Space Topics: Phoenix
Science Instruments
Robotic Arm
Both Mars Polar Lander and Mars Surveyor 2001 were equipped with robotic arms,
but the one built for Phoenix is longer than these two at 2.35 meters (7
feet, 9 inches). The arm is equipped with a digging tool that can also
be used to retrieve samples. It also carries the Robotic Arm Camera
and one component of the MECA instrument. The arm will dig to a depth
of half a meter or until it reaches an impenetrable ice layer, whichever
comes first. The back of the arm's scoop is equipped with ripping
tines and scrapers in order to facilitate the retrieval of a sample of ice.
Phoenix RAC
Originally built for the Mars Surveyor 2001 lander, RAC will capture close-up views of soil and ice. The two blue-dotted panels are light sources for illuminating images captured within the trench.
Credit: NASA / UA
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Robotic Arm Camera
Like the Microscopic Imager on the Mars Exploration Rovers, the RAC will enable
Phoenix to take close-up images of rocks, ice, and soil within reach of the
robotic arm, achieving a resolution of 23 micrometers per pixel. In
order to see the soils within the trench, the RAC also carries two lighting
assemblies to illuminate its view.
Surface Stereoscopic Imager (SSI)
The stereo imager is based upon the design of the Imager for Mars Pathfinder
and the stereo imager that was flown aboard Mars Polar Lander, but has nearly
four times better resolution at 0.25 mrad/pixel (a few percent sharper than
Pancam on the Mars Exploration Rovers). It will provide high-resolution
color panoramas of the landing site and also important positioning information
for the robotic arm from a viewpoint two meters off the ground.
Phoenix TEGA
Shown here under construction, Phoenix's TEGA instrument has eight ovens for heating samples.
Credit: NASA / UA
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Phoenix MECA
Phoenix's MECA instrument has four wet chemistry "beakers" (this
is one of them) that will be used to perform chemical analyses on soil
samples. Credit: NASA / UA |
Thermal and Evolved Gas Analyzer (TEGA)
Built to a design inherited from Mars Polar Lander, TEGA heats samples delivered
by the robotic arm to 1,000ºC (1,800ºF). The power required
to maintain a constant rate of heating within the oven gives clues to the
quantity and composition of volatile compounds within the sample as the heat
causes them to vaporize. The gases that are driven from the sample
are sent to a mass spectrometer, which measures abundances and isotope ratios
for hydrogen, oxygen, carbon, nitrogen, and heavier gases. The mass
spectrometer can detect gases with concentrations as low as 10 parts per
billion. TEGA has eight ovens; soil samples can be gathered by the
arm for study by TEGA from up to eight different depths below the surface.
Microscopy, Electrochemistry, and Conductivity Analyzer (MECA)
Built for Mars Surveyor 2001, MECA is a powerful suite of soil analysis tools
mounted on the lander, including an optical microscope, atomic-force microscope,
wet chemistry laboratory, and a thermal and electrical conductivity probe. The
microscopes can examine up to 10 different samples. The robotic arm
delivers samples to a wheel containing 69 different substrates, including
magnets, sticky spots, and bulk sampling buckets. The optical microscope
will examine soil grains on the wheel with a resolution of 4 micrometers
per pixel and a field of view one by two millimeters in size; and its atomic
force microscope can view selected grains at a resolution of approximately
10 nanometers. The wet chemistry laboratory consists of four tiny cells
containing a warmed solution, which can soak and stir soil samples (the water
is brought from Earth). After cycles of soaking, stirring, and measurement
lasting throughout the Martian day, the instrument drops in two chemical
pellets that will allow testing for carbonates, sulfates, and soil oxidants. The
chemical sensors in the wet chemistry lab measure the salt content and composition,
oxidation potential, acidity, and trace mineral concentrations in the soil. MECA
is critical to the mission's objective of understanding the habitability
of the Martian soil. MECA has four wet chemistry cells, so the experiment
will be performed once with a sample from the surface; once from below the
surface; and once from just above an ice layer. One MECA cell is reserved
as a spare.
Credit: NASA / JPL / MLSS |
Mars Descent Imager (MARDI)
MARDI will take pictures as Phoenix approaches for its landing, providing important
geological context for Phoenix's in-situ measurements. It has a 66-degree
field of view and will capture images from about eight kilometers (five miles)
elevation all the way down to the ground.
Meteorological Station (MET)
MET will allow Phoenix to act as a polar weather station, monitoring changes
in water abundance, dust, temperature, and other variables throughout Phoenix's
landed mission. MET includes temperature and pressure sensors and
a LIDAR instrument that is designed to measure the size and location of atmospheric
dust particles. The temperature and pressure sensors are based on heritage
from the Viking landers and Mars Pathfinder.
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