View Issue Details

IDProjectCategoryView StatusLast Update
0002380SkyChart1-Softwarepublic20-10-30 13:18
ReporterKen M Harrison Assigned ToPatrick Chevalley  
PrioritynormalSeverityminorReproducibilityalways
Status resolvedResolutionfixed 
PlatformAllOSAllOS VersionAll
Product Version4.3 beta 
Target Version4.4Fixed in Version4.3 beta 
Summary0002380: Saturn Satellite displayed position incorrect
DescriptionPhoebe satellite position is shown incorrectly.
Steps To ReproduceZoom in on Saturn.....
Additional Information(Observers seem to use: https://pds-rings.seti.org/tools/ )
TagsNo tags attached.

Activities

Patrick Chevalley

20-10-26 13:42

administrator   ~0006809

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.

Patrick Chevalley

20-10-27 15:46

administrator   ~0006811

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

Patrick Chevalley

20-10-27 20:36

administrator   ~0006812

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.

Patrick Chevalley

20-10-29 09:51

administrator   ~0006813

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.

Ken M Harrison

20-10-30 01:38

reporter   ~0006815

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.

Patrick Chevalley

20-10-30 13:18

administrator   ~0006816

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.

Issue History

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