MESSENGER Mission News September 4, 2003: MESSENGER Weighs In

On August 24 the MESSENGER assembly team rotated the spacecraft into
a vertical position, attached hoist cables to an overhead crane, and
lifted it just an inch or two off the Turnover Fixture for a few
minutes. You can just make out a slight gap between the Turnover
Fixture and the spacecraft. A time-lapse movie from that day
captures the full operation, as well as installation of the boom
for MESSENGER’s Magnetometer instrument

The crane also serves as a scale to give an accurate weight for the
spacecraft. Controlling the weight of a spacecraft is one of the
hardest challenges faced by any design and assembly team.

Every every kilogram (or pound) is precious. Each kilogram MESSENGER
weighs will require 233 kilograms of fuel on the launch vehicle to
get the spacecraft on the path to Mercury. (A kilogram equals 2.2
pounds.)

On August 24 MESSENGER weighed in at 331 kilograms (without fuel,
or "dry"), as expected at this stage of integration. MESSENGER’s
estimated dry launch mass is 513 kilograms; once the spacecraft is
fully fueled it will weigh 1,130 kilograms. For comparison, the
three-stage Delta 2 launch vehicle set to send MESSENGER on its
journey weighs 288,000 kilograms.