EX1-2 - LAND OB SATS

Question 1

1. Orbits

Answer 1

-An earth observing satellite is an artificial flying object, orbiting around Earth for
scientific, commercial or military purposes. There are two different orbit:
geostationary and sun-synchronous near polar orbits

Question 2

2. Sun synchronous orbits (examples of 1 or 2 satellites that follow this orbital path)

Answer 2

Sun-synchronous orbits are designed to reduce variations in illumination by systematically moving the orbital track such that it moves westward 360 degrees each year. Illumination observed under such conditions vary throughout the year, but repeat on a yearly basis. These satellites record an area always at the same local time.

LandSAT
Ikonos
SPOT
NOAA

Question 3

3. Geostationary orbits (examples of 1 or 2 satellites that follow this orbital path)

Answer 3

In a geostationary orbit at a distance of 36.000 km, the orbiting time is 24 hours corresponding to the earth’s rotation time. At this altitude a satellite above the equator will appear stationary in relation to the earth. Geostationary orbits are ideal for meteorological or communications satellites designed to maintain a constant position with respect to specific
region on the Earth’s surface

GOES
GMS

Question 4

4. Landsat MSS

Answer 4

Multi-spectral Scanner (MSS): Huge success

Due to malfunctioning RBV, focus shifted to MSS
• MSS was tailored to provide multispectral data without as much concern (as RBV) for positional accuracy
MSS Sensing Package
Band 4 0.5 - 0.6 Green 79 meters
Band 5 0.6 - 0.7 Red 79 meters
Band 6 0.7 - 0.8 NIR 79 meters
Band 7 0.8 – 1.1 NIR 79 meters
Band 8 10.4 – 12.6 Thermal 240 meters

MSS is a 6 bit system
 Data quantized on a scale of 0 to ____ ?
 Full scene in one wavelength consists of 2,400 rows and 3,240 columns of pixels
 A single band of data is: how many pixels? How many bytes?
 A full image is how many bytes (hint: depends on # of bands)

Question 5

5. Landsat TM

Answer 5

An upgraded form of MSS
introduced in Landsat 4
• TM provides finer spatial
resolution (30 m) , improved
geometric fidelity, greater
radiometric detail (8 bit), and
more detailed spectral
information in more precisely
defined spectral regions

 Use of 7 rather than 4 spectral bands and of a smaller pixel size means that TM images consist of
many more data values than MSS images
 Storage space is so cumbersome that analysts choose certain band combinations rather than using
them all.
 Hence suitable / best band combinations (remember previous lecture?) vary by purpose, season,
region etc

Question 6

6. ETM+ band configurations

Answer 6

This was the sensing package in Landsat 6 (never operational) and an
updated version of this package is on Landsat 7, launched and
successfully tested in April, 1999. It has an added panchromatic band, and
there is a finer spatial resolution thermal band (60m instead of 120m)
Band characteristics:
1 (Blue / Green): Best water penetration
2 (Green): Green plant reflection
3 (Red): Vegetation, soils, rocks
4 (NIR): Vegetation, soil / veg/land / water
5 (MIR): moisture; clouds; snow
6 (Thermal): Geothermal; veg and soil moisture
7 (MIR): rock formations
Pan (Visible): Human Interpretation

Question 7

7. Landsat 8 (advances over previous Landsats)

Answer 7

Landsat 8 was launched in February 2013
• Two new instruments: Operational Land Imager (OLI) and the Thermal Infrared
Sensor (TIRS)
• Push-broom technology as opposed to whisk-broom

Question 8

8. Landsat applications

Answer 8

-

Question 9

9. SPOT sensors – HRV, HRVIR, Vegetation

Answer 9

• SPOTs 1, 2, and 3 carry two identical sensors called the HRV (High
Resolution Visible)
• It is a pushbroom scanner
• The HRV can be operated in 2 modes:
• Panchromatic mode (PN mode) and Multispectral mode (XS mode)

SPOT 4, launched in 1998, contains HRVIR, an improved version of
HRV.
• With the addition of a MIR band(1.58 – 1.75), it is designed to provide
capabilities for geological reconnaissance, vegetation surveys and
snow cover surveys.
• It also contains a coarser resolution instrument for measuring
vegetation at a continental or global scale, simply called Vegetation

Question 10

10. GOES 15. GOES coverage

Answer 10

Designed to operate in geostationary orbit 35,790 km (22,240 statute miles)
above the earth
• The advanced GOES I–M spacecraft continuously view the continental
United States, the Pacific and Atlantic Oceans, Central, South America and
southern Canada.
• The three-axis, body-stabilized spacecraft design enables the sensors to
“stare” at the earth and thus more frequently image clouds, monitor
earth’s surface temperature and water vapour fields, and sound the
atmosphere for its vertical thermal and vapor structures.
• Thus the evolution of atmospheric phenomena can be followed, ensuring
real-time coverage of meteorological events such as severe
local storms and tropical cyclones that directly affect public safety, protection
of property, and ultimately, economic health and development. The
importance of this capability has been exemplified during
hurricanes Hugo (1989) and Andrew (1992).