Chapter 3 sensors and platforms part 1

Question 1

Platforms refer to

Answer 1

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

Question 2

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

Answer 2

the use of particular sensors

Question 3

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:

Answer 3

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

Question 4

There are three broad categories of remote sensing platforms:

Answer 4

ground based, airborne, and satellite.

Question 5

A represents

Answer 5

Spaceborne:
satellite
shuttle

Question 6

B represent

Answer 6

Airborne:
Aeroplane
Helicopter
Hot air ballon
Air ship
Tethered balloon

Question 7

C represent

Answer 7

Ground-based:

hand-held
Raised platform

Question 8

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

Answer 8

are hand held devices, tripods, towers and cranes

Question 9

Instruments that are ground-based are often used to

Answer 9

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

Question 10

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

Answer 10

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

Question 11

Laboratory instruments are used

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

Field instruments are largely used for

Answer 14

research purposes

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Doppler on Wheels (or DOW)

Question 17

DOW

Answer 17

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

Question 18

Answer 18

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

Question 19

Permanent ground platforms are typically used for

Answer 19

monitoring atmospheric phenomenon

Question 20

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

Answer 20

long-term monitoring of terrestrial features

Question 21

Towers and cranes are often used to support research projects where

Answer 21

a reasonably stable, long-term platform is necessary.

Question 22

Towers can be built

Answer 22

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

Question 23

Weather radars are the best examples for

Answer 23

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

Question 24

Answer 24

Doppler radar

Question 25

Airborne platforms were

Answer 25

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

Question 26

Balloons are rarely used today because

Answer 26

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

Question 27

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

Answer 27

are still used for some meteorological research.

Question 28

At present, airplanes are

Answer 28

the most common airborne platform

Question 29

Nearly the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_are used for remote sensing applications.

Answer 29

whole spectrum of civilian and military aircraft

Question 30

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

Answer 30

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

Question 31

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.

Answer 31

requirements for greater instrument stability or higher altitudes become necessary

Question 32

aircraft are divided into

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three categories (low, mid, and high)

Question 33

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

Answer 33

altitude restrictions

Question 34

In general, the higher an aircraft can fly, the

Answer 34

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

Question 35

Low altitude aircraft typically fly

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

Question 36

Low altitude aircraft are good for

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

Question 37

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

Answer 37

inexpensive to fly and can be found throughout the world

Question 38

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

Answer 38

mounting remote sensing instruments in the underside of the plane

Question 39

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

Answer 39

hung out the door using simple mounts

Question 40

Helicopters are usually used for

Answer 40

low altitude applications

Question 41

Helicopters are usually used for low altitude applications where

Answer 41

the ability to hover is required.

Question 42

Helicopters are quite \_\_\_\_\_\_\_\_\_\_\_\_\_to operate

Answer 42

expensive

Question 43

Helicopters are quite expensive to operate and they are typically used

Answer 43

only when needed

Question 44

Ultralight aircraft are

Answer 44

a class of aircraft that is gaining popularity

Question 45

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

Answer 45

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.

Question 46

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

Answer 46

inexpensive take off and land where larger aircraft cannot

Question 47

(ultralight) They are limited to flying at

Answer 47

lower elevations and at slow speeds.

Question 48

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

Answer 48

ultralight aircraft may be a reasonable alternative to larger aircraft.

Question 49

Mid-altitude aircraft have an altitude limit

Answer 49

under 30,000 feet above sea level

Question 50

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

Answer 50

number of turbo-prop aircraft

Question 51

. Often at higher altitudes, there is less

Answer 51

turbulence so stability is better

Question 52

(midlatitude) . This class of airplane is used when

Answer 52

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

Question 53

(mid latitude aircrafts) These aircraft can obtain

Answer 53

greater areal coverage more quickly than low altitude platforms.

Question 54

High altitude aircraft can fly at altitudes

Answer 54

greater than 30,000 feet above sea level

Question 55

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

Answer 55

jet engines

Question 56

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

Answer 56

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

Question 57

High altitude aircraft are good for acquiring

Answer 57

large areal coverage with typically lower spatial resolutions.

Question 58

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

Answer 58

is remote control aircraft, or drones

Question 59

Remotely controlled aircraft are often used for conditions when

Answer 59

it may be too hazardous to fly.

Question 60

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

Answer 60

the military

Question 61

The most stable platform aloft is

Answer 61

a satellite

Question 62

The most stable platform aloft is a satellite, which is

Answer 62

spaceborne

Question 63

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

Answer 63

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

Question 64

Satellites can be classified by their

Answer 64

orbital geometry and timing

Question 65

Three orbits commonly used for remote sensing satellites are

Answer 65

geostationary, equatorial and Sun synchronous

Question 66

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

Answer 66

Earth (24 hours)

Question 67

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

Answer 67

always stays over the same location on Earth.

Question 68

Communications and weather satellites often use

Answer 68

geostationary orbits with many of them located over the equator.

Question 69

In an equatorial orbit, a satellite circles Earth at a

Answer 69

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

Question 70

A represents

Answer 70

Polar orbit

Question 71

B represents

Answer 71

geostationary orbit

Question 72

Sun synchronous satellites have orbits with

Answer 72

high inclination angles, passing nearly over the poles

Question 73

Orbits are timed so that the satellite

Answer 73

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

Question 74

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

Answer 74

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

Question 75

Many remote sensing satellites are

Answer 75

Sun synchronous

Question 76

Many remote sensing satellites are Sun synchronous which ensures

Answer 76

repeatable sun illumination conditions during specific seasons.

Question 77

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

Answer 77

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

Question 78

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

Answer 78

sensor and orbital characteristics.

Question 79

For most remote sensing satellites the total coverage frequency ranges from

Answer 79

twice a day to once every 16 days

Question 80

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

Answer 80

altitude

Question 81

Low Earth orbit (LEO)

Answer 81

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

Question 82

Medium Earth orbit (MEO):

Answer 82

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.

Question 83

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

Answer 83

orbits around Earth matching Earth's sidereal rotation period.

Question 84

All geosynchronous and geostationary orbits have a

Answer 84

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

Question 85

All geostationary orbits are

Answer 85

also geosynchronous, but not all geosynchronous orbits are geostationary.

Question 86

A geostationary orbit stays

Answer 86

exactly above the equator

Question 87

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

Answer 87

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

Question 88

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

Answer 88

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

Question 89

High Earth orbit

Answer 89

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

Question 90

A Represents

Answer 90

LEO= Low earth orbit (100 - 1500 km)

Question 91

B represents

Answer 91

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

Question 92

C Represents

Answer 92

GEO= Geostationary Orbit (36,000 km)

Question 93

D Represents

Answer 93

HEO = Highly eliptical orbit

Question 94

Most remote sensing satellites have been designed to

Answer 94

transmit data to ground receiving stations located throughout the world.

Question 95

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

Answer 95

have a line of sight to the satellite.

Question 96

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

Answer 96

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

Question 97

. 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,

Answer 97

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.