[ Narrator ] NASA and the USGS are preparing a new satellite,
the Landsat Data Continuity Mission, called LDCM.
Landsat satellites have been orbiting earth since 1972,
taking scientific measurements of land cover and land use. LDCM is the eighth Landsat satellite
and will continue the world's longest global data record of changes of the Earth's land surfaces.
LDCM data will also play a critical role in monitoring, understanding, and managing
the world's forests, agriculture and water. [ Betsy Forsbacka ] What this data is useful for
is to provide information to the scientists, particularly
out in the Western states where water is a very
big deal. This data, this remote data allows them to determine
where areas are being irrigated, and how much and how often.
[ Jim Irons ] TIRS is the Thermal Infrared Sensor
that is being built and tested here at Goddard Space Flight Center for flight on the
next Landsat mission. It's designed to measure the amount of
thermal radiation emitted by the surface of the earth as a function of the earth's temperature.
All objects that are warmer than zero,
absolute zero, emit radiation.
The hotter an object is, the shorter in wavelength is the peak radiation.
[ Narrator ] For example, the sun is very hot, about 10,000 degrees,
and its radiation peaks at about 0.5 micrometers. That's exactly in the region
our eyes can see. Earth is much cooler, so its radiation has a much longer
wavelength, about 10 micrometers. And that's in the far infrared region, well beyond
what we can see. [ Jim Irons ] So, basically what the Thermal Infrared
Sensor allows us to do is to determine
the temperature of the surface of the earth at different locations around the globe.
[ Narrator ] Using these surface temperatures, resource managers can determine how fast
a field uses water. Rain or irrigation starts a cycle
in which water ultimately returns to the atmosphere. Evaporation of water
from the ground, and the transpiration of water from leaves, cools off both the soil and the plants.
[ Betsy Forsbacka ] You put those two words together and you have
the science term, evapotranspiration, and that's precisely what TIRS is measuring.
These hot and cold signatures, that give us
information on evapotranspiration where
the water is transpiring through the plants and evaporating into the atmosphere
The instrument is going to pick that up as a cool signature in areas that are not
irrigated well will come across as a warm area to the instrument.
[ Narrator ] To measure these warm areas and cool signatures, the TIRS instrument
uses a technology array developed primarily
at NASA's Goddard Space Flight Center, called
Quantum Well Infrared Photodetectors. These QWIPS are
more sensitive and precise than the thermal detectors used on previous
Landsat satellites. But to operate correctly they need to be kept very cold.
[ Betsy Forsbacka ] They have to be cooled to less than
43 degrees Kelvin and so that's only
43 degrees above absolute zero
which is the coldest you can get. Very, very cold.
[ Veronica Otero ] The interesting thing about TIRS is we have
different thermal zones, you know like
our detectors are around 43 Kelvin
and then you have our telescope at 180 Kelvin
and then you go to the warmer end of our instrument which is the
structure and some other components that are around,
you know, zero C or 273 Kelvin.
[ Narrator ] Keeping these different TIRS components at these different temperatures
is challenging because as the satellite orbits the earth every
90 minutes its either being blasted by the heat of the sun or being frozen
by the cold of space. [ Veronica Otero ] So you're exposing the
instrument to these two harsh conditions
and you're cycling it from one to the other.
One of the things that we do on our sensor unit is we have multi-
layer insulation blankets. These work really well
in space because there's no
environment, there's no air.
The blankets protect us from these extreme conditions
The other thing we use is we have an earth shield.
[ Betsy Forsbacka ] It is basically a five foot door.
It's about five feet long and it shields much of the instrument
from the earth, from parts of the earth
that we're not imaging. That's a tremendous help
in trying to make sure that we only detect the signals that we're interested in.
The heat sources that we're interested in. [ Narrator ] And detecting those heat
sources accurately helps to monitor water use in irrigated fields.
[ Jim Irons ] Observations that are collected with
Landsat sensors are much more than pretty pictures.
They are accurate,
well calibrated, precise
scientific measurements. One of the things we're learning
with thermal data and will continue to learn more about
with TIRS is just how much water
is being used for
food production and how much more
might be needed in the future to increase food production
to keep up with a growing population.
[ Narrator ] TIRS' thermal data, as part of the LDCM mission,
will add to the more than 3 Million images of the Earth that make up the Landsat data archive.