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.

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The Stanford Dish

The Stanford University Dish some 46m or 150′ in diameter was erected in 1961 and became one of world’s largest dish antennas, even today.  The Dish was commissioned by the Stanford Research Institute that later became SRI International.  This fact made complete sense when one was standing at the control position and proudly posted on the console was the amateur radio call-sign of W6SRI.  The dish is primarily used to support spacecraft operation as it is located in an electrically noisy area limiting radio astronomy work.

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Space Strikes Back, IMAGE Returns to Silence…

Just when everyone thought the story of IMAGE was going to have a Hollywood ending she has displayed a knack for dramatic flare.

On 2018-02-25 at 02:19:19.459 UTC IMAGE ended an approximately 48 hour series of off/on sequences of its TT&C beacon and returned to silence.  It’s been over two days now and the beacon has not returned to the air.

The signal sequence in the image above shows the last few minutes of IMAGE’s transmissions. Continue reading “Space Strikes Back, IMAGE Returns to Silence…”

Frequently Asked Questions about Satellite Tracking

We have received a lot of responses to the recovery of IMAGE.  It would be difficult to respond in great detail to each request so we have taken the time to compile some references to help our readers understand what we do and allow you to explore the world of satellite tracking based on the input of our colleagues in the hobby as well.

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