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Personal Earth Observation Satellites

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					Personal Earth Observation
         Satellites
             Sias Mostert
        mostert@sunspace.co.za

 Stellenbosch Satellite Engineering Group




                     AfricaGIS October 2005
                Overview
•   Background
•   User Requirements
•   System Requirement Specification
•   MMSat Functional Specification
•   Operational Overview
•   Constellation Deployment
•   Applications
•   Conclusion
                 Background
• Traditionally remote sensing satellites were very
  expensive (SPOT 5 = US$600M)
• Cost/Performance ratio has improved dramatically
• From concept to utilisation in 12 to 18 months
• Technology allows 10m GSD with a 70 kg satellite
• Personal earth observation satellites
                   Advantages
•   Unrestricted access to payload
•   Only required data to be downloaded
•   Mission dedicated satellites
•   Modular design (bus architecture, plug and play)
•   No delivery delay
        User Requirements

• High temporal resolution (daily)
• Short request to data turnaround time
• Low contention for available data -
  overspill can be sold at low cost or
  given away
• Ability to deploy of constellations
 System Requirement Specification

Consists of
• Operational satellite in space
• Command station
• Data reception station (S band)
• 30 second ground target reorientation
• Image memory download in 1 overpass
• Use of view finder (when in range)
          Mobile Multi-spectral Satellite
           (MMSat) Functional Specs
 Sensor              GSD (m)   Swath (km)     Spectral
                                               bands
 Matrix Viewfinder      8         1x1            1
 Multispectral        6.25        45             6

• On-board storage of 24 Gigabyte, expandable to 240
  Gigabyte
• 70 kg complete spacecraft including constellation
  management propulsion
• Mobile ground-station for in-situ operation
• Custom filters for multispectral wavebands
• Propulsion for orbit maintenance (5 years)
     Imager Spectral Content
440-510 nm    Blue
  Water bodies, soil/vegetation, deciduous / coniferous
520-540 nm    light-blue-green
  Silt in water and deforest-land / urban-areas
520-590 nm    Green
  Green-reflectance-peak for plant vigour
630-685 nm    Red
  Chlorophyll-absorption, detecting-roads/bare-soil
690-730 nm    Red-edge
  Plant stress
845-890 nm    NIR
  Plant-biomass-estimates, water-bodies/vegetation
    Overview of the MMSat Satellite

• Satellite model
  MMSat
• 3-Axis ADCS
  dwell, FMC,
  real-time scan
• Separate C&C and
  Data reception
• GaAs solar panel
• Lithium Ion
  batteries
• Dual-redundant
  in most aspects
      MMSat Satellite Layout




70 kg
6.25m GSD in 6 bands
45 km swath
12 month program
      MMSat imagery examples




6.2m GSD (RGB): 320 x 320 pixels                                       8m GSD (pan): 320 x 320 pixels
                            Resampled from 1m GSD Ikonos satellite imagery
                    Location: Lingshui, Hainan island, South China Sea (10 April 2001)
MMSat imagery examples
         Operational Overview
•   Diary mode vs. viewfinder mode
•   Coverage: Off-nadir angle ± 30°
•   Temporal resolution 4 days @ 660 km
•   Data downloaded from 5° el. on S-band
•   Swath is 45km. Length limited by storage
•   Storage 24 GB, downloadable in one pass
     Constellation Deployment
• Rapid access to information requires
  constellation
• Constellation maintenance requires
  propulsion system
• Height: resolution vs. atmospheric drag
• 4 satellites @ 500km / 3 satellites @ 660 km
  for near continuous coverage
             Applications
• Agriculture resource management
• Settlement management &
  infrastructure development
• Disaster mitigation, response and
  recovery
• Health hazard monitoring
• Regulatory control
• Food security

				
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