STEREO SEP Suite Pointing Data
STEREO atttitude and orbit data are distributed as SPICE kernels.
Since most SEP investigators would rather not deal with SPICE kernels,
Caltech provides text files containing transformation matrices for
converting vectors from the Spacecraft coordinate system to the
following coordinate systems: GEI, GSE, GSM, HCI, HEE, HEEQ, RTN.
Important Note: these data produced at Caltech for the benefit of SEP instrument suite
investigators. The data are not currently officially "blessed" by the larger STEREO
The format of each record in these files is as follows:
YYYY DoY Second Flag M_00 M_01 M_02 M_10 M_11 M_12 M_20 M_21 M_22
Where YYYY is the 4-digit year
DoY is the day-of-year (counting from 1)
Second is the second-of-day
Flag is 0 if the data are predictive, 1 if the data are definitive
M_ij are the transformation matrix elements from the S/C coordinate system
to the new coordinate system, where i is the row index, j is the column index.
The time cadence of records within these files is variable. A new record is appended only
At the beginning of each day, or
If the direction of the S/C X-axis changes by more than TOL degrees, or
If the direction of the S/C Y-axis changes by more than TOL degrees
Currently, TOL is set at 0.25 degrees.
Further information about the Spacecraft coordinate system, converting from an SEP
instrument coordinate system to the S/C coordinate system, and descriptions of the
geocentric and heliocentric coordinate systems listed above, may be found in
The daily updating of these data goes 40 days into the future, and 15 days
into the past. This is usually sufficient to ensure that all the data in the
files eventually get promoted form "predicted" to definitive". On occasion, I
take a manual look at the data to make sure that this is all working as
expected. Occasionally, the MOC has been very slow in delivering definitive
Coordinate system descriptions