Problem with spiceInterface

[schaubh]

I create a new spiceInterface with the current time UTCInit = "2021 MAY 1 00:30:00".
To test my spiceInterface I recorded spiceTimeOutMsg and printed the first value of J2000Current.
After checking the J2000 value I noticed diff of 69.18548 seconds to the UTCInit time. To be sure the recorder isnt the problem, I set the priority of the recorder module to the highest number. What could be the problem?

Thank you for your time

[schaubh]

Hello Claudio ,

Could you provide more details as to how you are passing this UTCInit value to the module ?

[schaubh]

Hello Benjamin,
this is my code:

# Spice model für eclipse und magnetfeld
   UTCInit = "2021 MAY 1 00:30:00" #!
   gravFactory.createSpiceInterface(
       bskPath + "/supportData/EphemerisData/", UTCInit , epochInMsg=False
   )
   scSim.AddModelToTask(simulationTaskName, gravFactory.spiceObject)

Thanks for your time!

[schaubh]

This appears to be linked to how Spice interprets the calendar representation of the input string.

I looked up the definition of the Spice routine str2et_c that is called inside SpiceInterface (see spiceInterface.cpp:184) :

In addition to specifying time zones, you may specify that the
string be interpreted as a formal calendar representation in
either the Barycentric Dynamical Time system (TDB) or the
Terrestrial Dynamical Time system (TDT). In These systems there
are no leapseconds.
 
Times in TDB are written as
1988 June 13, 12:29:48 TDB
 
TDT times are written as:
1988 June 13, 12:29:48 TDT
 
Finally, you may explicitly state that the time system is UTC
1988 June 13, 12:29:48 UTC.

I added a case in test_unitSpice.py in the spiceInterface folder using your time string "2021 MAY 1 00:30:00" and looked at the value of J2000EtInit in the debugger (I didn't need to invoke it but whatever) : it is interpreted as a UTC date by default. Had you added 'TDB' to the string, you would get the exact same round count of seconds as here

Hope this helps !