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Atmospheric remote sensing > Chapter 3 sensors and platforms part 1 > Flashcards

Chapter 3 sensors and platforms part 1 Flashcards

1
Q

Platforms refer to

A

the structures or vehicles on which remote sensing instruments are mounted.

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2
Q

The platform on which a particular sensor is housed determines a number of attributes, which may dictate

A

the use of particular sensors

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3
Q

The platform on which a particular sensor is housed determines a number of attributes, which may dictate the use of particular sensors. These attributes include:

A

distance the sensor is from the object of interest, periodicity of image acquisition, timing of image acquisition, and location and extent of coverage.

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4
Q

There are three broad categories of remote sensing platforms:

A

ground based, airborne, and satellite.

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5
Q

A represents

A

Spaceborne:
satellite
shuttle

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6
Q

B represent

A

Airborne:
Aeroplane
Helicopter
Hot air ballon
Air ship
Tethered balloon

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7
Q

C represent

A

Ground-based:

hand-held
Raised platform

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8
Q

A wide variety of ground based platforms are used in remote sensing. Some of the more common ones are

A

are hand held devices, tripods, towers and cranes

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9
Q

Instruments that are ground-based are often used to

A

to measure the quantity and quality of light coming from the sun or for close range characterization of objects.

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10
Q

used to measure the quantity and quality of light coming from the sun or for close range characterization of objects. For example, to

A

to study properties of a single plant or a small patch of grass, it would make sense to use a ground based instrument.

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11
Q

Laboratory instruments are used

A

almost exclusively for research, sensor calibration, and quality control.

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12
Q

Laboratory instruments are used almost exclusively for research, sensor calibration, and quality control. Much of what is learned from laboratory work is used to

A

understand how remote sensing can be better utilized to identify different materials.

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13
Q

Much of what is learned from laboratory work is used to understand how remote sensing can be better utilized to identify different materials. This contributes to

A

to the development of new sensors that improve on existing technologies.

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14
Q

Field instruments are largely used for

A

research purposes

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15
Q

Field instruments are also largely used for research purposes. This type of remote sensing instrument is often

A

hand-held or mounted on a tripod or other similar support

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16
Q

Field instruments are also largely used for research purposes. This type of remote sensing instrument is often hand-held or mounted on a tripod or other similar support. An example for field remote sensing instruments used in meteorology is

A

Doppler on Wheels (or DOW)

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17
Q

DOW

A

DOW is a fleet of radar trucks maintained by the Center for Severe Weather Research (CSWR) in Boulder, Colorado.

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18
Q
A

: Mobile ozone and aerosol lidar for field campaigns. Profiles ozone and aerosol between 100m‒4 km.

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19
Q

Permanent ground platforms are typically used for

A

monitoring atmospheric phenomenon

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20
Q

Permanent ground platforms are typically used for monitoring atmospheric phenomenon, although they are also used for

A

long-term monitoring of terrestrial features

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21
Q

Towers and cranes are often used to support research projects where

A

a reasonably stable, long-term platform is necessary.

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22
Q

Towers can be built

A

on site and can be tall enough to project through a forest canopy so that a range of measurements can be taken from the forest floor, through the canopy and from above the canopy

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23
Q

Weather radars are the best examples for

A

the permanent ground platforms that are typically used for monitoring atmospheric phenomenon.

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24
Q
A

Doppler radar

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25
Q

Airborne platforms were

A

the sole non-ground-based platforms for early remote sensing work.

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26
Q

Balloons are rarely used today because

A

they are not very stable and the course of flight is not always predictable

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27
Q

Balloons are rarely used today because they are not very stable and the course of flight is not always predictable, although small balloons carrying expendable probes

A

are still used for some meteorological research.

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28
Q

At present, airplanes are

A

the most common airborne platform

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29
Q

Nearly the ______________________________are used for remote sensing applications.

A

whole spectrum of civilian and military aircraft

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30
Q

Nearly the whole spectrum of civilian and military aircraft are used for remote sensing applications. When

A

altitude and stability requirements for a sensor are not too demanding, simple, low-cost aircraft can be used as platforms.

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31
Q

When altitude and stability requirements for a sensor are not too demanding, simple, low-cost aircraft can be used as platforms. However, as_______________________________, more sophisticated aircraft must be used.

A

requirements for greater instrument stability or higher altitudes become necessary

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32
Q

aircraft are divided into

A

three categories (low, mid, and high)

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33
Q

aircraft are divided into three categories (low, mid, and high) based on their

A

altitude restrictions

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34
Q

In general, the higher an aircraft can fly, the

A

more stable a platform it is, but correspondingly more costly to operate and maintain.

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35
Q

Low altitude aircraft typically fly

A

below altitudes where supplemental oxygen or pressurization are needed (12,500 feet above sea level)

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36
Q

Low altitude aircraft are good for

A

acquiring high spatial resolution data limited to a relatively small area.

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37
Q

Low altitude aircraft:

such as the Cessna 172 or 182, and Piper Cherokee. This class of aircraft is

A

inexpensive to fly and can be found throughout the world

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38
Q

This class of aircraft is inexpensive to fly and can be found throughout the world. Some of these airplanes are specially outfitted for

A

mounting remote sensing instruments in the underside of the plane

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39
Q

Some of these airplanes are specially outfitted for mounting remote sensing instruments in the underside of the plane, however, many times instruments are simply

A

hung out the door using simple mounts

40
Q

Helicopters are usually used for

A

low altitude applications

41
Q

Helicopters are usually used for low altitude applications where

A

the ability to hover is required.

42
Q

Helicopters are quite _____________to operate

A

expensive

43
Q

Helicopters are quite expensive to operate and they are typically used

A

only when needed

44
Q

Ultralight aircraft are

A

a class of aircraft that is gaining popularity

45
Q

The Federal Aviation Authority (FAA) defines an ultralight as a

A

single seat powered flying machine that weighs less than 254 pounds, has a top speed of 55 knots (63 mph), stalls at 24 knots (28 mph) or less and carries no more than 5 gal. of fuel.

46
Q

(ultralight) These small, often portable, aircraft are_________________ and are able to

A

inexpensive

take off and land where larger aircraft cannot

47
Q

(ultralight)

They are limited to flying at

A

lower elevations and at slow speeds.

48
Q

If the demands of the remote sensing requirement are not too strict,

A

ultralight aircraft may be a reasonable alternative to larger aircraft.

49
Q

Mid-altitude aircraft have an altitude limit

A

under 30,000 feet above sea level

50
Q

Mid-altitude aircraft have an altitude limit under 30,000 feet above sea level. This includes a

A

number of turbo-prop aircraft

51
Q

. Often at higher altitudes, there is less

A

turbulence so stability is better

52
Q

(midlatitude)

. This class of airplane is used when

A

stability is more important and when it is necessary or desired to acquire imagery from a greater distance than available from low altitude aircraft.

53
Q

(mid latitude aircrafts)

These aircraft can obtain

A

greater areal coverage more quickly than low altitude platforms.

54
Q

High altitude aircraft can fly at altitudes

A

greater than 30,000 feet above sea level

55
Q

High altitude aircraft can fly at altitudes greater than 30,000 feet above sea level. This class of airplane is usually powered by

A

jet engines

56
Q

High altitude aircraft can fly at altitudes greater than 30,000 feet above sea level. This class of airplane is usually powered by jet engines and is used for

A

specialized tasks, such as atmospheric studies, research to simulate satellite platforms, and other applications where a high altitude platform is required.

57
Q

High altitude aircraft are good for acquiring

A

large areal coverage with typically lower spatial resolutions.

58
Q

Another class of aircraft that has been in use for many years is

A

is remote control aircraft, or drones

59
Q

Remotely controlled aircraft are often used for conditions when

A

it may be too hazardous to fly.

60
Q

Remotely controlled aircraft are often used for conditions when it may be too hazardous to fly. They have been used extensively by

A

the military

61
Q

The most stable platform aloft is

A

a satellite

62
Q

The most stable platform aloft is a satellite, which is

A

spaceborne

63
Q

The first remote sensing satellite was launched in 1960 for meteorology purposes. Now, over a

A

a hundred remote sensing satellites have been launched and more are being launched every year.

64
Q

Satellites can be classified by their

A

orbital geometry and timing

65
Q

Three orbits commonly used for remote sensing satellites are

A

geostationary, equatorial and Sun synchronous

66
Q

A geostationary satellite has a period of rotation equal to that of

A

Earth (24 hours)

67
Q

A geostationary satellite has a period of rotation equal to that of Earth (24 hours) so the satellite

A

always stays over the same location on Earth.

68
Q

Communications and weather satellites often use

A

geostationary orbits with many of them located over the equator.

69
Q

In an equatorial orbit, a satellite circles Earth at a

A

low inclination (the angle between the orbital plane and the equatorial plane).

70
Q

A represents

A

Polar orbit

71
Q

B represents

A

geostationary orbit

72
Q

Sun synchronous satellites have orbits with

A

high inclination angles, passing nearly over the poles

73
Q

Orbits are timed so that the satellite

A

always passes over the equator at the same local sun time.

74
Q

. Orbits are timed so that the satellite always passes over the equator at the same local sun time. In this way the satellites maintain

A

the same relative position with the sun for all of its orbits.

75
Q

Many remote sensing satellites are

A

Sun synchronous

76
Q

Many remote sensing satellites are Sun synchronous which ensures

A

repeatable sun illumination conditions during specific seasons.

77
Q

. Because a Sun synchronous orbit does not pass directly over the poles, it is

A

not always possible to acquire data for the extreme polar regions.

78
Q

The frequency at which a satellite sensor can acquire data of the entire Earth depends on

A

sensor and orbital characteristics.

79
Q

For most remote sensing satellites the total coverage frequency ranges from

A

twice a day to once every 16 days

80
Q

The frequency at which a satellite sensor can acquire data of the entire Earth depends on sensor and orbital characteristics. For most remote sensing satellites the total coverage frequency ranges from twice a day to once every 16 days.

Another orbital characteristic is

A

altitude

81
Q

Low Earth orbit (LEO)

A

geocentric orbits with altitudes from up to 2,000 km.

82
Q

Medium Earth orbit (MEO):

A

geocentric orbits ranging in altitude from 2,000 km (1,240 miles) to just below geosynchronous orbit at 35,786 kilometers (22,236 mi). Also known as an intermediate circular orbit.

83
Q

Both geosynchronous orbit (GSO) and geostationary orbit (GEO) are

A

orbits around Earth matching Earth’s sidereal rotation period.

84
Q

All geosynchronous and geostationary orbits have a

A

semi-major axis of 42,164 km (26,199 mi).

85
Q

All geostationary orbits are

A

also geosynchronous, but not all geosynchronous orbits are geostationary.

86
Q

A geostationary orbit stays

A

exactly above the equator

87
Q

A geostationary orbit stays exactly above the equator, whereas a geosynchronous orbit

A

may swing north and south to cover more of the Earth’s surface.

88
Q

A geostationary orbit stays exactly above the equator, whereas a geosynchronous orbit may swing north and south to cover more of the Earth’s surface. Both complete

A

one full orbit of Earth per sidereal day (relative to the stars, not the Sun).

89
Q

High Earth orbit

A

geocentric orbits above the altitude of geosynchronous orbit 35,786 km (22,240 miles).

90
Q

A Represents

A

LEO= Low earth orbit (100 - 1500 km)

91
Q

B represents

A

MEO= medium earth orbit (5,000 - 10,000 km)

92
Q

C Represents

A

GEO= Geostationary Orbit (36,000 km)

93
Q

D Represents

A

HEO = Highly eliptical orbit

94
Q

Most remote sensing satellites have been designed to

A

transmit data to ground receiving stations located throughout the world.

95
Q

To receive data directly from a satellite, the receiving station must

A

have a line of sight to the satellite.

96
Q

If there are not sufficient designated receiving stations around the world, any given satellite may

A

not readily get a direct view to a station, leading to potential problems of data discontinuity.

97
Q

. If there are not sufficient designated receiving stations around the world, any given satellite may not readily get a direct view to a station, leading to potential problems of data discontinuity. To work around this problem,

A

data can be temporarily stored onboard the satellite and then later downloaded upon acquiring contact with the receiving station. Another alternative is to relay data through TDRSS (Tracking and Data Relay Satellite System), a network of geosynchronous (geostationary) communications satellites deployed to relay data from satellites to ground stations.

Atmospheric remote sensing (9 decks)

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