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Cassini Rework, how recent is xyzv data?
Posted: 03.09.2016, 16:31
by FarGetaNik
Hello everybody, I'm working on various spacecraft and want to continue with a rework of the Cassini mission soon. I just finnished a rework of the Galileo mission just to find the xyzv trajectory I created no better than the one in default Celestia, if not worse. Those 35 orbits already were pretty complicated to aquire, I greatly fear the hundrets of orbits Cassini loops around Saturn during 13 years, it would take me forever to aquire sufficient data from HORIZONS and it would be a shame to find the data being no different from the default.
So can anybody tell me when the current trajectory of Cassini was created? The changelogs give some hints but one can only guess how recent the data was. Assuming the data was up to date, I just want to redo the part after the xyzv was made, to correct any eventual deviations of Cassinis orbit. I saw such deviations on several other space missions like Messenger when redoing the trajectory.
HOROZONS has an option to create time-varying steps, but this seems not to be compatible with vectors necessary for xyzv data. This would solve the problem.
Another opion would be to use spice orbit, but is it worth wasting gigabytes of disc space for an incomplete trajectory? But considering the efforts necessary for creating a xyzv this might be an alternative...
Posted: 04.09.2016, 06:08
by John Van Vliet
it depends on the dataset used
from the web interface on horizons it is
Trajectory segment name Start date (TDB) End date (TDB)
-------------------------- ----------------- -----------------
000331R_SK_LP0_V1P32 1997-OCT-15 09:28 to 1998-MAY-28 21:23
000331B_SK_V1P32_V2P12 1998-MAY-28 21:23 to 1999-JUL-06 16:01
000331R_SK_V2P12_EP15 1999-JUL-06 16:01 to 1999-AUG-19 02:00
010420R_SCPSE_EP1_JP83 1999-AUG-19 02:00 to 2001-MAR-07 12:00
010423_SK_JP67_SP0 2001-MAR-07 12:00 to 2002-APR-11 00:00
020425B_SK_SM812_T45 2002-APR-11 00:00 to 2003-JAN-01 12:00
030201AP_OPK_SM546_T45 2003-JAN-01 12:00 to 2004-MAY-01 12:00
040622AP_OPK_04122_08222 2004-MAY-01 12:00 to 2004-OCT-01 12:00
041001AP_SK_04275_08222 2004-OCT-01 12:00 to 2004-NOV-24 00:00
041210AP_OPK_04329_08189 2004-NOV-24 00:00 to 2005-APR-29 00:59
050720AP_SCPSE_05119_08222 2005-APR-29 00:59 to 2006-MAR-23 00:00
060323AP_SCPSE_06082_08222 2006-MAR-23 00:00 to 2006-DEC-22 05:00
070209AP_SCPSE_06356_08222 2006-DEC-22 05:00 to 2007-SEP-18 12:00
070918AP_SCPSE_07261_10191 2007-SEP-18 12:00 to 2008-MAY-17 01:30
080806AP_SCPSE_08138_10182 2008-MAY-17 01:30 to 2009-JUL-17 15:53
090721AP_SCPSE_09198_17265 2009-JUL-17 15:53 to 2009-SEP-05 02:49
091005AP_SCPSE_09248_17265 2009-SEP-05 02:49 to 2011-JUN-24 08:43
110818AP_SCPSE_11175_17265 2011-JUN-24 08:43 to 2013-OCT-17 13:16
150901AP_SCPSE_13290_17272 2013-OCT-17 13:16 to 2017-SEP-29 00:00
for the time period "2013-OCT-17 13:16 to 2017-SEP-29 00:00"
it is the bsp " 150901AP_SCPSE_13290_17272" created on September 1 2015 ) 15 /09/01 as per the name
mind you AP kernels are alpha( first version ) PREDICTIVE kernels
and not Reconstructed like "160725R_SCPSE_16115_16146.bsp" that was created on July 25 2016
ftp://naif.jpl.nasa.gov/pub/naif/CASSINI/kernels/spk/
Posted: 04.09.2016, 09:01
by FarGetaNik
Thanks, that is a start. Comparing the dates with timeframes I found some to be not that up to date as I would like to:
Starting from 020425B_SK_SM812_T45 2002-APR-11 00:00 to 2003-JAN-01 they all seem to have been created during their timeframes. Well if that's HORIZONS data I can't possibly change anything about it, I'll have to assume no unsheduled trajectory changes occured during the mission. Now I need to know when the Celestia's data was created, to check which updates in HORIZONS there were since.
At the very least for the remake I want to split Cassini's orbit up a bit more, so you don't get lost in the muddle of loops around Saturn. And change something about Huygens...
Posted: 04.09.2016, 11:58
by selden
The subversion archive on sourceforge includes the dates when Celestia's Cassini xyzv files were updated.
See
https://sourceforge.net/p/celestia/code/HEAD/tree ... /extras-standard/cassini/data/
Posted: 04.09.2016, 17:06
by FarGetaNik
soltice part: 2010-05-24, So just before begin of solstice mission.
but main mission/equinox part is 2008-10-06, also at begin of equinox mission... that will be a lot of work if I redo the trajectory
I will have to find another way.
Well at least that answers my question. Thanks
