6th Responsive Space Conference April 28–May 1, 2008

Los Angeles, CA

Air Force Satellite Control Network (AFSCN) Support for Operational Responsive Space (ORS) Len Hodges 50th Space Wing, Plans & Programs Office (50 SW/XPP) Ron Woll 50 SW/XPP & HQ AFSPC/A3RN (Scitor Corp.)

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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

The AFSCN is a common user, unclassified network where all users share the network within a disciplined

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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.

KEY TO SYMBOLS

Operational Control Node

Remote Tracking Station (RTS)

Transportable ARTS Core

Transportable Antenna

AFSCN Resources

VTSVandenberg Tracking Station

Vandenberg AFB, CA

OAFSOnizuka Control Node

Onizuka Air Force StationSunnyvale, CA

HTSHawaii Tracking Station

Kaena Point, HI

TCSTelemetry & Command

SquadronOakhanger, England

NHSNew Hampshire StationNew Boston AFS, NH

TTSThule Tracking StationThule AB, Greenland

DGSDiego Garcia Station

Brit. Indian Ocean Terr.Diego Garcia Island

GTSGuam Tracking StationAndersen AFB, Guam

TVCFTransportable Vehicle Checkout Facility East

Cape Canaveral AFS, FL

TSTRTransportable Space Test

ResourceKirtland, AFB, NM

CTSColorado Tracking Station

Schriever AFB, CO

SAFBSchriever Control Node

Schriever AFB, CO

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

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

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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 de-configure 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

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

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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.

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.

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