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Answers

9-1: Since T must be in units of Kelvin, add 273 to 1800 = 2073 and divide that into 2898 = 1.398 µm. BACK


9-2: Again, temperature in Centigrade must be converted to Kelvin; this gives T = 290° K. The fourth power of that number is 7.0728 x 109. Multiplying that by the constant gives FB = 4.103 x 10-2. BACK


9-3: A simple calculation: Just multiply 4.103 x 10-2 by 0.9 to get 3.698 x 10-2. This is FR. BACK


9-4: The fourth root of the emissivity, 0.9, is calculated as the square root of the square root of this number. That value is 0.974. (Remember, the square root of a number between 0 and 1 becomes a higher value). T then is just 290 x 0.974 = 282.5 °K. BACK


9-5: Soil will show the largest diurnal temperature variations; steel the smallest. BACK


9-6: Assuming you did the math correctly, the P values calculate as: Limestone = 0.045; Sandstone = 0.075; Shale = 0.040; water = 0.036, in units of cal cm-2 sec1/2 °C. The sandstone is easily separated from all others, but limestone and shale are similar and shale and water are similar. In an image, with proper contrast stretching, each of these can probably be differentiated from the others, but mapping will be somewhat compromised by material types whose P values are nearly alike. BACK


9-7: Variations in Sun angle; dependency on composition, density, and texture; topographic irregularities; rainfall and moisture variations; near surface climatic conditions. Several others might make the top five under appropriate circumstances. BACK


9-8: At 4 AM, the water would be moderately warmer than the land; at 2 PM, the land would have bright gray tones and water moderate to dark tones. BACK


 

9-9: The 6 AM time is typically around dawn. The main source of heating, the Sun, has been inactive since the previous sunset, so that in general the ground will steadily lose heat throughout the night (exceptionally, the arrival of a warm air mass in the evening will slow this down), so that the temperature minimum will be reached just before the first solar rays of daylight resume the heating. A general rule is that surface temperature as measured as radiant emission increases with: increasing emissivity, increasing atmospheric temperatures, and decreasing albedo (low albedos involved greater absorption of solar radiation and consequent higher emissive temperatures); thermal inertia values tend to be lower at night and higher in the day, but at night the relative effect is higher P's have higher T's and at night lower P's have higher T's. BACK


9-10: The least in early morning, the most at noon (or shortly thereafter). BACK


9-11: Like your light bulb, they eventually burn out, and along the way their heated filaments tend to decrease in light output, so that their effective temperatures diminish - but this can be noticed as a systematic temperature drift, and compensated for. BACK


9-12: The Falls lie on the river about half way between the two lakes. If you have ever been there, you would perhaps remember that the to the south water backs up to a wider width as it prepares to go over the two individual segments of the Falls. A possible clue as to direction of river flow: Lake Erie is uniformly hot but Lake Ontario is hot mainly along its southern end; Lake Erie is flowing into Lake Ontario, adding some of its hot water. Toronto is notably larger than Buffalo; note its more extensive street patterns. A cluster of clouds lies along the southern coastal area of Lake Ontario. They are black, indicating they are among the coldest features in the scene. Since it originates usually from burning material, smoke is warmer than cloud vapor and should have a gray signature. BACK


9-13: Both silicates and clay minerals have a broad, deep absorption band in the 10 - 12 µm interval. Quartzite has two deep absorption bands at about 13 and 27 µm that are inconspicuous (but present) in the monzonite. The two carbonates, limestone and dolomite, have bands at 7 and 11.5 µm, but the first of these is not available to sensors owing to atmospheric bands at the same wavelength. Note that limestone can be distinguished from dolomite at the longer wavelengths of 27 and 29 µm - again, not in a spectral region available for sensing from space. Note also that the spectrum for the mix of carbonate, silicate, and clay minerals has peaks from all three of the mineral groups, each subdued because of "dilution". BACK


9-14: The Furnace Creek fan is warmer in the day and cooler at night than the fans to the west, coming from the Panamints. This implies that the near surface of the FC fan is drier (hence, the heat storage capacity of water-poor soil is less and this would reduce the tone in the nighttime image) than the surfaces of those coming off the Panamint Range ( possible vegetation differences may be a factor as well). The golf course area in the FC fan is, however, quite warm in the day. The resort gets its water from deep wells rather than surface runoff. BACK


9-15: You can use the principle of "overlapping", a variant of the stratigraphic concept of "cross-cutting". Thus a younger flow will have to cut across, and overlap, one or more of the older ones. Several of the flows in the image clearly show this kind of relationship, but not all. As I interpret this sequence, the oldest is green, then that is overlapped by the brown flow, and in turn the red crosses the brown, and the blue flow seems to be edged onto the red flow. The blackish flow appears younger than the brown but older than the red. Several flows near the top aren't in contact with those just mentioned, so their relative ages are undetermined, but they seem to be older than those just described. BACK


9-16: ATI = 1000 x 1.605 (1 - 0.3)/(30 - 15) = ~ 75 (If both N and C = 1, this value becomes 0.075, a value appropriate to a quartz sandstone). BACK


9-17: This is another subjective answer situation. But, let's note one special feature: the curved lenticular pattern that makes the Wyoming Valley (Wilkes-Barre and Scranton). It is very dark in the Day-VIS, suggesting widespread surface waste (coal and dark shales). As we noted in the test, it is bright during the day in the Day-IR, indicating high thermal energy absorption in a near blackbody. But in the Night-IR, it cannot even be recognized as a tonal anomaly; this implies that the absorbed heat is rapidly lost from the wastes and the valley reaches thermal equilibrium (temperature balance) with its enclosing ridges, thus minimizing tonal contrast. BACK


9-18: The purples on the land correspond to Lakes Erie and Ontario, which in daytime are cooler than land surfaces. The blues are cool clouds; the blacks are a dense, colder bank of clouds passing onto Lake Erie. In the Atlantic, the coldest waters lie about 160 km (100 miles) offshore from the Delmarva Peninsula and the New Jersey coast. The green marks the distinct Gulf Stream, a moving current of warmer water coming from equatorial regions and destined to pass east of New England and Newfoundland and eventually across the North Atlantic. BACK


9-19: There are many possibilities. Here are a few: The power in your house (and neighborhood) fails in the evening, and you need to get around. Or, you customarily walk home from work along roads that lack street lights. Or, you are a master spy who has to search a building for secret files, and can't risk turning on the lights or even a flashlight. Whatever the use, the Goggles aren't cheap but not prohibitively expensive either. BACK


9-20: The rectangular warm area on the roof is perhaps a "skylight" window. The irregular hot spot near but below the roof is probably near a vent that allows warm interior air to be expelled. The top of the auto's hood is very warm, from heat produced by the motor. The tires are warm also as a result of frictional heat generated by their rotation along the street. BACK


9-21: The Shuttle is in the landing mode - it has just touched down. The heat signature (white to red) around the nose and cockpit results from passage through the atmosphere - the leading edge is heated most. To the rear, the red area relates to residual heat from the burning of the thruster rockets as the craft began to slow for re-entry and glide to the landing area. BACK


9-22:Note the nose of the Shuttle. It is painted black, as seen in the picture on the right. Remember what was said about black bodies as perfect radiators and absorbers. The Shuttle experiences very high temperatures in passing through the atmosphere, heating the entire outer surface of the Shuttle. The white tile areas cool significantly during the last minutes before landing. The black nose (and leading front of the wings, also painted dark), having more efficiently absorbed heat, retain much of that heat longer and hence the black surface is still hot, showing up in images made by infrared sensors as a bright glow (compared with the warm main body of the Shuttle), almost like a searchlight. BACK