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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6
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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 ...
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How do two-line element sets handle rev numbers > 99,999?

In a two-line element set (TLE), five characters in line 2 -- columns 64-68 -- are for the rev number. (https://en.wikipedia.org/wiki/Two-line_element_set) But some satellites have been around the ...
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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.com/NORAD/elements/supplemental/...
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How can I plot a satellite TLE from its orbital parameters using python and skyfield?

I have a function that uses TLEs (Two-line elements) from Celestrak to plot the visibility of a satellite in Python. Is there a method with skyfield or poliastro to plot a TLE from given orbital ...
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What caused the ISS Two Line Element Day of Year problem beginning 12-24-2019?

Does anyone know happened at NORAD or NASA or wherever the published TLEs originate, that caused the ISS TLE wonkiness during the last week of 2019? It did not happen in 2018. What happened? The ...
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1answer
118 views

Why are there some NORAD catalog IDs larger than 80000 in space-track?

I was trying to find the international designator for the Starlink-2 constellation launch. Not finding anything in Celestrak I looked in Space-Track. The following space-track.org query builder setup ...
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139 views

What caused so many objects in Earth orbit to “go NEA”? (no elements availabe)

T. S. Kelso tweeted the following, is this a case of lost and found? How can so many substantial objects become lost like this? The list of 23 objects "formerly known as Prince NEA" all seem pretty ...
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Generating TLEs with STK Using SGP4 Propagator;

STK has two methods for generating TLEs; Trajectory Sampling method and Single Point method. I have read the differences both of them at http://help.agi.com/stk/index.htm#stk/tools-10.htm but I am ...
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Where is this LightSail-2 trajectory data coming from? Is there more than TLEs available to the public?

This tweet shows high granularity data for LightSail-2's perigee and apogee, showing that while the apogee-raising strategy is working nicely, currently atmospheric drag is taking its toll and the ...
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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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Distance between GRACE-FO 1 and 2

I calculated the distance between the two satellites by propagating some TLEs with the SGP4. Here’s the result: the solid lines are for TLEs 19197.90524586 (GRACE-FO 1) / 19197.90551489 (GRACE-FO 2) ...
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306 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 ...
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1answer
230 views

How frequent do TLEs of LEO satellites change?

I was doing some MATLAB simulations on LEO satellites using TLEs obtained from n2yo websites and I observed that n2yo was displaying a different TLE for the same satellite after a few days. I don't ...
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1answer
174 views

Why does 2018-099 (SpaceX, December 2018) still have a dozen unidentified payloads?

According to today's Raw SATCAT Data from Celestrak, the launch designated 2018-099 (SpaceX, December 2018) still has twelve unidentified payload objects! ...
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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) ...
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CSpOC’s identical TLEs

Identical TLEs are often published by CSpOC at https://www.space-track.org/. For example, here’s the first line of the three newest TLEs for IRNSS-1H: ...
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Who released pre-launch TLE data for the Space Shuttle?

The question Pre-launch TLEs for NASA launches asks: I was curious if the United States is on the verge of launching maned flights to the ISS, will anyone release Pre-Launch TLE data like was done ...
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Pre-launch TLEs for NASA launches

I was curious if the United States is on the verge of launching maned flights to the ISS, will anyone release Pre-Launch TLE data like was done back when the shuttle was flying.
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1answer
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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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2answers
207 views

What does it mean to ask for a date beyond epoch time?

I am fairly new to this industry. As I am playing around with a library on Python, ephem, I have encountered an error saying that: ...
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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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172 views

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

I want to use TLE data to calculate the azimuth and elevation of every GPS satellites at user's location. In order to verify the correctness of TLE calculation, I wrote an Android app that can be ...
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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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615 views

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 ...
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Can the deactivated satellites also be tracked through TLE?

TLE is used to track whether the satellites are in orbit or not. However, is it possible that a particular satellite is deactivated, decommissioned or deorbited yet its TLE is being updated regularly?
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TLE/SGP4 state vector accuracy assessment

I’m using the Planet Labs state vectors downloadable from http://ephemerides.planet-labs.com/planet.states or http://ephemerides.planet-labs.com/planet_YYYYMMDD.states to assess the TLEs/SGP4 accuracy ...
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1answer
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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, ...
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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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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" ...
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1answer
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Does this electronics box, or any other non-spacecraft released by astronauts have a TLE?

According to Space.com's 02-Feb-2018 article Cosmonauts Break Russian Spacewalk Record During Space Station Antenna Repair: The cosmonauts spent the day replacing an electronics box for a high-gain ...
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1answer
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Are there publicly-available non-amateur sources of TLEs other than Space-Track?

As an amateur satellite tracker, and sometime reentry analyst, I am always anxious to get the newest tracking data for low-orbiting spacecraft. I have had to rely exclusively on Space-Track for the ...
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Converting TLEs into the input data for SGP4

At face value this seems like a trivial question the TLE's are the input to SGP4, but my question is a little more specific. Given a TLE, the values are in specific units (eg. argument of perigee is ...
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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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1answer
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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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2answers
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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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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 only a ...
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1answer
340 views

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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How can I plot a precessing orbital plane of an artificial satellite on a polar plot from a TLE in Python?

How can I plot the orbital plane of an artificial satellite on a polar plot from a TLE in Python? Very new to all of this. As I understand it I need to extract TLE's from Space-track.org. Then use ...
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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://www.celestrak.com/NORAD/elements/ and I would like to use it to calculate an orbit. How can I ...
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1answer
430 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 ...
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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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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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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 ...
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1answer
558 views

How do “Deep space” corrections in SGP4 account for the Sun's and Moon's gravity?

The [Simplified Perturbations model][1] 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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300 views

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 ...
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1k views

Determine orbit type from TLE

I was wondering if, and how, one can tell from the values in a TLE whether an orbit is LEO, MEO, HEO, or GEO. I'd like to do this in code eventually, so any formulas or threshold values would be much ...
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Has IBEX “gone dark”?

I'm having a difficult time finding information on the Interstellar Boundary Explorer's (IBEX) orbit. Unless I've made some kind of error, the TLE's have stopped at TLE epoch ...
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What happens when the 3-letter suffix space of a SATCAT ID gets exhausted?

The ISS' SATCAT ID is 1998-067A. The CubeSats and other objects released from the space station are considered its sub-units, thus using different suffixes: 1998-067C, etc. The same principle applies ...
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322 views

Calculate ground track from CCSDS OEM

Are there open source solutions (preferable Python) to calculate the ground track of a spacecraft (i.e. in latitute/longitude) from CCSDS OEM (orbit ephemeris message) format (which is a dataset of ...
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426 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 ...