Block 1 Flashcards
(351 cards)
1
Q
Satellite communications (SATCOM) systems inherently facilitate…?
A
beyond line of sight connectivity
2
Q
A robust SATCOM architecture provides either ___ coverage or ___-___ coverage.
A
equatorial coverage (nonpolar)
high-latitude coverage (includes poles)
3
Q
SATCOM provides national and strategic leadership with a means to…?
A
maintain situational awareness and convey their intent to the operational commands responsible for conducting joint operations
4
Q
What are the three segments of SATCOM?
A
Space
Link
Ground
5
Q
The Space segment has __ parts and what are they?
A
Two parts:
- Platform
- Payload
6
Q
What is the “platform” part of the space segment?
A
consists of the basic frame of the satellite
7
Q
“What is the “payload” part of the space segment?
A
provides space-based capabilities to the users and distinguishes one type of satellite from another
The payload’s functions and capabilities are the main reason satellites are placed into orbit (for example the fact they provide communication)
8
Q
The Space segment is responsible for providing what?
A
Provides passive and directive gain through the use of transmit and receive antennas and onboard amplifiers.
9
Q
What is the “Link” segment?
A
Uplink and downlink to/from the terminals
10
Q
What is the “ground” segment?
A
Comprised of equipment that receives and transmits signals to the satellite from the Earth.
These can vary from hand held devices to fix or mobile terminals.
11
Q
What is the “control” portion of the ground segment?
A
Responsible for the operation of the overall system including platform, payload and network control.
This consists of worldwide satellite control facilities, systems onboard the satellite and communications networks linking the control facilities.
Satellite control is the means by which WGS and DSCS assets are used to maintain and restore maximum satellite performance under changing traffic conditions, natural or man-made stresses, disturbances, and equipment disruption.
12
Q
The Ground segment contains the RF equipment that transmits and receives.
What is the transmit path?
A
- Upconverts the IF (intermediate frequency) sub-carrier to the assigned frequency in the correct band range
- The outputs of the up-converters are then combined and amplified using HPA’s prior to reaching the antenna
13
Q
The Ground segment contains the RF equipment that transmits and receives.
What is the receive path?
A
- The distant end’s antenna provides reflector passive gain and then LNA provides directive gain by amplifying the signal
- The signal is split into multiple outputs for the down-converters to amplify the signals and convert them into IF (70 MHz) or L-Band (1-2 GHz)
14
Q
What is DCSS?
A
Digital Communication Subsystem within the Ground Segment that takes place at the TCF (Tech Control Facility)
15
Q
What kinds of things occur at the DCSS?
A
- Multiplexes/demultiplexes VF inputs and outputs
- Encrypts/decrypts VF inputs and outputs
- Multiplexes/demultiplexes digital inputs and outputs
- Modulates IF sub-carriers of 70 MHz and 1-2 GHz
16
Q
What are some users of WGS and DSCS?
A
- Commander in Chief (POTUS)
- Unified Combatant Commands (UCCs)
- National Airborne Operations Center (NAOC)
- White House Communications Agency (WHCA)
- North Atlantic Treaty Organization (NATO)
- Air Force Satellite Communications (AFSATCOM)
- Allied special users
17
Q
WGS and DSCS provides range extensions for which users?
A
- World Wide Military C2 System (WWMCCS)
- Department of Defense Information Network (DODIN)
- Jam Resistant Secure Communications (JRSC) Networks
- Tactical Warning/Attack Assessment Networks
- Global Broadcast System (GBS)
- Navy Flagship Command and Control Networks
- Ground Mobile Forces (GMF) and (C4I) AFLOAT
communications
18
Q
What is the electromagnetic spectrum?
A
The electromagnetic spectrum can best be described as the entire span of frequencies or wavelengths that can possibly be exhibited
by electromagnetic waves.
19
Q
What part of the frequency spectrum does satellite communications operate in?
A
UHF, SHF and EHF
But primarily, SHF
20
Q
What are the limitations to using EHF?
A
Technologically immature
Very susceptible to weather
21
Q
What is the frequency range for SHF?
A
3-30 GHz
22
Q
What is the frequency range for EHF?
A
30-300 GHz
23
Q
It is a characteristic of electromagnetic transmissions that noise power in a channel increases as the channel ___ increases.
A
bandwidth
24
Q
A satellite transponder is built to receive and transmit signals within…?
A
A specific band and channel of the spectrum
25
The number of hertz (Hz) spanned by this limited band of frequencies describes the transponder's...?
RF BW
26
____ ____ equals its potential capacity to pass communications and data at higher throughput rates.
Transponder Bandwidth
27
Greater BW increases ___ ___ only if the conditions in all parts of the transmission signal path can be adjusted to minimize noise and to maximize the signal power to noise ratio without distorting the signal.
throughput capacity
28
The WDC payload capabilities is applicable to which satellites?
Block II Follow-On (B2FO) F7
Block II Follow-On (B2FO) F8
29
WGS provides ___ transmit/receive beam pairs?
19
This means it supports 19 coverage areas
30
How many NCAs does WGS have?
8 Ka-band NCAs
31
How many ACAs does WGS have?
2 Ka-band ACAs
32
How many EC areas does WGS have?
1 X-Band EC area
33
How many shapeable beams does WGS have?
8 X-Band shapeable beams
34
Coverage areas for WGS are or are not impacted by the WDC upgrade?
Not impacted
35
WGS provides ___ antennas to support the 19 coverage areas.
14
36
For F4+, what were changed about the antennas of WGS?
The two 10-inch ACAs antennas were modified to be the same as NCAs. This made the east side of the pallet identical to the west side.
In addition, the ACAs were moved to the outside of the pallet.
In F1-F3 satellites, the ACA's were smaller than the NCAs.
37
What does NCA stand for?
Narrow Coverage Area
38
What does ACA stand for?
Area Coverage Area
39
What does RHCP stand for?
Right Hand Circular Polarization
40
What does LHCP stand for?
Left Hand Circular Polarization
41
What do lettered frequency bands indicate?
That they can be switched between prime and non-prime locations but cannot be assigned to both simultaneously.
Lettered channel designators
indicate that the channel can be selected, exclusively, from one of two beams.
42
What frequency band is WGS F1-F7?
X-Band and Ka-Band
43
How many redundant X-Band channelizer ports were activated for BOL (Beginning of Life) use on F7?
6 (3 UL and 3 DL)
** This is known as "redundant ports activation" or "RPA"
44
How many redundant Ka-Band Channelizer ports were activated for BOL (Beginningof Life) use on F7?
8 (4 UL and 4 DL)
45
What is the difference between footprints for WGS F1-F7 in X-Band and Ka-Band?
X-Band Antennas are steerable and shapeable beams and Earth coverage. They transmit LHCP and receive RHCP.
Ka-Band Antennas are gimbaled dish antennas offering Narrow coverage and Area coverage. They are diplexed polarized on both transmit and receive.
46
What is unique to satellites F4-F7 on WGS in the Ka-Band RF Bypass channels?
This allows users to occupy more than the legacy 125 MHz bandwidth. Now, there is one 400 MHz channel in each RF bypass beam
47
Ka-band RF bypass channels are processed through the..?
RF Bypass Channel Amplifiers (CAMPs)
When a bypass path is utilized, the corresponding CAMP is turned on, otherwise, when the bypass path is not utilized, the CAMP Is off.
48
When the WGS WDC frequency plan was implemented it allowed processing bandwidth to...?
quadruple from 125 MHz to 500 MHz
*** These 500 MHz channels are referred to as "super-channels" which differentiates it from the legacy channels used on F1-F7 WGS payloads
49
The WGS WDC Frequency plan applies to what?
F8+ (X-Band and Ka-Band)
50
Which beams on the WGS have switchable polarization?
NCA7, NCA8, ACA2
51
The switchable polarization is controlled by...?
Bandwidth selection switches
52
In the WGS Block II both the X-Band and the Ka-Band subsystems utilize frequency reuse via...?
spatial frequency reuse/spatial isolation
53
How is the digital channelizer able to crossband?
All X-band and Ka-band uplink channels are converted to a common baseband frequency through
two down conversions: RF to IF and IF to baseband. The down-converted signals then enter the analog front end of
the channelizer where they are converted from analog to digital signals. In addition, for the X-band signals, the
channelizer performs the input spectrum frequency inversion. The channelizer is a digital filter and switch, which
breaks each channel into 48 subchannels. Subchannels can be routed (individually or as groups) from any input to
any output(s) of the channelizer. Thus crossband connectivity is realized between X-band and Ka-band
54
The digital channelizer also allows gain of ___ or ___ of subchannels to be adjusted
individual or groups
55
The digital channelizer allows combination and/or replication of subchannels through the use of what...?
Fan ins
Fan outs
Spectral Monitoring
56
Each beam can contain up to ___ channels.
4
57
Each channel is 125 MHz and is broken down into 48 subchannels that are ___ MHz.
2.6 (rounded up)
125/48 = 2.60416
58
The 47 MHz channels (x-band rx/tx channel 1/4) each have ___ subchannels.
18
59
The 50 MHz channels (x-band earth coverage beam) each have ___ subchannels.
19
60
The ___ ___capability allows users who require more than 125 MHz of bandwidth to bypass the WGS beam to channel channelization processing (BDCA, channelizer and BUCA.)
RF Bypass
*** It provides this through two independent bypass paths.
61
What is channelization?
The process of separating a range of frequency into smaller groups of frequency
62
With channelization, each WDC port can process an entire 500 MHz beam (super-channel) whereas with the older model (F1-F7) up to 500 MHz of spectrum can be processed from a...?
coverage area beam
Essentially, a beam can only process one 500 MHz of spectrum where with WDC a designated channel can process 500 MHz
63
WDC still performs ___ ___ ___ but can now group subchannels across channel boundaries.
legacy channel processing
64
There are 4 channels and then 48 subchannels within F1-F7 satellites. How many subchannels are there in a super-channel?
192 subchannels (aka super-channel)
This is because superchannels combine 4 channels into one super channel. Those 48 subchannels x 4 channels = 192 subchannels.
It's important to remember that this is not creating a larger bandwidth to operate in overall the entire span of frequency given but creates a larger bandwidth within the channels themselves.
65
What is the total bandwidth of the F8?
8426 MHz over 73 total channels
- 1 x-band EC beam = 1 EC channel = 50 MHz BW (50 x 1)
- 8 x-band phased array beams = 32 channels = 3376 MHz BW (32 x 125)
- 10 ka-band GDA beams = 40 channels = 5000 MHz BW (40 x 125)
66
WGS Channelizer allows signals from any uplink beam to be routed to any downlink beam via...?
Frequency Cross Banding
67
The same frequency can be used in each coverage area.
Spatial frequency reuse
*** For example, same 125MHz channel can be downlinked into 2 different coverage areas.
68
What does CNPS stand for?
Common Network Planning Software
69
If the beams overlap during spatial frequency reuse, degradation will occur from...?
co-channel interference
Co-channel interference or CCI is crosstalk from two different radio transmitters using the same channel
70
Switchable polarization is possible through what?
Polarization Frequency Reuse
This is only possible on Ka-band antenna; up to 3 may be switched.
71
Polarization for antennas may be switched which allows Ka-band coverage areas to be...?
placed closer together
72
The biggest limiting factor to Polarization Frequency Reuse is...?
Rain
This can cause depolarization of the oppositely polarized spectra
73
Beam Select Switching is not applicable to F8 beams because?
They are already 500 MHz
Spatial Frequency Reuse can only combine
74
Beam Selecting Switching is possible through the __ __ __ which results in Spatial Frequency Reuse
Bandwidth Switch Matrix
* For the selectable channel paths, this chooses which beam to route the signal to in the beam combining network.
* Beam Selecting Switching is not applicable to F8+ beams which are all 500MHz (only applies to F1-F7)
75
Subchannels can be routed from any uplink antenna to multiple downlink antennas.
Fan-Out
76
Multiple uplink subchannels (or subchannel groups) from separate uplink coverage areas can be "___ ___" to a single downlink subchannel (or subchannel group) within a single downlink coverage area.
Fanned-in
77
What are some of the differences that came with the Digital Signal Processing (DSP) capabilities of the Widband Digital Channelizer (F8+)?
1. Divides 500 MHz super-channels into 192 subchannels (2.6 MHz) - Legacy divides 125 MHz channels into 48 subchannels
2. Provides TX Subchannel Automatic Level Control (SALC) - Legacy provides TX channel (not subchanne) ALC
3. Provides RX and TX suchannel limiters - legacy does not provide subchannel limiters
4. Provides RX and TX subchannel power meters - legacy provides only RX subchannel power meters
5. Provides RX and TX subchannel phase offset adjustment - legacy does not does provide this
78
Difference between F1-F7 Channelizer Switch and F8+ Channelizer Switch:
1. F1-F7 - 2 stages
F8+ - 3 stages (ingress, middle, egress)
2. F1-F7 - subject to back-plane routing constraints resulting in some blocked routing scenarios. F8+ - utilizes Re-Arrangeable Non-Blocking (RANB) design that allows existing traffic to be rerouted to allow new traffic to be routed without disruption
3. F1-F7 - 48 x 125 = 6,000 MHz capacity
F8+ - 28 x 500 = 14,000 MHz capacity
79
Automatic Level Control (ALC) has three modes:
Linear (bypass) Mode
Constant Power Mode
Limiter Mode
80
ALC is implemented at the __ side of the channelzer
TX
81
Nominally ALC will be enabled in which modes for F1-F7 and F8+?
F1-F7 = Limiter Mode (across the entire channel)
F8+ = Constant Power Mode (across selected subchannels group)
82
F8+ utilizes a new SALC that allows power to be level controlled...?
Across subchannels or group instead of entire channels.
83
Channelizer switch resource planning for F8+ is made via?
GSCCE whereas legacy satellites are through CNPS
84
Spectrum Monitoring System (SMS) is used interchangeably with what?
Spectrum Information Gather (SIG)
85
Channelizer only supports simultaneous operation of ___ SMS processes/scripts
two
86
What is SMS?
Permits monitoring segments of the uplink spectrum via a common downlink segment
This utilizes channelizer multicast capability to simultaneously route selected uplink segments to a monitoring downlink as well as the intended comm downlink
87
This utilizes channelizer digital switching/signal routing capability to select alternate in-band command channels when the current command channel is lost.
Command Channel Search
CCS
88
The ___ ___ ___ is what supports the CCS algorithm
Spacecraft Control Process (SCP)
89
This is an algorithm in the Spacecraft Control Processor (SCP) that provides the ability for the SCP to respond to certain payload faults.
Payload Fault Protection (PFP)
The PFP has 42 "test" in use
90
The __ ___ __ antenna design allows the total output power of the array to be distributed as specified by the planner.
TX phased array
This means the total array output power can be placed in a single beam or eventy distributed between beams.
91
The TX array power distribution is controlled by __ __ __ attenuator settings.
Beam Driver Assembly (BDA)
92
The SMS and CSS is utilized for F7 via CNPS whereas the F8+...?
uses GSCCE
93
This segment is comprised of equipment that receives and transmits signals to the satellite from earth.
Ground segment
These can vary from hand-held devices to fixed or mobile terminals
94
It is a characteristic of electromagnetic transmission that __ __ in a channel increases as the channel BW increases.
noise power
95
Increasing the ___ of a satellite transponder can expand the number of available channels.
amplification (transmit power)
*** however, more power requires more weight, so the number of channels also affects the launch weight limitation of the delivery vehicle. This necessitates the use of other means to increase capacity (i.e. multiple polarization techniques)
96
Greater BW increases throughput capacity only if the conditions in all parts of the transmission signal path can be adjusted to minimize the __ and to maximize the signal power to noise ratio without distorting the signal.
noise
97
The use of multiple ___ ___ increases the number of channels per satellite and allows USMILSATCOM users to stay within globally mandated bandwidth allocations
polarization techniques
*** The satellite's large footprint covers about 1/3 of the earth's surface
98
What are the modes of access?
FDMA
TDMA
NCW
SSMA
OFHMA
99
Which mode of access does a majority of WGS/DSCS traffic use?
FDMA
100
This mode of access is associated with early cell phones.
SSMA
Spread Spectrum Multiple Access
101
This mode of access provides anti-jam (AJ) SATCOM support.
OFHMA
Orthogonal Frequency-Hopping Multiple Access
102
How does FDMA work?
Users access the satellite transponder by transmitting carriers at different frequencies within the same channel.
103
What are the advantages of FDMA?
1. No special circuitry or equipment required
2. No network timing (like TDMA) required
3. Voice can be transmitted in normal analog form
4. Very high data rates
5. Relatively inexpensive
104
What are the disadvantages of FDMA?
1. Vulnerable to jamming
2. Intermodulation products waste power and add noise to the signal
3. Operating frequencies must be carefully selected to reduce intermodulation
4. Uplink power coordination is required
5. Requires guard bands which waste space
105
How does TDMA work?
Each earth terminal in a TDMA network is assigned a specific time slot to transmit and all uplinks use the same transmit frequency
106
What are the advantages of TDMA?
* Very efficient in terms of used BW
* High data rates
* Minimal earth terminal power coordination
* No intermodulation distortion for the carriers in the TDMA
Network
107
What are the disadvantages of TDMA?
* Very vulnerable to jamming
* Requires network timing, synchronization markers and
preamble coding
* Not suited to analog signals
* Requires 3 to 6 dB more transmit power
* Costly
108
How does SSMA work?
* Each earth terminal is assigned a specific transmit and receive
code.
* All users transmit in the same bandwidth simultaneously.
* Users employ signals which occupy a significantly larger
bandwidth than the symbol rate.
109
What are the advantages of SSMA?
* Very jam resistant
* Enemy cannot tell how much
data is being transmitted
* No guard bands required
* All terminals transmit on the
same frequency
* Low peak power required
* It can transmit under a FDMA or
TDMA signal.
110
What are the disadvantages of SSMA?
* Requires careful network planning, timing and synchronization
* Data rates generally lower and are greatly reduced if operating
in an anti-jam mode
* Is not well suited to analog signal formats
* Very costly
111
The signal transmitted from a ground terminal antenna up to a satellite is called an ___, and the transmission from a satellite to a ground terminal antenna is called a ___.
uplink
downlink
112
The most common type of MILSATCOM antenna is the ___ ___ which focuses the radio waves it collects into the opening of the waveguide.
parabolic dish
113
What pieces of equipment at the antenna site can restore the signal to a useful level for processing?
Reflectors, low noise amplifiers, and sophisticated receivers
114
The __ of an antenna is a measure of its ability to concentrate energy being beamed to or from the satellite.
gain
115
An antenna can be designed and ___ to focus a signal into a desired area.
shaped
116
If the dish is large, then..?
It will pick up more signals from space and be able to transmit with less power
117
If the dish is small, then...?
It will pick up fewer signals from the satellite and require more power.
118
If the low noise amp is powerful, then..?
The dish is small and less expensive
119
If the low noise amp is not so powerful, then...?
The dish must be bigger and more expensive
120
If the dish is close to the center of the footprint, then...?
The dish is small and the low noise amp does not need to be so powerful
121
If the dish is far from the center of the footprint, then...?
The dish must be larger and the low noise amp more powerful
122
What is JWICS?
Joint Worldwide Intelligence Communications System
123
Terminals are categorized by type. What are these types?
Anchor Stations: this consists of strategic or enterprise terminals
Mobile Terminals: this includes tactical and transportable, airborne terminals (fast mover) and shipboard terminals (C4I)
124
What is the terminal signal theory?
Uplink - the ground segment receives IF signals from one or more modulators, converts them to satellite uplink carrier frequencies, amplifies the carriers' power level, and transmits them to a satellite.
Downlink - the ground segment receives the satellite downlink signals, amplifies the signals, converts the signals to IF, and feeds them to one or more demodulators
125
What are the components to a terminal/ground segment?
Antenna
LNA/LNB
Transmitters (HPA)
IPAs
Upconverters
Downconverters
Modems
126
Earth terminals are broken down into three categories. These are...?
1. Standardized Tactical Entry Point terminal
2. Teleport Terminal
3. Monitoring Terminal
127
This terminal is a specially equipped strategic earth terminal designed to allow tactical terminals access to the Defense Information Systems Network (DISN)
STEP
128
___ dictates which strategic earth terminals can be used as STEP sites
DISA
129
The STEP program is not determined by a matter of SATCOM equipment compatibility, but instead by...?
Services that the data level user can provide
130
This terminal program is an extension of the STEP program.
Teleport
*** These terminals are strategic earth terminals equipped with the capabilities to access military and commercial C, X, Ku, Ka UHF, EHF and AEHF band satellites.
131
This terminal is any strategic earth terminal with the equipment to support spectrum monitoring functions, either WSOC's terminal, co-located, or remote.
Monitoring
*** AKA - MET terminal
132
The WSOC utilizes __, ___ and __ from METs to control and monitor multiple satellies at a time.
HPAs, LNAs and antennas
133
Explain the difference between strategic,operational and tactical levels.
Strategic - This level involves a strategic concept, plans
for preparing all national instruments of power for war or conflict, practical guidance for
preparing the armed forces, and leadership of the armed forces to achieve strategic
objectives.
Operational - The operational level is concerned with employing military forces in a theater of war or
theater of operations to obtain an advantage over the enemy and thereby attain strategic
goals through the design, organization, and conduct of campaigns and major operations.
Tactical - In the traditional sense, the various operations that make up a campaign are themselves
made up of maneuvers, engagements, and battles. From this perspective, the tactical level
translates potential combat power into success in battles and engagements through
decisions and actions that create advantages when in contact with or in proximity to the
enemy.
134
Which delta is in charge of SATCOM management, personnel, and facilities for RSSCs, operations and maintenance for WSOCs and provides WGS, DSCS and GBS SSE (SATCOM System Expert)
Delta 8
"The Task Force"
That's me!
135
Who is in charge of:
* Being the focal point for engineering, operational, and technical expertise for assigned systems.
* Supports the USSPACECOM integrated management framework to assess, plan, analyze, and integrate SATCOM.
* Manages assigned systems to ensure that standardized, high quality, integrated SATCOM.
SATCOM Office
136
Who is in charge of:
* Planning and coordinating Wideband transmission requirements.
* Creates Satellite payload reconfigurations and restoral plans.
* Analyzes requirements for day-to-day users.
RSSCs
137
Who are the Space Ops Squadrons?
53rd SOPS
4 SOPS
138
What is the difference between what 53rd SOPs and 4SOPS provides?
53rd SOPS -
Wideband Payload Control
Wideband Network Control
4SOPS -
Wideband Bus Control
MILSTAR Payload and bus control
EPS Payload and Bus control
139
What agencies are all involved in MILSATCOM?
1. Joint Chiefs of Staff (JCS)
2. Commander United States Space Command (USSPACECOM)
3. Combined Force Space Component Command (CFSCC)
4. Task Force - SATCOM/Del 8
5. SATCOM Office
140
Who is in charge of:
* Providing operational policy, guidance, and procedures for the planning, management, employment and use of SATCOM resources.
* Resolves conflict regarding satellite allocations and user precedence.
Chair of the Joint Chiefs of Staff (CJCS)
141
This person has operational and configuration authority for SATCOM on-orbit assets, control systems, and terminal infrastructure, including DOD gateways deemed necessary for the effective and efficient operation of SATCOM for the DOD.
Commander USSPACECOM
142
They serve as the Commander's senior staff representative concerning SATCOM.
J6
*** Falls under USSPACECOM
143
They integrate, synchronize, and ensure continuity of SATCOM support and serves as lead GBS Theater Information Manager (TIM)
J66
*** Falls under USSPACECOM
144
They provide leadership and oversight for implementation of Information Assurance (IA) policies for space systems.
J67
*** Falls under USSPACECOM
145
Who is in charge of:
* Conducting Space Force Enhancement to deliver tailored space effects, which includes SATCOM to US and coalition forces.
* Directs electromagnetic interference (EMI) activities documentation and develops TTPs.
Combined Force Space Component Command (CFSCC)
146
Who is responsible for the following:
* Providing SATCOM management and resources in support of Commander USSTRATCOM and Commander CFSCC
* Provides facilities, management, and personnel for Regional SATCOM
Support Centers (RSSC).
* Provides facilities, management, personnel, operations, and maintenance
for Wideband SATCOM Control Centers (WSOC).
Task Force SATCOM
147
Who is responsible for:
* Provides direct support to CFSCC and Commander USSPACECOM as the focal point for engineering, operational, and technical expertise for assigned
systems.
* Provides support for global payload resource management, global
situational awareness, and resolution and mitigation of SATCOM
interference anomalies.
* Cooperatively manages assigned systems to ensure that standardized, high
quality, integrated SATCOM resources are provided to customers.
* Responsible for establishing management structures that will enable
seamless integration between system segments and resolution of operational
issues.
* Maintain oversight by directing, coordinating, and consolidating specified
actions and products, as well as maintaining situational awareness over
related activities and implications to assigned systems.
Wideband Consolidated SATCOM Systems Expects (C-SSE) Responsibilities
148
Who is responsible for:
* Maintain expert knowledge and are focal point for engineering, operational,
and technical expertise for assigned systems.
* Provide direct support to Wideband C-SSE and indirect support to
USSPACECOM, CFSCC, EMI mangers, SATCOM acquisition activities, and
future SATCOM activities.
* 24 hour-a-day asset.
WGS, DSCS and GBS SATCOM System Expert (SSE)
149
Who is responsible for:
* Provide a single point of contact and direct support for Space Force
Enhancement SATCOM resource planning, link engineering, deliberate
planning, current action planning, crises action planning, modeling, and
apportionment support for Wideband authorized users.
* Plan and coordinate MILSATCOM transmission requirements, satellite
payload reconfigurations, and restoral plans.
* Process validated SARs for their assigned Combatant Commands and other
users
* Produce SAAs that describe specific plans for the mission's usage of satellite
resources
* Resolve conflicts between users for mission accomplishment
Regional SATCOM Support center (RSSC)
150
How many RSSC asssignments are there?
RSSC-West
RSSC-East
RSSC-Europe
RSSC-Pacific
151
EW0012-19
What does the "E" in the above signify?
Designates the RSSC that planned the mission.
C = RSSC EAST (CONUS)
E = RSSC EUR
W = RSSC WEST
P = RSSC PAC
152
EW0012-19
What does the "W" in the above signify?
Designates the frequency band(s) the mission will use
W = Wideband (X/KA Band)
C = Commerical (C/Ku Band)
153
EW0012-19
What does "0012" signify?
Indicates the order the mission was processed at the RSSC
154
EW0012-19
What does the "19" signify?
Indicates the year the mission started.
155
These are the roles and responsibilities of who?
* ___ are assigned tasks that include providing global Wideband
MILSATCOM payload control, telemetry monitoring, and transmissions
control in support of DSC and SSA.
* ___ provide monitoring and control of Wideband MILSATCOM terminals
and satellites, maintain Wideband MILSATCOM terminal transmissions
quality, ensure health and welfare of Wideband satellites, and execute
restoral plans in the event of a Wideband MILSATCOM satellite anomaly.
WSOC
156
How many WSOCs are there?
Five
Delta A-E
Delta A - Fort Detrick (WGS/DSCS)
Delta B - Fort Meade (WGS/DSCS)
Delta C - Germany (WGS)
Delta D - Hawaii (WGS/DSCS)
Delta E - Buckner (WGS)
157
Who is responsible for:
* ___ is responsible for conducting on-orbit operations and performing
platform (bus) control operations for WGS and DSCS satellites in support of
Wideband MILSATCOM missions.
* ___ provides monitoring and control of WGS and DSCS satellite platform
(bus) functions, maintains satellite attitude, ensures satellite health and
welfare, and executes restoral actions in the event of a satellite anomaly.
4 SOPS
158
Special users of the WGS and DSCS are provided what?
a block of bandwidth and power and are free to exercise full control over all carriers within their respective networks as long as the assigned bandwidth and power is not exceeded
159
Each sub network will designate at least one of its terminals as a...?
SUBNET Controller
*** This is for Special Users to access
160
Explain the X-Band Block Uplink Terminal Signal flow.
1. Mods
2. I/F P/P
3. Upconverters
4. Combiner
5. Amplifiers
6. Terminal
7. Satellite
161
Explain the X-Band Block Downlink Signal flow.
1. Satellite
2. Terminal
3. LNA
4. Splitter
5. Downconverter
6. I/F P/P
7. Demods
162
Explain Ka-Band block TerminalUplink Signal flow.
1. Mods
2. L-Band Combiner
3. Primary/Redundant Block Upconverter
4. Final Power Amplifier
5. Terminal
6. Satellite
163
Explain Ka-Band block Downlink Signal flow.
1. Satellite
2. Terminal
3. LNA
4. Primary/Redundant Block Downconverter
5. L Band Divider
6. Demods
164
This is the process by which the properties of a wave, called a carrier wave, are varied in accordance with a defined function (or method).
Through this process, digital data can be encoded in an analog signal, transmitted over longer distances, and then recovered in its original digital format via demodulation.
Modulation
165
This allows signals to be routed through their normal paths or to be interrupted and routed for tests or contingencies.
Patch Panel
166
These take a series of inputs and combine them into a series of smaller outputs. In X-Band this can be a 4-way ____, that takes 24 inputs from a series of upconverters and combines them into 12 outputs.
Combiners and Dividers
167
This takes a frequency like 70MHz and converts it to a different frequency for another piece of equipment to use.
Frequency converters (upconverters/downconverters)
*** A piece of equipment that does this at the WSOC is the FCS - Frequency Conversion Subsystem
168
In ground terminals, the conversion that takes place at the FCS happens to prepare it for...?
amplification
169
An ___ is a frequency translating device that is characterized by the frequency of the output signal being greater than the frequency of the input signal.
Simplified Upconverter
170
An upconverter takes an intermediate frequency (IF) of __MHz form the modem and translates it to a frequency between __-__MHz.
70 MHz
7900-8400 MHz
171
A __ is a frequency translating device but it is characterized by the frequency of the output signal being less than the frequency of the input signal.
Simplified Downcoverter
172
A downconverter takes a receive frequency between __-__ MHz and translates it to an intermediate frequency (IF) of __MHz for the modem
7250-7750 MHz
70Mhz
173
A ___ ___ is a frequency translating device that accepts multiple IF input frequencies from multiple modems.
Block Upconverter/Block Downconverter
174
Unlike simplified upconverters, block upconverters do not have progammable frequency ranges; frequencies are changed by...?
adjusting the IF output
175
This is a device that provides amplification. This is a process of providing an increase in amplitude.
Amplifier
176
This is a term that describes the size of a signal.
Amplitude
177
In the MILSATCOM environment, amplifiers are used to...?
Boost the signal levels within a user's uplink and downlink equipment, and within the satellite communications payload.
178
An amplifier is an active device that causes an increase in the magnitude of a..?
current, voltage or wattage
179
The task of an __ __ is to amplify a relatively narrow band of frequencies and attenuate all others.
RF amplifier
180
There are two basic types of RF amplifiers used in satellite communications. What are they?
* Small input signal RF amplifier (LNA)
* RF power amplifier (HPA)
181
Which RF amplifier is the following describing:
These amplifiers are designed to be drive by very small input signals, such as a signal that has traveled 22,600 miles from the satellite to the ground station, or from the ground station to the satellite.
Small input signal RF amplifier (LNA)
182
Which RF amplifier is the following describing:
These RF amplifiers are designed to take relatively high-amplitude RF input signal, amplify it, and produce enough power output to drive another high-power amplifier, exit a transmitting antenna, or operate other loads.
RF power amplifier (HPA)
183
In the transmit path, a amplifier is used for amplification of RF signals to...?
a level sufficient to overcome path loss between the user equipment and the spacecraft.
184
Some common transmit amplifiers are:
1. Intermediate Power Amplifier (IPA): Uplink Line Amplifier Assembly (ULAA)
2. Final Power Amplifiers: Traveling Wave Tube Amplifier (TWTA), Solid-Sate Power Amplifier (SSPA), High Power Amplifier (HPA)
185
In the receive path, an amplifier boosts the signal level of the received signal to...?
A level sufficient to drive subsequent downlink equipment and support the user's signal quality requirements.
186
Some common receive amplifiers are:
1. Low-Noise Amplifiers (LNA): Gallium-Arsenide Field Effect Transistor (GaAsFET) amplifier
2. Inter-Facility Link Amplifier (IFLA)
3. Downlink Line Amplifier Assembly (DLAA)
187
What does it mean for an amplifier to be linear?
Increased input amplitude produces a corresponding increase in output amplitude
188
What does it mean for an amplifier to be nonlinear?
Increased input amplitude produces less than a corresponding increase in output amplitude.
189
This is defined as the increased input amplitude produces no increase in output amplitude.
Saturation
190
This is one of the main characteristics of amplifier performance. This is the ratio of the output signal strength (amplitude) to the input signal strength.
The amplification factor (µ, or mu)
191
When it comes to the amplification factor, this is the minimum signal required to get a usable output.
Minimum Drive
192
When it comes to the amplification factor, this is the designed power limit of the device. The output will never exceed this value.
Maximum output
193
If any one or more pieces of equipment in the uplink chain alignment fails to perform properly, the rest of the chain must compensate. As the remaining equipment compensates, specifications required of the equipment are not met and...?
signal degradation occurs (i.e. uplink chain linearity is not achieved)
** A common example of this is no attenuation left at the upconverter (the HPAs are not pulling their share of the load)
194
All four HPAs are phase aligned to each other. This means that...?
Each amplifier in a composite of four will complement each other. If one of the four amplifiers are out of phase with the other three, the out-of-phase amplifier acts as an attenuator to the other three.
195
All amplifiers are phase aligned and then...?
power balanced
196
How are amplifiers power balanced?
The HPAs are "power maxed" to determine maximum amplification for each HPA.
They are then backed off 3dB to operate in the linear range of amplification.
The three highest producing amplifiers are backed off to the lowest producing amplifiers ability.
*** This ensures any HPA can be brought on-line or off-line without changing the required total power out (TPO)
197
When all four HPAs are phase aligned and power balanced correctly, any one of the four HPAs can be brought on-line with any of the other two, and all three HPAs compliment each other. If one of three HPAs fail, the composite amplification should not decrease by more than 1.5 dB. This is because...?
Link Margin will compensate for this until another HPA can be brought on-line
198
If amplifiers connected in series are not operating within the linear range, what will happen?
It will heighten intermodulation products
199
Theoretically, the amount of output power available for each signal is..?
less than the total power divided by the number of signal
*** Essentially, the total of all powers added together and then split evenly across each of them.
200
What is "wasted" power?
Intermodulation products (unwanted signals and noise)
201
Operating with reduced output powr capability or lower gain in one or more amplifiers would result in a reduction in each signal's share of available power. Intermodulation power would then become __ __ at these lower power levels since the effective linear operating range would be reduced.
more pronounced
202
The terminal uplink chain should provide a progressive order of saturation; that is, the HPA saturates first, followed by the upconverters, and in some cases modems. The progressive order of saturation ensures that...?
intermodulation products are not generated early in the uplink chain with subsequent amplification by the suceeding amplifiers. If the upconverter saturates before the HPA, excessive intermodulation products will be produced.
203
With block converters, modems have ___ that can be adjusted.
amplifiers
204
The nominal operational Eb/No is __ dB for a satellite link.
9.1 dB
205
The nominal attenuation of an upconverter is __ dB.
30 dB
206
This is utilized extensively throughout the WGS/DSCS in order to reduce the power requirements of a given link.
Forward Error Correction (FEC)
AKA - channel coding
207
How does FEC work?
This technique transmits redundant bits of data to reduce errors in demodulation at the distant end.
208
How do you get gain from coding?
This is realized by the insertion of bits into the information data stream, which enhances the probability of demodulating the intelligence correctly.
209
Actual coding gain is equal to...?
The difference between the Eb/No required without coding and the Eb/No required with coding for the same power.
210
What are the different types of coding?
1/2 Rate Coding: For this encoding scheme, each bit input results in two bits output (high redundancy)
3/4 Rate Coding: For this encoding scheme, each three bits input results in four bits output.
7/8 Rate Coding: For this encoding scheme, each seven bits input results in eight bits output (low redundancy)
211
What is the definition of modulation?
Modulation is defined as the process by which certain characteristics of a
wave, called the carrier, are varied in accordance with a modulating function.
212
What is Phase Shift Keying Modulation?
For PSK, the varied characteristic is the phase and the
modulating function shifts the instantaneous phase of the carrier between
predetermined discrete values.
213
Which PSK Modulation is the following description line up with?
One information bit is sent per phase shift
Binary Phase Shift Keying (BPSK)
214
Which PSK Modulation is the following description line up with?
Two information bits are sent per phase shift
Quadrature Phase Shift Keying (QPSK)
or
Offset QPSK (OQPSK)
215
Which PSK Modulation is the following description line up with?
Three information bits are sent per phase shift
8 Phase Shift Keying (8PSK)
216
In Wideband MILSATCOM systems, most modulation schemes are based on...?
phase-shift keying (PSK)
217
Which of the PSK Modulation variations is the following describing?
The modulation scheme shifts a carrier signal between 0 and 180 degrees to
indicate a "0" or "1" data bit.
Modulation occurs when the modulated
signal (a binary data stream) changes the phase of the carrier’s IF as each
transition of the binary signal occurs.
The information content of a ___ signal
is one binary digit (bit) per pulse.
Binary Phase Shift Keying (BPSK)
218
Which of the PSK Modulation variations is the following describing?
A modulation scheme which breaks digital traffic into two separate channels
and represents the four possible bit combinations of these two channels by
shifting a carrier signal between 45, 135, 225, and 315 degrees.
Quadrature Phase Shift Keying (QPSK)
*In QPSK,
two separate data sequences are simultaneously BPSK modulated on to
quadrature versions of the same carrier, referred to as I channel and Q
channel
By dividing the digital modulating stream into blocks of two bits and relating
every possible two bit combination to a specific phase shift angle, two binary
bits can be transmitted per pulse (symbol), one in each channel.
219
What are the four possible combinations that can be realized with two binary digits?
00
01
10
11
*** The four distinct phases of the carrier represent the four possible combinations of two digits.
220
In QPSK, the symbol rate is...?
Half of the information rate
221
The following describes which variation of PSK?
Attempts to alleviate
the problem with QPSK by defining a signal set such as having the phase never changes
more than 90 degrees between any two signals in the sequence.
Offset QPSK
*** One of the practical problems encountered when implementing QPSK is the need to produce 180 degree phase shifts in the signals in very short time intervals. The finite amount of time that is necessary to accomplish this phase
shift results in slowing down of the bit rate.
222
Both ___ and ___ appear identical on the downlink spectrum with clock nulls on both sides of the carrier at approximately the 3 dB point.
QPSK and OQPSK
223
In Offset QPSK (OQPSK), the __ channel is offset from the __ channel by one half the bit period, so that only transitions involving one of the bit pairs are possible.
In an OQPSK system, the symbol rate is one half the information rate.
Q
I
224
In this variation of PSK, a third bit stream is created but not fed into its own dedicated channel. Instead, the third bit further modifies the phase of the BPSK modulated I and Q channels before they are summed. The value of the third bit determines if either the I or the Q channel phase is modified, and only one channel is modified per third bit. These three modulating bits create eight possible combinations of bits and thus there are now eight possible phases.
8PSK
225
A modulation scheme which conveys data by changing (modulating) the
amplitude of two carrier waves. These two waves, usually sinusoids, are out
of phase with each other by 90° and are called quadrature carriers. This
allows each shift to represent more bits than would be allowed with PSK.
Quadrature Amplitude Modulation (QAM)
226
How many bits per shift are there in 8QAM?
3
227
How many bits per shift are there in 16QAM?
4
228
How many bits per shift are there in 64QAM?
5
229
How many bits per shift are there in 128QAM?
6
230
How many bits per shift are there in 256QAM?
7
231
The closer that the dots on a constellation diagram are makes them more susceptible to noise or other corruption. This results in...?
higher bit error rate but more data
232
In regards to QAM:
By moving to a higher-order constellation, it is possible to transmit more bits per symbol. However, if the average energy of the constellation is to remain the same (by way of making a fair comparison), the points must be...?
closer together
233
Wideband SATCOM uses ___ inside the modem to shape the main lobe and reduce the remaining side lobes to a point below the noise floor of the
transmitting and receiving equipment.
filters
*** In modern modems, this shaping is
accomplished by smoothing out the hard
transitions between the 1’s and 0’s, which
achieves the same effect as the old
physical filters in legacy modems.
234
Most of the power of the carrier resides at the...?
peak of the signal between the nulls
235
What is the "occupied bandwidth"?
The bandwidth of the carrier that contains 99% of the integrated power, centered on the assigned frequency.
(see slide 30 Terminal Signal Theory for pic reference)
236
This value is what CNPS uses to calculate carrier placement, adjacent carrier and co-channel interference values and whether or not a carrier impinges on another carrier or guard bands.
occupied bandwidth
237
When the demodulator switches back and forth between phases to detect the phase shifts, it cannot determine which phase represents a 1 and which phase represents a 0. Therefore, a phase shift keying process, is used to resolve the zero/one ambiguity.
Differential Encoding
238
Does Differential Encoding produce any process gain (coding gain)?
No
239
This used to denote how many times
the phase is changed in transmission of the information.
Symbol Rate or Transmission Rate
*** This is sometimes
called the signaling speed and given in pulses per second.
240
Symbol rate does or does not convey how many information bits per second are being transmitted?
Does not
241
Symbol rate can be measured in...?
Hertz or Symbols per second
** These terms are used interchangeably
242
There are a number of contexts when discussing bandwidth. What are the three predominant ones?
Signal Bandwidth
Filter Bandwidth
Channel Bandwidth
243
Which Bandwidth is the following describing?
a measure of the frequency spectrum occupied by the signal.
signal bandwidth
*** In ideal conditions, the channel BW and the signal BW will match.
244
Which Bandwidth is the following describing?
the frequency range passed by circuit filters.
filter bandwidth
245
Which Bandwidth is the following describing?
the overall bandwidth of the transmission channel.
Channel Bandwidth
*** In ideal conditions, the channel BW and the signal BW will match.
246
The performance of a digit link is measured in terms of average __ __ __ at the digital output of the link (the demodulator)
bit error rate
247
The average bit error rate (BER) is determined by...?
dividing the number of bit errors by the total number transmitted
248
In MILSATCOM operations, the standard BER performance is...?
10^-6
=
1 error in every 1,000,000 bits of data
249
This is obtained by measuring the signal strength of the carrier over the noise density.
(C+N)/N
Carrier Plus Noise to Noise Factor
250
This is the only performance measurement you can get from the spectrum analyzer
Carrier plus Noise-to-Noise Factor (C+N)/N
251
This is converted from (C+N)/N. In doing so, you can calculate either the Energy per bit to Noise ratio (Eb/No) or Carrier to Noise Density (C/kt.)
C/N
Carrier to Noise Ratio
252
This is a ratio of the energy density above noise density (per Hertz) required to
provide a specific BER.
Energy per bit to Noise Ratio (Eb/No)
253
The PSK modem performance is generally defined by the probability of error
expressed as a function of ___ required to realize a given performance.
Eb/No
254
What are the two types of Eb/No used in SATCOM?
Two types of Eb/No are used in SATCOM:
* Operational (Nominal) Eb/No
* Minimum Eb/No required for Modem Performance
255
The C/N and Eb/No can be interrelated to provide a simple method for
measuring the Eb/No from the C/N by use of formulas. This is referred to as:
Modulation Correction Factor (MCF)
256
This is the received carrier power to noise power density in a given bandwidth
expressed in dB
Carrier to Noise Density (Per Hertz) (C/kT)
C = Ratio of RF signal RX, or carrier level, at the Earth terminal
* k = Boltzman’s constant (-198.6 dBm/K)
* T = Receiving systems noise temperature
* kT is the noise power in a bandwidth of 1 hertz
257
There are two methods that can be used for system performance calculations. These are...?
The Textbook Method
The Symbol Rate Method
258
This method refers to the typical theoretical formula used to determine C/kT or Eb/No
The Textbook Method
C/kT = Eb/No + 10 log (TDR)
Eb/No = C/N + 10 log (ICSR/TDR)
Eb/No = C/N + 10 log (2/Ø x 1/Rc)
TDR = Transmit Data Rate
ICSR = I Channel Symbol Rate
Ø = number of phases (BPSK=2, OQPSK=4)
Rc = coded rate (u/c = 1, 1/2 rate = 0.5, 3/4 rate = 0.75)
259
This method refers to a short cut from the theoretical one which computes C/kT directly from the C/N and the ICSR when they are known.
The Symbol Rate Method
C/kT = C/N + 10 log (ICSR)
260
A satellite communications system can be power or bandwidth limited, or both. Continuous __-__ ___ must be performed to determine which links will use BPSK or QPSK modulation, with or without coding, to achieve maximum
use of the fixed satellite power and frequency spectrum assets.
trade-off analysis
261
When modems are used, it is normal to have a certain amount of error introduced into the data stream by the modem. A theoretical best BER can be calculated. However, it is very rare to have a modem operating at its theoretical best. The EBEM should be within 2 dB of the theoretical best BER for a given Eb/No. The amount of deviation from this theoretical best BER is the amount of...?
Implementation Loss (equipment loss)
262
All modern modems have an equipment loss of...?
2dB
263
DSCS consisted of how many subsystems?
8
* Attitude Control Subsystem (ACS)
* Propulsion Subsystem (PS)
* Telemetry, Tracking, and Command (TT&C)
* Electrical Power Distribution Subsystem (EPDS)
* Thermal Control Subsystem (TCS)
* Structure and Mechanism Subsystem
* Single Channel Transponder Subsystem (SCT)
* Communications Subsystem (COMM)
264
What components make up the Attitude Control Subsystem (ACS)?
* Attitude Control Electronics (ACE)
* Earth Sensor
* Sun Sensors
* Reaction Wheels
* Rate Gyro
* Propulsion Subsystem Thrusters
265
What is the ACE component in the ACS?
Heart of the ACS (microcomputer w/peripherals) consists of CPU, RAM, a
hardened RAM (HRAM), PROM, and seven peripherals: reaction wheels,
thruster, solar array drive, sensor analog to digital, telemetry and command interface, GDA drive electronics, and MBA BFN interface electronics.
*** The brain of the satellite
266
Which subsystem of DSCS is the following describing?
* Provides the capability to command the satellite and receive telemetry via
redundant X-band (SHF) and S-band (UHF) links.
* If commands come simultaneously from either link, S-band or X-band, Xband has priority over S-band.
* If commands are on the same link, the command decoder establishes priority
to prevent interference.
Telemetry, Tracking and Command (Control) TT&C
267
What are the output frequencies for DSCS beacons?
The output frequencies are 7600.000000 MHz for beacon A and
7604.705882 MHz for beacon B.
268
Where are the DSCS beacons located in the guard band frequency?
between channels 4
and 5
269
What is the purpose of "pseudo-beacons"?
Operation Centers (OCs) sometimes will have a pseudo-beacon transmitted on the reserve satellite so users can tell the difference between the prime satellites and the reserve satellites
270
The following describes which subsystem in DSCS?
* Converts solar energy to electrical energy.
* Regulates and distributes power to the satellite subsystems.
* Stores electrical energy for subsequent use during eclipse periods.
* Provides the electrical power for all subsystems throughout the life of thesatellite
Electrical Power and Distribution Subsystem (EPDS)
271
The occurrence of a satellite anomaly is a ___ event and may not be discussed in an unclassified environment, via unclassified means, or with individuals without proper clearance and need-to-know.
classified
272
What is "survival" mode of EPDS?
The survival mode of the EPDS operation is a load reduction method of
operation that is employed for either of two contingency modes: 80-minute timer timeout (Mode 1) or loss of Earth lock (Mode 2).
273
How long is the timer timeout for EPDS Survival Mode 1?
80 minutes
*** When this occurs, ALL SHF equipment is turned off and S-band downlink is turned on.
274
What is the biggest difference between EPDS Survival Mode 1 and 2?
All events of Mode 1 take place in Mode 2 in addition to the ACE being turned off
275
The following describes which subsystem of DSCS?
An autonomous active and passive temperature control system consisting of:
* Multi-layer insulation blankets
* Thermal coatings
* Insulation spacers
* RF transparent thermal shrouds
* Locally increased panel thickness
* Thermostats
* Control and survival heaters
* Flight temperature sensors
Thermal Control Subsystem (TCS)
276
Survival heaters are activated during survival mode conditions to maintain satellite-critical temperatures above...?
-24 degrees celcius
277
The following describes which DSCS subsystem?
* Provided secure and reliable dissemination of Emergency Action Message
(EAM) communications from Worldwide Command post ground stations and
aircraft to the Warfighter.
* Received and processed messages and commands transmitted to the DSCS
III satellite from a command post on either an SHF or UHF uplink and
retransmitted on a single UHF downlink channel.
* ___ was deactivated in late 2008 and ground terminals disassembled or
removed.
Single Channel Transponder Subsystem (SCTS)
278
The following describes which DSCS subsystem?
* Provides a flexible wide-band transmission media to users under varying
degrees of system stress.
* User terminals are distributed throughout the world and are of varying sizes.
* Transponder and antennas are changeable to accommodate various
communications needs.
Communications Subsystem (COMM)
279
The beacons on DSCS only apply on the uplink or the downlink?
Downlink
280
What is the translating frequency for DSCS?
725 MHz in all channels except 6 which is 200 MHz
281
The total uplink/downlink spectrum bandwidth for DSCS is...? And the total useable bandwidth is?
500 MHz
375 MHz - useable BW
282
How many communication antennas does the DSCS III satellite SHF have for the transmit side?
* Two 19 beam MBAs (M1X and M2X)
* Earth Coverage Transmit Horns (E1X and E2X)
* Gimbaled Dish Antenna (GDA)
283
How many communication antennas does the DSCS III satellite SHF have for the receive side?
* One 61 Beam MBA (MBR)
* Earth Coverage Receive Horns (E1R and E2R)
284
These antennas are horn antennas that provide coverage for approximately 1/3 of the Earth's surface.
Earth Coverage antennas
285
The __-__ antennas utilize a collection of small beams (singlets) to provide commandable, incrementally selective coverage. The singlets can be
combined with adjacent beams for increased range from single spot to Earth
coverage.
Multi-Beam Antennas (MBA)
286
This is a steerable high gain transmit
antenna that can be pointed at a specific area.
Gimbaled Dish Antenna
287
What are the three different types of coverage areas?
Earth Coverage - Earth Coverage has a diameter of 8000 statute miles
Area Coverage - Area Coverage has a
diameter between
1150 to 2300 statute miles
Narrow Coverage - Narrow Coverage has
a diameter between
400 to 1150 statute miles
288
To be on a common frame of reference, a ___ antenna is
what the satellite uses to receive user signals and a ___ antenna is what the satellite uses when it transmits signals to users.
receive
transmit
289
Four DSCS III satellites (A3, B6, B8, B11) have been upgraded in selected
areas to improve performance and extend the DSCS III family’s operational
life. This is done through...?
The DSCS III Service Life Enhancement Program (SLEP)
290
SLEP to DSCS included what kind of improvements...?
SLEP improvements (to include compatibility with 8PSK/16QAM modems) can compact fixed wideband traffic in ECH channels 5 & 6, and allow greater
support to tactical users in channels 1-4
291
With SLEP the useable bandwidth increased to...?
405 MHz
Legacy DSCS only used 375 MHz
292
WGS bus frame is built by...?
Boeing
293
WGS opened the ability to operate in both __ and __.
X-band and Ka-band
294
What is the design life for WGS?
14 years
*** 12 year min station-keeping life
295
What is the difference in solar panels between WGS and DSCS?
WGS - 5 panels
DSCS - 2 panels
296
The many subsystems of the WGS are split between two partitions. What are these called?
1. Bus Module - Includes the Structure, Power, Thermal Control and Orbit and Momentum Control
2. Payload Module - Includes Communications and TT&C
297
The following describes which subsystem of WGS?
The spacecraft structure provides a stable platform that
efficiently distributes launch loads, supports payload and bus
subsystem components, and maintains proper dimensional
relationships that satisfy system requirements relating to integration, test, launch, and on-orbit operations.
This structure is divided into the payload and bus modules.
Spacecraft Structure
under the Bus module
298
The following describes which subsystem of the WGS?
Provides electrical power to all spacecraft subsystems during all
mission phases.
Electrical Power Subsystem (EPS)
299
The following describes which subsystem of WGS?
Provides heat rejection capability for
approximately 9 kW of dissipated power.
Thermal Control Subsystem (TCS)
300
What are the components that make up the ACS on WGS?
1. Attitude Sensors - provides data for attitude determination (Star Trackers & HIRU)
2. Centralized Processing - Computes attitude and provides attitude control and momentum control commands to actuators (Spacecraft Control Processor (SCP))
3. Control Actuators - Maintain attitude and momentum control based on SCP commands (Reaction Wheel Assembly (RWA) and Xenon Thruster (XIPS))
301
What parts make up the On-Station sensor suite?
The on-station sensor suite allows for fully autonomous 3-axis attitude acquisition.
1. Star Trackers - provide inertial star position data
2. HIRU - provides continuous spacecraft body rate data
3. Reaction Wheels - maneuvering capability without thrusters
302
How does Star Tracker work?
* Stars are identified and matched with data in the Flight Star
Catalog in the SCP.
* By identifying at least 2 stars, the SCP can compute spacecraft
attitude in space, however 8 must be identified for continuous
operations.
303
The following describes which subsystem on WGS?
Consists of the Liquid Propulsion Subsystem (LPS) and the Xenon Ion Propulsion Subsystem (XIPS)
Propulsion Subsystem
304
What is the difference between LPS and XIPS on WGS?
The LPS is a bipropellant system that provides the thrust needed from launch
vehicle separation until start of XIPS ascent mode. The LPS is fully
expended by the time the satellite reaches operational orbit.
305
How many XIPS are on WGS?
4 XIPS controlled by 2 XIPS Power Controllers (XPC)
306
Under nominal station keeping conditions, each of the four thrusters is fired __ __ to accomplish all orbit control requirements.
once daily
307
XIPS is used to control...?
Orbit inclination and delta maneuver as well as momentum dumps
308
The following describes which subsystem on the WGS?
Provides telemetry and command processing for the WGS. The subsystem receives commands from the Sband uplink, the In-band uplink, and the spacecraft control processors (SCPs).
TT&C
309
The TT&C subsystem on WGS transmit telemetry via __ modulation.
BPSK
310
Telemetry on WGS can be transmitted at what rates?
1, 2, 4 kbps on S-band
1, 2, 4, and 8 via X-band and Ka-band beacons
311
There are two segments categorized below the TT&C subsystem on WGS. What are they?
1. The RF Subsystem - is made up of two T&C Transponders, two Ka-band 15W Traveling Wave Tube Amplifiers (TWTAs), the forward and aft omni antennas, two Earth coverage X-band antennas, one X-band beacon antenna, and one Ka-band beacon antenna.
2. The digital subsystem - consists of two Central Telemetry and Command Units (CTCUs), two Payload Services Units (PSUs), a T&C Digital Data Bus (DDB), and a Squib Driver Unit (SDU).
312
How many X-Band Beams are on WGS?
18
- 1 RX Earth Coverage
- 1 TX Earth Coverage
- 8 RX Shapeable
- 8 TX Shapeable
313
How many Ka-band beams are on WGS?
10
- 8 RX/TX Narrow Coverage Antenna
- 2 RX/TX Area Coverage Antenna
314
What is the WGS frequency band for X-Band?
Uplink - 7.9-8.4 GHz
Downlink - 7.25-7.75 GHz
315
What is the WGS frequency band for Ka-Band?
Uplink - 30-31 GHz
Downlink - 20.2-21.2 GHz
316
What is the WGS frequency band for S-band?
Space Ground Link System (SGLS):
Uplink - 2.2-2.29 GHz
Downlink - 1.761-1.842 GHz
Unified S-band (USB):
Uplink - 2.4-2.5 GHz
Downlink - 1.98-2.1 GHz
317
WGS operates in what frequency range?
UHF (s-band) 300MHz -3GHz
SHF (x-band) 3GHz-30Ghz
EHF (ka-band) 30GHz-300GHz
318
How many channels are there on the WGS X-Band?
4
319
What is X-Band's spectral bandwidth on WGS?
500MHz
320
What is Ka-Band's spectral bandwidth on WGS?
1000MHz (1GHz)
321
What is X-Band's spectral bandwidth on WGS when using Spatial Frequency Reuse?
1816MHz
322
What is Ka-Band's spectral bandwidth on WGS when using Spatial Frequency Reuse?
2750MHz
323
What is the X-Band Signal Flow for WGS?
1. 8 beam X-Band RX array
2. X to IF Downconverter & BW Switch Matrix
3. Gain Control & IF to Baseband Downconverter (BDCA)
4. Digital Channelizer
5. Baseband to IF Upconverter (BUCA)
5. Beam BW Select and IF to X-band Upconverter
6. 8 beam Tx array
324
What is the Ka-Band signal flow for WGS?
1. Ka to IF Downconverter and BW Switch Matrix
2. Gain Cntrl & IF to BB D/C (BDCA)
3. Digital Channelizer
4. BB - IF U/C (BUCA)
5. Beam BW Select & IF - Ka U/C
325
The WGS has two earth coverage antennas (1 RX & 1 TX) how are these polarized?
ECR (receive) - Right Hand Circular Polarized
ECX (transmit) - Left Hand Circular Polarized
326
The WGS has two X-Band phased arrays (1 RX & 1 TX) How many elements do they each have?
RX (receive) - 188
TX (transmit) - 312
327
When it comes to Phased Array Antennas on the WGS:
This shifts received phase and amplitude settings on each element for each beam.
Beam Forming Modules (BFM)
328
The WGS has 8 Ka-Band Narrow Coverage Gimballed Dish Antennas (NCA). How are they polarized?
Dual polarized
Antennas 1-6 - receive = RHCP and transmit = LHCP
Antennas 7 & 8 - switchable between RHCP and LHCP
329
The WGS has two Ka-band Area Coverage Gimballed Dish Antennas (ACA). How are they polarized?
Antenna 1 - receive = RHCP and transmit = LHCP
Antenna 2 = switchable between RHCP and LHCP
330
NCA7, NCA8 and ACA2 Antennas on WGS Ka-Band are switchable polarization antennas. How is this possible?
Through C-Switches that utilize orthomode transducers (OMT)
331
This piece of equipment on the WGS satellite does the following:
* Digitally filters channel into sub-channels
* Switches sub-channels from input ports to output ports
* Any input sub-channel can be switched to any output sub-channel
The Channelizer
332
How many X-Band Channels are there on WGS?
13 Channels x 125 MHz = 624 subchannels
3 channels x 47MHz = 54 subchannels
1 channel x 50MHz = 19 subchannels
333
How many Ka-band channels are there on WGS?
22 channels x 125 MHz = 1056 subchannels
334
How many total channels (between X and Ka-Band) are there on WGS?
39 channels = 1753 useable subchannels
335
The RX to TX __-__ provides connectivity between RX slices and TX slices.
back-plane
*** Each RX slice has one back-plane connection to each TX slice. 48 subchannels can be transferred across each back-plane connection.
336
What is the Channelizer RX slice composed of?
1. Power Bricks
2. Analog Front Ends
3. Receive ASICs
4. RX Switch ASICs
337
The main component of the digital channelizer is made up of 16 different multi-layer digital circuit boards, commonly referred to as..?
slices
338
How many RX and TX slices are there?
8
339
What does the ASIC do?
Application Specific Integrated Circuit
The Rx ASICs perform an analog to digital conversion on each channel and further channelize each channel into 48, 2.604 Megahertz (MHz), subchannels.
340
Each Rx slice has six input ports and each Tx slice has six output ports; each of which connect to an...?
ASIC
341
Connection between the Rx and Tx slices is facilitated by two layers of switch ASICs. The connections formed
by the switch ASICs form the ___ of the channelizer and through the ___
any Rx subchannel may be connected to any Tx subchannel.
backplane
342
This utilizes the channelizer multicast capability to simultaneously switch the sampled spectrum to the communications downlink and the monitoring downlink.
Spectrum Information Gathering System
343
How many SIG scripts can be simultaneously gathered?
The channelizer supports (these are referred to as SMS1 and SMS2)
344
Which satellites are WGS Block I and Block II?
WGS is divided into different blocks of satellites based on when they were laucnhed and the capabilities included.
Block I - WGS1 (F1), WGS2 (F2), and WGS3 (F3)
Block II - WGS 4 (F4), WGS 5 (F5), and WGS 6 (F6)
345
What are some of the notable updates from WGS Block I to Block II?
1. Ka RF Bypass created
2. ACS HIRU replaced with SSIRU - this is due to the parts being obsolete
3. ACA antennas diameter matches NCA antennas and were moved to the outside of the pallet
4. TOES removed - Transfer Earth Orbit Sensor was removed due to Star Trackers
346
This allows users to bypass the baseband downconverter assembly, channelizer and the baseband upconverter assembly.
This allows for users requiring more than 125 MHz to be supported with the 400 MHz bypass channel (i.e. predator feeds)
RF Bypass
347
There are two bypasses provided two independent paths. What are they?
Bypass 1 - NCR 4 to NCX 6
Bypass 2 - NCR 5 to NCX 3
348
The RF Bypass function is available in the __-band only
Ka-Band
349
What does CAMP stand for?
Channel Amplifiers
350
This section amplifies the RF bypass channel to compensate for power losses incurred from the hybrid network and adds gain control capabilities. This adds functionalities normally provided by the Channelizer.
It also provides two modes of operation: FGM and ALC.
CAMP
351
How many hemispherical resonator gyros are a part of the Block II WGS SSIRUs?
4
