CCSDS 508.0-R-1, Conjunction Data Message (Red Book, Issue 1 ...

DRAFT CCSDS RECOMMENDED STANDARD FOR CONJUNCTION DATA MESSAGES5 CDM DATA IN GENERAL5.1 OVERVIEWThe following rules apply for both KVN- and XML-formatted CDMs.5.2 RULES THAT APPLY IN KVN AND XML5.2.1 Some keywords represent obligatory items and some are optional. KVN and XMLassignments representing optional items may be omitted.5.2.2 The objects’ state vectors and covariance shall be given ‘at the time of closestapproach’, i.e., at the time specified in the TCA keyword.5.2.3 Table 3-4 is broken into four logical blocks, each of which has a descriptive heading.These descriptive headings shall not be included in a CDM, unless they appear in a properlyformatted COMMENT statement for the KVN implementation and with values between the and tags for the XML implementation.5.2.4 For C R •A/m, CR_AREA_OVER_MASS, a value of zero shall indicate no solarradiation pressure was taken into account in the orbit determination process.5.2.5 For C D •A/m, CD_AREA_OVER_MASS, a value of zero shall indicate no atmosphericdrag was taken into account in the orbit determination process.5.2.6 For acceleration due to in-track thrust, THRUST_ACCELERATION, a value of zeroshall indicate no in-track thrust acceleration was taken into account in the orbit determinationprocess.5.2.7 Values in the covariance matrix shall be presented sequentially from upper left [1,1]to lower right [9,9], lower triangular form, row by row, left to right. Variance and covariancevalues shall be expressed in standard double precision as related in 6.2.2.5.5.2.8 The covariance matrix is obligatory for the position and velocity terms, given in thelower triangular form of a 6x6 matrix. Optional terms for CD_AREA_OVER_MASS(denoted ‘DRG’), CR_AREA_OVER_MASS (denoted ‘SRP’), andTHRUST_ACCELERATION (denoted ‘THR’) should be added to the 6x6 matrix, in thelower triangular form, to complete a 9x9 matrix. If any element in any of these rows (7, 8, or9) is provided, then all of the elements for that row must be provided (i.e., a subset of theterms for any of these rows is not allowed).NOTE – The purpose for providing the 7, 8, and 9 terms is so that users, who have thepropagator model available, can correctly propagate the 6x6 position and velocitycovariance to another time point.CCSDS 508.0-R-1 Page 5-1 March 2012