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. ----------------------------------------------------------------------------- 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. --------------------------------------------------------------------------- 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 ! --------------------------------------------------------------------------- ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
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