MESSENGER Mission News: Batteries Included

A reliable battery system is critical to the success of any solar-
powered spacecraft. A temporary "workhorse" battery currently
supplies power to MESSENGER; the actual flight battery is being
assembled and will be installed just before environmental testing.
By using a temporary battery now, the team makes sure the flight
model is fresh and ready to last through the mission.

The newly installed duct seen in this week’s annotated Webcam image
supplies cool air to the temporary battery (hidden behind the
spacecraft), keeping it at a safe working temperature while the
MESSENGER team tests the spacecraft’s onboard electrical systems.
MESSENGER’s flight battery is 20-Ah (ampere hour) common-pressure-
vessel nickel-hydrogen type similar to that on the Mars Global
Surveyor spacecraft. It consists of 22 individual cells tied
together in pairs; it looks like 11 side-by-side pairs of 1-liter
soda bottles with rabbit-ear contacts sticking out of the top.

The Webcam image is posted at:

http://messenger.jhuapl.edu/webcam/annotatedimages/annotated-
20030904.html

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) is a scientific investigation of the planet Mercury, and
the first NASA mission designed to orbit the planet closest to the
Sun. Dr. Sean C. Solomon, of the Carnegie Institution of Washington,
leads the mission as principal investigator. The Johns Hopkins
University Applied Physics Laboratory in Laurel, Md., is building
and will operate the MESSENGER spacecraft and manages the Discovery-
class mission for NASA.

For more information on the mission, visit
http://messenger.jhuapl.edu.