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| [00:00:05.87] | [ Narrator ] NASA and the USGS are preparing a new satellite, |
| [00:00:08.55] | the Landsat Data Continuity Mission, called LDCM. |
| [00:00:12.73] | Landsat satellites have been orbiting earth since 1972, |
| [00:00:16.86] | taking scientific measurements of land cover and land use. LDCM is the eighth Landsat satellite |
| [00:00:20.96] | and will continue the world's longest global data record of changes of the Earth's land surfaces. |
| [00:00:21.09] | and will continue the world's longest global data record of changes of the Earth's land surfaces. |
| [00:00:25.28] | LDCM data will also play a critical role in monitoring, understanding, and managing |
| [00:00:29.46] | the world's forests, agriculture and water. [ Betsy Forsbacka ] What this data is useful for |
| [00:00:33.84] | is to provide information to the scientists, particularly |
| [00:00:38.02] | out in the Western states where water is a very |
| [00:00:42.20] | big deal. This data, this remote data allows them to determine |
| [00:00:46.38] | where areas are being irrigated, and how much and how often. |
| [00:00:50.56] | [ Jim Irons ] TIRS is the Thermal Infrared Sensor |
| [00:00:54.73] | that is being built and tested here at Goddard Space Flight Center for flight on the |
| [00:00:58.86] | next Landsat mission. It's designed to measure the amount of |
| [00:01:03.01] | thermal radiation emitted by the surface of the earth as a function of the earth's temperature. |
| [00:01:07.13] | All objects that are warmer than zero, |
| [00:01:11.24] | absolute zero, emit radiation. |
| [00:01:15.26] | The hotter an object is, the shorter in wavelength is the peak radiation. |
| [00:01:19.31] | [ Narrator ] For example, the sun is very hot, about 10,000 degrees, |
| [00:01:23.35] | and its radiation peaks at about 0.5 micrometers. That's exactly in the region |
| [00:01:27.48] | our eyes can see. Earth is much cooler, so its radiation has a much longer |
| [00:01:31.58] | wavelength, about 10 micrometers. And that's in the far infrared region, well beyond |
| [00:01:35.67] | what we can see. [ Jim Irons ] So, basically what the Thermal Infrared |
| [00:01:39.85] | Sensor allows us to do is to determine |
| [00:01:44.04] | the temperature of the surface of the earth at different locations around the globe. |
| [00:01:48.35] | [ Narrator ] Using these surface temperatures, resource managers can determine how fast |
| [00:01:52.43] | a field uses water. Rain or irrigation starts a cycle |
| [00:01:56.52] | in which water ultimately returns to the atmosphere. Evaporation of water |
| [00:02:00.59] | from the ground, and the transpiration of water from leaves, cools off both the soil and the plants. |
| [00:02:05.50] | [ Betsy Forsbacka ] You put those two words together and you have |
| [00:02:08.58] | the science term, evapotranspiration, and that's precisely what TIRS is measuring. |
| [00:02:12.64] | These hot and cold signatures, that give us |
| [00:02:16.68] | information on evapotranspiration where |
| [00:02:20.86] | the water is transpiring through the plants and evaporating into the atmosphere |
| [00:02:25.03] | The instrument is going to pick that up as a cool signature in areas that are not |
| [00:02:29.21] | irrigated well will come across as a warm area to the instrument. |
| [00:02:33.38] | [ Narrator ] To measure these warm areas and cool signatures, the TIRS instrument |
| [00:02:36.47] | uses a technology array developed primarily |
| [00:02:39.64] | at NASA's Goddard Space Flight Center, called |
| [00:02:42.69] | Quantum Well Infrared Photodetectors. These QWIPS are |
| [00:02:45.85] | more sensitive and precise than the thermal detectors used on previous |
| [00:02:48.88] | Landsat satellites. But to operate correctly they need to be kept very cold. |
| [00:02:52.02] | [ Betsy Forsbacka ] They have to be cooled to less than |
| [00:02:55.21] | 43 degrees Kelvin and so that's only |
| [00:02:58.33] | 43 degrees above absolute zero |
| [00:03:01.52] | which is the coldest you can get. Very, very cold. |
| [00:03:04.67] | [ Veronica Otero ] The interesting thing about TIRS is we have |
| [00:03:07.86] | different thermal zones, you know like |
| [00:03:10.97] | our detectors are around 43 Kelvin |
| [00:03:14.14] | and then you have our telescope at 180 Kelvin |
| [00:03:17.24] | and then you go to the warmer end of our instrument which is the |
| [00:03:20.42] | structure and some other components that are around, |
| [00:03:23.51] | you know, zero C or 273 Kelvin. |
| [00:03:26.69] | [ Narrator ] Keeping these different TIRS components at these different temperatures |
| [00:03:29.74] | is challenging because as the satellite orbits the earth every |
| [00:03:32.87] | 90 minutes its either being blasted by the heat of the sun or being frozen |
| [00:03:35.91] | by the cold of space. [ Veronica Otero ] So you're exposing the |
| [00:03:39.05] | instrument to these two harsh conditions |
| [00:03:42.23] | and you're cycling it from one to the other. |
| [00:03:45.38] | One of the things that we do on our sensor unit is we have multi- |
| [00:03:48.56] | layer insulation blankets. These work really well |
| [00:03:51.69] | in space because there's no |
| [00:03:54.86] | environment, there's no air. |
| [00:03:57.96] | The blankets protect us from these extreme conditions |
| [00:04:01.14] | The other thing we use is we have an earth shield. |
| [00:04:04.25] | [ Betsy Forsbacka ] It is basically a five foot door. |
| [00:04:07.43] | It's about five feet long and it shields much of the instrument |
| [00:04:10.53] | from the earth, from parts of the earth |
| [00:04:13.69] | that we're not imaging. That's a tremendous help |
| [00:04:16.76] | in trying to make sure that we only detect the signals that we're interested in. |
| [00:04:19.94] | The heat sources that we're interested in. [ Narrator ] And detecting those heat |
| [00:04:22.97] | sources accurately helps to monitor water use in irrigated fields. |
| [00:04:27.50] | [ Jim Irons ] Observations that are collected with |
| [00:04:29.18] | Landsat sensors are much more than pretty pictures. |
| [00:04:32.32] | They are accurate, |
| [00:04:35.50] | well calibrated, precise |
| [00:04:38.64] | scientific measurements. One of the things we're learning |
| [00:04:42.3] | with thermal data and will continue to learn more about |
| [00:04:44.95] | with TIRS is just how much water |
| [00:04:48.14] | is being used for |
| [00:04:51.25] | food production and how much more |
| [00:04:54.43] | might be needed in the future to increase food production |
| [00:04:57.53] | to keep up with a growing population. |
| [00:05:00.72] | [ Narrator ] TIRS' thermal data, as part of the LDCM mission, |
| [00:05:03.78] | will add to the more than 3 Million images of the Earth that make up the Landsat data archive. |
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