XMM-Newton SAS Home Page
XMM-Newton Science Analysis System

oal (oal-3.139) [xmmsas_20211130_0941-20.0.0]


There can be two types of orbit data in an ODF, viz. predicted and reconstructed ones. The former contain estimates values of the satellite state vector over the course of one revolution. Reconstructed orbit data have been computed on-ground using real position measurements and are hence intrinsically more accurate.

Allowed values for SAS_ORBIT are P (predicted) and R (reconstructed). If SAS_ORBIT is not set to either of the above values (or unset) the orbit access routines in the oal will first look for reconstructed orbit data in the ODF and, if none are found, for predicted ones.

The actual type of used orbit data shall be indicated by the boolean attribute ORB_RCNS (true: reconstructed orbit data, false: predicted orbit data) in the event list being processed.

Caution: Please use SAS_ORBIT only if you know exactly what you are doing. Inaccurate satellite positions can lead to wrong signal propagation delays (see above field method of SAS_OBT_MET_FIT).

XMM-Newton SOC -- 2021-11-30