Usage of SPICE#
Fun fact: SPICE stands for “Spacecraft Planet Instrument C-matrix Events,” which were the original primary concerns of those developing the library.
Static Kernels Generated at Libera SDC#
These kernels are part of the package data, are manually edited, and change rarely.
Frame Kernel (FK)#
e.g. libera_fk_v01.tf
Contains reference frame definitions for JPSS and Libera
Spacecraft Clock Kernel (SCLK)#
e.g. jpss_sclk_v01.tsc
Contains specification of the spacecraft clock on JPSS.
Instrument Kernel (IK)#
e.g. libera_cam_ik_v01.ti
, libera_rad_ik_v01.ti
Contains geometry specification data of the Libera instruments.
Dynamic Kernels Generated at Libera SDC#
These kernels are binary generated kernels. They are ancillary data products and are created as part of pipeline processing.
JPSS Ephemeris Kernel (SPK)#
e.g. libera_jpss_20210408t235850_20210409t015849_vM3m14p159_r25365125959.bsp
Contains ephemeris data – coordinates in ITRF93 frame – for the JPSS spacecraft body.
JPSS Attitude Kernel (CK)#
e.g. libera_jpss_20210408t235850_20210409t015849_vM3m14p159_r25365125959.bc
Contains attitude data – quaternion rotations from J2000 – for the JPSS spacecraft body.
Azimuth Rotation Mechanism Attitude Kernel (CK)#
e.g. libera_azrot_20210408t235850_20210409t015849_vM3m14p159_r25365125959.bc
Contains attitude data for the Libera Azimuth Rotation mechanism.
Note: there is currently no mechanism for creating this kernel because no telemetry data exists.
Elevation Scan Mechanism Attitude Kernel (CK)#
e.g. libera_elscan_20210408t235850_20210409t015849_vM3m14p159_r25365125959.bc
Contains attitude data for the Libera Elevation Scan mechanism.
Note: there is currently no mechanism for creating this kernel because no telemetry data exists.
Kernels Retrieved from NAIF#
These kernels are generated at NAIF. We download them as needed using the KernelFileCache
class,
which is configured with a NAIF index page URL and a regex string that finds the proper download URL
on the index page. The downloaded file is put in a cache so the download only occurs after the cached
data is of a specified age. If we want to effectively cache some kernels indefinitely, we can put
them in an S3 bucket and retrieve them from there instead of from the NAIF website.
Leapseconds Kernel (LSK)#
e.g. naif0012.tls
Contains leapsecond data used by time conversion routines.
Development Ephemeris Kernel (SPK)#
e.g. de440s.bsp
Contains ephemeris data for planetary bodies. The version with “s” appended to the filename covers only more recent time (starts in the 1500s) to reduce filesize.
High Precision Earth Binary Planetary Constants Kernel (PCK)#
e.g. earth_000101_211220_210926.bpc
Contains high precision orientation data for Earth in the ECEF ITRF93 reference frame.
ITRF93 is a more precise version of the standard IAU_EARTH reference frame provided in the text PCK below.
This kernel is regenerated several times per week so we should retrieve this from NAIF for every processing run.
ITFR93 Reference Frame Kernel for Earth#
e.g. earth_assoc_itrf93.tf
Used to designate ITRF93 as the default body-fixed frame associated with the Earth.
Standard Text Planetary Constants Kernel (PCK)#
e.g. pck00010.tpc
Contains orientation data and other planetary constants for planetary bodies.