqrt{\frac{\mu}{a^3}} (t-T_0)$$ How could I extract information from a TLE in order to calculate a mean anomaly? Would I use this equation, or something ...
Donny's user avatar
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3 votes
1 answer
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Are 1U cubesats sufficiently detectable to get at least minimally usefully predictive public TLEs, updated regularly?

Satellite radar cross-sections is a complex function of satellite structure, design, materials, instantaneous attitude, (radar) frequency, polarization, and if has moving parts, configuration, just to ...
uhoh's user avatar
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9 votes
2 answers
990 views

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

In this question I describe looking for a TLE for Mercury-Atlas 6, the spacecraft piloted by John Glenn on February 20, 1962. I'll post here the relevant information: While the TLE catalog available ...
uhoh's user avatar
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6 votes
1 answer
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Tutorial for orbits from TLE data

I've been looking for a new hobby, and have been reading some about satellite tracking. I was wondering if there was a good tutorial that walks through how to use TLE data. So far I have found ...
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1 answer
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Is TESS really lost? What does Celestrak mean exactly?

From this answer to the question What artificial satellite has the farthest orbit around the Earth?: I found the following "far out" spacecraft: TESS (Transiting Exoplanet Survey Satellite)...
uhoh's user avatar
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Why are Keplerian elements used in TLEs instead of Cartesian state vectors?

Propagating a state vector seems easier, you just account for the gravity, change the velocity and update the position. It also allows to easily apply perturbations, etc. Additionally, the ...
Mark's user avatar
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1 answer
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TEME state vector to TLE orbital elements

I was looking at time series of some TLE parameter(semimajor axis, inclination, etc..) and I wanted to how those parameters evolve between measured time points. So i decided to feed TLE element to ...
klobaska soslaninou's user avatar
3 votes
2 answers
216 views

PseudoTLE creation

I am developing a script in python to obtain pseudo TLEs of a satellite, starting from its state vector. I have always used TLEs to propagate the satellite and predict its next pass over a ground ...
Luca Pizzuto's user avatar
3 votes
1 answer
776 views

PRN number in TLE files are the same in RINEX files? (in GPS constellation)

I want to compare the position calculated with Pyephem and TLE files, with RINEX files and GPSTK library in a specific date and time, but I have not the certainly if the name of the satellite "...
mikesneider's user avatar
2 votes
1 answer
493 views

Why Celestrak has Archived TLEs for most space stations from Russia and the US, but not Tiangong-1, Tiangong-2 or Skylab?

Thinking about this question, I wanted to look at historical data. Then I noticed that while Celestrak does provide Archived TLE data for Salyut 7, Mir, Kvant-1, Kvant-2, Kristallm, Spektr, Priroda, ...
uhoh's user avatar
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1 vote
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change epoch to ( epoch year and Juilan day fraction )

the question asks you to make two line element it give you the given information and also everything is answered but the one thing i don't understand in here is how do the change the Epoch 29 sep 2010 ...
user54651's user avatar
13 votes
2 answers
3k views

Covariance matrix of a satellite position

In order to estimate the probability of collision with space debris, the covariance matrix of the primary and secondary objects should be calculated (JSPoC paper). I'm going to calculate the matrix ...
Leeloo's user avatar
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7 votes
1 answer
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How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time?

I have obtained TLE information of a satellite from space-track.org for three different times. I am trying to study any deviation of the satellite trajectory from its usual path. Here I am comparing ...
sudeep's user avatar
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2 answers
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How to construct $B^*$ drag term in TLE?

Is it possible to calculate $B^*$ term in TLE data using only a few or more velocity and position vectors for a satellite?
VolkanOzcan's user avatar
5 votes
1 answer
1k views

Recreating the eccentricity value of TLE

I cannot confirm the eccentricity value of a TLE using corresponding position and velocity vectors. Let me go through an example, ISS, to explain the situation. Using this TLE for ISS, 1 25544U ...
VolkanOzcan's user avatar
4 votes
1 answer
531 views

Plot ellipse using elements from TLE

I am trying to draw an ellipse as satellite orbit in three.js, It has an EllipseCurve class which takes these inputs and draws an ellipse around center. EllipseCurve( aX : Float, aY : Float, xRadius : ...
Sourav Anand's user avatar