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| click diagram to enlarge |
In two contributions to The Space Review (part 1 here and part 2 here) for the first instance, as well as two follow-up blog posts for later manoeuvers (here, and here), I analyzed three periodic orbit raising manoeuvers by the North Korean military reconnaissance satellite Malligyong-1 (2023-179A) done in February, June and September 2024. They followed a similar pattern: an orbit raise (orbit maintenance manoeuver) in five daily increments, all taking place on late evening passes (13 - 14h UTC = 22 - 23h local time) passes over North Korea.
Now Malligyong-1 has manoeuvered for a fourth time. And while there are some similarities, this time the followed pattern was different.
The orbit raising manoeuver was done between 2025 January 16 and 18, a month later than I had anticipated. However, as can be seen in the diagram above, it was this time done in three daily increments, not five as was the case in previous orbit raising events.
Compared to the previous orbit raises, the raise during each daily increment was larger, some 2.5 km per increment rather than 1.2 km as in the previous cases, for a total orbital altitude raise of about 7.5 km, which is also somewhat larger than the previous orbit raises (which was 4 km in February 2024 and 6 km in June and September 2024). As during the previous orbital altitude maintenance raises, it brought back the orbital altitude to the initial value from November 2023, when the satellite was launched. See the diagrams below:
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| click diagram to enlarge |
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The three sequential manoeuvers between January 16 and 18 raised both apogee and perigee. The daily rate of RAAN precession is still very close to the ideal sun-synchronous value.
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| click diagram to enlarge |
As was the case for all previous orbit raises, the times I reconstruct for the three incremental orbit raises correspond to the orbital plane of Malligyong-1 passing over or near North Korea (for the method used, see here);
# DATE UTC LAT LON ORBITS USED FOR ANALYSIS RAISE
M1 16-01-2025 13:14 28.6 N 53.4 W 25016.48110101 25017.33556354 2.50 km
M2 17-01-2025 12:52 19.4 N 46.3 W 25017.33556354 25018.12465384 2.51 km
M3 18-01-2025 12:33 20.5 N 41.7 W 25018.45348685 25019.24307946 2.52 km
However, there is a clear difference: all nominal positions do not plot near North Korea this time, but over the mid-Atlantic. Nominal manoeuver times were about half an hour before passing over/near North Korea.
The map below plots the nominal manoeuver positions I reconstruct, as well as a part of the ground trajectory from 10 minutes before to ten minutes after the nominal reconstructed manoeuver time.
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The red circle in the map is the area where the satellite would be above the horizon as seen from Pyongyang. Clearly - and unlike previous occasions - the manoeuver points do not coincide with this area, although the satellite would pass through the area about 30 minutes after the reconstructed manoeuver moments (for one of the manoeuver moments, I depicted a longer part of the ground trajectory as well with markers each 5 minutes of flight time).
The manoeuvers not conciding with the satellite being over the horizon as seen from the Pyongyang General Satellite Control Center (PGSC), is something new and intriguing. The nominal manoeuver points being over the mid-Atlantic is interesting.
So how where these manoeuvers initiated? Assuming my reconstruction of the manoeuver points is correct, here are three options, all having their own implications:
(1) use of a pre-programmed, automated orbit raising burn;
(2) an orbit raising burn command sent through a (Russian? Chinese?) relay satellite in GEO;
(3) an orbit raising burn command sent from a groundstation or ship near/around the mid-Atlantic.
The white area depicted in the map is from where a command from a ground station or ship should have been sent in the case of option (3), possibly a location in Brazil or the mid-Atlantic.
It might be interesting if someone better versed in that than me, could check the presence of North Korean vessels (and Russian and Chinese space tracking vessels) in the mid-Atlantic between January 16 and 18, 2025.
All three nominal positions correspond to a manoeuver just after passing through the Ascending Node, which is often a standard practise with orbit raising manoeuvers when smaller or larger alterations to the orbital inclination are required. However, no such alterations to the orbital inclination are apparent:
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This was the fourth orbit rasing manoeuver episode since Malligyong-1 was launched on 21 November 2023. Here are they all in a table:
# period incr raise before after interval
1 2024 19-23 Feb 5x 4.0 km 498 km 502 km 90 days
2 2024 03-07 Jun 5x 5.7 km 497 km 503 km 105 days
3 2024 06-10 Sep 5x 5.9 km 498 km 504 km 95 days
4 2025 16-18 Jan 3x 7.5 km 496 km 504 km 132 days
A next raise might occur in the period April to June 2025. It will be interesting to see where those manoeuver locations will end up geographically and whether at some point the orbital inclination is adjusted or not.
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