I have two TLE, the drag term for the first TLE is -26868-1, which I suppose equals to -0.026868. But on the second TLE, we have 00000+0. What does the "+" symbol represents here?

COSMOS 2549             
1 47546U 21008A   21040.52165678 -.00037182  00000-0 -26868-1 0  9998
2 47546  67.1483  54.1721 0006757 284.8888  75.1223 13.96668399   985

1 47613U 21010A   21036.34392819  .00000403 -56594-6  00000+0 0  9998
2 47613  28.3962   6.0839 7309460 180.1054 196.4507  2.28168883    27
  • $\begingroup$ My guess is that you place the decimal point towards the right. For example, 12345+1 will give 1.2345 opposed to 12345-1 which gives 0.012345. $\endgroup$ – Star Man Feb 9 at 20:18

While this was too rushed out question, in the mean time I managed to find an answer while playing with already existing TLE parsers.

The main difference between the + and - sign is that - multiplies whatever is left of the sign with 10 to the negative value, while the + multiplies whatever is left of the sign with 10 to the positive value.


If we have the drag term -26868+1, the extracted value is -2.6868. But if we have the drag term -26868-1, the value is -0.026868.

From Celestrak's What is the format for the two-line element sets?:

Fields 1.10 and 1.11 have a somewhat different format that the other fields. In particular, they use a modified exponential notation with an implied leading decimal point. This convention is inherited from FORTRAN where all such numbers range from 0 to less than 1. The first six columns of each field represent the mantissa and the last two represent the exponent. For example, the value -12345-6 corresponds to -0.12345 × 10-6. Each of these two fields can be blank, corresponding to a value of zero.

From NASA Spaceflight's Definition of Two-line Element Set Coordinate System:

Second Derivative of Mean Motion

(00000-0 = 0.00000) The second derivative of mean motion is a second order drag term in the SGP4 predictor used to model terminal orbit decay. It measures the second time derivative in daily mean motion, divided by 6. Units are revs/day^3. A leading decimal must be applied to this value. The last two characters define an applicable power of 10. (12345-5 = 0.0000012345).

Drag Term

(67960-4 = 0.000067960) Also called the radiation pressure coefficient (or BSTAR), the parameter is another drag term in the SGP4 predictor. Units are earth radii^-1. The last two characters define an applicable power of 10. Do not confuse this parameter with "B-Term", the USSPACECOM special perturbations factor of drag coefficient, multiplied by reference area, divided by weight.

  • 1
    $\begingroup$ Exactly. You could just write up the extended, implicit number, e.g -0.26868 * 10^1. $\endgroup$ – asdfex Feb 9 at 20:20
  • 1
    $\begingroup$ @uhoh thank you for the edit, will pay more attention next time! $\endgroup$ – lawndownunder Feb 9 at 20:53
  • $\begingroup$ It's also always okay to accept your own answer. I usually wait a few days to see if others have additional answer or comments. $\endgroup$ – uhoh Feb 9 at 22:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.