View Issue Details
ID | Project | Category | View Status | Date Submitted | Last Update |
---|---|---|---|---|---|
0002380 | SkyChart | 1-Software | public | 20-10-26 01:10 | 20-10-30 13:18 |
Reporter | Ken M Harrison | Assigned To | Patrick Chevalley | ||
Priority | normal | Severity | minor | Reproducibility | always |
Status | resolved | Resolution | fixed | ||
Platform | All | OS | All | OS Version | All |
Product Version | 4.3 beta | ||||
Target Version | 4.4 | Fixed in Version | 4.3 beta | ||
Summary | 0002380: Saturn Satellite displayed position incorrect | ||||
Description | Phoebe satellite position is shown incorrectly. | ||||
Steps To Reproduce | Zoom in on Saturn..... | ||||
Additional Information | (Observers seem to use: https://pds-rings.seti.org/tools/ ) | ||||
Tags | No tags attached. | ||||
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Thank you to report here. The issue is because CdC compute the planetary satellite position using a port to Pascal language of the Xplanet library libmoons: https://sourceforge.net/p/xplanet/code/HEAD/tree/trunk/src/libephemeris/libmoons/saturn.cpp#l141 Because Phoebe is not include in the precision ephemeris TASS 1.7 this code use a method given in the "Explanatory Supplement to the Astronomical Almanac". Unfortunately this method no more give acceptable result because of the old initial epoch. At the moment I see two options to solve that. 1. Generate orbital elements from Horizon for each month or year, put the elements in a file to use from CdC using simple Kepler orbit. 2. Implement precise orbit computation using SPICE ephemeris files for this satellites. The solution 2. is my preference for now but I need to look more in detail how this can be implemented, the size of the required data, ... From the indication in the web pages the site https://pds-rings.seti.org/tools/ use this second solution. Some interesting link about SPICE: https://naif.jpl.nasa.gov/naif/index.html the code: https://naif.jpl.nasa.gov/naif/toolkit.html the data files: https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/satellites/ To my knowledge there is no other option to compute this satellite position but any comment and addition are welcome. |
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I start to work on SPICE and the good news is the code is more easy to use than expected. I have all the necessary code to return the satellite vector. Now I need to add that to the CdC satellite computation. An issue is the size of the required data. For all the satellites this is about 6.5 GB. But we not need all the small satellites that are visible only by the spacecrafts. I prefer to keep the actual list of satellites in CdC, this already go to magnitude 23 or 24. Another way to limit the data size is to reduce the range of date to 2000-2050. Anyway for some satellites there is no data available out of this range. Fortunately there is a good tool to merge the data files using this criteria. At the moment I make a basic file with the 21 brighter satellites and an extension with 35 fainter. The file size are 300 MB and 1.7 GB. I plan to make two separated installer for them. The two files content is the following: Summary for: cdcbase.bsp Bodies Start of Interval (ET) End of Interval (ET) ------- ----------------------------- ----------------------------- 3 EARTH BARYCENTER 2000 JAN 01 00:00:00.000 2050 JAN 01 00:00:00.000 4 MARS BARYCENTER Same coverage as previous object 5 JUPITER BARYCENTER Same coverage as previous object 6 SATURN BARYCENTER Same coverage as previous object 7 URANUS BARYCENTER Same coverage as previous object 8 NEPTUNE BARYCENTER Same coverage as previous object 10 SUN Same coverage as previous object 399 EARTH Same coverage as previous object 401 PHOBOS Same coverage as previous object 402 DEIMOS Same coverage as previous object 499 MARS Same coverage as previous object 501 IO Same coverage as previous object 502 EUROPA Same coverage as previous object 503 GANYMEDE Same coverage as previous object 504 CALLISTO Same coverage as previous object 599 JUPITER Same coverage as previous object 601 MIMAS Same coverage as previous object 602 ENCELADUS Same coverage as previous object 603 TETHYS Same coverage as previous object 604 DIONE Same coverage as previous object 605 RHEA Same coverage as previous object 606 TITAN Same coverage as previous object 607 HYPERION Same coverage as previous object 608 IAPETUS Same coverage as previous object 699 SATURN Same coverage as previous object 701 ARIEL Same coverage as previous object 702 UMBRIEL Same coverage as previous object 703 TITANIA Same coverage as previous object 704 OBERON Same coverage as previous object 705 MIRANDA Same coverage as previous object 799 URANUS Same coverage as previous object 801 TRITON Same coverage as previous object 802 NEREID Same coverage as previous object 899 NEPTUNE Same coverage as previous object Summary for: cdcext.bsp Bodies Start of Interval (ET) End of Interval (ET) ------- ----------------------------- ----------------------------- 505 AMALTHEA 2000 JAN 01 00:01:04.183 2049 DEC 31 00:01:09.183 514 THEBE Same coverage as previous object 515 ADRASTEA Same coverage as previous object 516 METIS Same coverage as previous object 609 PHOEBE Same coverage as previous object 610 JANUS Same coverage as previous object 611 EPIMETHEUS Same coverage as previous object 612 HELENE Same coverage as previous object 613 TELESTO Same coverage as previous object 614 CALYPSO Same coverage as previous object 615 ATLAS Same coverage as previous object 616 PROMETHEUS Same coverage as previous object 617 PANDORA Same coverage as previous object 618 PAN Same coverage as previous object 635 DAPHNIS Same coverage as previous object 706 CORDELIA Same coverage as previous object 707 OPHELIA Same coverage as previous object 708 BIANCA Same coverage as previous object 709 CRESSIDA Same coverage as previous object 710 DESDEMONA Same coverage as previous object 711 JULIET Same coverage as previous object 712 PORTIA Same coverage as previous object 713 ROSALIND Same coverage as previous object 714 BELINDA Same coverage as previous object 715 PUCK Same coverage as previous object 725 PERDITA Same coverage as previous object 726 MAB Same coverage as previous object 727 CUPID Same coverage as previous object 803 NAIAD Same coverage as previous object 804 THALASSA Same coverage as previous object 805 DESPINA Same coverage as previous object 806 GALATEA Same coverage as previous object 807 LARISSA Same coverage as previous object 808 PROTEUS Same coverage as previous object 901 CHARON Same coverage as previous object |
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I just make a small correction to the list of satellite in each file so this match the current option "Show the faint satellites of the outer planets". 609 PHOEBE and 901 CHARON are now in the base file. |
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The new satellite computation is now implemented in Skychart and the result is very good with coordinates identical to those given by JPL Horizon. You can test the new program on Windows by downloading one of this files: https://vega.ap-i.net/tmp/skychart/ Then install this file with the main satellite kernel (215MB): https://sourceforge.net/projects/skychart/files/2-catalogs/SpiceKernel/skychart-spice-base-4.3-4182-windows.exe/download If you also want the small satellite, add this one (1.2GB): https://sourceforge.net/projects/skychart/files/2-catalogs/SpiceKernel/skychart-spice-ext-4.3-4182-windows.exe/download The version for Linux and Mac will be available in Monday beta version. |
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Patrick. Installed -4128 and the satellite data (both files) Works 100% for me. Appreciate your work in keeping CdC as one of the best sky mapping programs available to the amateur. |
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Thank you for the test Ken. I will announce that in the mail list on Monday after the program is available for all the platform. |
Date Modified | Username | Field | Change |
---|---|---|---|
20-10-26 01:10 | Ken M Harrison | New Issue | |
20-10-26 13:42 | Patrick Chevalley | Assigned To | => Patrick Chevalley |
20-10-26 13:42 | Patrick Chevalley | Status | new => assigned |
20-10-26 13:42 | Patrick Chevalley | Category | 2-Catalog data => 1-Software |
20-10-26 13:42 | Patrick Chevalley | OS | Windows => All |
20-10-26 13:42 | Patrick Chevalley | OS Version | 10 64bit => All |
20-10-26 13:42 | Patrick Chevalley | Platform | PC => All |
20-10-26 13:42 | Patrick Chevalley | Target Version | => 4.4 |
20-10-26 13:42 | Patrick Chevalley | Note Added: 0006809 | |
20-10-27 15:46 | Patrick Chevalley | Note Added: 0006811 | |
20-10-27 20:36 | Patrick Chevalley | Note Added: 0006812 | |
20-10-29 09:51 | Patrick Chevalley | Note Added: 0006813 | |
20-10-30 01:38 | Ken M Harrison | Note Added: 0006815 | |
20-10-30 13:18 | Patrick Chevalley | Status | assigned => resolved |
20-10-30 13:18 | Patrick Chevalley | Resolution | open => fixed |
20-10-30 13:18 | Patrick Chevalley | Fixed in Version | => 4.3 beta |
20-10-30 13:18 | Patrick Chevalley | Note Added: 0006816 |