Sven Grahn posted an estimate of the SZ 4 recovery time tomorrow, 11.04 GMT
I think (I have deleted your e-mail Sven !).
Well, this could be interesting. I am using the SZ 4 element set with an
epoch of Jan 4.458, and that gives a final equator crossing time of around
10.39 GMT. Landings for SZ 2 and 3 came 35-36 minutes after the final
equator crossing, so I am estimating a landing time tomorrow of 11.15 GMT.
Sven, have you dropped 10 minutes in your figures ?
Regarding the SZ 4 high orbit, way back in 2000 as an exercise I ran some
software to calculate the repeating orbit patterns for SZ orbits, and for a
31 circuit repeater at 42.4 minutes the repeating orbit period is 91.212
minutes. Using USSPACECOM data, SZ 4 manoeuvred straight into this orbit,
and the decay rate (or lack of, compared with SZ 2 and 3) makes me wonder
whether the Chinese are using regular low thrusts to maintain altitude.
There was a manoeuvre announced for January 2nd, but the change in altitude
was only of the order of 1-2 km - not 5-10 km as seen on the earlier
flights.
Also be interesting to see what happens to the SZ 4 orbital module. On SZ
2 the manoeuvre was the day after landing and was to a 388-404 km orbit: on
SZ 3 the manoeuvre was within a few hours of the landing and was to a much
lower 353-358 km orbit: only about 3.5 weeks later did the module go up to
382-388 km.
Phillip Clark
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Phillip S Clark Molniya Space
Consultancy
Flat 2 Wellington House
Castle Hill Passage
Hastings
East Sussex TN34 1PG
Publisher - Worldwide Satellite Launches
The only way to comprehend what
politicians say and do is to make the
basic assumption that their brains were
surgically removed before they
entered politics. (My own philosophy)
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