But TEGA Instrument May Short Circuit Again
The next sample delivered to NASA's Phoenix Mars Lander's
Thermal and Evolved-Gas Analyzer (TEGA) will be ice-rich,
researchers involved with the project said Thursday. But the
instrument may once again have difficulties in determining
that.
A team of engineers and scientists assembled to assess TEGA
after a short circuit was discovered in the instrument, has
concluded that another short circuit could occur when the oven is
used again.
"Since there is no way to assess the probability of another
short circuit occurring, we are taking the most conservative
approach and treating the next sample to TEGA as possibly our
last," said Peter Smith, Phoenix's principal investigator.
A sample taken from the trench informally named "Snow White"
that was in Phoenix's robotic arm's scoop earlier this week likely
has dried out, so the soil particles are to be delivered to the
lander's optical microscope on Thursday, and if material remains in
the scoop, the rest will be deposited in the Wet Chemistry
Laboratory, possibly early on Sunday.
The mission teams marked the Independence Day holiday with a
planned "stand down" from Thursday morning, July 3 to Saturday
evening, July 5. A skeleton crew at the University of Arizona in
Tucson, at NASA's Jet Propulsion Laboratory in Pasadena, CA, and
Lockheed Martin Space Systems in Denver, CO will continue to
monitor the spacecraft and its instruments over the holiday
period.
"The stand down is a chance for our team to rest, but Phoenix
won't get a holiday," Smith said. The spacecraft will be operating
from pre-programmed science commands, taking atmospheric readings
and panoramas and other images.
Once the sample is delivered to the chemistry experiment, Smith
said the highest priority will be obtaining the ice-rich sample and
delivering it to TEGA's oven number zero.
In a few days the Phoenix team will conduct tests so the
instruments can deliver the icy sample quickly, so no materials
sublimate, or change from a solid to a vapor, during the delivery
process.
The short circuit was believed to have been caused when TEGA's
oven number four was vibrated repeatedly over the course of several
days to break up clumpy soil delivered to oven number 4. Delivery
to any TEGA oven involves a vibration action, and turning on the
vibrator in any oven will cause oven number 4 to vibrate as
well.