1 DSL Distributed Systems Laboratory ATC 23 August 2005 Model Mission: Magnetospheric Multiscale (MMS) • Mission Goal “To study the microphysics of three fundamental plasma processes: magnetic reconnection, energetic particle acceleration, and turbulence*” • Constellation composed of 4 identical spacecraft maintaining a tetrahedral formation in regions of scientific interest within the magnetosphere • Each spacecraft has a suite of 4 primary payload sensors/subsystems (FPI, FIELDS, HPCA, EPD) * SWRI MMS webpage http://mms.space.swri.edu/
Transcript
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DSLDistributed
Systems Laboratory
ATC
23 August 2005
Model Mission:Magnetospheric Multiscale (MMS)
• Mission Goal“To study the microphysics of
three fundamental plasma processes: magnetic reconnection, energetic particle acceleration, and turbulence*”
• Constellation composed of 4 identical spacecraft maintaining a tetrahedral formation in regions of scientific interest within the magnetosphere
• Each spacecraft has a suite of 4 primary payload sensors/subsystems (FPI, FIELDS, HPCA, EPD)
* SWRI MMS webpage http://mms.space.swri.edu/
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MMS Mission (cont.)
• Plasma processes under investigation are inherently transient (magnetic reconnection in particular)
• Specific need for reactive on-board autonomy to enable high temporal and spatial resolution data acquisition during transient events (i.e. changes in particle, ion, and electromagnetic field measurements)
• Limited intra-constellation communication dedicated to coordinating reactive data acquisition– Only a measure of the “quality” of scientific data is transmitted (1
byte every 10 seconds) by each spacecraft– Quality byte is used as a trigger for the other spacecraft in the
constellation to start high resolution data acquisition
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23 August 2005
Operating Modes
• Each spacecraft has three modes of operation– Slow Survey– Fast Survey– Burst
• Slow Survey Mode is entered when a spacecraft is outside the regions of scientific interest (approx 60% of orbit)– Only a subset of payload sensors are active, providing a minimal
amount of data (primarily for health monitoring)– Acquired data is not stored for downlink
• Fast Survey Mode is entered when a spacecraft is inside a region of interest (approx 40% of orbital period)– All payload sensors are active, and data taken at moderate rates– Acquired data is analyzed for quality on-board and stored for later
downlink– Quality data is communicated throughout the constellation
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Operating Modes (cont.)
• Burst Mode is initiated by time-triggered commands or autonomously when measured conditions satisfy a set of rules– It can only be triggered while the spacecraft is already in Fast
Survey Mode– Approximately 40 min allowable per day (due to storage
constraints)– All sensors acquire high temporal resolution data– Acquired data is analyzed for quality and stored for downlink– Transition to Burst Mode is communicated throughout the
constellation via the quality byte• Does not necessarily force Burst Mode transition in other spacecraft• Transition based on weighted combination of conditions, local data
quality, and communicated quality
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23 August 2005
Phases of MMS Mission
• Three phases of operation targeting different regions of the magnetosphere
• Priority of payload data dependent on phase of mission as well as location in orbit
Image from SWRI MMS CSR p. F-16
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Payload Sensor Specifications
Sensor TypeBurst Fast Survey Slow Survey Burst Fast Survey Slow Survey
Demonstration Scenarios based on MMS Mission Model
• Simplifying assumptions– Only three spacecraft in a triangular formation (allowing potential
use of Microbots as hardware testbed)– Simulate payload sensor data and orbital information for
operating mode transitions– Use representative algorithms for compression, on-board
processing, etc.
• Three potential scenarios of increasing complexity– Nominal “Day in the Life” of MMS– Support of science community requests for alternate on-board
processing– Management of solid-state storage overflow conditions
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Demonstration Scenarios (cont.)
• “Day in the Life” scenario will demonstrate several aspects of mission operations under nominal conditions– Mode transitions based on orbital location (Slow/Fast)– Mode transition based on burst trigger commands, measured
conditions, and inter-constellation communication– Ground station interaction with the constellation
• “User Request” scenario will demonstrate support for multiple scientific user requests beyond the nominal operations– Users can modify or add to the on-board processing
• Alternate data rates• Compression schemes• Quality of data for downlink/storage
– Users can set time triggered commands to control mode transitions based on time (i.e. location in orbit)
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23 August 2005
Demonstration Scenarios (cont.)
• “Storage Overflow” scenario will demonstrate autonomous management of a fault or off-nominal conditions– Limited data storage space could be filled (by entering Burst
Mode often) or fail, while sensors/processors still operational– Several potential methods of managing situation
• Overwrite low quality or priority data
• Balance stored data across constellation during Slow Survey Mode
• Stream acquired data in realtime to other spacecraft for storage (assuming communication bandwidth sufficient)
– Specific methods to be implemented still under consideration
