Digital processing subsystem key to the MDR payload TRW FACT SHEET Posted: February 25, 2001 Milstar 2 satellites will benefit from a TRW-developed digital processing subsystem that delivers data 640 times faster than Milstar 1 payloads, while capitalizing on dramatic advances in microelectronics and manufacturing processes to lower payload costs, weight, and part counts. The result is a system well adapted to fast-moving tactical military uses, as well as one that preserves Milstar's core communications requirements for worldwide, antijam, scintillation-resistant services with low probability of interception. The digital processing subsystem, combined with the RF subsystem built by Boeing Satellite Systems, constitutes the medium data rate (MDR) payload electronics package. Boeing integrates the MDR payload for Milstar prime contractor Lockheed Martin. MDR services will provide U.S. military forces with on-demand availability of interactive voice, video, and data links at rates up to 1.544 megabits per second. Thatšs more than 50 times faster than the 28.8-kilobit-per-second modem used with many personal computers. The MDR payload is tailored to meet the needs of third world threats and regional conflicts. Flexible onboard processing instantly reconfigures networks to suit evolving command and control requirements. The use of EHF frequencies and highly directional nulling antennas reduce the probability of jamming and intercept. Lightweight portable terminals on land, sea, and in the air can be easily moved during tactical operations.
Benefits of Onboard Digital Processing Each MDR payload has eight antennas, each independently steerable and operating at extremely high frequencies (EHF). Terminal users may communicate with other users within the same antenna beam or with users located in other MDR antenna beams from any of the Milstar 2 satellites. The on-orbit digital router establishes and maintains links within and among beams and responds to users' changing and differing bandwidth requirements. From each uplink beam the MDR payload processes the communication data, sorting and routing them to the proper downlink beams. If a data destination is found to lie outside the areas covered by a satellitešs antenna beams, the payload routes the message via crosslink antenna to another satellite for downlinking. In addition to sorting and routing messages, the digital processing subsystem performs other key functions such as demodulation of the EHF signal, authenticating and granting user access, and dynamically configuring payload resources (antennas, receivers, processors, etc.) to establish networks and provide bandwidth on demand. To perform these complex functions, the MDR digital processing subsystem relies on 14 custom application-specific integrated circuits and 397 large-scale integrated (LSI) circuits, all fabricated in CMOS technology. This figure represents a decrease of 37 percent from the 630 custom LSI circuits required for each LDR payload.
Fast, Flexible, MDR Flight Software The software is responsible for managing all MDR payload resources (uplink, downlink, and crosslink) employed for user communication. The software acts as a "switchboard in space," dynamically changing the routing path of communications data, based upon user requests. In addition the software performs all the multisatellite coordination with other Milstar satellites to support worldwide communications without resorting to intermediate ground links. The ability to improve performance and functionality while lowering development risk and reducing cost stems largely from two key factors. One is the selection of the Milstar Advanced Processor (MAP) as the MDR resource controller. MAP is a high-performance, general-purpose computer, developed for the Milstar program and used in other capacities on Milstar spacecraft. The other risk- and cost-reduction factor is the extensive reuse of LDR processing design and software code, which shortened development time dramatically. In addition, Milstar requirements and external interfaces were already well defined by the time MDR development began. Although software in the MDR and LDR payloads provides similar functionality, the MDR software incorporates a number of important system improvements. MDR software:
Savings in Time, Weight and Power For example, the MDR digital processing subsystem requires only two configured items to perform demodulation and routing functions. The LDR payload management subsystem (PMS) required four configured items to perform the same two functions. Overall, the MDR's digital subsystem weighs about 40 percent less than its equivalent configured units on the LDR PMS. The MDR units consume only half the power of their LDR counterparts. The MDR design also paid off in savings of time and manpower. The integration and acceptance of the MDR digital processing subsystem took less than three months, about half the time required to complete the same tasks for the LDR PMS. In addition, the size of the crew needed for integration and test was reduced by one-fourth. Add the savings in support personnel and the manpower required for integration and acceptance testing was cut in half.
MDR Digital Processing Demonstrates Continuous Milstar Improvements |
Flight data file Vehicle: Titan 4B/Centaur Payload: Milstar 2-F2 Launch date: Feb. 27, 2001 Launch window: 1857-2257 GMT (1:57-5:57 p.m. EST) Launch site: SLC-40, Cape Canaveral AFS, Florida Pre-launch briefing Launch timeline - Chart with the key events to occur during the launch. Titan 4B - Description of America's most powerful unmanned rocket. Milstar satellite - A look at the Military Strategic and Tactical Relay satellite program. Communications - Overview of Boeing's Medium Data Rate and crosslink payloads on Milstar. Antennas - Technical description of Milstar's medium data rate nulling antennas made by TRW. Restricted zone - Map outlining the Launch Hazard Area where mariners should remain clear for the liftoff. Video vault The Lockheed Martin Titan 4/Centaur rocket delivers the Milstar satellite into Earth orbit as shown in launch animation. PLAY (256k, 42sec QuickTime file) Animation shows the Milstar spacecraft at work in orbit relaying secure military communications 22,300 miles above the planet. PLAY (255k, 29sec QuickTime file) |
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MISSION STATUS CENTER |