XMM-Newton Users Handbook

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4.1 XMM-Newton orbit

XMM-Newton was launched on the 10th December 1999 by an Ariane 5 launcher into a highly elliptical orbit, with an apogee of about 115,000 km and a perigee of ca. 6000 km (Fig. 117). XMM-Newton is operated with three ground stations, located at Perth, Kourou and Santiago de Chile (occasionally also ESAC, Madrid, Spain).

**Figure 117:** *Sketch of the highly elliptical XMM-Newton orbit. Original figure provided by Dornier Satellitensysteme GmbH.*
$\begin{figure}\begin{center} \leavevmode \epsfig{width=1.0\hsize, file=figs/xmm_orbit.ps} \end{center} \end{figure}$

Due to several perturbations, the orbit of XMM-Newton changes with time. In addition, an orbit correction manoeuvre was performed in February 2003 to ensure full ground station coverage during the entire science period. The orbital parameters for May 2013 are listed in Table 28. Such an orbit provides the best visibility in the southern celestial sky (§ 4.2.3).

**Table 28:** *Evolution of Orbital Parameters of XMM-Newton*
	May 2009	May 2011	May 2013	unit
Inclination	58.5	62.0	64.3	$^\circ$
Right ascension of ascending node	99.5	86.8	69.8	$^\circ$
Argument of perigee	112.9	101.6	94.6	$^\circ$
Apogee height	99.7	103.1	108.8	km
Perigee height	21.4	18.0	12.3	km
Eccentricity	0.59	0.64	0.72
Period	47.86	47.86	47.86	hours

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European Space Agency - XMM-Newton Science Operations Centre