PDS_VERSION_ID     = PDS3
RECORD_TYPE        = STREAM
OBJECT             = TEXT
  PUBLICATION_DATE = 2014-03-07
  NOTE             = "Initial delivery."
END_OBJECT         = TEXT
END

                        MESSENGER Science Data Archive
                           Radio Science Subsystem
                 Description of the Momentum Dump Maneuver file
                              November 7, 2013
                          Johns Hopkins University
                         Applied Physics Laboratory


The Momentum Dump Maneuver (MDM) file contains information on each momentum
dump maneuver. All of these events are commanded angular-momentum dumps;
MESSENGER has not performed any autonomous momentum dumps. The primary
purpose of the MDM file is to supply information to the navigation and Radio
Science teams for use in their trajectory-construction analyses. A new
version of the MDM file is created with each PDS release. There is one row
for each angular momentum dump. There are seventeen named data blocks,
including an unused block. The fields and named data blocks are described as
follows:

CMD_NUM - A unique number for each momentum dump, numbered sequentially
starting with the first momentum dump after entering orbit about Mercury.
IBFM_X - The X component of the initial body-frame angular momentum.
IBFM_Y - The Y component of the initial body-frame angular momentum.
IBFM_Z - The Z component of the initial body-frame angular momentum.
FBFM_X - The X component of the final body-frame angular momentum.
FBFM_Y - The Y component of the final body-frame angular momentum.
FBFM_Z - The Z component of the final body-frame angular momentum.
MOMENTUM_CHG - The total change in system angular momentum during the
            maneuver.
FIRST_THRUS - The time, in UTC, of the first use of a thruster for this
              maneuver.
LAST_THRUS - The time, in UTC, of the last use of a thruster for this
             maneuver.
THRUSTER_ON - The total duration, in seconds, that thrusters fired.
RESIDUAL_DELTA_V_X - The X component, in EME2000 coordinates, of the change
                     in spacecraft velocity, in millimeters per second, due
                     to this momentum dumping maneuver.
RESIDUAL_DELTA_V_Y - The Y component, in EME2000 coordinates, of the change
                     in spacecraft velocity, in millimeters per second, due
                     to this momentum dumping maneuver.
RESIDUAL_DELTA_V_Z - The Z component, in EME2000 coordinates, of the change
                     in spacecraft velocity, in millimeters per second, due
                     to this momentum dumping maneuver.
MASS_CONSUM        - The mass in grams of propellant used during the maneuver.
UNUSED             - A constant, zero.
POST_CMD_SC_MASS   - Total spacecraft mass in kilograms after the maneuver.
GC_POST_MANEUVER_SC_BODY_CM_X - The x-component of the post-maneuver center
                     of mass in the G&C coordinate system..
GC_POST_MANEUVER_SC_BODY_CM_Y - The y-component of the post-maneuver center
                     of mass in the G&C coordinate system..
GC_POST_MANEUVER_SC_BODY_CM_Z - The z-component of the post-maneuver center
                     of mass in the G&C coordinate system..
AR_POST_MANEUVER_SC_BODY_CM_X - The x-component of the post-maneuver center
                     of mass in the adapter-ring-coordinate system.
AR_POST_MANEUVER_SC_BODY_CM_Y - The y-component of the post-maneuver center
                     of mass in the adapter-ring coordinate system.
AR_POST_MANEUVER_SC_BODY_CM_Z - The z-component of the post-maneuver center
                     of mass in the adapter-ring coordinate system.
                  

Note on the Post Maneuver Spacecraft Body Center of Mass Fields:
The final six fields in this product relate to the post maneuver spacecraft
body center of mass data. These are provided in two coordinate systems (with
x,y,z components in meters) identified as Guidance & Control (G&C) and
adaptor-ring (AR). The adaptor-ring coordinate system is also called the
"development" coordinate system. The two systems differ only in the location
of the origin; both systems use the same orientation of the axes, as defined
in the spacecraft frames kernel (FK) file. The GC system places the origin so
that the solar-array rotation axes goes through the origin; this location is
closer to the physical center of the spacecraft. The development system
places the origin at the center of the adaptor ring, which is at one end of
the spacecraft, near the location of the planet-viewing instruments. The two
coordinate systems are separated by 0.89662 m along the Z axis. The GC origin
is located at (0,0,-0.89662) in the development system. The RS IK file uses
the development system.