LADEE turns the corner, bound for last perigee (9-28-13)

by | Sep 27, 2013 | General Comments

On Sep. 28 2013 05:33 UTC, LADEE is coming out of its last apogee and at an altitude of 214,000 km.

ECI_928

LADEE on 9-28-2013 5:46 UTC

top_927

LADEE on 9-28-2013 5:46 UTC (Top View)

 

 

 

Perigee occurs on 1 Oct near 11:00 UTC.  A final small midcourse maneuver will take place at 1 Oct 2013, 22:00 UTC.  This 0.9 m/sec maneuver will precisely target insertion parameters for the 6 Oct. 2013 10:57 UTC LOI-1 maneuver.  LOI-1 is designed to place the spacecraft into a 24 hr orbit, with a periselene altitude of 590 km [correction:  previously I said 750 km, this isn’t quite right.  For LADEE we aren’t capturing right at periselene, like orbital mechanics would recommend.  Instead we burn off periselene just a bit.  We wait until 5 minutes past we come out from behind the Moon, and start our burn.  This ends up being roughly 5.5 minutes after periselene. This allows the Deep Space Network to get a lock on us and telemetry to start flowing before the burn starts.  So the altitude at the end of this burn is at about 750 km, but the actual periselene altitude is closer to 590 km].  After 3 revolutions in this orbit, 3rd-body Earth gravitational perturbations will have lowered periselene to an altitude of 250 km (by design).  At this point, LOI-2 will be performed on 9 Oct 2013 10:37 UTC ( to place LADEE into a 4 hr orbit (also with a 250 km periselene altitude).  LADEE will spend 3 days in this orbit until LOI-3 (12 Oct 2013 10:37 UTC), which circularizes the orbit at 250 km.  LADEE will spend 30 days in this “commissioning orbit”, and will also perform tests using the laser communications experiment (LLCD). The timing and magnitudes of the maneuvers leading to the commissioning orbit are given below.

 

 

 

Rotating_927

LADEE on 9-28-2013 5:48 (Earth-Moon rotating frame)

Executed Maneuvers:

AM1 11 Sep 2013 23:00:00.000 9.34 m/sec

PM1 13 Sep 2013 16:36:08.000 16.96 m/sec

PM2 21 Sep 2013 11:53:19.000 17.492 m/sec

Planned Maneuvers

TCM1 01 Oct 2013 22:00:00.000 0.9 m/sec

LOI1 06 Oct 2013 10:57:00.210 329.86 m/sec

LAM1 07 Oct 2013 22:51:32.205 0 m/sec (error corrections for LOI-1)

LOI2 09 Oct 2013 10:37:55.651 295.99 m/sec

LOI3 12 Oct 2013 10:37:34.993 238.56 m/sec