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.

Continue reading “Chang’e 4 Lunar Orbit a Postmortem”

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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…”

A Trip to the Dark Side of the Moon?

On December 7th, 2018 at 1823 UTC the Chinese launched the much anticipated Chang’e 4 mission to the far side of the Moon.  Unfortunately, the launch was not broadcast live nor has there been much in the way of official word on what is going on with the mission.  Fortunately, we have both the Chang’e program history and Chang’e 4’s transmitter to help us fill in the blanks of what to expect and witness history in realtime without a filter.

So for those not accustomed to watching a space first unfold in the language of the Doppler effect here’s a primer of what has happened and what to expect.

Continue reading “A Trip to the Dark Side of the Moon?”