Propulsive Event Definitions (scroll down for table column heading details)

DESAT:  This initial firing of attitude control thrusters occurred soon after solar panel deployment. This thruster activity placed MESSENGER in a stable attitude with nearly zero rotation.

 

TCM-1:   Trajectory correction maneuver #1 removed most of the errors associated with launch and Earth orbit departure.

 

TCM-2:  Trajectory correction maneuver #2 removed the remaining errors associated with launch and Earth orbit departure.

 

TCM-3:  Trajectory correction maneuver #3 targeted the spacecraft for the Earth flyby aim point on August 2, 2005.

 

TCM-4:  cancelled (not necessary)

 

TCM-5:  Trajectory correction maneuver #5 targeted the spacecraft for the Earth flyby aim point on August 2, 2005.

 

TCM-6:  Trajectory correction maneuver #6 provided final targeting for the spacecraft for the Earth flyby aim point on August 2, 2005. The actual and target minimum altitudes differed by 1 km.

 

TCM-7:  cancelled (not necessary)

 

TCM-8:  cancelled (not necessary)

 

TCM-9:  Trajectory correction maneuver #9 targeted the spacecraft for the first Venus flyby aim point on October 24, 2006.

 

CMD-1:  Commanded momentum dump #1 used 8 of the smallest thrusters to reduce the spacecraft’s angular momentum to a safe level.

 

TCM-10:  Trajectory correction maneuver #10 provided a small adjustment to the first Venus flyby aim point on October 24, 2006.

 

CMD-2:  Commanded momentum dump #2 used 8 of the smallest thrusters to reduce the spacecraft’s angular momentum to a safe level.

 

TCM-11:  Trajectory correction maneuver #11, performed in two parts, targeted the spacecraft for the first Venus flyby aim point on October 24, 2006.

 

TCM-12:   Trajectory correction maneuver #12 provided final targeting for the spacecraft for the first Venus flyby on October 24, 2006. The actual and target minimum altitudes differed by 53 km.

 

AMD-1:  Autonomous momentum dump #1 used 8 of the smallest thrusters to reduce the spacecraft’s angular momentum to a safe level. This activity was initiated by the spacecraft when ground controllers were not able to monitor the spacecraft.

 

TCM-13:   Trajectory correction maneuver #13 corrected trajectory offsets from the first Venus flyby, directing the spacecraft very close to the desired aim point for the second Venus flyby on June 5, 2007.

 

TCM-14:  cancelled (not necessary)

 

TCM-15:   Trajectory correction maneuver #15 corrected trajectory offsets from TCM-13, directing the spacecraft very close to an updated aim point for the second Venus flyby on June 5, 2007.

 

TCM-16:   Trajectory correction maneuver #16 corrected trajectory offsets from TCM-15, directing the spacecraft within one mile of the final aim point for the second Venus flyby on June 5, 2007.

 

TCM-17:  cancelled (not necessary)

 

TCM-18:  Trajectory correction maneuver #18 targeted the spacecraft for the first Mercury flyby aim point on January 14, 2008.

 

TCM-19:   Trajectory correction maneuver #19 corrected trajectory offsets from TCM-18, directing the spacecraft within fives mile of the final aim point and within one mile of the target altitude for the first Mercury flyby on January 14, 2008.

 

TCM-20:  cancelled (not necessary)

 

TCM-21:  cancelled (not necessary)

 

TCM-22:  cancelled (not necessary)

 

Table Column Heading Descriptions

Time:

Units are hours:minutes:seconds in UTC (Universal Time Coordinated).

Distance:

Distance is measured at the start of the propulsive event. Distance is between the spacecraft and the center of the Earth or Sun.

AU:

Astronomical Unit. One AU, the average distance between the Sun and Earth, equals 149,597,870.691 km.

One-way light time:

This is the time required for signals to travel from the spacecraft to Earth, assuming that the signals travel at the speed of light in a vacuum.

ΔV:

Delta-V is the velocity change imparted to the spacecraft in direction (x, y, z) during the propulsive event.

Nav:

This denotes that the value is reported by the Navigation team. The observations of the change in spacecraft orbit made by this team lead to the most accurate assessment of velocity change (delta-V) imparted to the spacecraft.

EME2000:

This reference frame (or coordinate system) is based on the mean (average) orientation of Earth’s equator on January 1, 2000, at noon ephemeris time.

Duration:

This is the time required for the thrusters to impart the intended delta-V to the spacecraft trajectory. Duration does not include post-manuever thruster activity needed to fully stabilize the spacecraft attitude.

Propulsive ΔV:

This measure of fuel usage adds the delta-V observed as a velocity change imparted to the orbit to the delta-V used to control the orientation (or attitude) of the spacecraft. While the attitude control delta-V does not change the spacecraft’s orbit, this delta-V describes how much fuel is needed to keep the spacecraft pointed in the right direction during propulsive events.

Remaining ΔV:

This is the maximum expected amount of velocity change that the remaining propellant can impart to the spacecraft trajectory, given the current assumptions concerning which thrusters will be used for future planned maneuvers.