One 6x6 covariance block inside a parsed CCSDS OEM segment.
matrix is a row-major list of six six-element rows. cov_ref_frame is the optional COV_REF_FRAME override, or nil to inherit the segment frame.
matrix
cov_ref_frame
COV_REF_FRAME
nil
@type t() :: %Sidereon.CCSDS.OEM.Covariance{ cov_ref_frame: String.t() | nil, epoch: String.t(), matrix: [[float()]] }