User:Rv0824/sandbox/MultiMission Modular Spacecraft

The MultiMission Modular Spacecraft (MMS) is a multi-functional and reusable three-axis spacecraft that provides flexible serviceability to a wide variety of missions (ranging through many different orbits), designed by the National Aeronautics and Space Administration (NASA). The base design for the MMS includes three subsystems; those for power, attitude control, and command and data handling, which can be configured to add on more modules for mission-specific requirements. The MMS's compatibility has been shown through its usage in Delta, Atlas, Titan, and other NASA launch vehicles. It was used for the following missions/projects :


 * Solar Maximum Mission (SMM)
 * Landsat 4
 * Landsat 5
 * Upper Atmosphere Research Satellite (UARS)
 * Extreme-Ultraviolet Explorer (EUVE)
 * TOPEX/Poseidon

Program Background
The idea for the MMS was proposed by the Goddard Space Flight Center (GSFC) in the 1970's to reduce the cost of development for individual missions without needing special modifications of hardware components before each mission. It was planned to cover a broad number of earth-pointing, solar-pointing, and stellar-pointing observatory missions. The expectation for the MMS was to streamline the process of reducing costs of designing, building, integrating, testing, and flying space systems. The GSFC planned to execute this idea by applying the following considerations:


 * minimizing the amount of mechanical and electrical connections
 * having only one structural and thermal design for all of the design reference missions
 * maximizing the use of flight-approved and NASA standard components.

The guidelines for the design of this module were later expanded to require the compatibility to launch and retrieve the module through the use of the Space Transportation System (STS). This serviceability was to be required for the design, and no exceptions were to be allowed in favor of the cost-effective goal.

The GSFC's goal was to build a spacecraft as cars and aircraft are built in the modern industry, and this plan was key to reducing the historical costly investments in spacecraft production and testing.

Solar Maximum Mission (SMM)
The GSFC received approval for the full-scale production of the MMS in the mid 1970's, which was around the same time the Solar Maximum Mission (SMM) received it's go-ahead. As a result, the SMM satellite was chosen as the first satellite to be based on the MMS bus. This spacecraft was successfully placed into orbit in February of 1980. The mission lasted for nine years, and it underwent an in-orbit repair in 1984 known as the Solar Maximum Repair Mission (SMRM). The satellite eventually lost attitude control functionality and returned to orbit, burning up and landing in the Indian Ocean in December of 1989.

Modules
The MMS is composed of three default modules, which are mounted on a triangular-shaped (square pyramid) module support structure. The overall structure supports optional upgrades to suit the needs of mission-specific requirements.

Modular Power Subsystem (MPS)
The Modular Power Subsystem (MPS) provides power from an average of 1kW up to 3kW at 28 volts to the spacecraft being serviced using 2 solar arrays. This subsystem uses three 50-amp/hr nickel cadmium batteries, powered by solar energy collected during the daylight cycle of the satellite's orbit.

Modular Attitude Control Subsystem (MACS)
The Modular Attitude Control Subsystem (MACS) provides stabilization and proper orientation for the MMS. The MACS is required to provide attitude control with enough accuracy to meet mission-specific requirements. To satisfy this objective, the MACS applies a system that is capable of operating in stellar, solar, and earth pointing missions. The module contains an on-board computer (OBC) system and sensors, which use an algorithm processed by the OBC for attitude determination.

Communications and Data Handling (C&DH)
The Communications and Data Handling (C&DH) creates a telemetry link to transmit commands to and from Earth, collecting measurements from and passing commands to all spacecraft via NASA's Deep Space Network (DSN). Its Central Unit (CU) functions as a hub for telemetry data and commands. The module's dimensions are 4 feet x 4 feet x 1.5 feet, and it weighs 270 pounds (lbs) (accounting for an extra 60 lbs of mission-specific weight).

Mission-Specific (Optional) Modules
Some of the optional modules that have been configured onto the MMS and used in missions include (but are not limited to) the:
 * Propulsion Module (PM)
 * Payload Module
 * Equipment Deck Platform

Modular Adaptive Reconfigurable Systems (MARS)
Modular Adaptive Reconfigurable Systems (MARS) are classified as technologies that can streamline cost-effective and flexible missions. The MMS was the first design concept under NASA to attempt this concept of modularity. The MultiMission Modular Spacecraft unfortunately never matured to the point it needed to be, and it was gradually phased out. The concept of modularity that the MMS proposed has been extended beyond the traditional MMS module, as seen through the Rapid Spacecraft Development Office (RSDO).