Final Braking Maneuver Friday At 1624 EST
Earlier this week, NASA's Mars Reconnaissance Orbiter began its
final approach to the red planet after activating a sequence of
commands designed to get the spacecraft successfully into orbit.
But the ultimate test will come on Friday, March 10.
The approach sequence -- which began Tuesday -- will culminate
Friday afternoon with the firing of the craft's main thrusters for
about 27 minutes -- putting "a foot on the brakes," in the words of
Guy Webster with JPL -- and reducing velocity by about 20 percent
as the spacecraft swings around Mars at about 5,000 meters per
second. That's about 11,000 miles per hour.
Mission controllers at NASA's Jet Propulsion Laboratory,
Pasadena, CA and Lockheed Martin Space Systems in Denver, CO are
monitoring the events closely.
"We have been preparing for years for the critical events the
spacecraft must execute on Friday," said JPL's Jim Graf, project
manager. "By all indications, we're in great shape to
succeed, but Mars has taught us never to get overconfident. Two of
the last four orbiters NASA sent to Mars did not survive final
approach."
Mars Reconnaissance Orbiter will build upon discoveries by five
successful robots currently active at Mars: NASA rovers Spirit and
Opportunity, NASA orbiters Mars Global Surveyor and Mars Odyssey,
and the European Space Agency's Mars Express orbiter. It will
examine Mars' surface, atmosphere and underground layers in great
detail from a low orbit. It will aid future missions by scouting
possible landing sites and relaying communications. It will send
home up to 10 times as much data per minute as any previous Mars
mission.
But first, it must get into orbit -- and that's no easy task.
The necessary thruster burn will begin shortly after 4:24 pm PST on
Friday -- with the last third of the expected
27-minute burn occurring in the shadow of Mars, outside of contact
with Earth. Scientists won't be certain of its success
for approximately 30 minutes after loss of radio contact.
Engineers designed the burn to slow the spacecraft just enough
for Mars' gravity to capture it into a very elongated elliptical
orbit. Once there, a six-month period of more than 500 carefully
calculated dips into Mars' atmosphere -- a process called
aerobraking -- will use friction with the atmosphere to gradually
shrink the orbit to the size and nearly-circular shape chosen for
most advantageous use of the six onboard science instruments.
"Our primary science phase won't begin until November, but we'll
actually be studying the changeable structure of Mars' atmosphere
by sensing the density of the atmosphere at different altitudes
each time we fly through it during aerobraking," said JPL's Dr.
Richard Zurek, project scientist for the mission.
Aero-News will bring you Real Time coverage Friday, as the Mars
Reconnaissance Orbiter undergoes its most critical test yet. Stay
tuned...