METR180: Remote Sensing
Homework 1
Assigned 2/10/2010 Due 2/22/2010
1. If NOAA satellite orbit approximately 850km above the Earth’s surface, assume the
orbit is simple circular orbit, what is the period of this NOAA satellite?
2. In the Visible-NIR range (VNIR), water ice and dry ice (solid CO2) give
characteristic spectral curves, as shown here:
Over most of this range, the dry ice remains highly reflective but displays a
prominent set of absorption bands around 2 µm. Water ice reflects at shorter
wavelengths, but its reflectance diminishes beyond about 1 µm. Note that there
are several broad absorption bands that reduce reflectances to very low values.
Liquid water tends to absorb well over most of the range, reflecting slightly more
in the greens and blues.
From the above two curves, beyond the visible what wavelength regions should be
avoided in seeking information about the spectral characteristics of materials?
3.
From the above graph, calculate (approximately) the percent decrease in surface
irradiance (drop in power, in Watts/meter2/µm) of maximum solar radiation (close to 500
nanometers) from the moment it reaches the outer atmosphere until it reaches the Earth's
surface; assume a vertical rather than slant path through the atmosphere.
4. Given that 1 nanometer (NM) = 10-9 m, 1 micrometers = 10-6 m and 1
Angstrom (A) = 10-10 m, how many nanometers in a micrometer; how many
Angstrom units in a micrometer?
5. The atmospheric absorption figure below list the four principal windows
(by wavelength interval) open to effective remote sensing from above
the atmosphere.
Most remote sensing is conducted above the Earth either within or above the
atmosphere. When the primary objective is to sense the Earth's surface, the
strategy is to utilize parts of the EM spectrum that minimalize interactions
between radiation and the atmosphere. There are spectral intervals that
maximize transmission of radiances. These are called "windows". Here is a
generalized diagram showing relative atmospheric radiation transmission of
different wavelengths.
Are the following 4 regions “window”? Why?
(Intervals in micrometers). 1) Visible-Near IR (0.4 - 2.5); 2) Mid-IR (3 - 5); 3)
Thermal IR (8 - 14); 4) Microwave (1 - 30 centimeters)