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
- 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
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).
(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.