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2-line element calculation

Conversion of two line elements to one line Charlie elements


The purpose of this page is to help you convert NORAD 2 line elements to Charlie elements. Get hold of your original data as a text file. Try opening an example text listing of Cubesat 2 line elements. Use Microsoft Notepad or similar simple text reader.

From your text file, highlight and copy and paste your selected three lines of text data into the text input box below. Hint: Copy is Control C. Paste is Control V.  Then click the button below to make the conversion and generate the output text line.

One line Charlie element.

Analysis and processed output from line 1.

Analysis and processed output from line 2.

Unused miscellaneous data.

25th Sept 2016: This calculator is new and not fully tested. Use for the moment is for testing and verification purposes only. 

The result for drag is dubious. If the input is " 10000-3" as per the default above the Charlie output should be 6 digits.  I don't know how to convert this variable.  At present it converts as 000100

The other results may be in error and should not be used for for anything important or orbital manoeuvres or the navigation of real spacecraft. You have been warned ! If anyone uses this page and is able to do the calculations independently themselves or with other software please tell me eric@satsig.net  where I am right and where I am wrong.

Explanation of 2 line elements:


1 39189U 13031B   13322.55940486 -.00000028  00000-0  10000-3 0   390

2 39189   0.0361 358.2964 0001026   0.7257   0.9823  5.00115079  7309

         1         2         3         4         5         6

Full explanation of NORAD 2 line elements

First text line: Up to 24 text characters. Text name as used in common public documents and adverts. It may vary with time due to change of owner/lessee and marketing ideas. Names may be changed as a result of change in the orbit position of geostationary satellites.

Line 1 explanation: Column number meanings
1        If set to 1, indicates line 1 of two element data set
3-7     Satellite number
8        Classification: U=unclassified
10-11 International Designator (Last two digits of launch year 1957-1999, 2000-2056)
12-14 International Designator (Launch number of the year)
15-17 International Designator (Part off the launcher, letters A, B, C ... AA, AB,  etc)
19-20 Epoch Year (Last two digits of year 57-99, 00-56)
21-32 Epoch Day of the year with leading zeros and fractional portion of the day.
34-43 First Time Derivative of the Mean Motion
45-52 Second Time Derivative of Mean Motion (decimal point assumed)
54-61 BSTAR drag term " NNNNN-N" assumed to mean 0.NNNNN, then apply -N as power of 10
54:      First character may be + or blank. I am uncertain how this BSTAR drag term converts to 6 digits in Charlie one line elements. I have assumed that +12345-3 converts to 000123, units of revs/day^2. This may be all wrong. The term may alternatively be a drag coefficient.
63       Ephemeris type
65-68  Element number
69        Checksum

Line 2 explanation: Column number meanings
1         If set to 2, indicates line 2 of two elements data set
3-7     Satellite number
9-16   Inclination NNN.NNNN deg. Leading zeros may be absent. Converts to NNNNNN which means NNN.NNN
18-25 Right Ascension of the Ascending Node NNN.NNNN deg. Leading zeros may be absent.
27-33 Eccentricity NNNNNNN means .NNNNNNN
35-42 Argument of Perigee deg NNN.NNNN converts to NNNNNN which means NNN.NNN
44-51 Mean Anomaly deg NNN.NNNN converts to NNNNNN which means NNN.NNN
53-63 Mean Motion revs per day  NN.NNNNNNNN converts to NNNNNNNN which means NN.NNNNNN
64-68 Revolution number at epoch revs
69       Checksum

Explanation of One line Charlie elements

The one-line Charlie element format is still used as an input format for some older satellite dish pointing software and for some military applications. It comprises a single line of 60 decimal digits. The meaning of column numbers is as follows:

         1         2         3         4         5         6

1-5   NORAD Catalogue Number.
6-7   Epoch year (Last two digits of launch year 1957-1999, 2000-2056).
8-10 Epoch Day of year with leading zeros NNN
11-16 Fraction of a day of epoch NNNNNN means .NNNNNN
17-22 Drag. NNNNNN  Uncertain could be revs/day^2 or a drag coefficient
23-28 Inclination NNNNNN means NN.NNN deg
29-34 Right Ascension of Ascending Node (deg)  NNNNNN means NNN.NNN
35-40 Eccentricity NNNNNN means NNNNNN
41-46 Argument of Perigee (deg) NNNNNN means NNN.NNN
47-52 Mean Anomaly, (deg) NNN.NNNN convetts to NNNNNN means NNN.NNN
53-60 Mean Motion, (rev/day) NNNNNNNN means NN.NNNNN

Known possible software problem (not resolved)

The web page program needs to identify the start of each data line. It looks for matching sequences of "1 NNNNNT" or "2 NNNNN ", where N is a digit and T is text character, and space is a space character. This will not work properly if there is false match due to unusual satellite text name of the data input is not as I have assumed. Please tell me if you ever see this. 

Any problems, suggestions for improvements or comments, please e-mail me Eric Johnston
This calculator is copyright © 2016 Satellite Signals Ltd.

Page started 22 Sept 2016, amended 14 Dec 2023.