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Worksheetsremote Sensing and Communications Practice Quiz
Total questions: 99
Worksheet time: 50mins
Modern radar uses what region of the electromagnetic spectrum?
Infrared (IR)
Visible light
Microwaves
Which of the following statements are true about how microwaves move from and to a radar sensor? Select all that apply.
Power of the received energy is the same as transmitted
The energy spreads over an area that is increasing in proportion to the square of the distance from the source
Received wavelength is the same as transmitted
With radar, increasing the distance between the transmitter and the subject by a factor of 10 reduces the energy received by a factor of ____.
10000
1000
1
The changing frequency of a microwave as it moves relative to the observer is called ____.
Kipler effect
Marina effect
Which of the following statements are true about SAR? Select all that apply.
SAR produces three-dimensional images
SAR is undetectable by observers in the area being observed
SAR operates in two modes: spotlight mode and scan mode
Which of the following statements are true about LIDAR? Select all that apply.
Observers on the ground can tell when they are being imaged with LIDAR
Like radar, LIDAR uses microwave waves
LIDAR uses a laser in the ultraviolet, visible, or IR wavelengths
Which of the following explains angular resolution?
It defines the ability to distinguish between two sources and is a function of wavelength and aperture diameter in meters
It describes the smallest linear distance at nadir that can be resolved at a distance and can be calculated by converting the radius to diameter and then multiplying by altitude
How does a reflecting telescope work?
The user views an image through an eyepiece, which acts as a magnifying glass, and then manipulates the magnification by adjusting the distance between the eyepiece and the lens
It uses a lens to bend light and form an image
It uses an array of mirrors that are manipulated to focus and produce images
What is the difference between Spatial and Spectral resolution?
The relationship between the two is that you can have both types of resolution at the same time
Spatial resolution refers to a sensor’s ability to discern between individual objects or the distance between those objects; spectral resolution refers to a sensor’s ability to differentiate between the spectral differences between objects
They both offer very high resolution
Which of the following is a description of an Active Sensor?
An active sensor is one that is designed to emit energy toward its target area and then collect the reflected energy as it returns to the sensor
An active sensor is one that propagates its energy and receives energy 360 degrees
An active sensor requires precise pointing to transmit and receive data
Which of the following describes Light Detection and Ranging (LIDAR)?
It uses light through a pulsed laser to reflect off of target surfaces
It is a sensor that uses radio waves to determine the range, velocity, and angle of objects
It emits energy toward its target area and then collects the reflected energy as it returns to the sensor
What is one unique use of LIDAR?
To create precise maps
to create images of skyscrapers
to create images of weather formations
How does a Synthetic Aperture Radar (SAR) work?
It is an active sensor that sends energy towards its intended target and then collects on the reflected return energy
It can provide data that can be translated into a two-dimensional picture of an area
It is only able to image in good weather and is significantly impacted by inclement weather
Which of the following describes ground resolution?
It defines the ability to distinguish between two sources.
It describes the smallest linear distance at nadir that can be resolved at a distance
It is a function of wavelength and aperture diameter in meters
True or False. There are two types of active sensors: RADAR and LIDAR.
TRUE
FALSE
How does a refracting telescope work?
The objective lens focuses light onto the image
It uses curved mirrors to reflect light and form an image
It uses a lens to bend light and form an image
Where is the largest reflecting telescope on Earth located?
Spain
Canada
United States
What does the acronym LIDAR stand for?
Light Detection and Ranging
Light Detection and Reflection
Light Deflection and Ranging
What is the most common type of space-based radar called?
Synthetic Aperture Radar (SAR)
Position and Navigation
Pseudorange
What are the two modes in which SAR generally operates?
Scan and pace
Spotlight and scan
Pace and mapping
How would you define remote sensing?
It can be calculated by converting the radius to diameter and then multiplying by altitude
It describes the smallest linear distance at nadir that can be resolved at a distance
It refers to gathering information from a distance by detecting energy that is reflected or emitted from the surface
How is Ground Sample distance (GSD) calculated?
It can be calculated by converting the radius to diameter and then multiplying by altitude
It is the distance between pixel centers measured on the ground
It is calculated by doubling the ground image radius in meters
Which are the two general categories of sensors used for remote sensing?
Passive, Active
Active, Reactive
Passive, Military
Which of the following describes multi-spectral sensors?
The multi-spectral sensors collect information on specific bands across the visible and infrared bands
The multi-spectral imagers require nighttime conditions to image and are negatively affected by atmospheric conditions
The multi-spectral imagers require nighttime conditions to image and are not affected by atmospheric conditions
Which of the following describes Panchromatic sensors?
They combine the information captured in the visible spectrum of blue, green, and red into a single band
They display their data in full color
They offer lower spatial resolution
Which of the following describes hyperspectral sensors?
The hyperspectral sensors collect information on specific bands across the visible and infrared bands
The hyperspectral imagers offer higher spatial, but lower spectral, resolution when compared to Multispectral and Panchromatic images
The hyperspectral imagers require nighttime conditions to image and are not affected by atmospheric conditions
How would you describe spotlight mode?
In spotlight mode, the sensor stares at the same location for a period as the sensor moves through its orbit
In spotlight mode, lower resolution images of a smaller area can be produced
In spotlight mode, energy is constantly being sent along the sensor’s path
Which of the following factors can affect the GSD of images within the LEO orbit?
The ground image radius
The satellite’s orbit
The image captured in perigees
What are two key characteristics that are used to describe telescopes?
Aperture and swath width
Focal length and aperture
Swath width and triangulation
Which of the following describe Viewing Geometry?
It means that the sensor location within your field of view
It is the angular relationship between the sensor location in orbit and the target area
It means that the sensor location directly beneath the satellite
Why would you need to consider Ground Resolvable Distance (GRD) to further enhance an image's value?
Sensor location within your field of view
Calibrated targets, when imaged, can be used to evaluate a sensor’s imaging capabilities
The sensor's ability to capture images at nadir
What are two terms used to describe satellite imaging?
Swath width and sensor field of view
Field of view and focal length
Focal Length and aperture
True or false. An uplink only travels from ground station to ground station in SATCOM.
True
False
What is the simplest type of detector that processes data from a lens into a usable form?
Photographic film
Computer processor
Digital camera
Why is a charge-coupled device (CCD) detector advantageous in the space environment?
They provide a non-linear response
They have a high efficiency and sensitivity
They provide an optimal payload on a satellite
Which of the following describes Radio Detection and Ranging (RADAR)?
It emits energy toward its target area and then collects the reflected energy as it returns to the sensor
It uses light through a pulsed laser to reflect of target surfaces
It is a sensor that uses radio waves to determine the range, velocity, and angle of objects
Which of the following describe Viewing Geometry?
It means that the sensor location within your field of view
It is the angular relationship between the sensor location in orbit and the target area
It means that the sensor location directly beneath the satellite
What type of sensor is defined as being designed to collect energy being emitted from or reflected off a subject?
Passive
Active
Reactive
What are some limitations to SAR?
Image resolution lower compared to visual sensors
Radar glint
Image interpretation does not require special training
How would you describe scan mode?
In scan mode, the sensor stares at the same location for a period as the sensor moves through its orbit
In scan mode, higher resolution images of a smaller area can be produced
In scan mode, energy is constantly being sent along the sensor’s path
Because an area cannot be image using SAR without broadcasting the imaging, what advantage does this give adversaries?
They can detect nuclear blasts
They can detect when they are being imaged and implement countermeasures, such as jamming, to defeat a SAR imager
They can broadcast a user’s location somewhere on the sphere around the satellite
What is the Doppler Effect or Doppler Shift?
It is the way in which radar can detect space weather
It is the way in which a radar can detect velocities of objects
It is the way in which light energy reflects off the Earth
True or False. LIDAR has been used to map the bottom of the ocean.
TRUE
FALSE
What type of sensor is defined as a sensor that emits energy toward its target area and then collects the reflected energy as it returns to the sensor?
Passive
Active
Reactive
Which of the following are true about thermal infrared sensors?
They can be used for fire detection, missile launch detection, and low-light imaging
They require a basic cooling system
Their usable lifetime is determined by how much coolant is used by the sensor
Thermal Infrared imagers measure the differences in emitted thermal IR emissions between objects and their surroundings.
True
False
How is a Pan-sharpened Multispectral Image (MSI) produced?
It can be produced once data is downlinked to the ground station
It is done on board the satellite
It requires basic data processing ability at the satellite
Downlink is the data traveling from ________ of the data.
Ground station, to the end receiver
Satellite transmitter to satellite receiver
Satellite, to the end receiver
An uplink only travels from ground station to ground station in SATCOM.
True
False
Bent-pipe communications refers to the curvature of the satellite signal.
True
False
What type of SATCOM is displayed?
Bent-pipe
Downlink
Uplink
What are the three blocks of frequency ranges use for satellite communications in the electromagnetic spectrum? (select all that apply)
Super High Frequency (SHF)
Extremely High Frequency (EHF)
Ultra High Frequency (UHF)
Modulated High Frequency
What are the characteristics of UHF (Ultra High Frequency)?
Small wavelength that can penetrate the scintillation environment
Large amounts of data can be transmitted and received with comparatively minimal atmospheric or solar effects on the signal
Long wavelengths and comparatively inexpensive user terminals
Small amounts of data transmitted
What are the characteristics of SHF (Super High Frequency)?
Small wavelength that can penetrate the scintillation environment Small amounts of data transmitted
Large amounts of data can be transmitted and received with comparatively minimal atmospheric or solar effects on the signal
Long wavelengths and comparatively inexpensive user terminals
What are the characteristics of EHF (Extremely High Frequency)?
Small wavelength that can penetrate the scintillation environment
Large amounts of data can be transmitted and received with comparatively minimal atmospheric or solar effects on the signal
Small amounts of data transmitted
Long wavelengths and comparatively inexpensive user terminals
What must engineers take into consideration when calculating a SATCOM link?
The number of satellites in orbit
The atmospheric effects on the signal and noise
The loss of solar power
The amount of space debris in LEO
What are the amount of frequency ranges use for satellite communications in the electromagnetic spectrum?
UHF, SHF, EHF
MHF, GHF, SHF
AHF, BASF, EHF
How would you define Electromagnetic Interference (EMI)?
An intentional electromagnetic disturbance created on a communications link to steal data passing over the link
An electromagnetic disturbance created on a communications link from an internal source
An electromagnetic disturbance created on a communications link from an external source
What does satellite hardening mean and what does it incorporate?
Protect satellites from radiation, interference, and solar effects
Limit the data rates and decrease traffic
increase the difficulty of access to the satellite's data
Why is the military less willing to risk interruption of link traffic by switching frequencies?
Due to the importance of switching frequencies regularly to protect data
Due to the critical nature of military communications
Due to the importance of accurate satellite orbit selection
Which of the following describes antennas?
They are the interfaces between communication points that transit and receive RF energy
They are the interfaces between high frequency and SATCOM devices
They are the interfaces to transmit uplink traffic
What are the characteristics of UHF?
Large amounts of data can be transmitted and received with comparatively minimal atmospheric or solar effects on the signal
Small wavelength that can penetrate the scintillation environment
Long wavelengths and comparatively inexpensive user terminals
The most common tool for interference detection is called:
A frequency detector
The Aries DefenderShield
A spectrum analyzer
Which one of the following can a spectrum analyzer detect?
Power anomalies when there is signal interference
Energy that spills over into multiple receiving channels, producing a weak signal
When a power shield’s circuitry is overloaded
What is the primary appeal of satellite communications?
The ability to transmit communications globally without having to rely exclusively on terrestrial communications lines
The ability to use radio frequencies to transmit communications within a region
The ability to transmit over thousands of kilometers
What are the two ways to employ a communications constellation in LEO?
Use larger satellites and higher orbits
Launch enough satellites so that there is always one in view of the user and use cross-linking
Launch satellites in a phased approach and in higher orbit
Why are high frequency (HF) links not ideal for communicating large amounts of data?
HF links can transmit over thousands of kilometers
HF links require optimal conditions even to send voice data or very simple data files
HF links can transmit at high data rates locally, but not globally
What are the three broad categories of antennas?
Multidimensional, omnidirectional, phased array
Parabolic dish, omnidirectional, phased array
Single dimension, hyperbolic, omnidirectional
Which type of antenna can finely direct the RF energy?
Dipole
Omnidirectional
Parabolic dish
If you were to choose the best frequency that is unaffected by atmospheric effects and the antenna pointing doesn’t need to be as precise as others, which would it be?
UHF
SHF
EHF
How would you define bandwidth?
The unintentional electronic interference on a link
The range of radio frequencies occupied by a modulated carrier wave
The use of at least three navigational signals from three separate satellites
Which one of the following is the definition of geolocating?
Locating two satellites in GEO
Locating the source of interference
locating two satellites in the same orbit (GEO or LEO)
How can you improve your signal to noise ratio?
Increase the transmitting power of the signal
Decrease the gain in the antenna
Increase the signal's bandwidth
How would you describe jamming?
A deliberate electromagnetic interference on a targeted link
An unintentional electromagnetic interference on a targeted link
A deliberate electromagnetic interference on random links
What is an uplink?
It is the data travelling from its SATCOM transmitter up to the satellite
It is the data travelling from the satellite to the end receiver of the data
It means the first part of communication is sent on one frequency and the second part is send on a different frequency
What plays a key factor in how a satellite will perform in space?
Orbit selection
Sensor selection
Antenna selection
Why is downlink jamming not as desirable as uplink jamming?
There is no difference
Downlink jamming moves the adversary out of harm’s way
Downlink jamming only effects a local area
What is cross linking?
It is establishing a communications link between the satellites in orbit with the user on the ground
It is establishing a view with the user
It is increasing the ground architecture footprint
Which type of antenna can propagate their energy and receive energy 360 degrees around it?
Omnidirectional
Parabolic dish
Phased array
What is the overall equation used to determine whether a link design will function?
Transmitter Power
Signal to noise
Link budget
Which of the following is a unique characteristic of GEO orbits?
In GEO, the ground architecture footprint can be reduced
At latitudes below 81 degrees have difficulty viewing GEO satellites
At a certain distance and location, a satellite in GEO orbits the Earth at the same rate as the Earth spins
What type of orbit can be used to communicate in the polar regions?
Low earth orbit
Highly elliptical orbit (HEO)
Geosynchronous orbit
Which orbit constellation design method is used to evenly distribute a constellation of satellites across the same orbital plane?
Walker
Molniya
Delta
Which of the following is used to calculate the link budget?
Orbit
Transmitter Power
Receiver antenna loss
Which type of antenna has the unique ability to change the shape and direction of the radiation pattern without physically moving the antenna?
Parabolic dish
Omnidirectional
Phased array
What do commercial entities value more--throughput or encryption?
Throughput
Encryption
What does the military value more--throughput or encryption?
Encryption
Throughput
What does SATCOM give us the ability to do?
Communicate and transmit data depending on your geographic location
Send voice data or very simple data files via fiber optic cable underground
Communicate and transmit large amounts of data reliably
What is the downlink?
It is the data travelling from its SATCOM transmitter up to the satellite
It means the first part of communication is sent on one frequency and the second part is sent on a different frequency
It is the data travelling from the satellite to the end receiver of the data
What is uplink jamming?
Interference that disrupts the signal going from the ground station or user terminal to the satellite
Interference that disrupts the signal going from the satellite to the ground station or user terminal
Interference that disrupts the local signal going from the ground station or user terminal to the antenna
What is downlink jamming?
Interference that disrupts the local signal going from the ground station or user terminal to the antenna
Interference that disrupts the signal going from the ground station or user terminal to the satellite
Interference that disrupts the signal going from the satellite to the ground station or user terminal
How can you mitigate the interference if the offender is unresponsive?
Move your antenna on the satellite so the interference is outside the footprint
Maintain your signal's frequency
Do not use a phased array antenna to turn off individual elements receiving the
True or false. Hollywood uses GPS PNT to help time camera shots in production.
True
False
GPS broadcasts on two signals referred to as the L1 and L2. What are the two different ways to encode the GPS signal?
Course Tracking (CT) and Preliminary (PY)
Coarse Acquisition (CA) and Precision (PY)
Target Acquisition (TA) and Pre-tracking (PT)
What is the single largest factor in achieving the highest possible accuracy from the GPS signal?
Navigation
NUDET
Timing
Position
What is the time-stamped GPS signal called?
Space Situational Awareness (SSA)
Over-the-Horizon (OTH)
Low probability of detection (LPD)
GPS Pseudorange
What is another key factor in determining how accurate a navigation signal will be?
Signal Reflection
Augmentation
Modernization
Dilution of Precision (DOP)
What is the code that broadcasts on both L1 and L2 and is used when a military application requires an encrypted and more robust navigation signal?
C/A
P(Y)
C/B
P/N
When is the current block of GPS satellites, that are in production, set to launch?
2026
2024
2034
