Second Correction Planned For Mid-October
On Friday, NASA's Phoenix Mars Lander accomplished the first and
largest of six course corrections planned during the spacecraft's
flight from Earth to Mars.
As ANN reported, Phoenix left
Earth August 4, bound for a challenging touchdown on May 25, 2008,
at a site farther north than any previous Mars landing. It will
robotically dig to underground ice and run laboratory tests
assessing whether the site could ever have been hospitable to
microbial life.
Phoenix is traveling at about 33,180 meters per second (74,200
miles per hour) in relation to the sun. The first
trajectory-correction maneuver was calculated to tweak the velocity
by about 18.5 meters per second (41 miles per hour). The spacecraft
fired its four mid-size thrusters for three minutes and 17 seconds
to adjust its trajectory.
"All the subsystems are functioning as expected with few
deviations from predicted performance," said Joe Guinn, Phoenix
mission system manager at NASA's Jet Propulsion Laboratory in
Pasadena, CA.
Key activities in the next few weeks will include checkouts of
science instruments, radar and the communication system that will
be used during and after the landing.
The second trajectory-correction maneuver is planned for
mid-October.
"These first two together take out the bias intentionally put in
at launch," said JPL's Brian Portock, Phoenix navigation team
chief.
Without the correction maneuvers, the spacecraft's course after
launch day would miss Mars by about 950,000 kilometers (590,000
miles), an intentional offset to prevent the third stage of the
launch vehicle from hitting Mars.
NASA says the Delta II launch vehicle is not subject to the
rigorous cleanliness requirements that the spacecraft must meet as
a protection against letting Earth organisms get a foothold on
Mars.
The burn began at 1130 Pacific Daylight Time. Each of the four
trajectory-correction thrusters provides about 15.6 newtons (3.5
pounds) of force. Smaller, attitude-control thrusters pivoted the
spacecraft to the desired orientation a few minutes before the main
burn and returned it afterward to the right orientation for
catching solar energy while communicating with Earth. Their thrust
capacity is about 4.4 newtons (1 pound) apiece.
The twelve largest thrusters on Phoenix, delivering about 293
newtons (66 pounds) apiece, will operate only during the final
minute before landing on Mars.