# Meteosat 11 big deboost/reboost

Before Feb 2018, the meteosat 11 (MSG-4) were periodically reboosted approximately every 85 days:

EDIT: added the orbital inclination plot to show the clearly visible variation to both semi-major axis and inclination with a single burn.

After the big deboost and reboost that took place on Feb 11/14:

the reboost period increased to about 114 days (but only 1 reboost is currently available).

Question 1: why that big change in the radius vector?
Question 2: why the reboosts are now bigger?

• Can you take a look at the sub-satellite longitude in Earth-fixed coordinates? I"m wondering if this could be related to station-keeping, and the altitude changes are just a "side-effect". Then maybe something was "coming through" in mid-February and they had to get out of it's way perhaps? – uhoh Sep 22 '18 at 15:42
• ya in GEO spacecraft don't "loose altitude" this fast naturally, do they? I wonder if it is using constant electric propulsion to hold a specific sub-satellite longitude, and the side-effect of that is a small loss of altitude? – uhoh Sep 22 '18 at 15:46
• EUMETSAT give very good explanations here: eumetsat.int/website/home/Satellites/LaunchesandOrbits/… but I found nothing about the single manoeuvres. – Cristiano Sep 22 '18 at 16:25
• What you say explains the smaller reboosts, but surely doesn't explain the big manoeuvre (question1) and the recent (bigger) reboost (question 2). – Cristiano Sep 22 '18 at 21:03
• If someone is interested in this topic, I uploaded some additional graphs to my lean and mean site: cristianopi.altervista.org/as – Cristiano Sep 27 '18 at 15:42

Before February, the satellite longitude range was 3.2 $$\div$$ 3.6 deg west.
When EUMETSAT needed to replace the Meteosat-10, they deboosted the Meteosat-11 ($$\Delta V \simeq 1.3 m/s$$) to increase the orbital speed and to start moving it eastward.
When the satellite reached the new intended longitude, they reboosted the satellite ($$\Delta V \simeq 1.5 m/s$$) to decrease the orbital speed, stopping the eastward motion.
EUMETSAT is now doing the normal station keeping manoeuvres to keep the longitude in the range -0.2 $$\div$$ 0.8 deg, with a similar range used for the Meteosat-10: https://www.eumetsat.int/website/home/Satellites/LaunchesandOrbits/SatelliteOrbits/Satellitemanoeuvres/index.html.