RE: North Korea satellite: retrograde ground track displayed in launch control centre

From: Ted Molczan (
Date: Wed Apr 11 2012 - 12:33:48 UTC

  • Next message: Bob Christy: "Re: North Korea satellite: retrograde ground track displayed in launch control centre"

    I wrote:
    > To be precisely sun-synch, a 500 km orbit must be inclined 97.4 deg. The apparent nearly 3
    > deg deficit may be an indication of the performance limitation of the launcher. I do not
    > exclude the possibility that the displayed track was faked to mislead the news media, but
    > it should not have been more difficult to produce a high-fidelity fake, assuming the work
    > was done by the trajectory specialists. Considering the relative position of the numerals
    > 4 and 7 on a keypad, a simple, honest typo also cannot be excluded.
    Building on the typo hypothesis, if the ground track displayed in the launch control centre resulted from a set of
    orbital elements with a typo affecting a single digit of the inclination, such that 97.45 was entered as 94.45, then the
    true orbit can be recovered from the TLE I estimated from the track, simply by correcting the typo. Here is the TLE with
    the supposed typo:
    1 79802U          12103.11415511  .00000000  00000-0  00000-0 0    05
    2 79802  94.4500 182.0500 0002000 359.9726 179.8827 15.21000000    00
    Here is the correction:
    1 79802U          12103.11415512  .00000000  00000-0  00000-0 0    06
    2 79802  97.4500 182.0500 0002000 359.9726 179.8827 15.21000000    03
    Adding this to the earlier plot shows that the point of intersection with the NOTAM (ascent) trajectory would be shifted
    farther south downrange:
    Here is a view closer to the ascent trajectory:
    Correcting the hypothetical error shifts the point of intersection from about 28.25 N, 124.5 E - about 1270 km
    downrange, to about 20.54 N, 124.39 E - about 2130 km downrange. Returning to David Wright's analysis, the caption
    beneath Fig.2 states:
    "A comparison of computer modeling of the Unha-2 launch from 2009 (red) and a potential Unha-3 launch (blue) that
    carries more fuel in its third stage. The solid lines show the launcher's trajectory; in both cases the launcher burns
    out and releases the satellite at range of about 2,100 km and an altitude of about 500 km."
    The agreement seems very good; however, there may be other trajectory simulations with different results, and the orbits
    I estimated from the LCC display and my plot of the NOTAMs track are not perfect, which affects the accuracy of the
    intersection points. Also, typo or not, the possibility that the track displayed in the LCC was faked cannot yet be
    excluded. Let's see what additional information North Korea provides, what additional evidence the journalists may
    extract, and whether anything reaches orbit.
    Ted Molczan
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