Air Force Satellite Control Network (AFSCN) - Responsive Space

6th Responsive Space Conference
RS6-2008-1006
Air Force Satellite Control Network
(AFSCN) Support for Operational
Responsive Space (ORS)
Len Hodges
50 th Space Wing, Plans & Programs Office
(50 SW/XPP)
Ron Woll
50 SW/XPP & HQ AFSPC/A3RN (Scitor Corp.)
6th Responsive Space Conference
April 28–May 1, 2008
Los Angeles, CA

AIAA-RS6-2008-1006
Air Force Satellite Control Network (AFSCN)
Support For
Operational Responsive Space (ORS)
Len Hodges
AFSCN Program Support Manager (PSM)
50th Space Wing, Plans & Programs Office (50 SW/XP)
210 Falcon Parkway, Schriever AFB, CO 80912
DAF Civilian, (719) 567-2967
Len.Hodges@Schriever.Af.Mil
Ron Woll
50 SW/XPP & HQ AFSPC/A3RN
AFSCN Systems Engineer
Program Requirement Analysis
Scitor Corp, (408) 489-2688
Rwoll@Scitor.Com
ABSTRACT
The AFSCN is a common user, satellite control network that supports the Department of Defense (DoD), the
Intelligence Community (IC), National Aeronautics and Space Administration (NASA) and National Oceanic and
Atmospheric Administration (NOAA) programs. The AFSCN can provide a worldwide network communications
infrastructure to ORS programs that should be considered as primary ground communications architecture for ORS
planning and requirements. There is no charge for DoD or IC use of the AFSCN. Currently the AFSCN has eight
remote ground facilities (RGFs) located around the world with a total of 15 antennas or remote tracking stations
(RTS). Future plans are to expand to 10 RGFs with 19 RTSs. The tracking stations operate in the L-band for uplink
and S-band downlink (e.g. Space Ground Link Subsystem [SGLS]). Future plans are to also include S-band for both
up and down link communication (e.g. Unified S-Band [USB]). The AFSCN is composed of three segments: the
Range Segment, consisting of 15 RTS, which provides the ground to spacecraft interface; the Communication
Segment which connects the RTS to the two Operational Control Nodes (OCN); and the Network Management
Segment which provides network scheduling and network status. The user must provide the command and control
(C2) system (i.e. SOC), and have a scheduling and communications control interface to the AFSCN. The user must
build a RTS configuration database (includes the uplink frequency, command rate, downlink frequency and signal
format, etc.). As a common user network each user’s requirements are satisfied according to their mission priority.
The user submits a schedule request to the AFSCN Network Operations Center (NOC) for arbitration. The AFSCN
can be used by ORS to provide ground system to space craft communications. This provides satellite Telemetry,
Tracking and Commanding for the satellite bus and possibly the payload. NOTE: Although the ground system is
many times the last piece of the puzzle in a satellite program, it is a necessity that cannot be placed at the end of the
planning and funding cycle. Whether the AFSCN is used or not, the ORS ground system must be planned at the
same time as the space craft and tested with the space craft before launch. (i.e. a critical lesson learned).
This paper is declared a work of the U.S. Government
and is not subject to copyright protection in the United
States.
AFSCN
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AIAA/6th Responsive Space Conference 2008
The AFSCN is a common user, unclassified network
where all users share the network within a disciplined

AIAA-RS6-2008-1006
network schedule. The AFSCN is composed of three
segments: range, communications and network
management. Each segment will be addressed below. A
complete definition for all segments is available in the
System Interface Specification listed in the supporting
documents of this paper.
The AFSCN is a global network consisting of eight
ground locations with 15 remote tracking stations
operating in the (SGLS) frequency spectrum. The
primarily northern hemisphere tracking stations provide
support for Low Earth Orbit (LEO), Medium Earth
Orbit (MEO), Highly Elliptical Orbit (HEO),
Geosynchronous Earth Orbit (GEO) and L1 & L2 (i.e.
first and second Sun-Earth Libration [or Lagrange]
Point) orbits. In progress network upgrades will add a
16th remote tracking station at Diego Garcia about FY-
10. There is also an initiative to become interoperable
with multiple space networks (e.g. GPS, NASA-
NOAA) that could affectively increase the network to
even more available tracking stations.
AFSCN Resources
OAFS
Onizuka Control Node
Onizuka Air Force Station
Sunnyvale, CA
NHS
New Hampshire Station
New Boston AFS, NH
TTS
Thule Tracking Station
Thule AB, Greenland
TCS
Telemetry & Command
Squadron
Oakhanger, England
VTS
Vandenberg Tracking Station
Vandenberg AFB, CA
GTS
Guam Tracking Station
Andersen AFB, Guam
HTS
Hawaii Tracking Station
Kaena Point, HI
SAFB
Schriever Control Node
Schriever AFB, CO
KEY TO SYMBOLS
Operational Control
Node
Remote Tracking
Station (RTS)
CTS
Colorado Tracking Station
Schriever AFB, CO
TSTR
Transportable Space Test
Resource
Kirtland, AFB, NM
TVCF
Transportable Vehicle
Checkout Facility East
Cape Canaveral AFS, FL
DGS
Diego Garcia Station
Brit. Indian Ocean Terr.
Diego Garcia Island
Transportable ARTS
Core
Transportable
Antenna
Range Segment
The range segment is the actual ground stations
composed of the core electronic equipment and the
antenna. The antennas are currently a mixture of several
sizes ranging from 10 meters to large, high power 60
foot diameter dish. The current upgrade will replace all
antennas with a three axis, 13 meter antenna to provide
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network standardization. The AFSCN operational
frequency spectrum is L band, 1760-1842 MHz, uplink
and S band, 2200-2300 MHz, downlink. With the
completion of the RTS Block Change (RBC) upgrade
an S band, 2025-2110 MHz uplink will be included
along with the current S band 2200-2300 MHz,
downlink capabilities. The RTS electronics core allows
multiple common data formats to support the user

AIAA-RS6-2008-1006
needs. It is vital for early integration of the AFSCN
engineering personnel with the satellite program
engineering personnel to define and coordinate the
wave forms, and the power requirements and the
network availability (i.e. loading analysis).
Communication Segment
The AFSCN communications architecture is Node
centric. Node centric means all users access the AFSCN
by connecting to one of the two geographically
separated nodes located at Schriever AFB, Colorado
and Onizuka AFS, California. Some users are
connected to both nodes to provide redundancy. The
communication segment connects the two nodes with
each other and all the remote tracking stations. When
scheduled, the user configures the communication
segment for the required connectivity to the RTS for the
space vehicle contact. The device used to perform the
circuit configuration is the distributed communications
controller (DCC). The DCC is a personal computer
(PC) with AFSCN provided software application
located at each user location or satellite operation
centers (SOC). At the scheduled time the DCC allows
the user to configure or establish the required
communication circuits from the scheduled RTS to the
SOC. The user configures the communication segment
to fit their individual satellite command and telemetry
requirements. The user is also responsible to deconfigure
the communication links upon completion of
the contact. User discipline is essential in a common
user network. Future plans are to automate the
communication link configurations chosen during the
scheduling process. The user is responsible to provide
communications from their SOC or facility to the
AFSCN, node or nodes if redundancy is required.
Network Management Segment:
The network operation center (NOC) is responsible for
the day-to-day management and scheduling of all
AFSCN resources. The NOC has final decision on all
user requests. It is a 24 hour, 7 days per week operation
staffed by a Network Crew Commander and network
schedulers.
The network management system is a stand alone
computer network which connects all users to the NOC.
The system allows the users to submit their satellite
contact requests and disseminates the compiled and
coordinated network schedule to all users. The
scheduling process begins with the user submitting their
requested contacts to include the space vehicle,
location, and time. The schedulers compile the requests
and create a network tasking order (NTO) to identify all
scheduled contacts and users for the next 24 hour
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period. The NTO is then disseminated to all users and
remote tracking stations for execution. Any and all
changes to the NTO such as vehicle emergencies must
be coordinated and approved by the NOC. The AFSCN
has 23 priority levels to aid in the coordination and
scheduling process.
Network equipment status is also tracked and managed
by the NOC to maintain an operational system
capability. Any operational change will be disseminated
by the scheduling system. The AFSCN currently
supports on average 420 contacts per day with a success
rate in excess of 99%.
Modernization
The AFSCN has existed for nearly 50 years and has
been through many changes. To continue providing
outstanding customer support, we are planning and
performing many upgrades and improvements. The
Remote Tracking Station (RTS) Block Change (RBC),
Electronic Scheduling System and communications
segment upgrades are to name a few. The RBC is the
complete replacement of the older automated remote
tracking stations (ARTS) with new core electronics
equipment and new 13 meter, three axis antennas.
Completion of RBC will provide at least two antennas
at all ground locations except Colorado Tracking
Station, which will remain a single antenna RTS. The
electronic schedule dissemination system is old
technology and reaching the end of its technical and
logistical life cycle. There is a program to replace this
system with modern technology equipment and
improved performance. The current communication
transport format on the communication segment is
serial circuits over an asynchronous transfer mode
(ATM) network. An upgrade will enable Internet
Protocol (IP) circuits over the ATM network with
eventual conversion to an all IP network.
Operational Responsive Space (ORS)
The current AFSCN users are the Department of
Defense (DoD), the Intelligence Community (IC),
National Aeronautics and Space Administration
(NASA) and National Oceanic and Atmospheric
Administration (NOAA) programs. The AFSCN is
capable of providing worldwide support to Operational
Responsive Space (ORS) missions. The AFSCN has
already supported the ORS TacSat-2 experiment and is
currently planning to support future missions to include
TacSat-1A, TacSat-3, TacSat-4 and others as
appropriate.
The AFSCN stands ready to support the ORS mission,
but will require some necessary selected changes to the

AIAA-RS6-2008-1006
long established 50th Space Wing timelines. The
current user integration process will need to be
modified to meet the shortened timelines required for
responsive space operations. The current nominal
timeline to receive documented program requirements
and integrate new missions into the AFSCN is two
years prior to launch. However, this interface between a
program and the 50 SW can begin as early as five years
prior, with attendance at the various program reviews
(e.g. system requirements review [SRR] and
preliminary design review [PDR]). The early interface
is to ensure the space vehicle and the C2 systems are
compatible with the AFSCN. This early and critical
interface between the program and the AFSCN ensures
incompatibilities are identified during the design phase
of the satellite to minimize/eliminate negative effects
during production or later when even small changes can
cause significant cost and schedule impacts. These
same interactions developed over time with the various
program offices are every bit as critical with ORS in the
design of space vehicles that will be placed in the
inventory for warfighter support. The quick reaction to
warfighter' requirements will require prior planning to
ensure a capability is designed and available for
immediate launch. This is also true with the launch
capabilities that will require preplanned booster and
launch plans to be responsive. The bus operations and
the payload operational plans will require critical
preplanning to achieve the responsive goals of the
program.
References
The following system interface specifications support
this paper.
1. SIS 000502E, AIR FORCE SATELLITE
CONTROL NETWORK (AFSCN)
STANDARDIZED
INTERFACE
SPECIFICATION (SIS) BETWEEN THE
RANGE SEGMENT AND SPACE
VEHICLE, 20 January 2005
2. SIS 000508F, STANDARDIZED
INTERFACE SPECIFICATION BETWEEN
AIR FORCE SATELLITE CONTROL
NETWORK (AFSCN), RANGE
SEGMENT/COMMUNICATIONS
SEGMENT AND COMMAND AND
CONTROL CENTERS, 06 October 2005
3. SIS 000509E, STANDARDIZED
INTERFACE SPECIFICATION (SIS)
BETWEEN THE AIR FORCE SATELLITE
CONTROL NETWORK (AFSCN)
NETWORK MANAGEMENT SEGMENT
(NMS) AND USERS, 25 January 2006
Although the current plans by ORS to meet the
warfighter’s needs are still in development, early,
modified and continuous AFSCN planning will clearly
be required. The 50th Space Wing is available to
support the Warfighter and ORS requirements.
However, we will require early involvement to ensure
the ORS needs are known and supported.
The 50 SW Plans and Program Office, AFSCN User
Integration and System Integration (50 SW/XPP), is the
office to work ORS requirements to fly on the AFSCN.
The 50 SW/XPP will work with the ORS program
requirement officers to create a program requirements
document that defines the ORS requirements on the
AFSCN. The response to the ORS program requirement
document (PRD) is the AFSCN program support plan
(PSP) stating how the AFSCN will support the ORS
requirements. Contact the 50 SW/XXP office via e-mail
at 50 SW.XPPSM@Schriever.af.mil. The telephone
numbers for the AFSCN Program Support Manager
(PSM) are DSN 560-2967 or 560-6560. The
commercial telephone numbers are (719) 567-2967 or
(719) 567-6560.
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