[FPSPACE] Re: Shenzhou-2 has maneuvered

[Phillip Clark]

On Wed, 10 Jan 2001, Sven Grahn wrote:
> The initial orbit of Shenzhou-2 was 196.5-333.8 km. NASA;s OIG website just 
> shows that the new orbit is 327.7-332.7 km (epoch at 19:58:40 UT, today 10 
> Jan). So, it is changing orbits!
> Sven Grahn

I have just e-mailed the following to various correspondents.   The
repeating orbit discussion was sent out at about 01.00 GMT today and has
been added to back up the repeating pattern.
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NOTE:   The post-manoeuvre orbit is very close to the 31 circuit repeater
in the table below.

So, what does this mean ?   Shen Zhou 1 was in orbit for 21h 11min: so
for ~7 days in orbit this means three cycles of (2d -52.3 min), or
a predicted lifetime of 162 hours 34 minutes.   Let's see how far wrong
this figure is !


==========================================================================
Catalogue      Orbital      Orbital    Orbital  Perigee    Apogee   Arg of
  Number        Epoch     Inclination   Period                     Perigee
                              deg         min      km        km      deg
--------------------------------------------------------------------------
2001-001A        SHEN ZHOU 2
26664       2001 Jan  9.88   42.61       89.84      197       336    130
26664       2001 Jan 10.01   42.58       89.84      198       335    131
26664       2001 Jan 10.08   42.58       89.83      197       335    132
26664       2001 Jan 10.14   42.58       89.83      198       334    132
26664       2001 Jan 10.25   42.58       89.82      198       334    133
26664       2001 Jan 10.40   42.58       89.81      197       333    134
26664       2001 Jan 10.83   42.58       91.16      329       334    209

2001-001B        CZ-2F SECOND STAGE
26665       2001 Jan  9.94   42.58       89.80      199       330    130
26665       2001 Jan 10.19   42.57       89.77      197       328    132
26665       2001 Jan 10.25   42.58       89.76      197       328    133
26665       2001 Jan 10.26   42.58       89.76      197       328    133
26665       2001 Jan 10.37   42.58       89.75      197       327    134
==========================================================================


The following table is extracted from my CHINESE SPACE ACTIVITIES
1996-2000 report and shows the repeating orbit patterns for the Shen
Zhou orbital inclination of 42.6 deg.   I have assumed a slightly
eccentric orbit, but the value is so low that it should net affect the
results to a noticeable effect.

Shen Zhou 2's initial orbit is 197-336 km, so I am thinking of how it
could manoeuvre.   If it manoeuvres about 24 hours after launch then
for a landing after a lifetime of ~7 days they would need either a
2-days or 3-days repeater: to repeat after 31 orbits we could expect
the spacecraft to circularise its orbit at roughly the apogee
altitude: to repeat after 47 orbits you would have an orbit a little
lower than the initial apogee.   So ..... and this is guesswork - I
would guess that of all of the manoeuvres that they could do, the
Chinese might go for one of these two repeating patterns.

Of course, this could be completely wrong .......

Phil



Incl   Eccentricity  Circuits  Period    Altitude    Ground   Interval
  o                              min        km     Track, deg  d   min

42.6     0.00100        16      88.253   181 - 195   22.500   1  -28.0
42.6     0.00100        79      89.416   239 - 252   22.785   5 -136.1
42.6     0.00100        63      89.712   254 - 267   22.857   4 -108.2
42.6     0.00100        47      90.208   278 - 291   22.979   3  -80.2
42.6     0.00100        78      90.609   298 - 311   23.077   5 -132.5
42.6     0.00100        31      91.216   328 - 341   23.226   2  -52.3
42.6     0.00100        77      91.831   358 - 371   23.377   5 -129.0
42.6     0.00100        46      92.246   378 - 391   23.478   3  -76.7
42.6     0.00100        61      92.769   403 - 417   23.607   4 -101.1
42.6     0.00100        76      93.085   419 - 432   23.684   5 -125.5
42.6     0.00100        15      94.372   481 - 495   24.000   1  -24.4

The time intervals between ground track  repetitions are shown in the
format "days" and "minutes": for example, a 42.6 deg 79 circuits
pattern repeats after 5 days less 136.1 minutes.

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Phillip S Clark                                     22 Winterbourne Close
Molniya Space Consultancy                           Hastings
Compiler/Publisher, Worldwide Satellite Launches    E Sussex  TN34 1XG
                                                    U.K.

Specialist in "space archeology" - the older and more obscure the more 
interesting it is !
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