Queqiao’s Earth-Moon L2 Halo Orbit

Queqiao was launched by China on May 25, 2018 towards the far side of the Moon where it ultimately took up shop at the Earth-Moon L2 point in a halo orbit.  It’s mission is to provide communications for the first landing on the Moon’s far side by Chang’e 4.

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Chang’e 4 Lunar Orbit a Postmortem

On January 3, 2019, 02:26 UTC Chang’e 4 landed on the far side of the Moon ending over a fortnight of tracking the trajectory of the mission as it left Earth, arrived in lunar orbit made orbital adjustments and then finally landed.  I discuss the results of our tracking attempts focusing mostly on the final analysis where the landing time was predicted and compare that to a final analysis performed after reviewing the crumbs of data shared from Chinese state media videos to see how close we got.

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Basic Orbital Dynamics

There has been a recent surge in interest in a software package written by Cees Bassa known as ‘strf’, Sattools Radio Frequency.  Once over the initial installation and basic usage hump users quickly reach a wall about how to use the software because of a limited understanding of orbital dynamics.  I hope this brief post will help users understand some of the basic concepts so they can use strf as a tool.

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When will Chang’e 4 Land?

Continued radio monitoring of Chang’e 4 in orbit around the Moon has allowed amateurs to develop an orbital model and propagate that model to predict a tentative landing date and time.  Data supplied by radio amateurs Edgar Kaiser, DF2MZ and Paul Marsh, M0EYT suggest a possible first landing window of early January 1st or 2nd, 2019.  So is it time to start a friendly betting pool at the office?

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Chang’e 4 in Lunar Orbit

After a few days of head scratching the data being received from the Moon by amateurs clearly shows Chang’e 4 in lunar orbit, just not the expected orbit.  The plane of the Chang’e 4 appears to be about 90 degree off of what was expected based on the Chang’e 3 trajectory assuming we understand it correctly.  Communication activity appears limited to direct communication with Earth on X-band as there have been no signs of activity from Queqiao or on S-band from Chang’e 4.  Chang’e 3 has made some brief appearances apparently being told to keep quiet while Chang’e 4 gets ready to land.

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Eating Static from the Moon…

Xinhua reported today that Chang’e 4 entered lunar orbit at about 08:39 UTC on Dec 12th.  No amateur observers reported observing the event; however, three highly competent amateur observers in Europe shared observations hours after the lunar orbit insertion burn was executed. No evidence of a signal from Chang’e 4 has been noted since my loss of signal earlier on Dec 12th.  I later conducted similar observations and searched around the Moon for the signal and found nothing we can relate to Chang’e 4. Only signals from Chang’e 5T-1 and Queqiao where noted.

[UPDATED – Dec 13th, 2018] Continue reading “Eating Static from the Moon…”