**XMM-Newton Science Analysis System
**

oal (oal-3.111.6) [xmmsas_20041122_1834-6.1.0]

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`SAS_ORBIT`

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/SSC -- 2004-11-22