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AAS 1 > Satellite Communications (Satcom) > Flashcards

Satellite Communications (Satcom) Flashcards

1
Q

Who are the three most common providers of uplink and downlink for aviation use?

A

Globalstar
Inmarsat
Iridium

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2
Q

Satellite systems work in:

A

Duplex or Simplex

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3
Q

What does duplex mean?

A

Duplex means that two different frequencies are used to transmit and receive info

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4
Q

What is Phase Shift Keying (PSK)?

A

a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave.

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5
Q

What is a Simplex?

A

Transmit only system
No return is given

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6
Q

Duplex system allows for what to happen simultaneously?

A

transmit and receive capability

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7
Q

Frequency FROM aircraft TO satellite is known as:

A

Uplink

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8
Q

Frequency TO the aircraft FROM the satellite is known as:

A

Downlink

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9
Q

Three common frequencies used with Satcom are:

A

UHF, SHF, and EHF

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10
Q

What three segments is the Satcom system divided into?

A

The Space Segment (Space Vehicles)

The Control Segment (Communication and control of Satellites)

The User Segment (Those using the satellites for communication)

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11
Q

A satellite transponder consists of:

A

A low noise amplifier, mixer, local oscillator, and a power supply

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12
Q

What does the Low Noise Amplifier do?

A

Receives the uplink and provides the signal to the mixer

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13
Q

Along with the uplink, what else does the mixer receive?

A

A local oscillator input

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14
Q

Signals sent from the satellite transponder are:

A

Multiplexed

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15
Q

What is Multiplexing?

A

A method of dividing several simultaneous signals into small pieces, which can be transmitted on a single channel.

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16
Q

A single satellite contains many transponders, each of which do what?

A

Retransmits multiplexed signals

17
Q

What does demultiplexed mean?

A

It’s the extracting of signals

18
Q

Satellites use what system?

A

A Phased Array System

19
Q

What is included in a Phased Array system?

A

An array, or group of antennas, that are connected together with phase shift networks

20
Q

Phased arrays exhibit high:

A

gain and directionality

21
Q

By controlling the phase shift networks, the pattern can be:

A

changed without need to physically move or re-aim the antenna

22
Q

What is InMarsat?

A

(British sat company)
An international corporation providing two-way communication services to governments, aid agencies, media outlets, and businesses with a need to communicate to remote regions or where there is no reliable ground network.

23
Q

The InMarsat system uses what components?

A

Two satellite data units (SDU)
Two radio frequency units
And several other LRU’s with a sophisticated antenna system (which contains its own LRU’s)

24
Q

The Satellite Data Units (SDU) are connected with what systems?

A

The Inertial Reference Systems (IRS)
The automated Dependent Surveillance System (ADS-C)
And the audio systems

25
Q

The IRS connection allows Inmarsat to determine what?

A

aircraft location in order to control the radiation/ reception pattern using the Phased Array.

26
Q

What is GlobalStar?

A

A low earth orbit constellation consisting of 44 satellites for satellite phone and low speed communications

27
Q

The GlobalStar space vehicles provide signal coverage for most of where?

A

The Northern Hemisphere

28
Q

What other services are available through GlobalStar?

A

Internet and private network connections, position location, and texting.

29
Q

The GlobalStar system covers where?

A

Most continental areas for data services

30
Q

The aircraft on-board GlobalStar system consists of:

A

A transceiver, antenna, and control panel or headset

31
Q

Data terminal devices are available with integrated:

A

GPS receivers that provide position information and connections to computers and printers.

32
Q

What is Iridium?

A

a US based company that operates 66 satellites in low-earth orbit

33
Q

Iridium is a cross-linked system to provide voice and data communication where?

A

Worldwide
And it is the world’s largest commercial constellation

34
Q

What type of broadcast satellite system is Sirius?

A

Downlink only

35
Q

The Sirius XM system uses:

A

Two geo-stationary satellites

36
Q

What is one issue that can be had with Sirius systems?

A

Propagation control which causes an echo because of the time delay in the transmitting and receiving of waves

AAS 1 (25 decks)

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