LOAD KERNEL






Syntax 



   LOAD KERNEL @file


Description



The LOAD KERNEL command is used to make SPICE kernels (data files) available to PERCY. Until kernels have been loaded PERCY can not do very much for you. Kernels give the program access to the position, velocity, orientation and shape of solar system objects. \index{LOAD KERNEL}

The following kernels are recognized by the program:

LEAPSECONDS

The leapseconds kernel contains information required for converting be Coordinated Universal Time (UTC) and Barycentric Dynamical Time (TDB). It is needed for translating various calendar epochs that can be input to PERCY.
SCLK

The SCLK (pronounced ``ess-clock'') kernel is required for converting between spacecraft clock time and TDB. An appropriate SCLK kernel is required whenever orientation data for a spacecraft is stored in a SPICE C-kernel.
Text PCK

The text PCK file contains shape and orientation information for natural solar system bodies. These files are text based and use a simple keyword = value format.
Binary PCK

Binary PCK files are as the name implies ``binary'' files. The data they contain are stored native machine representations. These files are typically used when very high precision orientation models are required. Binary PCK files contain only orientation information, no shape information is available through Binary PCK files.
CK

CK files are SPICE C-kernels. They contain orientation information for spacecraft (and spacecraft structures) as a function of spacecraft clock. Retrieval of data from C-kernels requires you to load a suitable SCLK file.
SPK

SPK files contain position and velocity information for the trajectories of spacecraft and natural solar system objects.
FRAMES

Frame kernels are text based kernels that define various reference frames needed to describe the position and orientation of various objects.
Regardless of the type of kernel, you use the same command to load it 

   LOAD KERNEL filename
Depending upon what you plan to do with PERCY, you may need to load several types of SPICE kernels. If you are using the same set of files repeatedly, you may wish to gather a collection of LOAD KERNEL commands in a PERCY start up file. By doing so you can can load all needed kernels at program initialization by using the command line argument ``-start''.

You can determine the currently loaded kernels at any time using the ``SHOW ENVIRONMENT'' command.



Examples





A Startup File



This example shows how you might create a start up file that loads all of the SPICE kernels required for your routine PERCY sessions. Below are the contents of a PERCY procedure we shall call ``standard.begin'.' 

   ;
   ;  Standard Start up Configuration of Kernels
   ;
   ;  We use our standard Leapseconds kernel
   ;
      LOAD KERNEL myleapseconds.ker;
   ;
   ;  SPK files used.
   ;
      LOAD KERNEL de403.bsp;
      LOAD KERNEL jupitersatellites.bsp;
      LOAD KERNEL saturnsatellites.bsp;
      LOAD KERNEL phobosdeimos.bsp;
      LOAD KERNEL basicasteroids.bsp;
   ;
   ;  PCK file
   ;
      LOAD KERNEL pck00008.tpc;
   ;
   ;  Station Frame Kernels
   ;
      LOAD KERNEL frames.tfr;
   ;
      EXIT;
To load this kernel automatically at start up, start PERCY as shown here. 

   percy -start standard.begin


Related Topics



  1. The Working Environment
  2. The Percy Help System