****************************************************************************** dorismail 09-Dec-2009 10:17:58 Message No 0633 ****************************************************************************** Author: "Ferrage Pascale" Subject: Spot4 orbit change Dear Colleagues, In order to avoid the conflicts and the jammings between SPOT4 and SPOT5 led by the link of 2 satellites, it is intended to move the satellite SPOT4 on its orbit. To realize this phase shift, a drift of 2 months is scheduled, starting by a serie of three manoeuvers increasing the semi major axis by 2.3 km, allowing the orbit to drift , and 2 months later, a serie of three other manoeuvers are planned, to get down again Spot4 at its nominal altitude. A total interruption of the mission is scheduled from December 7th, 2009 until February 5th, 2010. However The DORIS instrument is still operational, and the DORIS data will be delivered with no interruption. Just note that the DORIS instrument will be in "wait" mode during the 2 series of manoeuvers. The planned dates and times of the maneuvers are summarized below: MANEUVERS TO GO: (along track , delta a= + 2.3 km) 08/12 00H27 MCC1 (46s), DV = 0.44m/s , Delta a = +850km 08/12 12H29 MCC2 (46s), DV= 0.44m/s , Delta a = +850 km 09/12 01H25 MCC3 (38s), DV=0.40m/s , Delta a =~ +650 km MANOEUVERS to RETURN (along track , delta a= - 2.3 km): From February 1 to 3 2010, 1 manoeuver per day, same amplitude / opposite direction than the previous serie of manoeuvers. Best regards Pascale FERRAGE _____________________________________________________ CNES - International DORIS Service (IDS): http://ids-doris.org/ DCT/ME/OT- Bpi 612 Phone : 33 - (0)5 61 28 30 66 18, avenue Edouard Belin Fax : 33 - (0)5 61 28 25 95 31 401 TOULOUSE CEDEX 9 Email : Pascale.ferrage@cnes.fr _____________________________________________________ Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr