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Milstar 3 / Advanced Extremely High Frequency (AEHF)

AEHF had its share of technical problems, including interface control redesigns, delayed delivery of signal-encryption products, disqualified parts, and unplanned component testing. But the program suffered as much, if not more, from as many as six changes in the requirements and number of satellites, from budget fiuctuations and from constant program replanning and rebaselining.

The first Advanced Extremely High Frequency (AEHF) satellite was launched from Cape Canaveral aboard an Atlas V rocket provided by the United Launch Alliance from Launch Pad 41 Aug. 14, 2010 at 7:07 a.m. The launch was supervised by the 45th Space Wing. The satellite is the most technologically advanced military communications satellite ever developed and will provide significantly improved global, survivable, highly secure, protected, communications for warfighters operating on ground, sea and air platforms.

The Advanced Extremely High Frequency (AEHF) satellite communications system is designed to provide secure, survivable communications to U.S. warfighters during all levels of conflict. It will follow Milstar as the protected backbone of DoD's military satellite communications architecture. The first flight of the AEHF satellite program, named Pathfinder, will be programmed to operate initially as a Milstar II satellite (in lieu of an additional Milstar satellite to replace Flight 3, which placed the satellite in a non-operational orbit). The second flight will then be launched as a fully capable AEHF satellite. After it is operational, Pathfinder will be reprogrammed on-orbit as an AEHF satellite.

The first three program phases: AEHF Technology, Engineering Models, and System Definition have been completed. At Milestone B, the Defense Acquisition Board authorized fabrication and assembly of the first two satellites (SV1, SV2), development and deployment of the ground command and control segment, and advanced procurement for three additional satellites (SV3, SV4, and SV5) within the Future Years Defense Program. A separate tailored Milestone C was anticipated, following completion of the system-level Critical Design Review (CDR), to provide final authorization for production of SV3, SV4, and SV5. However, a February 2003-approved Acquisition Program Baseline incorporates a revised strategy that deletes SV4 and SV5 with a decision point in 1QFY05 to evaluate Transformational Communications development and the need, if any, for additional AEHF satellites. The first AEHF launch is scheduled for 1QFY07 and the second launch for 2QFY08. Advanced EHF is to consist of four cross-linked satellites covering the globe from 65 degrees north to 65 degrees south, providing 10 times the data rate available through MILSTAR.

In August 1996, the Department approved its future Military Satellite Communications (MILSATCOM) architecture that aligned military requirements into three core functional segments: protected, wideband, and mobile communications. The intent of this alignment was to move all users who required protected communications (e.g., front-line tactical forces and strategic nuclear forces) to a single military-unique system, current Military Strategic Tactical and Relay (MILSTAR) and its Advanced Extremely High Frequency (EHF) follow-on program launching in 2006. This move allows the two other segments, wideband and mobile, to be as commercial-like as possible to best leverage the technology and investments being made in the exploding commercial satellite communications market.

On 23 August 1999 Lockheed Martin Corp., Sunnyvale, Calif., and Hughes Space and Communications Company, El Segundo, Calif., were awarded a $44,499,925 ($22,250,000 Lockheed Martin; $22,249,925 Hughes Space) firm-fixed-price contract to provide for system definition of the advanced Extremely High Frequency (EHF) communication satellite program. Each contractor will perform system requirements analyses to develop a final system specification and develop an advanced EHF design. There were nine firms solicited and two proposals received. Expected contract completion date is March 31, 2001. Solicitation issue date was May 6, 1999. Negotiation completion date was Aug. 5, 1999. Space and Missile Systems Center, Los Angeles AFB, Calif., is the contracting activity.

The Advanced Extremely High Frequency (AEHF) Engineering and Manufacturing Development (EMD) effort will result in the development, deployment, and sustainment of the AEHF MILSATCOM constellation and associated Mission Control System upgrades. The program was initially structured to deliver the AEHF satellites to meet a first launch in June 2006, with satellite delivery April 2006, a second launch nine months after, and the remaining launches in six month increments.

In April 2000, the Defense Department decided to award the Advanced EHF contract to a "national team" consisting of Hughes, Lockheed Martin, and TRW. On 30 May 2000 Lockheed Martin was awarded a $98,000,000 firm-fixed-price contract to create a teaming arrangement consisting of Lockheed Martin, TRW and Hughes. This action enables the contract team to perform the system definition phase of the advanced Extremely High Frequency (AEHF) satellite communication system. This modification combines two system definition efforts into the current teaming arrangement. The work is expected to be completed March 2001.

The total value of the Advanced EHF program, including the satellites, one spare and ground segment modifications, is estimated at $2.5 billion. The first Advanced EHF satellite -- the Pathfinder satellite -- will be delivered by December 2004, 18 months ahead of the originally scheduled launch in June 2006. The Advanced EHF program was restructured, and the schedule accelerated, in response to the April 1999 incident in which a MILSTAR satellite was launched into an incorrect orbit.

The Engineering Model program was created to develop and test prototype digital processing subsystem designs for the next generation of EHF satellites that will replace the MILSTAR I and II systems. The EM program is part of an initiative leading to higher power efficiency, lower bus and payload weights, improved performance, additional features, and increased reliability while meeting the military needs for secure, survivable communications into the next century. The Engineering Model program is a hardware and software development effort intended to functionally demonstrate digital processing functions, including crosslink processing, associated with the Advanced EHF communications system. The Engineering Model program will develop a space qualifiable digital processing architecture capable of satisfying the next generation EHF communications requirements while reducing the weight, power, and life cycle cost associated with the current generation of MILSTAR payload digital processing. The following four features are viewed as important in the Engineering Model development program: (1) the ability to accommodate technology insertion over the entire mission life cycle with minimum of design breakage, (2) the ability to accommodate known and emerging commercial requirements, (3) the ability to meet mission availability and reliability requirements, and (4) the ability to adapt to future communications requirements.

The primary reason for considering options to the current Milstar program was to reduce system cost. The Bottom Up Review considered several options, all of which would launch the original two Milstar 1 satellites and eventually transition to Advanced EHF satellites that would be developed in the mid-to-late 1990s. The successor system would maintain as much LDR and MDR capability as possible while reducing satellite weight, which should help to reduce costs. The alternatives to the current program differed as to when the initial Advanced EHF satellite would be launched and, consequently, the MILSATCOM capabilities that would be provided in the meantime.

Option 1 (Milstar 2/Advanced EHF) would retain four Milstar 2 satellites, with a first launch in FY 1999 (as in the FY93 program), but it would eliminate the fifth Milstar 2 satellite (planned for delivery as a spare satellite in FY 2003) as well as subsequent Milstar-2 satellites. Full operational capability for LDR and MDR would be achieved on the same schedule as under the FY93 program. Under this option, Advanced EHF satellites (Milstar 3) would be developed using advanced technology, to provide LDR and MDR capabilities comparable to those of Milstar 2. Advanced EHF satellites would begin replenishing Milstar satellites around FY 2006.

Option 2 (MDR-Only/Advanced EHF) would cancel Milstar 2 and replace the four Milstar 2 satellites with satellites providing an MDR capability, but eliminating the LDR capability. The first MDR-only satellite would be launched in FY 2000, with a four-satellite constellation on orbit in FY 2003. This option would also develop Advanced EHF satellites with both MDR and LDR capability. The first of those satellites would be launched in about FY 2007.

Option 3 (Advanced EHF Only) would also cancel Milstar 2, but it would replace that system with Advanced EHF satellites having both MDR and LDR capabilities. The first Advanced EHF satellite would be launched in FY 2003, with a four-satellite constellation in place in FY 2006.

Option 4 (Accelerated Advanced EHF) is similar to Option 3, except that it accelerates development of the Advanced EHF satellite, achieving a first launch in FY 2000 and a four-satellite constellation in FY 2003. This alternative would, if necessary, trade capability for weight on the initial satellites to maintain an FY 2000 launch date. Subsequent satellites could incorporate performance improvements, if needed.

Evaluation of Options

An outside Technical Support Group was established to review the options and assess the level of risk, as well as to develop and evaluate additional Milstar alternatives. The Technical Support Group concluded that the most effective way to provide the desired communications capability in a cost-constrained environment would be with the new-design Advanced EHF Milstar 3 satellites, deployed in geostationary orbits and providing both LDR and MDR capability.

The Bottom Up Review Military Satellite Communications Technical Support Group recommended that DoD take advantage of recent technological advances to build substantially lighter satellites that could nevertheless provide performance comparable to Milstar 2. The group concluded that a reasonable objective would be to transition to a lighter, advanced EHF satellite that could be boosted into orbit by a medium-launch vehicle (MLV). This would limit costs, which have historically been related to satellite weight.

The consensus of the Technical Support Group was that an Advanced EHF satellite that could be launched from an MLV could be available by 2003. However, the four-year delay between the scheduled launch of the first Milstar 2 satellite and the postulated launch of the first Advanced EHF satellite was a concern. Consequently, the Technical Support Group considered what capabilities could be provided on an Advanced EHF satellite if the first launch was accelerated to 2000.

The Technical Support Group did not reach a consensus on whether such an accelerated deployment of Advanced EHF satellites was possible. It identified as a major risk the lack of maturity in the packaging for microwave and digital electronics. A first launch in 2000 would be possible, according to some of the group members, using technology already developed or currently under development. Other members of the group concluded that there would be major risks associated with the concurrent technology demonstration, satellite design, and streamlined test program inherent in Option 4.

Total space segment costs (including launch costs) in FY 1994-2011 for the alternatives considered in the review ranged from $6.1 billion for the least costly option (Option 3) to $13.9 billion for the current program. Cost estimates for Option 4 varied from $7.2 billion to $11.3 billion, depending upon assumptions about risk of payload weight growth or schedule slippage.

Option 1 has essentially the same FY 1994-99 costs as the Bush program because it retained the first four Milstar II satellites, although it does achieve about $300 million in cost savings by canceling the Milstar II spare satellite. Further cost savings are achieved beyond the FYDP period by transitioning to the lower cost Advanced EHF satellite. FYDP savings of the other three options come predominantly from canceling the Milstar 2 program immediately and deferring MDR capability.

There were also differences in launch costs among the options, driven primarily by the differences in costs of the launch vehicles for the Milstar Il satellites (Titan IV) and Advanced EHF satellites (Atlas IIAS). The Titan IV costs approximately $285 million per launch and the Atlas IIAS about $ 115 million.

The LDR shortfall was most severe in Option 2 because that option provides no substantial LDR capability until Advanced EHF satellites are launched beginning in 2007. Option 3, which provides for initial operations of Advanced EHF satellites in FY 2003, would delay initial MDR service by four years relative to the current program. Options 2 and 4 would delay MDR service by one year.

Options 2 and 3 were judged unacceptable in the Bottom Up Review because their schedules provide capabilities much later than did the Bush program or Option 1. The technical, cost, and schedule risks of Option 4 were considered to be too high by the Joint Staff, which also concluded that the LDR capability provided by Advanced EHF satellites would be reduced relative to Milstar 2 because these satellites would provide fewer antennas than Milstar 2.

The options containing four Milstar 2s were determined to be most preferable because a constellation of that size would meet military requirements and provide the most operational capability at the earliest date. Option 3 was considered unacceptable because it would delay LDR and MDR capability by four years. Option 4 would provide capability sooner, but its schedule was considered high risk.

The Decision

The Bottom Up Review decided to proceed with Option 1, deploying both Milstar 1 and the initial constellation of Milstar 2 satellites, then transitioning to a lower-cost, lower-weight Advanced EHF Milstar 3 satellite that was projected to be launched initially by FY 2006.

Developing an advanced EHF satellite required ingenuity within the DoD and industry and was not without risk. Reducing the weight of the Milstar II payload by a factor of three to four and providing a sufficient number of narrow-beam EHF antennas to connect the tactical forces needed to fight a regional conflict was a higher-risk, but potentially lower-cost, approach than the continued development of Milstar 2 satellites. The Department examined a wide range of potentially applicable technologies -- inflatable antennas, carbon-carbon structures, lightweight beam-forming networks, advanced technology crosslinks, digital electronics, inflatable solar arrays, high-energy batteries, integrated electronics, etc. The review provided the foundation for the technology development necessary to support concept definition and development of a future, lower-cost EHF satellite design.

First launched in late 2010, AEHF provides continuous 24-hour coverage between 65 degrees north and 65 degrees south latitude. The AEHF system is composed of three segments: space (the satellites), ground (mission control and associated communications links) and terminals (the users). The segments will provide communications in a specified set of data rates from 75 bps to approximately 8 Mbps. The space segment consists of a cross-linked constellation of five planned satellites as well as the five legacy Milstar satellites. The mission control segment controls satellites on orbit, monitors satellite health and provides communications system planning and monitoring. This segment is highly survivable, with both fixed and mobile control stations. System uplinks and crosslinks will operate in the extremely high frequency (EHF) range and downlinks in the super high frequency (SHF) range. The terminal segment includes fixed and ground mobile terminals, ship and submarine terminals, and airborne terminals used by all of the Services and international partners (Canada, Netherlands and UK).


  1. Space Vehicle 1 - Aug 14, 10
  2. Space Vehicle 2 - May 4, 12
  3. Space Vehicle 3 - Sep 18, 13
  4. Space Vehicle 4 - TBD
  5. Space Vehicle 5 - TBD

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Page last modified: 28-03-2016 20:55:23 ZULU