[Spice_discussion] spkezr question

[William Thompson]

I should have mentioned that there are some examples of using these coordinate 
frames in

http://sohowww.nascom.nasa.gov/solarsoft/stereo/ssc/idl/spice/

Bill Thompson

William Thompson wrote:
> Aimee:
> 
> You may be interested in these frame definition files I put together for 
> the STEREO project.  The file heliospheric.tf is generic, and can be 
> used for any mission.  The stereo_rtn.tf is an implementation of the 
> HGRTN coordinate system specific to the two STEREO spacecraft--you can 
> use it as a template for your own mission.
> 
> http://sohowww.nascom.nasa.gov/solarsoft/stereo/gen/data/spice/gen/heliospheric.tf 
> 
> http://sohowww.nascom.nasa.gov/solarsoft/stereo/gen/data/spice/gen/stereo_rtn.tf 
> 
> 
> Bill Thompson
> 
> 
> Aimee Mostella wrote:
> 
>> Hello,
>> I'm using spkezr to get the position of a spacecraft (target) in the 
>> J2000 reference frame with the observer as the Sun.  What coordinate 
>> system is this based upon?  Is it Heliocentric Aries Ecliptic HAEJ2000? 
>> Ultimately, I need to get the lat and lon of the spacecraft based on 
>> the Heliocentric of Date (HCD) coordinate system so that I can convert 
>> to Heliocentric RTN (HGRTN).  I thought I could either get the 
>> position of the spacecraft in HAEJ2000 and convert to HCD from there 
>> or get the position in GEIJ2000 and convert from there.  However, when 
>> I tried the GEIJ2000 route, my calculations were more off than they 
>> were when I did it from scratch.  I tried the algorithm in the SPK 
>> Required Reading but still didn't get a good answer.  Any suggestions? 
>>
>> Thanks
>>
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Aimee Mostella
>> Research Analyst
>>
>> Southwest Research Institute
>>
>> Space Science Division
>>
>> (210) 522-6735
>>
>>
>>
>> ------------------------------------------------------------------------
>>
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> 
> 

-- 
William Thompson
NASA Goddard Space Flight Center
Code 612.1
Greenbelt, MD  20771
USA

301-286-2040
William.T.Thompson.1 at gsfc.nasa.gov